Arc welding machines and stick welders have been around for many, many years. According to wikipedia.com the first recorded use of an arc welding machine was way back in the early 1800's.

Slowly over time the development of the stick welder and arc welding machine were greatly improved. The evolution of mankind demanded better ways of joining metal together.

Anyone who has even remotly looked into welding has most likely heard of, or seen an arc welding machine.

To understand the stick welder you need to understand that you are dealing with electricity. All electricity that is supplied to your workshop, shed, garage or house is what is called AC power.

AC power is short for "alternating current". In english this means that the power coming out of your wall socket will go from positive (+), to negative (-) really fast over a short amount of time.


In my country of Australia we are on 240volt AC power at 50Hz. So this means that my power will go up to 240V positive, then back down to negative 240V at 50Hz. Hz is Hertz, which means that the power will go from +240V to -240V at 50times per second. Pretty quick huh!

On a side note this is why the light bulbs in you house do not flicker, as the change from positive to negative is so fast. But if the Hz was only say 5 instead of 50 you would probably see the light globe flicker on, off, on, off.

The majority are DC output.

DC is direct current. That is the power does not go up and down like a wave but rather in just a straight line.

This gives us a consistent current power source of DC power which is ideal for arc welding.
Here is a video that I did about Arc Welding Machines and their basic setup.

It is much easier for me to show you in a video rather than you having to read through page after page of welding information.

In the video I show two different types of arc welding machines. The first machine is the type of welder that you would buy from the local hardware store for a hundred or so dollars.

The second machine is a more heavy duty industrial machine that is physically bigger and will offer more power output for bigger welds, and it has a higher duty cycle. The second machine has a high voltage output option as well.

In the video I go over how to attatch the welding leads, how to adjust the welding power output, and how to put the electrode into the "stinger".

click here to watch the video

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Based in Huddersfield, West Yorkshire, FWS provide a complete friction welding service. Supply of a range of standard machines. Special design friction welding machines. Supply and remanufactured, and or modified used friction welding machines, sub-contract friction welding services, friction welding consultancy.

Standard design friction welding machines

FWS manufacture and supply its own standard range of machines from 5 to 200 tonnes end load capacity

» Single or double headed layout.
» Automation systems for component handling.
» CNC flash removal systems.
» DC and inverter drives.
» Weld orientation capabilities.
» Advanced single screen, control systems, windows
environment.
» Full in process monitoring. Database for weld data retention.
» In house Workholding and tooling solutions.
Special design friction welding machines

FWS manufacture and supply machines to customers precise requirements, with up to 300 tonnes end load capacity.

» Our experienced engineers have unique experience in solving
the special workholding requirements of customized
applications.
» In house chuck and workholding manufacture.
» In house automation design and manufacture

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The “TIG” in TIG welding stands for Tungsten Inert Gas. But before it was named so, it was called “Heliarc” because of the helium that was dominantly used when the process was invented. But then someone discovered that argon worked better and so it was called “TIG” because inert gas could refer to either helium or argon.

Later, it was again discovered that small additions of hydrogen worked well for some metals. The word “inert” then no longer held true and so it was renamed. So nowadays, the technical term for what used to be called “TIG” and “Hiliarc” is Gas Tungsten Arc Welding or “GTAW”.

Compare to other arc welding processes, TIG welding is more difficult to use though. Just like gas welding, one is required to use both hands with the torch held in one hand and the filter rod in the other. Oftentimes, a foot pedal amperage control is also used which makes it more inconvenient.

The TIG torch can either be water or air cooled. It is designed also to give shielding gas and welding current through a tungsten electrode. A ceramic nozzle leads the shielding gas to the weld puddle and internal copper parts like the collet and the body holds the electrode in place. The tungsten electrode is sharpened for applications where the arc need to be pinpointed and for very low amperage.

The arc that is made between the tungsten electrode and workpiece creates the heat that melts the metal and makes the weld puddle. The arc is shielded by argon, or helium or the mixture of both. Sometimes for certain alloys, hydrogen is added in small percentage to improve the flow of puddle. The arc is very smooth, quiet and clean when DC current is used. However, when the TIG welding machine is set on Alternating current, it is slightly noisier but still clean and smooth.

Here is a list of some popular metals that can be welded using the TIG welding process: Carbon and low alloy steels like 1010 carbon and 4130 chromoly steels; 301, 321 and 17-7ph stainless steels; inconel 718 Nickel alloy and X Hastelloy; Aluminim alloy like 6061 and 5052; az31b Magnesium alloys; 6a14v Titanium alloys and those that are commercially pure; Stellite 6b and 1605 Cobalt alloys; copper alloys like Nibral bronze and pure copper and a whole lot more.

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What are the different types of welding and what are they used for? If you are looking for a 20,000 foot view of the different types of welding along with applications, stick around for a minute, I think I can help.

Stick welding

Stick welding is often called Arc welding although that is kind of a misnomer because TIG welding and MIG welding are actually arc welding processes too. But ARC welding is what most people still call stick welding. Stick welding is the old school kind of welding that grandpa used to do to fix his tractor in the barn. It uses a stick electrode like a 6013, 6011, or 7018 welding rod that is chucked up in an electrode holder that looks a little bit like a battery jumper cable clamp. The rod is struck like a match to get the arc going and the rod is fed into the puddle as it burns. Stick welding is pretty simple and the stick welding machine is simple too and also pretty cheap. You can buy a Lincoln 225 AC welding machine at any Home Depot for way less than 300 dollars.

MIG welding

Mig welding is considered one of the easiest types of welding to learn. Why? Because the rod does not have to be fed as it shortens like with stick welding. A wire is fed thru a cable and out the end of the mig welding gun and all the operator is required to do is to pull the trigger and weld. Sounds easy right? Well it is not that easy. It is a little bit easier to learn than stick welding but only a little.

Mig welding actually kind of describes 2 types of welding...bare wire mig, AND flux core welding.

Bare wire mig is cleaner, and will weld thinner metal, but flux core is easier to use outdoors and does not require a cylinder of mig welding gas or a flow meter. Flux core welding is usually either used for cheap hobby welder s where the buyer does not want to spend the money for gas and a gas conversion kit, or for really heavy duty applications like earth moving equipment and heavy production welding.

TIG welding

TIG welding is considered one of the more difficult types of welding to learn...harder to master than mig or stick welding. That is because both hands are needed to tig weld. One hand holds a tig torch with a tungsten electrode that provides the arc and heat...and the other hand feeds the rod. TIG welding equipment is generally more expensive and more difficult to set up because there is often a remote amperage foot pedal included and it takes a cylinder of argon or argon mix shielding gas to work.

Tig welding is the most versatile type of welding of all. Virtually all conventional metals can be welded with the tig process. Carbon and low alloy steels, stainless steel, nickel alloys, aluminum, magnesium, titanium, cobalt, and copper alloys can all be welded using this type of welding.

Plasma arc welding

Plasma arc welding is similar to tig welding except that the tungsten electrode is recessed inside a nozzle and the heat is created by ionizing gasses flowing around the arc. Plasma arc welding is used where high precision is required and in situations where a recessed electrode is beneficial. Plasma arc welding is used extensively in aerospace applications for dimensional restoration of air seals and jet engine blade repair where thicknesses are often below .015" and amperages used are often single digit.

Gas welding

Gas welding is one of the old school types of welding. Oxygen and Acetylene is the most popular setup for a gas welding kit and gas welding is still used a lot for automotive exhaust applications, as well as by homebuilt airplane enthusiasts for welding 4130 chromoly tubing for airplane fuselages. It works. It's portable. And it is fairly versatile... There are still some people that swear by gas welding even for welding aluminum.

Some people believe that tig welding is much better than gas welding. I am one of those people.

Electron beam and laser welding.

These types of welding are considered high energy welding processes because they pinpoint heat so much better than older more conventional types of welding. Electron beam welding can penetrate through 6 inches of steel without any bevel.

Laser welding can pinpoint heat so precisely that weld metal can be deposited on a tool steel injection mold cavity so precisely that heat treatments can be eliminated and only minimal machining is needed in order to restore dimensions.

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Today welding is the most common method used for joining steel fabrications largely because of the speed at which joints can be made and the reliability of these joints in service. However because most welding operations are now relatively simple to perform it is all too easy to forget the complexity of the chemical and metallurgical actions that are taking place when the weld is being deposited. Therefore not surprisingly welds occasionally fail.

The most common causes of weld failure can be attributed to one of the following causes:-

Overload.
Before applying the various design formulas, the problem itself must be analysed and clearly stated. This is not always obvious, and trying to solve the wrong problem can quickly lead to insufficient design stresses. When a load is placed on a member, stress and strain result. Stress is the internal resistance to the applied force. Strain is the amount of "give or deformation caused by the stress, such as deflection in bending, elongation in tension, contraction in compression, and angular twist in torsion.

For example of this is a lifting lug on a pressure vessel. If the vessel is lifted by a spreader beam the loading condition on the lug consists of a simple vertical force putting the attachment welds either in tension or shear. However if the vessel is lifted with a rope sling the loading condition becomes more complex because there is now a horizontal component of the force to consider as well a the vertical one, which effectively increases the loading on the welds.

Joint Design.
A welded joint should be designed such that the welder can easily manipulate the electrode to ensure good fusion, particularly in the root of the joint. The profile of each run should be roughly as wide as it is deep; wide shallow weld beads and particularly deep narrow beads are both ideal candidates for hot cracking.


Solidification Crack
This type of cracking occurs when the weld is starting to solidify, in the pasty state, as it posses very little strength and therefore any residual loading is likely to cause it to break before it has fully solidified. The problem can be compounded by impurities that are forced out of the solidifying weld, becoming trapped in the centre of the weld during final solidification. Hot cracking can occur where their is a high degree of restraint in the structure of the fabrication or where the structure moves slightly as the weld solidifies.

A good example of this type of failure is on the weld used to secure the small plug in the mandrill hole of a spun dished head on a pressure vessel, a weld that many people do not take seriously because of its size. As the weld cools it contracts causing the plug to move , if the weld at the other side of the plug is still solidifying it could easily fail. This is because of the very high contraction stresses generated by the plug as the weld starts to solidify.

Bad Welding Method.Hydrogen Crack
It is very important when carrying out any welding to ensure that it is done correctly. Consideration has to be given to all aspects of the process and also the environment. Often welding has to be carried out under site conditions, the welding is often carried out in situation so that small general purpose electrodes are used resulting in low weld heat input which when combined with no preheat gives very rapid heat dissipation Which can create a hard micro structure particularly in the location of the heat affected zone. This along with high levels of residual stress will create the ideal condition for hydrogen Hydrogen Fisheyes In A Tensile Test Pieceinduced cracking,
which although normally associated with high strength steels can occur in low carbon steels if the conditions are right. The resulting crack may not occur immediately the weld cools down but some time afterward, therefore if this type of failure is expected non destructive examination should be delayed by at least 48 hours after welding.




Metallurgical failure.
Materials that are to be welded have to tolerate severe thermal transients created by the welding process without suffering deterioration of their mechanical properties or adverse phase changes. The metallurgical composition or temper conditions of certain types of metal may make them unsuitable to weld or may require special controls to be imposed during the welding operation. For example some steels that are easy to machine may contain high levels of sulphur that may result in cracking of any attaching weld. Therefore this type of material should not be used on load bearing fabricated items such as the eye bolts that are often found holding down manway covers on pressure vessels.

Weld Defects.
They can usually be attributed to the welders inability to set up and manipulate the welding equipment; although bad joint design and faulty welding equipment can also be responsible. The most significant defects are cracks and those that resemble cracks such as lack of fusion, cold overlap etc. This is because of the risk that the crack may become unstable and propagate when loaded causing a dramatic failure often by brittle fracture.

Lack Of Fusion Defect
Porosity seldom causes weld failure in multi-run welds however it is a sign that something has gone wrong with welding operation and can often be caused by other defects that may not have been detected such as lack of side wall fusion. Weld profile can also cause failure, if the weld size is too small because the joint is underfilled with weld then its load carrying capability will be reduced, if the joint contains excessive weld metal this can create a notch effect which can lead to failure by fatigue if the loading condition fluctuates. Bad fit up excessive root penetration on single sided welds can create defects in the root of the weld such as wormholes and even cracking. Distortion of welded joints can cause failure by buckling if the welded member is subjected to compressive loads.

Guidance on imperfection levels of welded joints is given in EN ISO 5817

To minimise these problems the following points should be considered:-

1.Design of the weld based on the loading condition(s) the joint will carry

2.Accessibility to enable ease of welding

3.Control of distortion

4.Careful consideration of the welding environment

5.Matching welding process with materials

6.A factor of safty applied to the design stress of the weld which should be based on the consequance of weld failure and the level of non destructive testing that is to be carried out.


For example a pressure vessel made to PD5500 category 3, (no radiographic inspection), can be up to twice a thick as an equivalent vessel made to category 2, (10% Radiography). Fillet welds and Partial Penetration welds should be used with care as they contain lack of fusion, they are only suitable for relatively low stressed joints that are not subject to any form of fatigue loading and should be used with a suitable factor of safety, which for fillet welds is at least two.

Once the weld has been designed it is then necessary to decide upon the welding method, this is then documented in the form of a welding procedure specification. The European Welding Standard for welding procedures, EN ISO 15609-1 (formerly EN288 Part 2), gives guidance on the content and format of such a specification.

However this document on its own is not sufficient because we need to prove that this welding method will produce a weld of acceptable quality possessing the right mechanical properties. Therefore it is necessary to simulate the joint in all essential features and weld it under normal production conditions. The completed joint can then be subject to both non destructive and destructive examinations to determine if the joint is going to be suitable for the application.

For most stringent applications the European Standard EN ISO 15614 Part 1 (formerly EN 288 Part 3) is preferred for welding procedure tests in steel materials and part 2 for Aluminium and its alloys. There are other parts of EN 288 that deal with alternative routes for qualifying procedures, other than a procedure test, for less onerous applications. See Welding Procedure Section for details.

Once we have established that the proposed welding method is satisfactory we then have to ensure that the production welds will also be of the same quality. This involves making sure the welders posses the required skill and knowledge to deposit sound welds in accordance with the approved procedure. Whilst we can be confident that the welder who did the procedure will be able, any other welder used must also demonstrate his ability by successfully completing a welder approval test. The preferred standard for this is EN 287 Part 1 for steel and part 2 for aluminium and its alloys. This standard not only tests the performance of the welder but also requires it to be monitored and revalidated every 2 years to ensure that the welders skill can be relied upon.

Finally make sure that when the welding operation is being carried out it is supervised and coordinated by properly qualified personnel.

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There are two industries that require tig welding certification.

1. Industrial piping, (including boiler tubes)
2. Aerospace and aviation (manufacture and overhaul/repair)

For tig welding certification in piping, pressure vessels, and boilers, ASME section IX of the "Boiler and Pressure Vessel Code" specifies the criteria for acceptable welding tests.

For Aerospace tig welding, the American Welding Society (AWS) D17.1 - "Specification for Fusion welding for Aerospace Applications" is the code for welding certification tests.

More often than not, a 6G position welding test is required to certify for Pipe welding jobs. On many boiler jobs, 2" heavy wall tubing is tig welded all the way out in the 6G position making the welder either switch hands, or at least get in some uncomfortable positions. That is why 6G position Tig welding tests are considered the most difficult.

Most of the time, sheet metal test pieces in the 0.020"-0.125" thickness range are used for aerospace welder qualification testing. The 6G welding test is only used occasionally because it does not accurately represent the scope of welding tasks performed for most aerospace and aviation welding applications. AWS D17.1 even has a provision for welders to certify on a scrap part or mock up of a weld that is not represented well by a plain groove or fillet weld.

ASME section IX Boiler and Pressure Vessel Code has been around for a very long time, but AWS D17.1 is relatively new and was written to replace 2 old Mil standards... 1595a and 2219.

One thing both welding certification specifications have in common is that the test welds that are selected to be used for certification tests only qualify the welder for a range of positions, thicknesses, and joint types. No single test qualifies for all the possible material, thickness, positions, and joint types that are possible. That is why some welders hold a dozen or more certifications.

One main difference in welding tests for these 2 industries is that the initial welding test for Pipe welding jobs are largely done using low carbon steel or stainless steel. Other materials like inconel are sometimes used also but not nearly as much as carbon steel and stainless.

In the Aerospace and aviation industries, It is not uncommon for a welder to be tested on carbon or low alloy steels, stainless steels, nickel alloys, aluminum, magnesium, titanium, cobalt alloys, and even some refractory alloys like Niobium...with separate welding tests required for each material category.

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Welder qualifications are governed by the AWS/AASHTO D1.5 Bridge Welding Code and the Department’s Supplemental Specification 1011. Part B of SS1011 explains the administrative procedures required to qualify as an approved welder for the Ohio Department of Transportation. It is the individual welders responsibility to make sure all required samples, test data, and employment records are on file with the Office of Materials Management.

Qualified welders are listed in the Department’s Construction Management System.
Each welder should be checked to make sure they are qualified to weld on ODOT projects.
To confirm a welder is qualified for ODOT projects enter the Construction Management System and use the Fastpath WELD or LWELD to check for the following information:

Last Update: The welder’s qualification is in effect for 5 years unless the welder is not engaged in a given process for a period exceeding six months. Employment records are the welder’s responsibility to send to the Office of Materials Management. If the date listed on the CMS screen exceeds the six month period inform the welder they must update their work records. All welders are given a six month grace period if they have forgotten to send in their employment records. If the date listed on the CMS screen exceeds 1 year (required six month update plus the six month grace period) then the welder is no longer qualified and must retest.
Process: Welder’s must be qualified for the process for which they are welding in. Typical field welding processes are listed below:
SMAW (Shielded Metal Arc Welding) also known as stick welding
FCAW (Flux-cored arc welding) also know as wire welding
• Note: FCAW welding on main member structural steel requires Procedure Qualification testing by the Contractor per the AWS/AASHTO D1.5 Bridge Welding Code.
Weld Type: FI (Fillet welding) or GR (Groove welding)
Position: Welder’s must be qualified for the position in which they are welding.

F - Flat position
H – Horizontal position
V – Vertical position
OH – Overhead position


Any questions concerning welder qualifications can be directed to the Office of Materials Management, Structural Welding and Metals section.

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If you need to make permanent repairs underwater in any industry, underwater welding is probably a concern. It doesn’t matter whether you’re in oil and gas, shipping, defense, or marine infrastructure. You need to make sure all your underwater components are stable and functional.

Underwater welding is an important part of maintaining any metal structure existing in full or in part below the water. However, most conventional underwater welding systems have a number of problems. They’re expensive, can provide only temporary repairs, dangerous, and/or hard to move around.

Some dry underwater welding systems, like the Neptune System, have a number of advantages over wet welding methods. They allow the creation of high quality dry welds without the use of time consuming, costly hyperbaric chambers.

Gas and oil operators will enjoy the cost and time savings they can get with dry underwater welding of this sort. Since infrastructures and platforms are aging, the demand for good repair, maintenance and inspection services is going up. A fast, easy, relatively cheap solution for underwater welding is vital.

Oil rigs, subsea pipelines, platforms, and just about any other underwater structure with metal construction will benefit from high quality underwater welding options. You can create a customized habitat and configure it to work in almost any situation where underwater welds might be required.

If you own or operate a ship, you’ll also enjoy the savings that can be had using portable dry underwater welding methods. It keeps you from having to prematurely put your vessel into dry dock - the welds produced cost around the same as a wet weld, but they’re a lot stronger. Previously, a temporary underwater repair was the only thing available, with the other option being an early dry dock for the vessel.

The big problem with wet weld repairing is that it’s a quick fix. These welds can be quickly and cheaply performed, but they require constant reworking, making them cost more in the long term. It’s also important to regularly inspect a wet weld.

Eventually, temporary wet underwater welds have to be removed, and the vessel dry docked to be repaired correctly. A wet weld isn’t enough to match the original strength and integrity of the hull. Dry docking takes time and can be quite expensive.

Dry welding using a technology similar to Neptune’s NEPSYS can allow you to maintain a ship while underwater and effect permanent repairs. Corrosion, cracks, pitting and holes and hull tears can all be repaired. It’s possible to weld complete insert plates into the hull, with full penetration.

This rapidly deployable, portable technology is also good for permanent repairs in military operations and marine infrastructure. In fact, dry underwater welding is important for any subsea industry where a repair might be needed.

If wet underwater welding has previously been your only option for below water repairs, consider a portable, affordable dry welding option. Just about any underwater repair application can benefit from this technology, from pipelines to ship hulls.

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Spot welding is ideal for sheet metals, used widely in the automotive industry, steel pail production, even braces used in orthodontics. Sheets that are between .5 and 3 mm are ideal, as thicker metals can pose problems as it’s often difficult to heat in a single spot.

When it comes to welding equipment, and spot welders are the most common form, probably because they are easy and fast to use. It’s high speed forms a weld in a fraction of a second, which makes spot welding ideal for assembly lines.

This makes spot welding easily adaptable to automation. More and more manufacturing lines are using robotics in the interest of efficiency, consistency and speed. A large number of materials can be welded very quickly to the level of consistent perfection that’s demanded in the product manufacturing. You can rely on the same weld every time, insuring the uniformity of production.

Two shaped copper alloy electrodes concentrate the force of the welding current between the two objects being joined. A small “spot” results, and is quickly heated to its melting point, forming a small nugget of welding material after the current has been removed. Heat is controlled according to the strength of application and the length of which the current is applied.

Because spot welding is relatively easy to learn, it’s often used by artists and hobbyists, and is common in many home garages or studios.

Spot welding can also be done on aluminum, although as much as a 3 times higher thermal conductivity is required. This will require larger and more expensive welding equipment and spot welders.

As with any type of welding, safety is essential. Although it is a relatively easy weld to learn, spot welding is dangerous and requires proper safety equipment. It uses large amounts of current and heat. Electrodes must be clamped tightly. Wear eye protection to protect both against sparks and high amounts of ultraviolet light. Hands should also be protected, as the objects can become very hot. Spot welding should always be done in as controlled an environment as possible.

Unfortunately, the spot welding process tends to harden the metal, especially thick metals, causing it to wrap and reduce its material fatigue strength. This can lead to internal cracking, surface cracks and a bad appearance, as well as compromising the integrity of the metal. For most applications, however, spot welding works just fine and is easy to do, which is probably why it is so common.

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Carr’s welding has been Laser welding since 1998, and has always invested in the latest and the best equipment. Using Yag lasers to clad components, to repair tools and recover worn parts is what Carr’s do every day. Their latest Laser moves into new territory.


The Trumpf 1006D Laser, welds steel and titanium at a fantastic rate, and can fuse joints and seams with a precision key-hole weld. The 6 axis robotic arm, delivers the laser to 3D assemblies with the accuracy and repeatability that can never be achieved manually. An assembly can be jigged and once the Robot Laser is programmed, can be welded in seconds, giving a small unit cost.

Batch sizes can be small with minimal scrap rates, but the beauty of Laser welding is that the condition of the weld is so neat that there is often no after welding operation or fettling. Good fit up is essential however, so no gaps can be left for the small Laser spot to disappear down. Joint design which favours the Lasers should be discussed at an early stage. Filler wires are not normally added when running at high weld rates, so excess material can be left on the joint design if “proud of flush” welds are required.

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MIG is an abbreviation for the term “metal inert gas.” First developed during the Second World War, MIG welding gave manufacturers a much more efficient way to weld huge numbers of aluminum parts for weapons and equipment. The introduction of MIG welding technology early in the war had an immediate and important impact on the war effort for the United States and the Allies.

In the case of the System10 MIG welding cell, an automated robotic welding arm moves a “gun” fixed on a contact tip into place to make welds. At the end of the contact tip a solid-steel wire is fed through a liner.

When MIG welding commences, electricity charges the contact tip on the gun, liquefies the wire, and creates a weld puddle. At the same time inert gas flows out of the tip of the gun, sealing off the weld puddle from the atmosphere, allowing for a weld to join two metal pieces together.

While MIG welding has been around for years, companies today still use the most advanced MIG welding technologies to manufacture production runs of high-quality welded industrial parts. The latest robotic MIG welding technology on the market has many advantages for companies in search of low cost, precision welding.


Some advantages of the Lincoln Electric System10 at Ohio Laser include:

Fanuc ARC Mate 100 iB/6s robot with a 37″ reach to accommodate precision welding in tight spaces

Dual fixed welding work station with automatic interlocked access doors permit you to simultaneously load and unload parts while welding

A metal surround flash barrier and bi-fold doors with interlocks

100% duty cycle, 450 amp STT welding technology power supply

Less distortion, smoke and splatter

Specialized engineering, tooling and programming capabilities to enable cost effective welding

Robotic arc welding is the latest value added fabrication service offered by Ohio Laser. Already a full service industrial fabricator, Ohio Laser is competent with PPAP Level I to Level IV, laser cuts flat sheets, tubes and pipes, engineers parts using 2D, 3D CAD/CAM software, provides high accuracy bending, and offers welding processes GMAW, FCAW, and GTAW.

In addition the company does heat treating and finishing, water jet cutting, sanding and grinding services, assembly and packaging, and machining of various alloys.

Ohio Laser serves clients both large and small in virtually all major manufacturing industries in North America including automotive, furniture, point of display, food equipment, and heavy industrial equipment producers.

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Although many metals are TIG welded, the metal most frequently associated with the process is aluminum, especially with metals of a smaller thickness. Many other processes, of course, can join aluminum, but in the lighter gauges the most applicable process is TIG. The popularity of aluminum in automotive applications has brought TIG welding to a new golden age. Mechanically strong and visually appealing, TIG welding is the number one process chosen by professional welders for professional racing teams, and the avid auto enthusiast or hobbyist.

The process is well suited for aluminum, but there are a few characteristics of the metal that bring up points that must be considered if this material is to be welded with consistent ease and quality.

The pure metal has a melting point less than 1200ºF and does not exhibit the color changes before melting so characteristic of most metals. For this reason, aluminum does not tell you when it is hot or ready to melt. The oxide or "skin" that forms so rapidly on its surface has a melting point almost three times as high (3200º+F). To add to this confusion, aluminum even boils at a lower temperature (2880ºF) than this oxide melts. The oxide is also heavier than aluminum and, when melted, tends to sink or be trapped in the molten aluminum. For these reasons, it is easy to see why as much as possible of this oxide "skin" must be removed before welding. Luckily, the reverse polarity half of the AC arc does an outstanding job of cleaning off quantities of this oxide ahead of the weld!

That Aluminum is Hot!
Aluminum is an excellent conductor of heat. It requires large heat inputs when welding is begun, since much heat is lost in heating the surrounding base metal. After welding has progressed a while, much of this heat has moved ahead of the arc and pre-heated the base metal to a temperature requiring less welding current than the original cold plate. If the weld is continued farther on to the end of the two plates where there is nowhere for this pre-heat to go, it can pile up to such a degree as to make welding difficult unless the current is decreased. This explains why a foot or hand Amptrol™ (current control) is recommended with your Precision TIG™ 185 or Precision TIG 275 – it enables you to easily change the current while simultaneously welding.

Some aluminum alloys exhibit “hot short” tendencies and are crack sensitive. This means that at the range of temperatures where the liquid alloy is slushy (part solid and part liquid) or just turned solid, it has not quite enough tensile strength to resist the shrinkage stresses that are occurring from cooling and transformation. The proper choice of filler metal and welding procedures along with smaller beads can help eliminate many problems of this kind. Some experts recommend backstepping the first inch or so of each aluminum weld before finishing in the normal direction.

Filling the Gap
The metal produced in the weld pool is a combination of filler and parent metals that must have the strength, ductility, freedom from cracking, and the corrosion resistance required by the application. See table below for recommended filler metals for various aluminum alloys.

Maximum rate of deposition is obtained with filler wire or rod of the largest practical diameter while welding at the maximum practical welding current. Wire diameter best suited for a specific application depends upon the current that can be used to make the weld. In turn, the current is governed by the available power supply, joint design, alloy type and thickness, and the welding position.

A Quality Deposit
Good weld quality is obtained only if the filler wire is clean and of high quality. If the wire is not clean, a large amount of contaminant may be introduced into the weld pool, because of the relatively large surface area of the filler wire with respect to the amount of weld metal being deposited.

Contaminants on the filler wire are most often an oil or a hydrated oxide. The heat of the welding releases the hydrogen from these sources, causing porosity in the weld. Lincoln ER4043 and Lincoln ER5356 aluminum welding wire is manufactured under rigorous control to exacting standards and is packaged to prevent contamination during storage. Since filler wire is alloyed, or diluted, with the base metal in the weld pool, the compositions of both the filler wire and the base metal affect the quality of the weld.

The Three Cs: Clean, Clean and CLEAN!
Pieces to be welded are usually formed, sheared, sawed, or machined prior to the welding operation. Complete removal of all lubricants from these operations is a prerequisite for high-quality welds. Particular care must be taken to remove all oil, other hydrocarbons, and loose particles from sawed or seared edges prior to welding. Sheared edges should be clean and smooth – not ragged. For ease of cleaning, lubricants used in fabrication should be promptly removed.

To reduce the possibility of porosity and dross in welds, cleanliness of the welding surfaces cannot be overemphasized. Hydrogen can cause porosity, and oxygen can cause dross in welds. Oxides, greases, and oil films contain oxygen and hydrogen that, if left on the edges to be welded, will cause unsound welds with poor mechanical and electrical properties. Cleaning should be done just prior to welding. A summary of general cleaning procedures is given in the table below.

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Welding Preparation

In Welding work plan should be first to do a Construction made, how to make, how the use of equipment / construction, the things that may occur with the construction. To obtain a construction joint is good and true, then several things need to be as follows:
1. Welding Procedure Specification (WPS) and Procedure Qualification Record (PQR).
2. Human factors
3. The Machine
4. Las standard equipment in accordance
5. Material (material) and the weld wire (electrode)
6. Environment.

Welding Procedure Specification (WPS) and Procedure Qualification Record (PQR).
a. Welding Procedure Specification (WPS)
Before production begins las, specifications detail the procedures that must be created and qualification welded to demonstrate that the mechanical nature of the appropriate (strength, ductility and violence) and the welded/ free from defects can be made through the procedure. Quality welded must be tested with the non-destructive and destructive. Procedures must be obeyed, except when there are changes that are desired by a specific company (in particular the variables essential)
b. Procedure Qualification Record (PQR)
Every detail and procedure that must be qualification Record and should be complete viewing results to qualification procedure. Records must be maintained during the procedure is still used.


Human factors.
Interpreter service and the joint will be to handle the implementation of joint construction work, before carrying out construction works weld, need to test with the WPS that has been tested and passed with a similar material that will be used in the construction joint. Testing and interpreter service, commonly called las welder performance test (WPT).
During the process of implementation of the test operator and weld interpreter, experts and inspection of all parties concerned with a construction joint is present and witnesses, including experts from government inspection authorities. After the test is declared passed, then the interpreter weld service and are given a certificate of test weld or welding operator / welder certificate by government authorities. fabricator next party or the equipment that employ weld interpretersor operator is permitted to create weld construction accordance WPS that has been set. Welding in the process of examination is very important to obtain quality results in accordance with weld standard that have been defined.construction phases weld inspections, the first examination before welding process, both during the examination elding process, after the third weld examination.

Welding preparation machine
Welding machine is a source of energy (heat) in the weld process. For the construction weld machine needs to be matched with the weld process used. In the case of weld construction, weld machine that is used depends on the weld process used. Polarity machine consists of weld machine AC or DC (DCEP / DCEN) with a capacity of 30 ampere - 500 ampere.

Preparation Tools.
No equipment is good and will lead to complete not only the weld results not perfect, can even lead to things worse such as accidents, fire / explosion, electrical that can harm workers or other people. Avoid for things that do not want to work before then pwelding needs to be done a few things, namely:

a. Tool Safety:
- Preparation protective clothing
- Gloves
- Safety glass
- Apron
- Safety-shoes

b. Additional Tools:
- Chipping hammer
- brush wire
- Carved cuneiform
- grinder hands
- Pinchpenny rough
c. Measure Tool:
- The length of
- The level
- Welding gauge.

Material
Material / material that is prepared:
a. Preparing the work objects, work objects must be clean and rust, oil, fat or other substances contamination, in order to avoid the occurrence of porosity on the welding results . Materials used in the joint work should be prepared and reviewed by supervisors and welding by welding inspector.
b. The selection of add (pole)
Add or electrode material in the shielded metal arc welding (SMAW) in addition to functioning as a material also functions as a bow menghasikan power (electrode). Weld wire used in the welding process, strength at least equal to the material strength will through.

Connection preparation
a. Connection weld preparation.
Make sure the connection surface cleanliness must be flat and free from dirt, there is no oil, fat or other chemical substances terkontaminasi. Do not touch the surface is clean by hand or with objects that can cause contamination, if permitted to use clean cloth.

b. Setting machine las
- The las: SMAW
- polarity electrode positive (DCEP)
- Large flow: 70 - 140 amp (as needed)

c. Sketch material and tack Weld
Put the snippet in the pipe work table with the surface at the top of the dibevel, ltake wire V-shaped spacer that Bevel pipe above the surface (size of wire spacer 2.4 s / d 3.2 mm).

Put part pipe above the second wire on the pipe spacer ago Align the first and second-level connection with the water-pipe to pass a connection into the straight and perfect. Make tack along Weld 10 mm s / d 15 mm between the two connection pipes by using a filler rod strength stronger pull from the base-metal. Tack Weld must permeate the perfect connection between the two pipes. High penetration weld can not be more than 1.6 mm.

Shift the wire on the end of the spacer and do Bevel Weld tack of making the second If there is a root of the wide gap side, then do the making of the third tack Weld. Tack due to pulling out of Weld, the distance at the gap that will be the same gap

Making do tack on Weld pipes with the length and the same distance. Making a connection with the preparation las perfectly welding facilitate the implementation of the weld quality is good. (Before starting the preparation pengelasan joint review by supervisor / welding supervisor or inspektor).
Welding Procedure Specification (WPS): - Example
Weld Procedure Number 30 P1 TIG A Issue 01
Qualifying Welding Procedure (WPAR) WP T17 / A

Manufacturer: National Fabs Ltd
25 Lane End
Birkenshaw
Leeds

Location: Workshop

Welding Process: Manual TIG
Joint Type: Single sided Butt Weld
Method Of Preparation
and Cleaning: Machine and Degrease
Parent Metal Specification: Grade 304L Stainless Steel
Parent Metal Thickness 3 to 8mm Wall
Pipe Outside Diameter 25 to 100mm
Welding Position: All Positions
Welding Progression: upwards

Joint Design Welding sequences

Run Process Of Size
Metal filler Current
A Voltage
Type Of V
Current / Polarity Wire Feed
Travel Speed
Speed Heat Input
1
2 And Subs TIG
TIG 1.2mm
1.6mm 70 - 90
80 - 140 N / A DC -
DC-N / A N / A N / A

Welding Consumables: --
Type, Designation Trade Name:
Any Special Baking or drying:
Gas flux:
Gas Flow Rate - Shield:
- Backing:
Tungsten Electrode Type / Size:
Details of Back Gouging / Backing:
Preheat Temperature:
Interpass temperature:
Post Weld Heat Treatment
Time, temperature, method:
Heating and Cooling Rates *:

BS 2901 Part 2: 308S92
No
Argon 99.99% Purity
8 - 12 LPM
5 LPM
2% Thoriated 2.4mm Dia
Backing Gas
Min 5 ° C
200 ° C Max
Not Required
Production Sequence

1. Clean Weld 25mm and borders to bright metal using approved solvent.
2. Position items to be welded Ensuring good fit up and apply purge
3. Tack Weld parts together using TIG, tacks to at least 5mm min length
4. Deposit root run using 1.2mm dia. wire.
5. Inspect the root run Internally
6. Complete Weld using 1.6mm dia wire using Stringer Beads as required.
7. 100% Visual inspection of completed Weld

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Introduction

Different materials have different properties. Think of the difference between the engine of a car and its wheels; the metal in a wire and its insulator. All these objects can only be made out of materials that have properties suited to their application. Materials science is the study of the properties of materials. It focuses on the factors that make one material different from another. Understandably, there are many such factors, some obvious and some subtle. Examples of these factors might include elemental composition, arrangement, bonding, impurities, surface structure, length scale and so on. The ability to understand the relationships between these factors and the properties of a material has been crucial to most of mankind's technological breakthroughs. Today, materials science is a multidisciplinary subject. It draws upon just about every field of science and engineering, providing insights for other researchers to use in their field.

This book is aimed at those studying materials science at the undergraduate level in university whether as their major field or as a single module of a related engineering course.

Structure of Matter

Atomic Structure and Bonding

Fundamentally, two types of bonding exist- bonds between atoms and bonds between ions. Bonds between atoms of nonmetals are covalent, meaning that they share a pair of electrons in the space between them. These two atoms are bound together and cannot be separated by simple physical means. If these two atoms have similar electronegativity, neither atom has more pull on the electron pair than the other. This type of covalent bond is called Non Polar. Examples of non polar covalent compounds are methane, carbon dioxide and graphite. In graphite, all atoms are identical and so no atom has stronger pull than any of the others. In methane, the carbon-hydrogen bonds are very slightly polar, and the polarities are cancelled because the bonds all point to the same locus.


Crystal Structure
Defects

Defects of materials are subject to intense study. However there are some methods to determine the source of defects and, if occurred, the size, shape and position of defects in the materials. There are: destructive testing methods and Non destructive testing methods (NDT).

Thermodynamics of Material

Phase Diagrams

Phase diagrams provide a graphical means of presenting the results of experimental studies of complex natural processes, such that at a given temperature and pressure for a specific system at equilibrium the phase or phases present can be determined.


SYSTEM - Any portion of the universe which is of interest and can be studied experimentally.

PHASE- any particular portion of a system, which is physically homogeneous, has a specific composition, and can be mechanically removed or separated from any other phase in the system.

* e.g. A system containing a mixture of ol and pl in equilibrium contains two phases - ol and pl.

In petrology we generally deal with primary phases - any crystalline phase which can coexist with liquid, i.e. it formed/crystallized directly from the liquid.

EQUILIBRIUM - The condition of minimum energy for the system such that the state of a reaction will not change with time provided that pressure and temperature are kept constant.


In experimental petrology there are three practical criteria used to test for equilibrium.

1. Time - with time the system does not change its physical or chemical makeup.
2. Approach equilibrium from two directions,
e.g. the melting point of Albite.
* begin with a liquid of Ab composition (Na2O-Al2O3-6SiO2) and cool until Ab crystallizes - T=1100°C
* begin with the same mixture of solid Albite and heat it up until liquid forms - T=1120°C
Melting point of albite = 1110°C + 10°C.
3. Attainment of equilibrium by using different reactants and procedures.
To determine the melting temperature of Albite
* grind up a sample of pure albite
* combine powdered oxides to give pure Ab composition
Use both to determine Ab melting point.

One final term to be defined prior to examining phase diagrams.

COMPONENT - the smallest number of independent variable chemical constituents necessary to define any phase in the system.

* components may be oxides, elements or minerals, dependant on the system being examined.

For example, experiments carried out in the H2O system, show that the phases which appear over a wide temperature and pressure range are ice, liquid water and water vapour. The composition of each phase is H2O and only one chemical parameter or component is required to describe the composition of each phase. Systems which can be defined by a single component are called Unary Systems. H2O System In this system pressures from 0 to 15 kbars seven phases, each with the same composition - H2O have been recognized:

* Ice I
* Ice II
* Ice III
* Ice IV(actually not exist)
* Ice V
* Water
* Steam

SiO2 System In the one component SiO2 system in the temperature range from 0 to 2,000°C and a pressure range from 0 to 30 kbars six phases of SiO2 are recognized. At pressures > 30 kbar a seventh phase, stishovite, exists. The six phases of SiO2 are:

* coesite
* alpha quartz (Trigonal)
* beta quartz (hexagonal)
* tridymite
* cristobalite
* anhydrous melt

Materials Processing

In order to produce an article for any application out of a particular material there are several steps that may be required. The first step is usually to obtain the raw materials from our environment. This may involve discovering where these raw materials are located (often achieved with knowledge of geology) and developing processes to extract them from these locations (e.g. mining the ores, drilling for oil etc.). Otherwise, it may be possible to find sources of material suitable for recycling or reprocessing. Once these raw materials have been obtained they may need to undergo some initial processing to get them into a usable form. This may be some form of extractive metallurgy, chemical synthesis or some other chemical process. It may also be necessary to mix different raw materials to achieve a certain composition (e.g. alloying in metals) that is appropriate for or has been optimised the application. The application will usually require that the material be in a particular shape and a suitable shaping process or combination of process must be employed to achieve this. Often, it may be possible to produce a shape out of a material with any one of the many different shaping processes. However, there is usually one particular process that either results in particular benefits in terms of the properties of the material or the article that is produced or meets some other important criteria - such as low cost - that it is selected over the other options. Finally, it may be necessary or beneficial to process the article further, once it has been formed, in order to optimise the properties of the material.

Firstly, this chapter will present the various chemical processes that may be necessary to produce suitable materials from the raw materials in our environment. The different methods for shaping these materials will then be presented. Finally, the processes used to optimise the properties of the materials will be discussed.

Chemical Processing

Extraction of Raw Materials

Chemical Synthesis of Materials

Shaping Processes

Melt Processing

Casting

Physical Processing

Forging

Rolling

Extrusion
Powder Process

Powder processes are used in the production of metallic and ceramic parts. The use of metal powders is commonly referred to as Powder Metallurgy (P/M).

There are 4 main stages to producing products with, they are: Powder Mixing, Compaction, Sintering and final finishing.

A metal or ceramic powder is prepared, then compacted into a desired shape. This part is then heated in a furnace causing the powders to weld together forming a solid part. The part is then final processed by final shaping, minor smoothing, or drilling.

Using Powders to produce parts is viable when you require a high volume of simple parts that need to be cost efficient. All though casting can also do this, P/M offers near net shape products. This means that the part that comes out of the process needs little or no finishing done to it.

Ceramics lend themselves well to powder processing as they are very hard and brittle, thus a near net shape is highly beneficial.

Mixing

Mixing is mainly done to add waxes for the compaction, binders to temporarily strengthen the compacts and sometimes to get the right chemistry.

As most suppliers recommend lubricant for idea compaction, mixing is a very important process, so a homogenous mixture is required. Optimum mixing occurs with turbulent mixing and at low centrifugal forces.

Along with ensuring a homogenous mix, the mixing process also provides some milling of the powders. As we all know you can put more tennis balls in an area than beach balls, thus increasing the surface area of the balls. The same is true with powders, more surface area, the better the final product is.

Compaction

Compaction is the process of squishing the powders into the desired shape with enough force so as to hold its shape. This is called a green body, as it still has moisture in it and needs to be Sintered. Same basic concept as pottery, the plate or cup is considered "green" until it is fired

There are 2 categories of pressing: Isostatic and Axial.

Sintering

Sintering is simply the furnace heating of a compacted powder object, also known as a green body to form a solid part. The powders can be either metallic or ceramic. They can be in elemental form, as an alloy, or mixture of both. Most sintering processes are done in a protective atmosphere, such as nitrogen or hydrogen mixed gas, to avoid degradation of the green bodies, and at a temperature lower than the melting point, approximately 60~90% of the main elements meting point. The specific atmosphere and temperature is dependant upon the material being processed.

If the material being sintered is an alloy, it is possible that one or more of the constitutes has a melting point lower than the sintering temperature, thus causing a small amount of liquid to form. This is called Liquid Phase Sintering. Caution needs to be taken when choosing a temperature as too much liquid will result in the deformation of the part. This is referred to as slumping.

The mechanism of sintering is the diffusion of the atoms across the particle boundaries of compacted powders. As the atoms diffuse, all voids are filled and the material forms one solid part. As the voids between particles are no longer present, the part increases in density, and experiences shrinkage. However, due to the nature of this process, only 93%-98% theoretical density can be achieved, thus further mechanical processing is needed to obtain 100% dense material.

The resultant microscopic structure resembles the starting green compact. The starting particle boundaries eventually turn into the final grain boundaries.

As the voids between the powder particles are filled during the sintering process, the gases need to be expelled from the compact. These gases are; air trapped between powders and gasses from additives added during the mixing and/or compaction process. These gases are expelled through capillaries formed by the particle boundaries. If the compacts are hated to fast, these capillaries can be “pinched” off and if these gasses are not expelled, the part will have defects such as warpage, porosity, or even holes.

A typical industrial sintering process is done on a traveling grate furnace with a 2 stages of heating. The green bodies are placed on a conveyor which travels into the furnace which has a positive pressure protective atmosphere blown onto the conveyor belt. The parts travel into the first temperature zone to vaporize and wax and degas. The second temperature zone is to do the actual sintering of the material. After the appropriate sinter time, the parts travel through a cooling zone to allow the parts to be handled, or to lock properties for continued processing. Degas and sinter times vary based on material.

Finishing

Machining

Welding

Materials Optimisation

Heat Treatment:It is defined as combination of heating and cooling cycles given to a particular material of interest to achieve desired properties.

Surface Engineering

Materials Characterisation

An important aspect of materials science is the characterisation of the materials that we use or study in order to learn more about them. Today, there is a vast array of scientific techniques available to the materials scientist that enables this characterisation. These techniques will be introduced and explained in this section.

Macroscopic Observation

The first step in any characterisation of a material or an object made of a material is often a macroscopic observation. This is simply looking at the material with the naked eye. This simple process can yield a large amount of information about the material such as the colour of the material, its lustre (does it display a metallic lustre), its shape (whether it displays a regular, crystalline form), its composition (is it made up of different phases), its structural features (does it contain porosity) etc. Often, this investigation yields clues as to what other tests could be performed to fully identify the material or to solve a problem that has been experienced in use.

Microscopic Observation

Microscopy is a technique that, combined with other scientific techniques and chemical processes, allows the determination of both the composition and the structure of a material. It is essentially the process of viewing the structure on a much finer scale than is possible with the naked eye and is necessary because many of the properties of materials are dependent on extremely fine features and defects that are only possible to observe using one of the following techniques in this field.

Optical Microscopy

Optical microscopes are formed of lenses that magnify and focus light. This light may have been transmitted through a material or reflected from a material's surface and can be used to ascertain a great deal of information about that material under evaluation. This can include whether the material is dense or contains porosity, what colour the material is, whether the material is composed of a single phase or contains multiple phases etc.

A common practice performed in conjunction with optical microscopy is that of targeted and controlled chemical attack of the material using one of many chemical reagents available. For metallic materials, this technique combined with optical microscopy is know as optical metallography. The basis of this combined technique is that regions of different composition within a material as well as entirely different materials are affected differently when exposed to certain chemicals. These chemical effects are catalogued in various works (for example the ASM Metals Handbook or Metallographic Etching by G. Petzow) and through an understanding of these effects and a systematic experimental process they can be used to determine material composition and structure.

There are several limitations to the usefulness of optical microscopy. The first is that the maximum resolving power is limited by diffraction effects to approximately 0.2 micrometres at a magnification of around 1500X (see reference). Many of the defects and structural features important in determining material properties, and therefore of interest to materials scientists, are of atomic scale. (for reference, the diameter of a helium atom is approximately 100 picometers) The second major limitation in optical microscopy is limited depth of field. This limitation means that surfaces with features at different heights - such as the rough surfaces of a fractured specimen for example - cannot be seen in sharp focus at the same time. This means that flat or polished surfaces are preferred for this technique. Furthermore, the chemical techniques required for identifying different phases within a structure are destructive. Thus, if a only a small amount of a certain portion of the sample is present then this may be destroyed by the process by the etching technique.

Electron Microscopy

Scanning Electron Microscopy

Transmission Electron Microscopy

Chemical Analysis in Electron Microscopy

Diffraction Techniques

Principles of Diffraction

X-Ray Diffraction

Neutron Diffraction

Electron Diffraction

Spectroscopic Techniques

Energy Dispersive X-Ray Spectroscopy

Wavelength Dispersive X-Ray Spectroscopy

Electron Energy Loss Spectroscopy

X-Ray Photoelectron Spectroscopy

Auger Electron Spectroscopy

Infra-red and Raman Spectroscopy

Ultra-violet and Visible Spectroscopy

Electrical and Magnetic Techniques

Electrical Resistance

Impedance Spectroscopy

Thermal Techniques

Thermogravimetric Analysis (TGA)

Differential Scanning Calorimetry (DSC)

Mechanical Testing

Strength

Hardness

Hardness is defined as the resistance of a material to penetration by an indentor. The Mohs scale of hardness has ten level and diamond is the material with the highest level of hardness ever known. There are several methods used to determine material's hardness, such as: Brinell, Rockwell, Vickers and Poldy.

Hardness Brinell (HB)

Is the method used for raw metallic materials. It uses a spherical ball indentor in order to stamp a print in the material. An external force transmitted through the indentor over the surface of the material determines the material's penetration.

Hardness Rockwell (HRB/HRC)

Is the method used for heat treated metallic materials. It has two variants regarding the indenter shape (ball or cone).

Hardness Vickers (HV)

Is a method used for the determination of hardness of special metallic materials, such as high alloyed materials, characterized by a very high degree of hardness.

Non destructive testing (NDT)

Some of the NDT methods available are: ultrasonic method, radiation penetration method.

Metals

Metals are materials made of elements on the left hand side of the periodic tables 'stair step' border starting on the left of Boron and going down and right and finishing at polonium. These elements can be mixed and combined with other elements (metals or non-metals) to create materials called alloys. Alloys are just a mix of elements and materials to create a new material with favorable properties.

Metals can be generally identified by a set of few physical properties (these a very general and there are plenty of exceptions). The main definition of a metal is an element that readily loses electrons and forms positive ions. The general bulk properties that are used to simply identify metals is that they tend to be lustrous (shiny when not oxidised), they are malleable (so can be beaten into a shape and not break), they are ductile (they can be drawn out into a wire) and that they conduct electricity; this rises from the fact that they readily lose electrons so there is a free electron 'gas' where the electrons can move around and this means that a charge can flow when an electric field is placed across the metal.

The metal that has changed the way the whole world functions and takes up a huge majority of the industry even now after over a century of its discovery and use (in terms of its modern production and composition). This metal is steel and is an alloy of mainly iron (Fe) and carbon (C) with many other constituent elements added depending on the type of steel wanted and the properties required.

Steel can be produced in a number of ways. Traditional methods utilise integrated steel processes which use energy intensive blast furnaces (to produce iron) sand basic oxygen steelmaking (to convert iron to steel). More modern methods use electric arc furnaces in which scrap steel is melted using electric currents and then formed into slabs or ingots for further processing. When the steel slab or ingot has cooled, a variety of forming operations such as rolling or extrusion are used to form the metal into flat sheet for use in cars, fridges, filing cabinets or radiators, or into beams, and heavy plate for use in construction and ship building

Ceramics

inorganic and non-metallic materials bimevox Ceramic From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about ceramic materials. For the fine art, see Ceramic art.

Fixed Partial Denture, or "Bridge"The word ceramic is derived from the Greek word κεραμικός (keramikos). The term covers inorganic non-metallic materials which are formed by the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass. Clay-based ceramics are described in the article on pottery. A composite material of ceramic and metal is known as cermet. The word ceramic can be an adjective, and can also be used as a noun to refer to a ceramic material, or a product of ceramic manufacture. Ceramics may also be used as a singular noun referring to the art of making things out of ceramic materials. The technology of manufacturing and usage of ceramic materials is part of the field of ceramic engineering.

Many ceramic materials are hard, porous, and brittle. The study and development of ceramics includes methods to mitigate problems associated with these characteristics, and to accentuate the strengths of the materials as well as to investigate novel applications.

The American Society for Testing and Materials (ASTM) defines a ceramic article as “an article having a glazed or unglazed body of crystalline or partly crystalline structure, or of glass, which body is produced from essentially inorganic, non-metallic substances and either is formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by the action of the heat.”[1]

Polymers

Polymer is a group of substances that has large molecules consisting of at least five repeated chemical units bonded together with a same type of linkage, like beads on a string.Polymer usually contains more than five repeated units and some polymers contain hundreds or thousands of monomers in each of their polymer chains. Polymer materials can be natural or synthetic. Polymer material is a large group of materials whereby they can be further classified specifically into plastics, elastomers and composites!

Composites

Materials for the Future

Ceramic From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about ceramic materials. For the fine art, see Ceramic art.

Fixed Partial Denture, or "Bridge"The word ceramic is derived from the Greek word κεραμικός (keramikos). The term covers inorganic non-metallic materials which are formed by the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass. Clay-based ceramics are described in the article on pottery. A composite material of ceramic and metal is known as cermet. The word ceramic can be an adjective, and can also be used as a noun to refer to a ceramic material, or a product of ceramic manufacture. Ceramics may also be used as a singular noun referring to the art of making things out of ceramic materials. The technology of manufacturing and usage of ceramic materials is part of the field of ceramic engineering.

Many ceramic materials are hard, porous, and brittle. The study and development of ceramics includes methods to mitigate problems associated with these characteristics, and to accentuate the strengths of the materials as well as to investigate novel applications.

The American Society for Testing and Materials (ASTM) defines a ceramic article as “an article having a glazed or unglazed body of crystalline or partly crystalline structure, or of glass, which body is produced from essentially inorganic, non-metallic substances and either is formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by the action of the heat

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Laser welding is a commercial process used extensively to weld a wide range of materials. The laser beam is focused toward a seam or area which causes the materials to from change from solid to liquid and, as the laser energy is removed, back to solid. Laser welding is a type of fusion welding which may be used to produce selective area spot welds or linear continuous seam welds. There are two types of laser welding processes, conduction and penetration.

Laser conduction welding relies on the conductivity of the material being welded. The laser beam is focused on a specific area on the material which by proximity will conduct heat into the joint area to be welded. By focusing laser beam at a location, heat is generated which is conducted into the joint causing the material change from a solid to a liquid and combine to the two separate liquid materials. After the material from the two material change back to a solid the two material are joined or welded at that location. Laser conduction welds are used for spot welding , continuous and partial penetration seam welding.

Laser penetration welding is produced by focusing the laser beam energy at a single location until the stacked materials are heated to a liquid state and some of the material vaporizes creating a hole within the material equal to the thickness of the material. When the stacked materials cool from a liquid to a solid state the material has been joined at that location through both stacked materials. Similar to the Spot / Lap weld joint illustration shown below, except the weld is completely through both materials.

Laser Weld Type	Illustration
Butt Weld Joint
Edge Weld Joint
Spot / Lap Weld Joint
Lap Weld Joint
Tee Weld Joint
Corner Weld Joint

There are two common types of laser welding technologies in use,

• CO₂ Gas laser
• Solid state lasers ( YAG type )

CO2 lasers use a mixture of high purity carbon dioxide with helium and nitrogen as the lasing medium. Here are some of the key characteristics for CO2 lasers:

• Infrared ( 10.6 micro-meters )
• Beam transmission by mirror only (not fiber optic)
• Cutting lasers are typically from 0.5 to 2 kw
• Can cut non-metallic materials
• High cutting speed

YAG lasers use a solid bar of yttrium aluminum garnet doped with neodymium as the lasing medium. Here are some of the key characteristics for YAG lasers:

• Infrared (1.06 micro-meters)
• Beam transmission by optical fiber possible
• Available to 2 kw
• Wavelength absorbed well by metallic materials ( including Al & Cu )
• Not used for cutting non-metallic materials

Both CO2 and YAG lasers can operate in either continuous or pulsed operating modes.

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ACETONE:
A flammable, volatile liquid used in acetylene cylinders to dissolve and stabilize acetylene under high pressure.
ACETYLENE:
A highly combustible gas composed of carbon and hydrogen. Used as a fuel gas in the oxyacetylene welding process.
ACTUAL THROAT:
See THROAT OF FILLET WELD.

AIR-ACETYLENE:
A low temperature flare produced by burning acetylene with air instead of oxygen.

AIR-ARC CUTTING:
An arc cutting process in which metals to be cut are melted by the heat of the carbon arc.

ALLOY:
A mixture with metallic properties composed of two or more elements, of which at least one is a metal.

ALTERNATING CURRENT:
An electric current that reverses its direction at regularly recurring intervals.

AMMETER:
An instrument for measuring electrical current in amperes by an indicator activated by the movement of a coil in a magnetic field or by the longitudinal expansion of a wire carrying the current.


ANNEALING:
A comprehensive term used to describe the heating and cooling cycle of steel in the solid state. The term annealing usually implies relatively slow cooling. In annealing, the temperature of the operation, the rate of heating and cooling, and the time the metal is held at heat depend upon the composition, shape, and size of the steel product being treated, and the purpose of the treatment. The more important purposes for which steel is annealed are as follows: to remove stresses; to induce softness; to alter ductility, toughness, electric, magnetic, or other physical and mechanical properties; to change the crystalline structure; to remove gases; and to produce a definite microstructure.

ARC BLOW:
The deflection of an electric arc from its normal path because of magnetic forces.

ARC BRAZING:
A brazing process wherein the heat is obtained from an electric arc formed between the base metal and an electrode, or between two electrodes.

ARC CUTTING:
A group of cutting processes in which the cutting of metals is accomplished by melting with the heat of an arc between the electrode and the base metal. See CARBON-ARC CUTTING, METAL-ARC CUTTING, ARC-OXYGEN CUTTING, AND AIR-ARC CUTTING.

ARC LENGTH:
The distance between the tip of the electrode and the weld puddle.

ARC-OXYGEN CUTTING:
An oxygen-cutting process used to sever metals by a chemical reaction of oxygen with a base metal at elevated temperatures.

ARC VOLTAGE:
The voltage across the welding arc.

ARC WELDING:
A group of welding processes in which fusion is obtained by heating with an electric arc or arcs, with or without the use of filler metal.

AS WELDED:
The condition of weld metal, welded joints, and weldments after welding and prior to any subsequent thermal, mechanical, or chemical treatments.

ATOMIC HYDROGEN WELDING:
An arc welding process in which fusion is obtained by heating with an arc maintained between two metal electrodes in an atmosphere of hydrogen. Pressure and/or filler metal may or may not be used.

AUSTENITE:
The non-magnetic form of iron characterized by a face-centered cubic lattice crystal structure. It is produced by heating steel above the upper critical temperature and has a high solid solubility for carbon and alloying elements.

AXIS OF A WELD:
A line through the length of a weld, perpendicular to a cross section at its center of gravity.
BACK FIRE:
The momentary burning back of a flame into the tip, followed by a snap or pop, then immediate reappearance or burning out of the flame.

BACK PASS:
A pass made to deposit a back weld.

BACK UP:
In flash and upset welding, a locator used to transmit all or a portion of the upsetting force to the workpieces.

BACK WELD:
A weld deposited at the back of a single groove weld.

BACKHAND WELDING:
A welding technique in which the flame is directed towards the completed weld.

BACKING STRIP:
A piece of material used to retain molten metal at the root of the weld and/or increase the thermal capacity of the joint so as to prevent excessive warping of the base metal.

BACKING WELD:
A weld bead applied to the root of a single groove joint to assure complete root penetration.

BACKSTEP:
A sequence in which weld bead increments are deposited in a direction opposite to the direction of progress.

BARE ELECTRODE:
An arc welding electrode that has no coating other than that incidental to the drawing of the wire.

BARE METAL-ARC WELDING:
An arc welding process in which fusion is obtained by heating with an unshielded arc between a bare or lightly coated electrode and the work. Pressure is not used and filler metal is obtained from the electrode.

BASE METAL:
The metal to be welded or cut. In alloys, it is the metal present in the largest proportion.

BEAD WELD:
A type of weld composed of one or more string or weave beads deposited on an unbroken surface.

BEADING:
See STRING BEAD WELDING and WEAVE BEAD.

BEVEL ANGLE:
The angle formed between the prepared edge of a member and a plane perpendicular to the surface of the member.

BLACKSMITH WELDING:
See FORGE WELDING.

BLOCK BRAZING:
A brazing process in which bonding is produced by the heat obtained from heated blocks applied to the parts to be joined and by a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metal. The filler metal is distributed in the joint by capillary attraction.

BLOCK SEQUENCE:
A building up sequence of continuous multipass welds in which separated lengths of the weld are completely or partially built up before intervening lengths are deposited. See BUILDUP SEQUENCE.

BLOW HOLE:
see GAS POCKET.

BOND:
The junction of the welding metal and the base metal.

BOXING:
The operation of continuing a fillet weld around a corner of a member as an extension of the principal weld.

BRAZING:
A group of welding processes in which a groove, fillet, lap, or flange joint is bonded by using a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metals. Filler metal is distributed in the joint by capillary attraction.

BRAZE WELDING:
A method of welding by using a filler metal that liquefies above 450 °C (842 °F) and below the solid state of the base metals. Unlike brazing, in braze welding, the filler metal is not distributed in the joint by capillary action.

BRIDGING:
A welding defect caused by poor penetration. A void at the root of the weld is spanned by weld metal.

BUCKLING:
Distortion caused by the heat of a welding process.

BUILDUP SEQUENCE:
The order in which the weld beads of a multipass weld are deposited with respect to the cross section of a joint. See BLOCK SEQUENCE.

BUTT JOINT:
A joint between two workpieces in such a manner that the weld joining the parts is between the surface planes of both of the pieces joined.

BUTT WELD:
A weld in a butt joint.

BUTTER WELD:
A weld caused of one or more string or weave beads laid down on an unbroken surface to obtain desired properties or dimensions.
CAPILLARY ATTRACTION:
The phenomenon by which adhesion between the molten filler metal and the base metals, together with surface tension of the molten filler metal, causes distribution of the filler metal between the properly fitted surfaces of the joint to be brazed.

CARBIDE PRECIPITATION:
A condition occurring in austenitic stainless steel which contains carbon in a supersaturated solid solution. This condition is unstable. Agitation of the steel during welding causes the excess carbon in solution to precipitate. This effect is also called weld decay.

CARBON-ARC CUTTING:
A process of cutting metals with the heat of an arc between a carbon electrode and the work.

CARBON-ARC WELDING:
A welding process in which fusion is produced by an arc between a carbon electrode and the work. Pressure and/or filler metal and/or shielding may or may not be used.

CARBONIZING FLAME:
An oxyacetylene flame in which there is an excess of acetylene. Also called excess acetylene or reducing flame.

CASCADE SEQUENCE: Subsequent beads are stopped short of a previous bead, giving a cascade effect.

CASE HARDENING:
A process of surface hardening involving a change in the composition of the outer layer of an iron base alloy by inward diffusion from a gas or liquid, followed by appropriate thermal treatment. Typical hardening processes are carbonizing, cyaniding, carbonitriding, and nitriding.

CHAIN INTERMITTENT FILLET WELDS:
Two lines of intermittent fillet welds in a T or lap joint in which the welds in one line are approximately opposite those in the other line.

CHAMFERING:
The preparation of a welding contour, other than for a square groove weld, on the edge of a joint member.

COALESCENCE:
The uniting or fusing of metals upon heating.

COATED ELECTRODE:
An electrode having a flux applied externally by dipping, spraying, painting, or other similar methods. Upon burning, the coat produces a gas which envelopes the arc.

COMMUTORY CONTROLLED WELDING:
The making of a number of spot or projection welds in which several electrodes, in simultaneous contact with the work, progressively function under the control of an electrical commutating device.

COMPOSITE ELECTRODE:
A filler metal electrode used in arc welding, consisting of more than one metal component combined mechanically. It may or may not include materials that improve the properties of the weld, or stabilize the arc.

COMPOSITE JOINT:
A joint in which both a thermal and mechanical process are used to unite the base metal parts.

CONCAVITY:
The maximum perpendicular distance from the face of a concave weld to a line joining the toes.

CONCURRENT HEATING:
Supplemental heat applied to a structure during the course of welding.

CONE:
The conical part of a gas flame next to the orifice of the tip.

CONSUMABLE INSERT:
Preplaced filler metal which is completely fused into the root of the joint and becomes part of the weld.

CONVEXITY:
The maximum perpendicular distance from the face of a convex fillet weld to a line joining the toes.

CORNER JOINT:
A joint between two members located approximately at right angles to each other in the form of an L.

COVER GLASS:
A clear glass used in goggles, hand shields, and helmets to protect the filter glass from spattering material.

COVERED ELECTRODE:
A metal electrode with a covering material which stabilizes the arc and improves the properties of the welding metal. The material may be an external wrapping of paper, asbestos, and other materials or a flux covering.

CRACK:
A fracture type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.

CRATER:
A depression at the termination of an arc weld.

CRITICAL TEMPERATURE:
The transition temperature of a substance from one crystalline form to another.

CURRENT DENSITY:
Amperes per square inch of the electrode cross sectional area.

CUTTING TIP:
A gas torch tip especially adapted for cutting.

CUTTING TORCH:
A device used in gas cutting for controlling the gases used for preheating and the oxygen used for cutting the metal.

CYLINDER:
A portable cylindrical container used for the storage of a compressed gas.

DEFECT:
A discontinuity or discontinuities which, by nature or accumulated effect (for example, total crack length), render a part or product unable to meet the minimum applicable acceptance standards or specifications. This term designates rejectability.

DEPOSITED METAL:
Filler metal that has been added during a welding operation.

DEPOSITION EFFICIENCY:
The ratio of the weight of deposited metal to the net weight of electrodes consumed, exclusive of stubs.

DEPTH OF FUSION:
The distance from the original surface of the base metal to that point at which fusion ceases in a welding operation.

DIE:
a. Resistance Welding. A member, usually shaped to the work contour, used to clamp the parts being welded and conduct the welding current.
b. Forge Welding. A device used in forge welding primarily to form the work while hot and apply the necessary pressure.

DIE WELDING:
A forge welding process in which fusion is produced by heating in a furnace and by applying pressure by means of dies.

DIP BRAZING:
A brazing process in which bonding is produced by heating in a molten chemical or metal bath and by using a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metals. The filler metal is distributed in the joint by capillary attraction. When a metal bath is used, the bath provides the filler metal.

DIRECT CURRENT ELECTRODE NEGATIVE (DCEN):
The arrangement of direct current arc welding leads in which the work is the positive pole and the electrode is the negative pole of the welding arc.

DIRECT CURRENT ELECTRODE POSITIVE (DCEP):
The arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc.

DISCONTINUITY:
An interruption of the typical structure of a weldment, such as lack of homogeneity in the mechanical, metallurgical, or physical characteristics of the material or weldment. A discontinuity is not necessarily a defect.

DRAG:
The horizontal distance between the point of entrance and the point of exit of a cutting oxygen stream.

DUCTILITY:
The property of a metal which allows it to be permanently deformed, in tension, before final rupture. Ductility is commonly evaluated by tensile testing in which the amount of elongation and the reduction of area of the broken specimen, as compared to the original test specimen, are measured and calculated.

DUTY CYCLE:
The percentage of time during an arbitrary test period, usually 10 minutes, during which a power supply can be operated at its rated output without overloading.

EDGE JOINT:
A joint between the edges of two or more parallel or nearly parallel members.

EDGE PREPARATION:
The contour prepared on the edge of a joint member for welding.

EFFECTIVE LENGTH OF WELD:
The length of weld throughout which the correctly proportioned cross section exits.

ELECTRODE:
a. Metal-Arc. Filler metal in the form of a wire or rod, whether bare or covered, through which current is conducted between the electrode holder and the arc.
b. Carbon-Arc. A carbon or graphite rod through which current is conducted between the electrode holder and the arc.
c.Atomic . One of the two tungsten rods between the points of which the arc is maintained.
d. Electrolytic Oxygen-Hydrogen Generation. The conductors by which current enters and leaves the water, which is decomposed by the passage of the current.
e. Resistance Welding. The part or parts of a resistance welding machine through which the welding current and the pressure are applied directly to the work.

ELECTRODE FORCE:
a. Dynamic. In spot, seam, and projection welding, the force (pounds) between the electrodes during the actual welding cycle.
b. Theoretical. In spot, seam, and projection welding, the force, neglecting friction and inertia, available at the electrodes of a resistance welding machine by virtue of the initial force application and the theoretical mechanical advantage of the system.
c. Static. In spot, seam, and projection welding, the force between the electrodes under welding conditions, but with no current flowing and no movement in the welding machine.

ELECTRODE HOLDER:
A device used for mechanically holding the electrode and conduct- ing current to it.

ELECTRODE SKID:
The sliding of an electrode along the surface of the work during spot, seam, or projection welding.

EMBOSSMENT:
A rise or protrusion from the surface of a metal.

ETCHING:
A process of preparing metallic specimens and welds for macrographic or micrographic examination.

FACE REINFORCEMENT:
Reinforcement of weld at the side of the joint from which welding was done.

FACE OF WELD:
The exposed surface of a weld, made by an arc or gas welding process, on the side from which welding was done.

FAYING SURFACE:
That surface of a member that is in contact with another member to which it is joined.

FERRITE:
The virtually pure form of iron existing below the lower critical temperature and characterized by a body-centered cubic lattice crystal structure. It is magnetic and has very slight solid solubility for carbon.

FILLER METAL:
Metal to be added in making a weld.

FILLET WELD:
A weld of approximately triangular cross section, as used in a lap joint, joining two surfaces at approximately right angles to each other.

FILTER GLASS:
A colored glass used in goggles, helmets, and shields to exclude harmful light rays.

FLAME CUTTING:
see OXYGEN CUTTING.

FLAME GOUGING:
See OXYGEN GOUGING.

FLAME HARDENING:
A method for hardening a steel surface by heating with a gas flame followed by a rapid quench.

FLAME SOFTENING:
A method for softening steel by heating with a gas flame followed by slow cooling.

FLASH:
Metal and oxide expelled from a joint made by a resistance welding process.

FLASH WELDING:
A resistance welding process in which fusion is produced, simultaneously over the entire area of abutting surfaces, by the heat obtained from resistance to the flow of current between two surfaces and by the application of pressure after heating is substantially completed. Flashing is accompanied by expulsion of metal from the joint.

FLASHBACK:
The burning of gases within the torch or beyond the torch in the hose, usually with a shrill, hissing sound.

FLAT POSITION:
The position in which welding is performed from the upper side of the joint and the face of the weld is approximately horizontal.

FILM BRAZING:
A process in which bonding is produced by heating with a molten nonferrous filler metal poured over the joint until the brazing temperature is attained. The filler metal is distributed in the joint by capillary attraction. See BRAZING.

FLOW WELDING:
A process in which fusion is produced by heating with molten filler metal poured over the surfaces to be welded until the welding temperature is attained and the required filler metal has been added. The filler metal is not distributed in the joint by capillary attraction.

FLUX:
A cleaning agent used to dissolve oxides, release trapped gases and slag, and to cleanse metals for welding, soldering, and brazing.

FOREHAND WELDING:
A gas welding technique in which the flare is directed against the base metal ahead of the completed weld.

FORGE WELDING:
A group of welding processes in which fusion is produced by heating in a forge or furnace and applying pressure or blows.

FREE BEND TEST:
A method of testing weld specimens without the use of a guide.

FULL FILLET WELD:
A fillet weld whose size is equal to the thickness of the thinner member joined.

FURNACE BRAZING:
A process in which bonding is produced by the furnace heat and a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metals. The filler metal is distributed in the joint by capillary attraction.

FUSION:
A thorough and complete mixing between the two edges of the base metal to be joined or between the base metal and the filler metal added during welding.

FUSION ZONE (FILLER PENETRATION):
The area of base metal melted as determined on the cross section of a weld.

GAS CARBON-ARC WELDING:
An arc welding process in which fusion is produced by heating with an electric arc between a carbon electrode and the work. Shielding is obtained from an inert gas such as helium or argon. Pressure and/or filler metal may or may not be used.

GAS METAL-ARC (MIG) WELDING (GMAW):
An arc welding process in which fusion is produced by heating with an electric arc between a metal electrode and the work. Shielding is obtained from an inert gas such as helium or argon. Pressure and/or filler metal may or my not be used.

GAS POCKET:
A weld cavity caused by the trapping of gases released by the metal when cooling.

GAS TUNGSTEN-ARC (TIG) WELDING (GTAW):
An arc welding process in which fusion is produced by heating with an electric arc between a tungsten electrode and the work while an inert gas forms around the weld area to prevent oxidation. No flux is used.

GAS WELDING:
A process in which the welding heat is obtained from a gas flame.

GLOBULAR TRANSFER (ARC WELDING):
A type of metal transfer in which molten filler metal is transferred across the arc in large droplets.

GOGGLES:
A device with colored lenses which protect the eyes from harmful radiation during welding and cutting operations.

GROOVE:
The opening provided between two members to be joined by a groove weld.

GROOVE ANGLE:
The total included angle of the groove between parts to be joined by a groove weld.

GROOVE FACE:
That surface of a member included in the groove.

GROOVE RADIUS:
The radius of a J or U groove.

GROOVE WELD:
A weld made by depositing filler metal in a groove between two members to be joined.

GROUND CONNECTION:
The connection of the work lead to the work.

GROUND LEAD:
See WORK LEAD.

GUIDED BEND TEST:
A bending test in which the test specimen is bent to a definite shape by means of a jig.

HAMMER WELDING:
A forge welding process.

HAND SHIELD:
A device used in arc welding to protect the face and neck. It is equipped with a filter glass lens and is designed to be held by hand.

HARD FACING:
A particular form of surfacing in which a coating or cladding is applied to a surface for the main purpose of reducing wear or loss of material by abrasion, impact, erosion, galling, and cavitations.

HARD SURFACING:
The application of a hard, wear-resistant alloy to the surface of a softer metal.

HARDENING:
a. The heating and quenching of certain iron-base alloys from a temperature above the critical temperature range for the purpose of producing a hardness superior to that obtained when the alloy is not quenched. This term is usually restricted to the formation of martensite.
b. Any process of increasing the hardness of metal by suitable treatment, usually involving heating and cooling.

HEAT AFFECTED ZONE:
That portion of the base metal whose structure or properties have been changed by the heat of welding or cutting.

HEAT TIME:
The duration of each current impulse in pulse welding.

HEAT TREATMENT:
An operation or combination of operations involving the heating and cooling of a metal or an alloy in the solid state for the purpose of obtaining certain desirable conditions or properties. Heating and cooling for the sole purpose of mechanical working are excluded from the meaning of the definition.

HEATING GATE:
The opening in a thermit mold through which the parts to be welded are preheated.

HELMET:
A device used in arc welding to protect the face and neck. It is equipped with a filter glass and is designed to be worn on the head.

HOLD TIME:
The time that pressure is maintained at the electrodes after the welding current has stopped.

HORIZONTAL WELD:
A bead or butt welding process with its linear direction horizontal or inclined at an angle less than 45 degrees to the horizontal, and the parts welded being vertically or approximately vertically disposed.

HORN:
The electrode holding arm of a resistance spot welding machine.

HORN SPACING:
In a resistance welding machine, the unobstructed work clearance between horns or platens at right angles to the throat depth. This distance is measured with the horns parallel and horizontal at the end of the downstroke.

HOT SHORT:
A condition which occurs when a metal is heated to that point, prior to melting, where all strength is lost but the shape is still maintained.

HYDROGEN BRAZING:
A method of furnace brazing in a hydrogen atmosphere.

HYDROMATIC WELDING:
See PRESSURE CONTROLLED WELDING.

HYGROSCOPIC:
Readily absorbing and retaining moisture.

IMPACT TEST:
A test in which one or more blows are suddenly applied to a specimen. The results are usually expressed in terms of energy absorbed or number of blows of a given intensity required to break the specimen.

IMPREGNATED-TAPE METAL-ARC WELDING
An arc welding process in which fusion is produced by heating with an electric arc between a metal electrode and the work. Shielding is obtained from decomposition of impregnated tape wrapped around the electrode as it is fed to the arc. Pressure is not used, and filler metal is obtained from the electrode.

INDUCTION BRAZING:
A process in which bonding is produced by the heat obtained from the resistance of the work to the flow of induced electric current and by using a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metals. The filler metal is distributed in the joint by capillary attraction.

INDUCTION WELDING:
A process in which fusion is produced by heat obtained from resistance of the work to the flow of induced electric current, with or without the application of pressure.

INERT GAS:
A gas which does not normally combine chemically with the base metal or filler metal.

INTERPASS TEMPERATURE:
In a multipass weld, the lowest temperature of the deposited weld meal before the next pass is started.

JOINT:
The portion of a structure in which separate base metal parts are joined.

JOINT PENETRATION:
The maximum depth a groove weld extends from its face into a joint, exclusive of reinforcement.

KERF:
The space from which metal has been removed by a cutting process.

LAP JOINT:
A joint between two overlapping members.

LAYER:
A stratum of weld metal, consisting of one or more weld beads.

LEG OF A FILLET WELD:
The distance from the root of the joint to the toe of the fillet weld.

LIQUIDUS:
The lowest temperature at which a metal or an alloy is completely liquid.

LOCAL PREHEATING:
Preheating a specific portion of a structure.

LOCAL STRESS RELIEVING:
Stress relieving heat treatment of a specific portion of a structure.

MANIFOLD:
A multiple header for connecting several cylinders to one or more torch supply lines.

MARTENSITE:
Martensite is a microconstituent or structure in quenched steel characterized by an acicular or needle-like pattern on the surface of polish. It has the maximum hardness of any of the structures resulting from the decomposition products of austenite.

MASH SEAM WELDING:
A seam weld made in a lap joint in which the thickness at the lap is reduced to approximately the thickness of one of the lapped joints by applying pressure while the metal is in a plastic state.

MELTING POINT:
The temperature at which a metal begins to liquefy.

MELTING RANGE:
The temperature range between solidus and liquidus.

MELTING RATE:
The weight or length of electrode melted in a unit of time.

METAL-ARC CUTTING:
The process of cutting metals by melting with the heat of the metal arc.

METAL-ARC WELDING:
An arc welding process in which a metal electrode is held so that the heat of the arc fuses both the electrode and the work to form a weld.

METALLIZING:
A method of overlay or metal bonding to repair worn parts.

MIXING CHAMBER:
That part of a welding or cutting torch in which the gases are mixed for combustion.

MULTI-IMPULSE WELDING:
The making of spot, projection, and upset welds by more than one impulse of current. When alternating current is used each impulse may consist of a fraction of a cycle or a number of cycles.

NEUTRAL FLAME:
A gas flame in which the oxygen and acetylene volumes are balanced and both gases are completely burned.

NICK BREAK TEST:
A method for testing the soundness of welds by nicking each end of the weld, then giving the test specimen a sharp hammer blow to break the weld from nick to nick. Visual inspection will show any weld defects.

NONFERROUS:
Metals which contain no iron. Aluminum, brass, bronze, copper, lead, nickel, and titanium are nonferrous.

NORMALIZING:
Heating iron-base alloys to approximately 100 °F (38 °C) above the critical temperature range followed by cooling to below that range in still air at ordinary temperature.

NUGGET:
The fused metal zone of a resistance weld.

OPEN CIRCUIT VOLTAGE:
The voltage between the terminals of the welding source when no current is flowing in the welding circuit.

OVERHEAD POSITION:
The position in which welding is performed from the underside of a joint and the face of the weld is approximately horizontal.

OVERLAP:
The protrusion of weld metal beyond the bond at the toe of the weld.

OXIDIZING FLAME:
An oxyacetylene flame in which there is an excess of oxygen. The unburned excess tends to oxidize the weld metal.

OXYACETYLENE CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by flames obtained from the combustion of acetylene with oxygen.

OXYACETYLENE WELDING:
A welding process in which the required temperature is attained by flames obtained from the combustion of acetylene with oxygen.

OXY-ARC CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by means of an arc between an electrode and the base metal.

OXY-CITY GAS CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by flames obtained from the combustion of city gas with oxygen.

OXYGEN CUTTING:
A process of cutting ferrous metals by means of the chemical action of oxygen on elements in the base metal at elevated temperatures.

OXYGEN GOUGING:
An application of oxygen cutting in which a chamfer or groove is formed.

OXY-HYDROGEN CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by flames obtained from the combustion of city gas with oxygen.

OXY-HYDROGEN WELDING:
A gas welding process in which the required welding temperature is attained by flames obtained from the combustion of hydrogen with oxygen.

OXY-NATURAL GAS CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by flames obtained by the combustion of natural gas with oxygen.

OXY-PROPANE CUTTING:
An oxygen cutting process in which the necessary cutting temperature is maintained by flames obtained from the combustion of propane with oxygen.

PASS:
The weld metal deposited in one general progression along the axis of the weld.

PEENING:
The mechanical working of metals by means of hammer blows. Peening tends to stretch the surface of the cold metal, thereby relieving contraction stresses.

PENETRANT INSPECTION:
a. Fluorescent. A water washable penetrant with high fluorescence and low surface tension. It is drawn into small surface openings by capillary action. When exposed to black light, the dye will fluoresce.
b. Dye. A process which involves the use of three noncorrosive liquids. First, the surface cleaner solution is used. Then the penetrant is applied and allowed to stand at least 5 minutes. After standing, the penetrant is removed with the leaner solution and the developer is applied. The dye penetrant, which has remained in the surface discontinuity, will be drawn to the surface by the developer resulting in bright red indications.

PERCUSSIVE WELDING:
A resistance welding process in which a discharge of electrical energy and the application of high pressure occurs simultaneously, or with the electrical discharge occurring slightly before the application of pressure.

PERLITE:
Perlite is the lamellar aggregate of ferrite and iron carbide resulting from the direct transformation of austenite at the lower critical point.

PITCH:
Center to center spacing of welds.

PLUG WELD:
A weld is made in a hole in one member of a lap joint, joining that member to that portion of the surface of the other member which is exposed through the hole. The walls of the hole may or may not be parallel, and the hole may be partially or completely filled with the weld metal.

POKE WELDING:
A spot welding process in which pressure is applied manually to one electrode. The other electrode is clamped to any part of the metal much in the same manner that arc welding is grounded.

POROSITY:
The presence of gas pockets or inclusions in welding.

POSITIONS OF WELDING:
All welding is accomplished in one of four positions: flat, horizontal, overhead, and vertical. The limiting angles of the various positions depend somewhat as to whether the weld is a fillet or groove weld.

POSTHEATING:
The application of heat to an assembly after a welding, brazing, soldering, thermal spraying, or cutting operation.

POSTWELD INTERVAL:
In resistance welding, the heat time between the end of weld time, or weld interval, and the start of hold time. During this interval, the weld is subjected to mechanical and heat treatment.

PREHEATING:
The application of heat to a base metal prior to a welding or cutting operation.

PRESSURE CONTROLLED WELDING:
The making of a number of spot or projection welds in which several electrodes function progressively under the control of a pressure sequencing device.

PRESSURE WELDING:
Any welding process or method in which pressure is used to complete the weld.

PREWELD INTERVAL:
In spot, projection, and upset welding, the time between the end of squeeze time and the start of weld time or weld interval during which the material is preheated. In flash welding, it is the time during which the material is preheated.

PROCEDURE QUALIFICATION:
The demonstration that welds made by a specific procedure can meet prescribed standards.

PROJECTION WELDING:
A resistance welding process between two or more surfaces or between the ends of one member and the surface of another. The welds are localized at predetermined points or projections.

PULSATION WELDING:
A spot, projection, or seam welding process in which the welding current is interrupted one or more times without the release of pressure or change of location of electrodes.

PUSH WELDING:
The making of a spot or projection weld in which the force is aping current is interrupted one or more times without the release of pressure or change of location of electrodes.

PUSH WELDING:
The making of a spot or projection weld in which the force is applied manually to one electrode and the work or a backing bar takes the place of the other electrode.

QUENCHING:
The sudden cooling of heated metal with oil, water, or compressed air.

REACTION STRESS:
The residual stress which could not otherwise exist if the members or parts being welded were isolated as free bodies without connection to other parts of the structure.

REDUCING FLAME:
See CARBONIZING FLAME.

REGULATOR:
A device used to reduce cylinder pressure to a suitable torch working pressure.

REINFORCED WELD:
The weld metal built up above the surface of the two abutting sheets or plates in excess of that required for the size of the weld specified.

RESIDUAL STRESS:
Stress remaining in a structure or member as a result of thermal and/or mechanical treatment.

RESISTANCE BRAZING:
A brazing process in which bonding is produced by the heat obtained from resistance to the flow of electric current in a circuit of which the workpiece is a part, and by using a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metals. The filler metal is distributed in the joint by capillary attraction.

RESISTANCE BUTT WELDING:
A group of resistance welding processes in which the weld occurs simultaneously over the entire contact area of the parts being joined.

RESISTANCE WELDING:
A group of welding processes in which fusion is produced by heat obtained from resistance to the flow of electric current in a circuit of which the workpiece is a part and by the application of pressure.

REVERSE POLARITY:
The arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc.

ROCKWELL HARDNESS TEST:
In this test a machine measures hardness by determining the depth of penetration of a penetrator into the specimen under certain arbitrary fixed conditions of test. The penetrator may be either a steel ball or a diamond spherocone.

ROOT:
See ROOT OF JOINT and ROOT OF WELD.

ROOT CRACK:
A crack in the weld or base metal which occurs at the root of a weld.

ROOT EDGE:
The edge of a part to be welded which is adjacent to the root.

ROOT FACE:
The portion of the prepared edge of a member to be joined by a groove weld which is not beveled or grooved.

ROOT OF JOINT:
That portion of a joint to be welded where the members approach closest to each other. In cross section, the root of a joint may be a point, a line, or an area.

ROOT OF WELD:
The points, as shown in cross section, at which the bottom of the weld intersects the base metal surfaces.

ROOT OPENING:
The separation between the members to be joined at the root of the joint.

ROOT PENETRATION:
The depth a groove weld extends into the root of a joint measured on the centerline of the root cross section.

SCARF:
The chamfered surface of a joint.

SCARFING:
A process for removing defects and checks which develop in the rolling of steel billets by the use of a low velocity oxygen deseaming torch.

SEAL WELD:
A weld used primarily to obtain tightness and to prevent leakage.

SEAM WELDING:
Welding a lengthwise seam in sheet metal either by abutting or overlapping joints.

SELECTIVE BLOCK SEQUENCE:
A block sequence in which successive blocks are completed in a certain order selected to create a predetermined stress pattern.

SERIES WELDING:
A resistance welding process in which two or more welds are made simultaneously by a single welding transformer with the total current passing through each weld.

SHEET SEPARATION:
In spot, seam, and projection welding, the gap surrounding the weld between faying surfaces, after the joint has been welded.

SHIELDED WELDING:
An arc welding process in which protection from the atmosphere is obtained through use of a flux, decomposition of the electrode covering, or an inert gas.

SHOULDER:
See ROOT FACE.

SHRINKAGE STRESS:
See RESIDUAL STRESS.

SINGLE IMPULSE WELDING:
The making of spot, projection, and upset welds by a single impulse of current. When alternating current is used, an impulse may consist of a fraction of a cycle or a number of cycles.

SIZE OF WELD:
a. Groove weld. The joint penetration (depth of chamfering plus the root penetration when specified).
b. Equal leg fillet welds. The leg length of the largest isosceles right triangle which can be inscribed within the fillet weld cross section.
c. Unequal leg fillet welds. The leg length of the largest right triangle which can be inscribed within the fillet weld cross section.
d. Flange weld. The weld metal thickness measured at the root of the weld.

SKIP SEQUENCE:
See WANDERING SEQUENCE.

SLAG INCLUSION:
Non-metallic solid material entrapped in the weld metal or between the weld metal and the base metal.

SLOT WELD:
A weld made in an elongated hole in one member of a lap or tee joint joining that member to that portion of the surface of the other member which is exposed through the hole. The hole may be open at one end and may be partially or completely filled with weld metal. (A fillet welded slot should not be construed as conforming to this definition.)

SLUGGING:
Adding a separate piece or pieces of material in a joint before or during welding with a resultant welded joint that does not comply with design drawing or specification requirements.

SOLDERING:
A group of welding processes which produce coalescence of materials by heating them to suitable temperature and by using a filler metal having a liquidus not exceeding 450 °C (842 °F) and below the solidus of the base materials. The filler metal is distributed between the closely fitted surfaces of the joint by capillary action.

SOLIDUS:
The highest temperature at which a metal or alloy is completely solid.

SPACER STRIP:
A metal strip or bar inserted in the root of a joint prepared for a groove weld to serve as a backing and to maintain the root opening during welding.

SPALL:
Small chips or fragments which are sometimes given off by electrodes during the welding operation. This problem is especially common with heavy coated electrodes.

SPATTER:
The metal particles expelled during arc and gas welding which do not form a part of the weld.

SPOT WELDING:
A resistance welding process in which fusion is produced by the heat obtained from the resistance to the flow of electric current through the workpieces held together under pressure by electrodes. The size and shape of the individually formed welds are limited by the size and contour of the electrodes.

SPRAY TRANSFER:
A type of metal transfer in which molten filler metal is propelled axially across the arc in small droplets.

STAGGERED INTERMITTENT FILLET WELD:
Two lines of intermittent welding on a joint, such as a tee joint, wherein the fillet increments in one line are staggered with respect to those in the other line.

STORED ENERGY WELDING:
The making of a weld with electrical energy accumulated electrostatically, electromagnetically, or electrochemically at a relatively low rate and made available at the required welding rate.

STRAIGHT POLARITY:
The arrangement of direct current arc welding leads in which the work is the positive pole and the electrode is the negative pole of the welding arc.

STRESS RELIEVING:
A process of reducing internal residual stresses in a metal object by heating to a suitable temperature and holding for a proper time at that temperature. This treatment may he applied to relieve stresses induced by casting, quenching, normalizing, machining, cold working, or welding.

STRING BEAD WELDING:
A method of metal arc welding on pieces 3/4 in. (19 mm) thick or heavier in which the weld metal is deposited in layers composed of strings of beads applied directly to the face of the bevel.

STUD WELDING:
An arc welding process in which fusion is produced by heating with an electric arc drawn between a metal stud, or similar part, and the other workpiece, until the surfaces to be joined are properly heated. They are brought together under pressure.

SUBMERGED ARC WELDING:
An arc welding process in which fusion is produced by heating with an electric arc or arcs between a bare metal electrode or electrodes and the work. The welding is shield by a blanket of granular, fusible material on the work. Pressure is not used. Filler metal is obtained from the electrode, and sometimes from a supplementary welding rod.

SURFACING:
The deposition of filler metal on a metal surface to obtain desired properties or dimensions.

TACK WELD:
A weld made to hold parts of a weldment in proper alignment until the final welds are made.

TEE JOINT:
A joint between two members located approximately at right angles to each other in the form of a T.

TEMPER COLORS:
The colors which appear on the surface of steel heated at low temperature in an oxidizing atmosphere.

TEMPER TIME:
In resistance welding, that part of the postweld interval during which a current suitable for tempering or heat treatment flows. The current can be single or multiple impulse, with varying heat and cool intervals.

TEMPERING:
Reheating hardened steel to some temperature below the lower critical temperature, followed by a desired rate of cooling. The object of tempering a steel that has been hardened by quenching is to release stresses set up, to restore some of its ductility, and to develop toughness through the regulation or readjustment of the embrittled structural constituents of the metal. The temperature conditions for tempering may be selected for a given composition of steel to obtain almost any desired combination of properties.

TENSILE STRENGTH:
The maximum load per unit of original cross-sectional area sustained by a material during the tension test.

TENSION TEST:
A test in which a specimen is broken by applying an increasing load to the two ends. During the test, the elastic properties and the ultimate tensile strength of the material are determined. After rupture, the broken specimen may be measured for elongation and reduction of area.

THERMIT CRUCIBLE
The vessel in which the thermit reaction takes place.

THERMIT MIXTURE:
A mixture of metal oxide and finely divided aluminum with the addition of alloying metals as required.

THERMIT MOLD:
A mold formed around the parts to be welded to receive the molten metal.

THERMIT REACTION:
The chemical reaction between metal oxide and aluminum which produces superheated molten metal and aluminum oxide slag.

THERMIT WELDING:
A group of welding processes in which fusion is produced by heating with superheated liquid metal and slag resulting from a chemical reaction between a metal oxide and aluminum, with or without the application of pressure. Filler metal, when used, is obtained from the liquid metal.

THROAT DEPTH:
In a resistance welding machine, the distance from the centerline of the electrodes or platens to the nearest point of interference for flatwork or sheets. In a seam welding machine with a universal head, the throat depth is measured with the machine arranged for transverse welding.

THROAT OF FILLET WELD:
a. Theoretical. The distance from the beginning of the root of the joint perpendicular to the hypotenuse of the largest right triangle that can be inscribed within the fillet-weld cross section.
b. Actual. The distance from the root of the fillet weld to the center of its face.

TOE CRACK:
A crack in the base metal occurring at the toe of the weld.

TOE OF THE WELD:
The junction between the face of the weld and the base metal.

TORCH:
See CUTTING TORCH or WELDING TORCH.

TORCH BRAZING:
A brazing process in which bonding is produced by heating with a gas flame and by using a nonferrous filler metal having a melting point above 800 °F (427 °C), but below that of the base metal. The filler metal is distributed in the joint of capillary attraction.

TRANSVERSE SEAM WELDING:
The making of a seam weld in a direction essentially at right angles to the throat depth of a seam welding machine.

TUNGSTEN ELECTRODE:
A non-filler metal electrode used in arc welding or cutting, made principally of tungsten.

UNDERBEAD CRACK:
A crack in the heat affected zone not extending to the surface of the base metal.

UNDERCUT:
A groove melted into the base metal adjacent to the toe or root of a weld and left unfilled by weld metal.

UNDERCUTTING:
An undesirable crater at the edge of the weld caused by poor weaving technique or excessive welding speed.

UPSET:
A localized increase in volume in the region of a weld, resulting from the application of pressure.

UPSET WELDING:
A resistance welding process in which fusion is produced simultaneously over the entire area of abutting surfaces, or progressively along a joint, by the heat obtained from resistance to the flow of electric current through the area of contact of those surfaces. Pressure is applied before heating is started and is maintained throughout the heating period.

UPSETTING FORCE:
The force exerted at the welding surfaces in flash or upset welding.

VERTICAL POSITION:
The position of welding in which the axis of the weld is approximately vertical. In pipe welding, the pipe is in a vertical position and the welding is done in a horizontal position.

WANDERING BLOCK SEQUENCE:
A block welding sequence in which successive weld blocks are completed at random after several starting blocks have been completed.

WANDERING SEQUENCE:
A longitudinal sequence in which the weld bead increments are deposited at random.

WAX PATTERN:
Wax molded around the parts to be welded by a thermit welding process to the form desired for the completed weld.

WEAVE BEAD:
A type of weld bead made with transverse oscillation.

WEAVING:
A technique of depositing weld metal in which the electrode is oscillated. It is usually accomplished by a semicircular motion of the arc to the right and left of the direction of welding. Weaving serves to increase the width of the deposit, decreases overlap, and assists in slag formation.

WELD:
A localized fusion of metals produced by heating to suitable temperatures. Pressure and/or filler metal may or may not be used. The filler material has a melting point approximately the same or below that of the base metals, but always above 800 °F (427 °C).

WELD BEAD:
A weld deposit resulting from a pass.

WELD GAUGE:
A device designed for checking the shape and size of welds.

WELD METAL:
That portion of a weld that has been melted during welding.

WELD SYMBOL:
A picture used to indicate the desired type of weld.

WELDABILITY:
The capacity of a material to form a strong bond of adherence under pressure or when solidifying from a liquid.

WELDER CERTIFICATION:
Certification in writing that a welder has produced welds meeting prescribed standards.

WELDER PERFORMANCE QUALIFICATION:
The demonstration of a welder's ability to produce welds meeting prescribed standards.

WELDING LEADS:
a. Electrode lead. The electrical conductor between the source of the arc welding current and the electrode holder.
b. Work lead. The electrical conductor between the source of the arc welding current and the workpiece.

WELDING PRESSURE:
The pressure exerted during the welding operation on the parts being welded.

WELDING PROCEDURE:
The detailed methods and practices including all joint welding procedures involved in the production of a weldment.

WELDING ROD:
Filler metal in wire or rod form, used in gas welding and brazing processes and in those arc welding processes in which the electrode does not provide the filler metal.

WELDING SYMBOL:
The assembled symbol consists of the following eight elements, or such of these as are necessary: reference line, arrow, basic weld symbols, dimension and other data, supplementary symbols, finish symbols, tail, specification, process, or other references.

WELDING TECHNIQUE:
The details of a manual, machine, or semiautomatic welding operation which, within the limitations of the prescribed joint welding procedure, are controlled by the welder or welding operator.

WELDING TIP:
The tip of a gas torch especially adapted to welding.

WELDING TORCH:
A device used in gas welding and torch brazing for mixing and controlling the flow of gases.

WELDING TRANSFORMER:
A device for providing current of the desired voltage.

WELDMENT:
An assembly whose component parts are formed by welding.

WIRE FEED SPEED:
The rate of speed in mm/sec or in./min at which a filler metal is consumed in arc welding or thermal spraying.

WORK LEAD:
The electric conductor (cable) between the source of arc welding current and the workpiece.
X-RAY:
A radiographic test method used to detect internal defects in a weld.

YIELD POINT:
The yield point is the load per unit area value at which a marked increase in deformation of the specimen occurs with little or no increase of load; in other words, the yield point is the stress at which a marked increase in strain occurs with little or no increase in stress.

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