Welding technology encompasses the broad range of techniques and methodologies employed to accomplish a successful weld--the joining of two or more formerly separate pieces of material into a single unit. Some welds, such as cosmetic welds, have relatively limited quality requirements.

Welding Commonalities

All welding aims to join two or more pieces of material into a conjoined unit. Usually the two objects are of identical chemical composition (e.g. two plates of steel), but welding can also be used to join distinct materials. The melted material then cools and forms the bond.

Arc Welding
In arc welding, an arc of electricity between a cathode (electron emitter) and an anode, or the objects to be welded, produces the heat necessary to join the materials. Arc welders often use specialized welding power supplies that employ sophisticated solid-state power electronics.
Gas-shielded Arc Welding
Gas-shielded welding methods (such as gas tungsten arc welding (GTAW) or shielded metal arc welding (SMAW)) employ an inert shielding gas such as argon or helium to surround the active welding point. Usually a "filler metal" is placed near or between the two objects being welded. During welding the high-temperature electric arc heats this filler, which then releases the protective gas. The shielding gas prevents oxidative damage to the metals, and can promote a stronger weld of higher quality.
Gas Flame Welding
Gas welding uses a very high-temperature flame from a welding torch to generate the heat necessary to weld two objects together. The most common form of gas welding employs oxygen and acetylene gas, and produces a flame temperature near 6,000 °F. There are other customized welding gases that include more common fuels such as propane and butane.
Laser and Particle-beam Welding
Laser welding delivers heat to the weld point via a visible or invisible laser beam. This allows extremely focused welds that can be highly customized by changing the laser wavelength or power output. Electron beam welding (EBW) generates welding heat through a focused stream of high-energy electrons.
Explosive and Magnetic Welding
Friction welding generates a weld by basic friction, sometimes involving high-speed rotation. This type of welding generally doesn't generate sufficient heat to cause full melting at the weld point. Instead the combination of elevated temperature and extreme pressure joins the materials together. Explosive welding utilizes actual high explosives to drive pieces of metal together with so much energy that they weld. Magnetic pulse welding (MPW) achieves a similar effect with extreme magnetic fields.
Underwater Welding
Electric-arc welding is the most common underwater welding method, though hydrogen/oxygen gas flames can also be used. Some underwater welding tasks can only be conducted by a robot.

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RF welding is a basic technology, and the basic devices necessary to affect such a weld have not changed since the inception of the process. Today, as in 1942, we need a generator to provide RF, a transmission line to transfer power, a press to apply force and an electrode in the desired geometric pattern to be welded.

The terms "Radio Frequency (RF) Welding or Sealing" are often used interchangeably with "High Frequency (HF) or dielectric welding or sealing." When matter is brought into contact with an electromagnetic field, some portion of the electromagnetic field will go through a change of energy state. As a result, it will be converted to heat and dissipated within the contacted matter. The degree to which this con-version will occur, or the efficiency of this conversion of energy state is dependent on the atomic and molecular structure of the matter, the frequency of the electromagnetic field, and the field potential (Volt-age/cm). The term dielectric heating correctly describes this phenomenon at any frequency while RF or HF heating describes the process over the lim-ited frequency range from 1 to 200 megacycles/sec (megahertz/sec).

The area where most of the technological changes have taken place is in the components from which the individual devices are constructed. Solid state components have replaced mercury vapor rectifier tubes. Digital timers have replaced industrial timers. Programmable Logic Controllers (PLC) have replaced relay logic.

When a PLC is used with linear and optical encodes, precise control can be achieved over the various functions that determine the specific characteristics of the weld. Using these types of devices it is possible to monitor and control functions of time, pressure, current and voltage and their profiles.

When modern material handling systems are used in conjunction with these devices, high speed automatic production systems can be built. Many hundreds of such systems are in use throughout the U.S. These systems manufacture a wide variety of products for the automotive, stationary products, and medical industries.

The continuing stream of new RF responsive materials being brought to the market further impact the industry. In addition, additives and RF responsive adhesives are continually being developed for specialized applications. It is now possible to bond materials that in the past were considered unsuitable for the RF process. These changes are opening up a new range of products that can now be manufactured by this time proven technology. This will have a great effect in the medical industry, as it tries to eliminate the use of vinyl.

Both electron beam and laser welding, when initially discovered, were thought to be possible replacement technologies. However, these technologies have been found to be more applicable for spot or seam welding of metals or other rigid materials where welding times are measured in minutes and hours. In RF welded products, welding times are measured in seconds or fractions thereof. Guideline believes the likelihood of these becoming competing technologies is very low. In Guideline's opinion there is nothing on the horizon that will replace RF welding in the next 5 to 10 years. Its place will be as secure as it is today, not only as the economically preferred way to weld certain materials, but in many cases the only feasible method.

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RF welding is a basic technology, and the basic devices necessary to affect such a weld have not changed since the inception of the process. Today, as in 1942, we need a generator to provide RF, a transmission line to transfer power, a press to apply force and an electrode in the desired geometric pattern to be welded.

The terms "Radio Frequency (RF) Welding or Sealing" are often used interchangeably with "High Frequency (HF) or dielectric welding or sealing." When matter is brought into contact with an electromagnetic field, some portion of the electromagnetic field will go through a change of energy state. As a result, it will be converted to heat and dissipated within the contacted matter. The degree to which this con-version will occur, or the efficiency of this conversion of energy state is dependent on the atomic and molecular structure of the matter, the frequency of the electromagnetic field, and the field potential (Volt-age/cm). The term dielectric heating correctly describes this phenomenon at any frequency while RF or HF heating describes the process over the lim-ited frequency range from 1 to 200 megacycles/sec (megahertz/sec).

The area where most of the technological changes have taken place is in the components from which the individual devices are constructed. Solid state components have replaced mercury vapor rectifier tubes. Digital timers have replaced industrial timers. Programmable Logic Controllers (PLC) have replaced relay logic.

When a PLC is used with linear and optical encodes, precise control can be achieved over the various functions that determine the specific characteristics of the weld. Using these types of devices it is possible to monitor and control functions of time, pressure, current and voltage and their profiles.

When modern material handling systems are used in conjunction with these devices, high speed automatic production systems can be built. Many hundreds of such systems are in use throughout the U.S. These systems manufacture a wide variety of products for the automotive, stationary products, and medical industries.

The continuing stream of new RF responsive materials being brought to the market further impact the industry. In addition, additives and RF responsive adhesives are continually being developed for specialized applications. It is now possible to bond materials that in the past were considered unsuitable for the RF process. These changes are opening up a new range of products that can now be manufactured by this time proven technology. This will have a great effect in the medical industry, as it tries to eliminate the use of vinyl.

Both electron beam and laser welding, when initially discovered, were thought to be possible replacement technologies. However, these technologies have been found to be more applicable for spot or seam welding of metals or other rigid materials where welding times are measured in minutes and hours. In RF welded products, welding times are measured in seconds or fractions thereof. Guideline believes the likelihood of these becoming competing technologies is very low. In Guideline's opinion there is nothing on the horizon that will replace RF welding in the next 5 to 10 years. Its place will be as secure as it is today, not only as the economically preferred way to weld certain materials, but in many cases the only feasible method.

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Over the years, a number of people have expressed an interest in careers in underwater welding, but were unsure how to get started. Welders, students, divers, and other interested men and women have contacted the American Welding Society (AWS) for guidance. In order to help those prospective underwater welder-divers, the D3B Subcommittee on Underwater Welding has provided answers for eight commonly asked questions.

This article was prepared by the American Welding Society's D3B Subcommittee on Underwater Welding.

The answer to the questions presented in the article are not intended as recommended practice nor as endorsement of any definitive means of pursuing underwater welding as an occupation. Rather, the aim is to provide enough useful information to assist those interested, as well as define some of the mis-conceptions associated with the trade. For additional information and/or a need for specialized training, the subcommittee recommends ANSI/AWS D3.6, Specification for Underwater Welding, as a comprehensive reference and resource for industry-accepted practice.

1. What skills are prerequisite to entering the field of underwater welding?
The skills suggested for entering the field of underwater welding can best be defined by the following typical description of a welder-diver from the AWS D3.6 Standard and the qualifications generally recognized.

"Welder-diver: A certified welder who is also a commercial diver, capable of performing tasks associated with commercial subsea work, weld setup and preparation, and who has the ability to weld in accordance with the AWS D3.6, Specification for Underwater Welding Specification for Underwater Welding (i.e., wet or dry), and other weld-related activities (see item 7.0)."

By description, an experienced welder-diver must possess: commercial diving skills (i.e., be familiar with the use of specialized commercial diving equipment, have an understanding of diving physiology, diving safety, rigging, the underwater environment, communication, etc.); weld setup and preparation skills (i.e., the ability to perform tasks typically assigned to a fitter or rigger, such as materials alignment and materials preparation including beveling, stripping of concrete, fitting a steel patch or repair plate, etc.,); and the ability to certify to a required underwater weld procedure.

2. I am a certified surface welder, what other training do I need to qualify as a welder-diver?
The majority of work performed by an average welder-diver does not involve the welding operation itself, but rather executing the tasks that lead up to and follow the actual welding activities. Except under special circumstances, a welder-diver in most cases must posses both certified welder skills and commercial diving skills.

It is suggested that if you have no prior commercial diving experience you should attend one of the recognized commercial diving schools. Commercial dive schools vary insofar as duration of course, cost, etc., however, most offer a basic commercial diver certificate upon successful completion. The candidate may be required to pass a diving physical prior to school acceptance and in some cases a written exam. It is suggested that a dive physical be taken regardless, to avoid going through the expense of training only to later find you have a disability that prevents your entering the profession. A listing of U.S. commercial diving schools accredited by the Association of Commercial Diving Educators can be obtained by contacting: Association of Diving Contractors International (ADC), 1960 FM 1960 W., Suite 202, Houston, TX 77069; (281) 893-8388; FAX (281) 893-5118.

As a general rule, candidates seeking underwater welding as a career will decide whether or not they are comfortable with their career choice after completing basic commercial dive training.

Once that basic commercial diver training is completed, it is common practice to apply for employment at one of many commercial diving companies that offer underwater welding as a service. An interview with the company of your choice is recommended to express your career goals in underwater welding and past welding experience. Expect to begin your career as a diver tender (apprentice diver) initially. As a diver tender you will gain valuable practical experience while learning the trade.

Before performing on-the-job underwater welding, most diving contractors will require that you achieve sufficient skill in wet and/or dry underwater welding to pass qualification tests and be certified in accordance with the requirements of ANSI/AWS D3.6, Specification for Underwater Welding. The time required to advance to welder-diver varies subject to supply and demand of welder-diver personnel, skill, motivation, experience and other factors. Most commercial diving firms have their own policies and procedures regarding this matter.

3. I am already a certified diver, what other training do I need to qualify as a welder-diver?
The welding processes, classes of weld and qualification tests associated with underwater welding are described in ANSI/AWS D3.6. We recommend the specification as a reference for weld procedure and welder qualification. It is also a good source of other helpful information.

If you are already certified as a "commercial diver" and work for a company that offers underwater welding services, it is recommended that you communicate to your company your career objectives and ask what welder skills they are looking for. If you are unemployed or do not work for a company that offers underwater welding services, it is suggested that you communicate with the commercial diving firm of your choice that offers underwater welding services and train to its requirements.

If you are certified as a "scuba diver" (e.g., NAUI, PADI, etc.), it is suggested that you attend a commercial diving school. Sport dive training does not include the safe use of commercial diving equipment, offshore commercial work environment/safety, and other education as recommended by the Association of Diving Contractors Consensus Standards for Commercial Diving Operations.

Underwater welding is a skill you also have to master once you obtain the basic commercial diving skills required. Again, it is suggested that you communicate with the commercial diving firm of your choice that offers underwater welding services, and train to its requirements. Each commercial diving firm has its own policies and procedures regarding this matter.

4. What are the age limitations of a welder-diver?
There is no age restriction on commercial welder-divers. There are, however, physical requirements. It is recommended and generally required that all commercial divers pass an annual dive physical. ADC has an industry-accepted dive physical format that is used by many of its members in the United States and other countries (e.g., some companies may have other requirements, subject to the regulations of the country where they are located, etc.).

The commercial diving profession is physical demanding. It is rare to see an active commercial welder-diver over the age of 50.

5. What is the availability of work for an entry-level welder-diver?
This is a difficult question to answer. It is more appropriate to ask the company with whom you seek and/or gain employment. There are a number of diving procedures that serve the various types of underwater industrial requirements, each of which have different underwater welding needs. Like many professions, work availability is always subject to: supply vs. demand, the economics of a given industry, whether you are free to relocate outside your place of residence (including overseas), what other related skills you have in addition to diving and welding, etc. A number of welder-divers have established a reputation of high-quality workmanship and/or productivity and are asked for by name. The company you choose to work for is also a factor.

The answer to the question is that there is work available for entry-level welder-divers; however, the amount of work available is subject to the aforementioned variables.

6. What salary can I expect to make as a welder-diver?
An average salary vs. grade index would be interesting to look at if there were one, but the truth of the matter is that salaries for welder-divers cover a wide range. We know some welder-divers earn $15,000 per year while others earn in excess of $100,000. Because the majority of welder-divers are paid on a project-by-project basis, salaries are subject to the same variables as work availability. In addition, other factors such as depth, dive method and diving environment affect pay rates. The company with whom you gain employment should be able to tell you the salary range you can expect to earn.

7. What other skills are recommended to supplement my qualifications as a welder-diver?
The commercial diving and underwater welding industry is as diverse as the customers it serves. The welder-diver qualifications required for a given assignment vary from project to project. Ideally, a diving contractor would like its welder-divers to be "a jack of all trades and a master of them all!" Practically speaking, possessing the skills that are common to underwater welding operations, in addition to welding and diving, are recommended. Primarily these skills are: underwater cutting (oxyfuel, abrasive water jet, mechanical cutting equipment, etc.); fitting and rigging; inspection and nondestructive testing (visual, magnetic particle, ultrasonics, radiography, eddy current, etc.); drafting; and underwater photography (still photo and video).

Not all welder-divers posses the variety of skills that may be required to complete an underwater welding project. Diving contractors typically combine personnel resources to satisfy the capabilities required. Hence, the more skills the welder-diver maintains the more valuable he becomes in meeting project qualification requirements. The most desirable underwater welder-divers are those who are qualified to: assist the diving contractor in pre-job planning (e.g., having the ability to photograph/video, draft and report on work requirements prior to the actual underwater welding operation); cut, clean, rig, install, and fit up the sections they will weld; and work with personnel responsible for inspecting the completed welds.

Formal training is recommended for whatever skills you wish to qualify for. Many diving contractors, and the customers they serve, work under quality programs that demand evidence of training and/or qualifications. Therefore, it is recommended that the training you receive be accredited or offer a certificate of completion (e.g., a welding certificate, a diving certificate, an ASNT Level II or CSWIP ultrasonic certificate, riggers certificate, etc.). Maintaining the qualifications you obtain is just as important as receiving them as there has been many a job lost to a welder-diver who has let his certification lapse.

8. What future career opportunities are there for an experienced welder-diver?
There are a number of career opportunities for experienced welder-divers. Many go on to become engineers, instructors, and diving operations supervisors, fill management positions, qualify as AWS Certified Welding Inspectors (CWI), and serve as consultants for underwater welding operations and other related fields.

Ideally, a career as a welder-diver should serve as a stepping stone to other opportunities for those who choose the profession.

Industry has and will continue to demand higher quality standards for underwater welds and more certification of underwater welding systems and personnel. These demands will challenge the underwater welding community to meet more complex technical specifications, safety standards, welding criteria, inspection methods, environmental factors, and other considerations. To meet these challenges, tomorrow's welder-divers will rely on the knowledge and experience of their predecessors who have gone on to become welding engineers, welding engineer divers, supervisors and instructors. These individuals will provide the technical support needed for coming underwater welding operations.

A career as a welder-diver can be an exciting and rewarding profession. It cannot be overstated that safety through training is paramount to any welder-diver candidate.

The majority of work performed by an average welder-diver does not involve the welding operation itself, but rather executing the task that lead up to and follow the actual welding activities. Except under special circumstances, a welder-diver in most cases must possess both certified welder skills and commercial diving skills.

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Welding is a progression using heat or pressure to join mutually materials such as metal or synthetic. Welding Equipment is a ordinary way for joining metals, and is used in the production of many goods, including automobiles, ships, trains, buildings, and bridges.

MIG Welding Equipment

MIG Welding equipments are obtainable in various sizes ranging from a small, portable 115v, 20 amp model to full sized shop automotive service equipment. MIG welders are widely known for high quality performance, though cost-effectively priced. You can exercise control over the superiority of the weld with the aid of many diverse settings. MIG Welding equipments come with cold running temperatures. The machines also recommend advantageous warranty opportunities.

It is universal knowledge that MIG Welders use a wire feed and produce a lower heat. This stops metal distortion and allows for a high quality job on thinner metals such as those involved in auto body job.

MIG welders feed a constant stream of wire with a pull of the trigger. You must be additional cautious in choosing the consumables. Wire, for instance, comes in easy-to-use flux core wire for a rapid job on thicker resources, or a gas/solid wire amalgamation for all other work.

TIG Welders

Most TIG welding machines come with more than a few attractive features. With push button control panels, the machines are exceptionally accessible and some high-end models give you the option to easily adjust for repeatable weld cycles, start, and weld crater. To make specially the shape and size of the bead, you can choose models with true square wave AC output and pulse mode. Purchase models that have safety features like warning code circuitry and voltage protection.

One of the principal advantages of TIG welder is it heats and joins the two metal pieces together exclusive of the need for filler materials. Most operators know that MIG welders join metals much faster than TIG welders. But, TIG welders produce greater degree of precision, so essential for certain types of jobs. The possibility of preventing cracked seals or damaging the weld is also considerably decreased in TIG machines.

Plasma Cutting

Some latest models of plasma cutters come with a host of features - single-dial controls for easy adjustments, pressure gauges and air pressure regulators all aimed at cleaner and sharper cuts. Other features comprise parts-in-place indicators, line voltage compensation, and thermostatic protection. Above all, if you wish to do monotonous work with complex cuts, CNC robotic interfaces will make sure consistent and precise cuts every time. Please know that most up-to-date types of plasma cutters have an inverter in place of the transformer.

With several different styles of plasma cutters available, your choice becomes wider. Duty cycle is a key aspect in your business decision. Usually, you will find that bigger machines can handle thicker metals and run longer to give it a larger duty cycle. Furthermore watch for the rating that is assigned to plasma cutters by the producer. This will tell you how long each division can cut through mild steel before needing to be cooled down.

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Oxy Acetylene Welding and Cutting Materials

Oxy-acetylene welding is an autogenous welding process, in which two parts of the same or different metals are joined by causing the edges to melt and unite while molten without the aid of hammering or compression. When cool, the parts will form one whole piece of metal.

The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a special welding torch or blowpipe, producing, when burned, a heat of 6,300 degrees, which is more than twice the melting temperature of the most common metals. This flame, while being of intense heat, is of very small size.

Oxy Acetylene Cutting

The process of cutting metals with the oxy-acetylene flame produced from oxygen and acetylene depends on the fact that a jet of oxygen directed upon hot metal causes the metal itself to burn away with great rapidity, resulting in a narrow slot through the section cut. The action is so fast that metal is not injured on either side of the cut.

Carbon Removal Process

This process depends on the fact that carbon will burn and almost completely vanish if the action is assisted with a supply of pure oxygen gas. After the combustion is started with any convenient flame, it continues as long as carbon remains in the path of the jet of oxygen.

Materials

For the performance of the above operations we require the two gases, oxygen and acetylene, to produce the flames; rods of metal which may be added to the joints while molten in order to give the weld sufficient strength and proper form, and various chemical powders, called fluxes, which assist in the flow of metal and in doing away with many of the impurities and other objectionable features.

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Nickel and nickel-alloy weld metals do not flow and spread like steel weld metal. The operator must direct the flow of the puddle so the weld metal wets the joint sidewalls and the joint is filled appropriately. This is sometimes accomplished by weaving the electrode slightly. The amount of
weave will depend on such factors as joint design, welding position, and type of electrodes. A straight drag (stringer) bead deposited without weaving may be used for single-bead work, or in close quarters on thick sections such as in the bottom of a deep groove. However, a weave bead is generally desirable. When the weave progression is used, it should not be wider than three times the electrode core diameter. Regardless of whether the welder uses weaving or the straight stringer technique, all weld beads should be deposited such that they exhibit the recommended slightly convex surface contour.


When used properly, SMC flux covered welding electrodes should exhibit a smooth arc and no pronounced spatter. When excessive spatter occurs, it is generally an indication that the arc is too long, amperage is too high, polarity is not reversed, or that the electrode has absorbed moisture. Excessive spatter can also be caused by magnetic arc below.

When the welder is ready to break the arc, it should first be shortened slightly and the travel speed increased to reduce the puddle size. This practice reduces the possibility of crater cracking and oxidation, eliminates the rolled leading edge of the crater, and prepares the way for the restrike.

The manner in which the restrike is made will significantly influence the soundness of the weld. A
reverse or “T” restrike is recommended. The arc should be struck at the leading edge of the crater and carried back to the extreme rear of the crater at a normal drag-bead speed. The direction is then reversed, weaving started, and the weld continued. This restrike method has several advantages. It establishes the correct arc length away from the unwelded joint so any porosity resulting from the strike will not be introduced into the weld. The first drops of quenched or rapidly cooled weld metal are deposited where they will be remelted, thus, minimizing porosity.

Another commonly used restrike technique is to strike the arc on the existing bead In this manner, the weld metal likely to be porous can be readily removed by grinding. The restrike is made 1/2 to 1 in. (13 to 25 mm) behind the crater on top of the previous pass, and the restrike area is later ground level with the rest of the bead. This technique is often used for applications requiring that welds meet stringent radiographic inspection standards. It is also noteworthy that it is much easier for welders with lesser levels of skill to produce high quality welds than they can using the “T” restrike technique.

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Orbital welding is Automatic Tungsten inert gas welding. It eliminates chances of manual errors in welding. It produces identical welds for hundred of times hence accuracy in welding.

Orbital welding was first used in the 1960's when the aerospace industry recognized the need for a superior joining technique for aerospace hydraulic lines. A mechanism was developed in which the arc from a tungsten electrode was rotated around the tubing weld joint. The arc welding current was regulated with a control system thus automating the entire process. The result was a more precision and reliable method than the manual welding method it replaced.
Orbital welding became practical for many industries in the early 1980's when combination power supply / control systems were developed that operated from 110 V AC and were physically small enough to be carried from place to place on a construction site for multiple in-place welds. Modern day orbital welding systems offer computer control where welding parameters for a variety of applications can be stored in memory and called up when needed for a specific application. The skills of a certified welder are thus built into the welding system, producing enormous numbers of identical welds and leaving significantly less room for error or defects.

Orbital Welding Equipment

In the orbital welding process, tubes / pipes are clamped in place and an orbital weld head rotates an electrode and electric arc around the weld joint to make the required weld. An orbital welding system consists of a power supply and an orbital weld head.

Power Supply: The power supply / control system supplies and controls the welding parameters according to the specific weld program created or recalled from memory. The power supply provides the control parameters, the arc welding current, the power to drive the motor in the weld head and switches the shield gas (es) on / off as necessary.

Weld Head: Orbital weld heads are normally of the enclosed type and provide an inert atmosphere chamber that surrounds the weld joint. Standard enclosed orbital weld heads are practical in welding tube sizes from 1/16 inch (1.6mm) to 6 inches (152mm) with wall thickness' of up to 0.154 inches (3.9mm) Larger diameters and wall thickness' can be accommodated with open style weld heads.

The Physics of the GTAW Process

The orbital welding process uses the Gas Tungsten Arc Welding process (GTAW) as the source of the electric arc that melts the base material and forms the weld. In the GTAW process (also referred to as the Tungsten Inert Gas process - TIG) an electric arc is established between a Tungsten electrode and the part to be welded. To start the arc, an RF or high voltage signal (usually 3.5 to 7 KV) is used to break down (ionize) the insulating properties of the shield gas and make it electrically conductive in order to pass through a tiny amount of current. A capacitor dumps current into this electrical path, which reduces the arc voltage to a level where the power supply can then supply current for the arc. The power supply responds to the demand and provides weld current to keep the arc established. The metal to be welded is melted by the intense heat of the arc and fuses together.

Reasons for Using Orbital Welding Equipment

There are many reasons for using orbital welding equipment. The ability to make high quality, consistent welds repeatedly at a speed close to the maximum weld speed offer many benefits to the user:

* Productivity. An orbital welding system will drastically outperform manual welders, many times paying for the cost of the orbital equipment in a single job.

* Quality. The quality of a weld created by an orbital welding system with the correct weld program will be superior to that of manual welding. In applications such as semiconductor or pharmaceutical tube welding, orbital welding is the only means to reach the weld quality requirements.

* Consistency. Once a weld program has been established an orbital welding system can repeatedly perform the same weld hundreds of times, eliminating the normal variability, inconsistencies, errors and defects of manual welding.

* Orbital welding may be used in applications where a tube or pipe to be welded cannot be rotated or where rotation of the part is not practical.

* Orbital welding may be used in applications where access space restrictions limit the physical size of the welding device. Weld heads may be used in rows of boiler tubing where it would be difficult for a manual welder to use a welding torch or view the weld joint.

* Many other reasons exist for the use of orbital equipment over manual welding. Examples are applications where inspection of the internal weld is not practical for each weld created. By making a sample weld coupon that passes certification, the logic holds that if the sample weld is acceptable, that successive welds created by an automatic machine with the same input parameters should also be sound.

Industries and Applications for Orbital Welding

Aerospace: As noted earlier, the aerospace industry was the first industry to recognize the requirement for orbital welding. The high-pressure systems of a single plane can have over 1,500 welded joints, all automatically created with orbital equipment.

Boiler Tube: Boiler tube installation and repairs offer a perfect application for orbital welding. Compact orbital weld heads can be clamped in place between rows of heat exchanger tubing where a manual welder would experience severe difficulty making repeatable welds.

Food, Dairy and Beverage Industries: The food, dairy and beverage industries require consistent full penetration welds on all weld joints. Most of these tubing / piping systems have schedules for cleaning and sterilization in place. For maximum piping system efficiency the tubing must be as smooth as possible. Any pit, crevice, crack or incomplete weld joint can form a place for the fluid inside the tubing to be trapped and form a bacteria harbor.

Nuclear Piping: The nuclear industry with its severe operating environment and associated specifications for a high quality weld has long been an advocate of orbital welding.

Offshore Applications: Sub-sea hydraulic lines use materials whose properties can be altered during the thermal changes that are normal with a weld cycle. Hydraulic joints welded with orbital equipment offer superior corrosion resistance and mechanical properties.

Pharmaceutical Industry: Pharmaceutical process lines and piping systems deliver high quality water to their processes. This requires high quality welds to ensure a source of water from the tubes that is uncontaminated by bacteria, rust or other contaminant. Orbital welding ensures full penetration welds with no overheating occurring that could undermine the corrosion resistance of the final weld zone.

Semiconductor Industry: The semiconductor industry requires piping systems with extremely smooth internal surface finish in order to prevent contaminant buildup on the tubing walls or weld joints. Once large enough, a build up of particulate, moisture or contaminant could release and ruin the batch process.

Tube/Pipe Fittings, Valves and Regulators: Hydraulic lines and liquid and gas delivery systems all require tubing with connector fittings. Orbital systems provide a means to ensure high productivity of welding and improved weld quality. Sometimes the tubing may be welded in place to a valve or regulator body. Here the orbital weld head provides the ability to produce high quality welds in applications with restricted access to the weld joint.

A manual weld taken from an operating plant.

This weld has defects that include lack-of- penetration, misalignment,

a huge crevice, and discoloration due to poor ID purge. This weld would be considered unacceptable by any standard

An orbital weld on 316L-electropolished stainless steel. The weld is fully penetrated with a uniform crevice-free inner weld bead with good alignment. The ID was purged with argon, which resulted in slight discoloration of the HAZ.

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Product Description

*Uses self-shielding flux-core welding wire--no need for gas or gas regulator*On-board wire-spool storage with trigger-control line feed, infinitely adjustable wire speed*Operates on 120-volt AC/24A power; no special wiring required; 14 AWG CUL-listed power cord*Duty cycle 18% @ 60 amps, 10% @ 90 amps; wire capacity 0.035" or 0.030"*Includes torch with 7' cable, 6' 8AWG ground cord & clamp, flux-core welding wire, nozzle & tipEasy-to-operate MIGwelder for sheet metal and light steel, comes ready to weld right out of the box. Includes torch/cable, grounding cord & clamp, 4" spool 0.030" flux-cored welding wire, carry handle, nozzle and 2 copper tips. Dimensions 14-1/2"L x 14"H (with handle), 8"W, 34 lbs.
Product Features

* Dual Flux/Mig welder
* welding Amp Range: 55-90 Amp
* Rated AC Input: 120VAC, 60Hz, 18 Amps (for use on a 20 Amps Branch circuit)
* Torch Power Cable: 6AWG Single Insulation
* Ground Cable: 6AWG Single Insulation

Technical Details

* Power Cord: 3-Core, 14AWG Double Insulated
* Thermal Overload: Both settings: 6 minutes shutdown, 10 minutes back on with light
* welder Tip: 0.030" and ---0.040"
* Wire Size: 0.030"---0.040" flux core wire
* Includes: 0.01" welder Tip, welding Face Shield, Wire Brush/Hammer combination

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Welding is the process of fusion of two metal surfaces together by heating them in a forge. Welds made with good forge are really strong and delicate, and it’s very hard to detect the welding mark with the naked eye. Welding is useful for a wide spectrum of industries due to the distinct properties that this process can alone offer.

There are different types of welding. Each welding process is distinct in application and properties. There are varieties like arc welding, gas welding, and plasma welding. To suit the application, any of these welding processes may be selected. It is found that carbon dioxide could not be used alone because of the high plasma back, so combinations of gases are employed in gas welding. Welding is useful in joining beams when constructing buildings, bridges, and other structures, and pipes in nuclear power plants and refineries.

Lincoln Electric Company is a leader in offering do-it-yourself welding projects. Ornamental entry gates, snow blowers, wheel chair ramps, ice fishing coops, and metal sculptures could be constructed using Lincoln welding equipment. Zena’s mobile welding equipment can fit into trucks, emergency vehicles, forklifts, construction equipment, watercraft, and lawn tractors/mowers.

Diamond Ground Products, Inc. is one of the major manufacturers in welding supplies with operations in the U.S., Canada, and the United Kingdom. They specialize in tungsten arc welding products and electrodes. Torch Mate CNC cutting systems give hypothermic plasma systems, which are more accurate than the regular plasma process. CNC retrofit kits, CNC rout, plasma cutter, and software are the specialty products of Applied Robotics Incorporation, which markets its products under the trademark Torch Mate CNC Cutting Systems.

The welding tools came from painstaking research. The training and expertise needed to operate the welding equipments is essential to get welding jobs. The machining processes as well as the welding processes are useful in different sectors like aeronautics, machine tooling for vehicles, surgical tooling, rails, steel and iron furniture, shipbuilding, domestic product manufacturing, and structural engineering. The precision-based CNC grinding and welding is ruling the world of welding. Technical institutions offer courses to train the operations and the methodology of the computerized process. There is good demand for them. Persons who aspire to take up a career in welding can best utilize the crash courses and workshops on CNC cutting and welding.

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Welding Certification tests are numbered by position and joint type. For instance a 1 G indicates a flat position groove weld. The 1 means flat position, and the G indicates a groove weld.

I saw a video the other day that advertised a mobile welding lab that was used to train and certify welders.

A few students as well as the instructor were interviewed and described the 8 weeks of welding training that led up to welding certification tests in the 1G position.

What?

That's right, 8 weeks of welding training per process to be able to certify in a 1 G weld test.

I don't get it. After 8 weeks of training in a welding process, why can't the welder pass some other positions like 3G and 4G welding tests?

Did you know that a 3G plate test combined with a 4G plate test certifies a welder in ALL positions?

That's all positions. Like 1G , 2G, 3G, and 4G. as well as every position of fillet welds imaginable too.

A 1G welding test certifies a welder to weld in how many positions? One ! that's it ...just one.

You get a lot more bang for your buck by training welders to certify in both the 3G and 4G positions.

Another issue is that 1G welding tests typically don't have very good pass rates.

You know why?

Gravity. That's right., gravity is working against you and not for you. Gravity lets the slag flow ahead of the arc on a 1G welding test and if you are not careful, it can cause cold lap and slag inclusions.

Gravity works For you and not against you on a 3G vertical plate welding test.

Gravity keeps the flux behind the arc. The arc is then allowed to do its thing and penetrate into the base metal. As long as you maintain enough amperage and a tight arc, things will go well on a 3G vertical plate test.

The AWS (American Welding Society) classifies the 1G position welding test as the easiest.

I disagree with that when it comes to beveled groove welds.

I believe 2G horizontal and 3G vertical welding certification tests have better pass rates when it comes to a bend test or x ray testing.

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Multi-chamber IV bag has two categories: fluid multi-chamber IV bag and fluid-powder multi-chamber IV bag. It’s defined as the separate storage of different medicine in different sub-chambers by weldingduring production, storage and transportation. In application, the separate sub-chambers are connected by external forces, and the contents are mixed. Multi-chamber IV bag is mainly used for the contents that are unstable after mixing, and can not guarantee long term storage. This article analyzes the testing of two key factors for multi-chamber IV bags: welding and barrier property.

1.The Analysis and Testing of Welding Strength

For the welding strength of multi-chamber IV bag, its convenience, safety and protection for isolated contents during storage and transportation must be maintained. Therefore, multi-chamber welding process control is the key procedure in the whole production. Welding is determined by three indexes: temperature, time and pressure. Multi-chamber IV bags, to achieve safe storage and transportation as well as easy clinical operation, can only maintain a mediate welding strength, which is also called heat seal strength. How to control this index successfully is a focus for multi-chamber IV bag manufacturers.

Labthink HST-H3 Heat Seal Tester and XLW (PC) Auto Tensile Tester are the professional testers for multi-chamber IV bag and its indexes. When testing the finished multi-chamber IV bags, a specimen of the welding place is prepared. This specimen can be automatically tested after clamping and pressing the ‘heat seal’ button on XLW (PC). Besides, for the proper welding strength, the manufacturer needs to make researches on temperature, time and pressure. HST-H3 Heat Seal Tester can be applied with the auto tensile tester for the best heat seal temperature, time and pressure indexes.

2.The Analysis and Testing of Barrier

Barrier property is the most important factor affecting the quality of fluid and fluid-powder multi-chamber IV bags. Owing to the low barrier property of the content contact package, a barrier package is needed for prevention of oxygen and moisture permeation. Besides, nitrogen is applied to take place of the air between the inner package and barrier package. Therefore, oxygen transmission as well as nitrogen and moisture transmission should be tested. Labthink VAC-V series of differential pressure gas permeation testers can accomplish relevant testing.

The application of multi-chamber IV bags is the great development of IV bags. As the most strictly required package for medicine, its tensile strength, elongation, heat seal strength, puncture performance of film and closure and seal property all need to be tested. Labthink, as the excellent provider of testing instruments and services, has been providing most excellent and thorough quality control solutions for the global medical industry. Labthink is willing to have more communication and cooperation will pharmaceutical companies and institutions

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How to mig weld aluminum like a pro. Here are some of my pointers to get you up and running welding aluminum with your mig welder.

1. Use the shortest possible mig welding gun so that there is less internal resistance. The more resistance there is on the welding wire the harder it is going to be for it to feed through smoothly. The biggest problem that people face when mig welding aluminum is that they cannot get the wire to feed through smoothly.

2. Make sure that you use a use a u grooved feed roller. There are many different types of feed rollers for different welding wire applications. For ally wire you need to use a u grooved roller. The design of this feed roller will make it easier for the wire to be gripped more evenly, which makes it easier to feed through the liner.

3. When you are mig welding aluminum you also need to use a larger size contact tip. This is so that the wire does not stick.

4. Also when you weld aluminium with a mig welder the standard steel liner in the welding torch needs to be replaced. You replace the steel liner that you would normally use with a solid mig wire with a teflon or plastic liner. These are special liners that are designed to help feed the ally wire through smoothly.

5. Make sure your material is clean. To do this you use a stainless steel brush. This must be a dedicated brush for aluminium only.

6. The welding gas you need to use his argon, which you can hire from your local welding supply shop.

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These are only Ten of the many many welding mistakes that can be fatal. I use a bit of coarse language here in an attempt to keep it fun and hopefully you will actually pay attention. Unfortunately welding safety to most of us men is kind of like the instruction manual that comes with a VCR. It just gets ignored until there is a problem.

1. Hauling oxygen and acetylene cylinders in your trunk. A little leak here,,, a little leak there… a static spark…boom!! Your Ass is Killed! This goes for truck tool boxes also. Throwing a set of pony bottles in your truck tool box can turn into a bomb and…you guessed it …………can Kill your Ass!

2. Moving high pressure cylinders with no protective cap. The cylinder falls…the valve gets knocked off…2500 psi escapes out of a hole the size of a nickel and you have a missile….Oops! Your Ass or someone else’s Ass just got Killed!!

3. Making oxygen and acetylene balloon bombs. A little fuel gas like acetylene…a little oxygen…mixed together in a balloon so that you can impress the neighbors on July 4th…a static spark between the 5 balloons you so hid so cleverly in a plastic garbage bag…boom!! Your ASS is Killed!

4. Weldinginside a tank or any enclosed area with Mig or Tig. Both use Argon. Argon is an inert, colorless, odorless gas that is about twice as heavy as air. It is almost like an invisible liquid the way it can fill up an unventilated room. No air, no life. Breathing Air with no oxygen in it will kill Your Ass. In fact it will often kill 2 Asses. You and your working partner who comes to try to rescue Your ASS.

5. Welding in Water Can Kill Your Ass. Don’t get a mental picture of standing in a bucket of water. I am more thinking of lying underneath a pipe making a weld with a puddle of water on the concrete that you didn’t quite get dried up. Granted welding current is low voltage and high amperage but it can still kill your Ass.

6. Welding without a fire watch when there is stuff around you that can catch on fire. Welding requires skill. Skill requires focus and attention. Put that together with the fact that you’re wearing a welding helmet and can’t see what might be catching on fire and you have a situation that could definitely Kill your Ass.

7. Welding a gas tank or any container that held something flammable. Special precautions can be taken that can actually make it pretty safe (like washing the tank with soap and water and then purging with argon) but if you are not thorough enough or forget something or don’t purge well enough……You guessed it…It can totally Kill your ASS.

8. Blowing off your clothes with oxygen from a cutting torch can turn you into a roman candle and you guessed it…Can Kill Your Ass.!

9. Inflating a tire with Oxygen is a really bad idea and can be a lot worse than having a under inflated or flat tire. Why? I am glad you asked. Because it can explode and Kill your Ass!

10. Keeping a Bic Lighter in your shirt pocket while welding is like playing Russian roulette. One little spark and you get to experience what its like to have an eighth of a stick of dynamite explode a few inches from your heart. Uh...I mean...I am no Doctor... but I am pretty sure this could Kill your ASS too?

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A wire strain gage can effectively measure strain in only one direction. To determine the three independent components of plane strain, three linearly independent strain measures are needed, i.e., three strain gages positioned in a rosette-like layout.

Consider a strain rosette attached on the surface with an angle a from the x-axis. The rosette itself contains three strain gages with the internal angles b and g, as illustrated on the right.

Suppose that the strain measured from these three strain gages are ea, eb, and ec, respectively.

The following coordinate transformation equation is used to convert the longitudinal strain from each strain gage into strain expressed in the x-y coordinates,

Applying this equation to each of the three strain gages results in the following system of equations,


These equations are then used to solve for the three unknowns, ex, ey, and exy.

Note: 1. The above formulas use the strain measure exy as opposed to the engineering shear strain gxy, .
To use gxy, the above equations should be adjusted accordingly.
2. The free surface on which the strain rosette is attached is actually in a state of plane stress, while the formulas used above are for plane strain. However, the normal direction of the free surface is indeed a principal axis for strain. Therefore, the strain transform in the free surface plane can be applied.

Special Cases of Strain Rosette Layouts
Case 1: 45º strain rosette aligned with the x-y axes, i.e., a = 0º, b = g = 45º.





Case 2: 60º strain rosette, the middle of which is aligned with the y-axis, i.e., a = 30º, b = g = 60º.

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In a nutshell here are the 6 main things to remember when TIG welding 4130 chromoly tubing:

1. Preheat is not necessary for tubing under .120" thick. however it sure won’t hurt anything. If the ambient temperature is less than 60 F, I would say preheat to at least 100F. You can easily do this with a small propane torch from Home Depot.

2. Weld a little slower than normal. This just makes sense. Think about it. If there is an ongoing argument about GAS welding being superior than TIG welding for Chromoly tubing, then it makes sense to go just a little slower when TIG welding. This will slow the cooling rate and negate any chance of the welded area cooling too fast.

3. Don’t allow any Breeze or drafts in the room and do not speed cool the welds.

4. Use a TIG machine with high frequency starting to eliminate arc strikes. I had a "German Eye" pocket knife once that someone had used to cut a live wire. The small arc on the blade stuck out like a diamond and would not wear down with a file or sharpening stone. The same thing happens but to a lesser extent when you get an arc strike on 4130 chromoly. You get a hard brittle spot and a crack will definitely start there.

5. Do not use 4130 rod. Using a slightly under matched filler metal gives better overall properties and just plain works a lot better . Use E70S2 Tig rod and call it a day.

6. Taper off amperage slowly to avoid crater holes that will turn into cracks later on.

Have you ever tried to bend a piece of 4130 Chromoly tubing? OMG! This stuff is harder than Japanese arithmetic. Compare it to 1010 steel as far as how hard it is to bend and there really is no comparison. Just get a piece of 1/2 inch tubing and try it. You will strain your left testicle trying to bend chromoly tubing.

There are other chromium molybdenum steels like 4140 and 4340 but one of the most common chromoly steels is 4130 chromoly steel.

Back in the day, chromoly tubing was welded with oxy-acetylene. Why?

Because it worked... and because that is what most shops had available. And then years later I am sure some old timer said "because that’s the way we have always done it" .

But research has been done to prove that Tig welding can be the fastest, cleanest and best way to weld 4130 chromoly tubing without risk of compromising material properties(provided the thickness does not exceed .120").
Wyatt Swaim (also known as Mister Tig or "Mr. Tig")
Wyatt Swaim (also known as Mister Tig or "Mr. Tig") has been promoting Tig welding of 4130 chromoly tubing for several years now and even holds seminars and workshops for EAA (experimental aircraft association) enthusiasts to get them acquainted with the TIG welding process. But what does the number 4130 mean? What does the term "chromoly" signify? What is it most used for and why? And what is so difficult about welding 4130?

Chromoly refers to a steel alloy which contains chromium and molybdenum among otherelements. The word ‘Chromoly’ is a short term for “Chromium-Molybdenum" steel. Thenumber ‘4130’ is a code of the American Iron & Steel Institute (AISI 4-digit codesystem) and defines the approximate chemical composition of the steel. The ‘41’indicates a low alloy steel containing chromium and molybdenum and the ‘30’ indicates acarbon content of 0.30 percent.(that’s 3/10ths or 30 one hundredths of a percent) 4130 is often used for high end bicycle frames and race-car roll cages due to its high tensile strength, malleability and easy weldability. In addition, it is considerably stronger and more durable than standard 1020 steel tubing, which is also known as "plain carbon steel".
More details on AISI numbering system for alloy steels
Alloy steels differ from carbon steels in that they have compositions that extend beyond the limits set for carbon steels. Usually this refers to constituents such as boron, carbon, chromium, manganese, molybdenum, silicon and vanadium. They also have chromium contents less than 4%. Steels with chromium contents of greater than 4% become classified as stainless or tool steels. As a general guide, an alloy steel will have:

• Manganese content >1.65%

• Silicon content >0.5%

• Copper content >0.6%

The American Iron and Steel Institute (AISI) naming system is one of the most widely accepted systems.

Designations usually consist of a four digit number, but sometimes this extends to five. The first two digits indicate what the major alloying element is, while the last 2 or three indicate the carbon content in hundredths of a percent.

Example: AISI 4340 is a Nickel,Chromium,Molybdenum containing alloy steel with a 0.40% average carbon content.there also something called a "carbon equivalent formula" that basically calculates the effect that elements like chromium and vanadium etc. have on the hardenability of a steel. In other words, because aisi 4340 has 0.4% carbon but also has around 0.8% chromium, the hardenability might be the equivalent of a plain carbon steel having 0.5% Carbon.

The American Iron and Steel Institute has a numbering system for steels and the 4100 series indicates a chromium molybdenum steel. The "30" in 4130 indicates 0.3% carbon. 4130 also contains 0.4 to 0.6% manganese, 0.8 to 1.1% chromium, 0.15 to 0.25% molybdenum, 0.04% phosphorus, 0.04% sulfur, and 0.2 to 0.35% silicon, but like all steels, it is mostly iron. 4130 chromoly is an ideal material for BMX bicycle frames, roll cages for race cars, and for fuselages on small aircraft because of its high tensile strength and high strength-to-weight ratio.

Welding 4130 is not that much different than welding steel or stainless steel as far as technique is concerned. There are just additional considerations to keep in mind.

Remember...

watch your arc strikes,

dont speed cool,

use E70S2 tig welding rod,

pay attention to good fit ups,

weld a little slower,

use a little preheat if it is chilly in the shop,

taper off your amperage to avoid crater cracks.

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Spherical Pressure Vessel

Consider a spherical pressure vessel with radius r and wall thickness t subjected to an internal gage pressure p.
For reasons of symmetry, all four normal stresses on a small stress element in the wall must be identical. Furthermore, there can be no shear stress.

The normal stresses s can be related to the pressure p by inspecting a free body diagram of the pressure vessel. To simplify the analysis, we cut the vessel in half as illustrated.



Since the vessel is under static equilibrium, it must satisfy Newton's first law of motion. In other words, the stress around the wall must have a net resultant to balance the internal pressure across the cross-section.







Cylindrical Pressure Vessel

Consider a cylindrical pressure vessel with radius r and wall thickness t subjected to an internal gage pressure p.

The coordinates used to describe the cylindrical vessel can take advantage of its axial symmetry. It is natural to align one coordinate along the axis of the vessel (i.e. in the longitudinal direction). To analyze the stress state in the vessel wall, a second coordinate is then aligned along the hoop direction.

With this choice of axisymmetric coordinates, there is no shear stress. The hoop stress sh and the longitudinal stress sl are the principal stresses.
To determine the longitudinal stress sl, we make a cut across the cylinder similar to analyzing the spherical pressure vessel. The free body, illustrated on the left, is in static equilibrium. This implies that the stress around the wall must have a resultant to balance the internal pressure across the cross-section.

Applying Newton's first law of motion, we have,

To determine the hoop stress sh, we make a cut along the longitudinal axis and construct a small slice as illustrated on the right.

The free body is in static equilibrium. According to Newton's first law of motion, the hoop stress yields,


Remarks
• The above formulas are good for thin-walled pressure vessels. Generally, a pressure vessel is considered to be "thin-walled" if its radius r is larger than 5 times its wall thickness t (r > 5 · t).
• When a pressure vessel is subjected to external pressure, the above formulas are still valid. However, the stresses are now negative since the wall is now in compression instead of tension.
• The hoop stress is twice as much as the longitudinal stress for the cylindrical pressure vessel. This is why an overcooked hotdog usually cracks along the longitudinal direction first (i.e. its skin fails from hoop stress, generated by internal steam pressure).

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4130 Chromoly tubing is used for all kinds of applications, but 2 of the main ones are for airplanes and for racing just about anything from motorcycles, to mountain bikes, to go-carts.

AISI 4130 tubing is strong. It's real strong. So the reason it is so popular among race car and airplane builders can use thinner tubing and that translates into speed and less weight.

Welding 4130 steel tubing is not that hard. There seems to be some mystique around it but it actually welds better than plain carbon steel.

So then whats all the fuss about? Well there is one thing. If it cools too quickly, 4130 chromoly tubing will be hard and brittle in the heat affected zone of the weld.

Thats the main thing to be concerned about. So how do you prevent the weld area from cooling too quickly?

1. Make sure the ambient temperature is above 60 degrees F.
2. Use a small propane torch to preheat weld area to about 100-150 F. 300 degrees F if room air is below 60 degrees.
3. Weld a little bit slower than you would for plain carbon steel.
4. Dont use 4130 tig welding rods. Use E70S2.
5. Never speed cool anything.

Some frequently asked questions about tig welding 4130 steel tubing are:

Q. Do I need to heat treat the weld when I am done welding?

A. No, the term heat treat is often misused. What is usually meant when it comes to welding chromoly is "stress relief". A stress relief can be done with an oxyfuel torch and a 900 degree F temp stick or a digital pyrometer. But it is usually unnecessary unless the thickness exceeds one eighth inch.

Q. Do I need to back purge my Chromoly welds with argon gas?

A. It always helps, but think about how many oxy acetylene welds there are out there doing fine that were done with no purge.

Q. What about using 308 stainless for welding chromoly?

A. there is a bunch of discussion on Baja Racing forums on this subject. I can tell you that lots of welders are using er308 tig welding rod with success, but for airplanes, E70S2 is the way to go. One thing that might not occur to you that you should consider is that if you ever needed to weld repair something and all you had was a gas welding torch, the E70s2 would be easily welded over with an oxyfuel rig. The 308 stainless welds? Not so much.

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If welding with a solid wire is satisfactory, why use a higher priced flux-cored wire? A flux-cored wire is optimized to obtain performance not possible with a solid wire. For many welding applications like vertical-up welding, flat welding, welding over galvanized, or welding hard-to-weld steels, a flux-cored wire can do it better and faster.

Although gas metal arc welding (GMAW) with a solid mild steel wire is popular, easy-to-use, and effective for many applications, it does have limitations and drawbacks. For example, GMAW is slow for out-of-position welding. It is either limited to short-circuit transfer, which is restricted by many welding codes due to the tendency for lack-of-fusion, or pulse transfer, requiring a special welding power source. It also requires very clean steel.

The ability to add a variety of materials to the core of the welding wire allows many performance enhancements to be made. Slag formers are added to shield the weld pool and shape and support the weld. Iron powder is used to increase deposition rates. Powdered alloys are added to produce low-alloy deposits or improving the mechanical properties. Scavengers and fluxing agents are used to refine the weld metal.

Flux-cored arc welding gas-shielded (FCAW-G) wires were introduced to the market around 1957. The flux-cored arc welding self-shielded (FCAW-S) wires were introduced to the market later, around 1961.

The core ingredients for FCAW-G wires have been formulated to obtain performance impossible to achieve with a solid GMAW wire. As all of shielding is provided by the shielding gas, the core materials may be carefully selected to maximize a certain area of welding performance, such as obtaining smooth spray-type transfer with 100% carbon dioxide shielding gas and welding speeds twice as fast in the vertical position.

The FCAW-S wires on the other hand, the core materials must provide all of the shielding. The core materials generate its own shielding gases, slag formers, and compounds to refine the weld pool. The benefits of self-shielded flux-cored wires lie in its simplicity. They may be used outdoors in heavy winds without tenting and the additional equipment required for gas shielding.

Now, we're going to discuss several popular types of flux-cored wires and how they can increase welding productivity.

For semi-automatic out-of-position welding, E71T-1 wires offer unsurpassed performance. Its fast freezing rutile slag provides the highest deposition rates in the vertical-up position, up to 7 pounds per hour, unmatched by any other semi-automatic arc welding process. In addition, the E71T-1 wires also offer an exceptionally smooth welding arc and minimal spatter, even with 100% carbon dioxide shielding gas. Argon/carbon dioxide blends are used for the smoothest arc and best out-of-position performance. These are reasons why E71T-1 is the world's most popular flux-cored wire. It is a top choice for shipbuilding, structural steel, and general steel fabrication applications.

For semi-automatic out-of-position welding without shielding gas, E71T-8 wires offer the highest deposition rates. Lincoln Electric's NR®-232 can deposit 4.5 lbs./hr. in the vertical-up position, 50% faster than other E71T-8 wires. Since this wire is self-shielded, it is widely used outdoors and in field erection of structural steel.

For semi-automatic welding in the flat position, the fastest way to join thick steel plate is with an E70T-4. It offers the highest semi-automatic deposition rates, up to 40 pounds per hour. This wire is widely used to join thick steels where there is no Charpy impact toughness requirement. This wire is also self-shielded, allowing it to be easily used outdoors.

The highest deposition rate gas-shielded flux-cored wire is E70T-1. Compared to E70T-4, they offer slightly lower deposition rates of up to 30 pounds per hour, but they offer a smoother welding arc and Charpy impact toughness properties. It offers higher deposition rates than GMAW, handles dirtier plates, and uses lower cost 100% carbon dioxide shielding gas. E70T-1s are widely used in structural steel fabrication shops.

For welding coated and galvanized sheet steels, E71T-14 is the wire of choice. The self-shielded E71T-14 wire has core materials which explode in the arc, volatizing the steel coating, minimizing cracking and porosity. The result is higher quality welds and fast welding speeds. E71T-14 wires are widely used in the automotive industry for fabricating galvanized steels.

What is the fastest way to weld hard-to-weld steels? E70T-5 gas shielded wire offer excellent crack resistance on hard-to-weld steels, such as T-1 quench and tempered steels, abrasion resistant steels, and free machining steels. E70T-5 has a basic slag system, similar to 7018 stick electrode, which removes phosphorus and sulfur from the weld metal, which can cause cracking, porosity, and poor toughness. E70T-5s have lowest diffusible hydrogen levels among the flux-cored wires, resulting in excellent resistance to delayed hydrogen cracking, as. In addition, they offer exceptional Charpy impact toughness properties.

Flux-cored wires offer higher productivity for many mild steel semi-automatic welding applications:

E71T-1 (FCAW-G): Highest deposition rates out-of-position.
E71T-8 (FCAW-S): Highest deposition rates out-of-position without a shielding gas.
E70T-4 (FCAW-S): Highest deposition rates in the flat position.
E70T-1 (FCAW-G): Highest deposition rates in the flat position with Charpy properties.
E71T-14 (FCAW-S): Fastest travel speed on galvanized and coated steels.
E70T-5 (FCAW-G): Fastest way to weld hard-to-weld steels.

Why be limited by a solid wire when a flux-cored wire can do it better and faster? Select the flux-cored wire optimized for your welding application. Use it and increase your productivity and lower your welding costs.

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Underwater welding techniques are most commonly used in executing marine engineering projects such as installation of oil and gas rigs. Underwater welding is mostly related to welding work pieces made from different types of metals such as steel, aluminum, copper, and others.

Underwater welding can be classified according to the type of equipment used and the type of processes followed. The most common underwater welding process is known as manual metal arc welding (MMA) which has the advantage of being relatively insensitive to depth. This makes it the most suited technique for undertaking deep-water repair activities.

Cofferdam welding involves the use of a rigid structure to house the welders, which is sealed against the side of the structure to be welded. Another type of underwater welding technique is commonly known as Hyperbaric welding in which an enclosure is sealed around the structure to be welded, and is filled with a gas (commonly helium containing 0.5 bar of oxygen) at the prevailing pressure. This welding technique is often combined with MMA (SMA), TIG (GTA), or FCAW for effecting high integrity welds, particularly for deep-water welds, including tie-ins in pipelines and risers in the oil and gas industries.

Underwater welding techniques are used for welding steel pipelines, other offshore structures, submerged parts of large ships, and underwater structures supporting a harbor. Welding in depths of 500 to 1000 meters generates high weld metal diffusible hydrogen, which can increase the risk of hydrogen-assisted cracking. This can be prevented with the use of electrode coating formulations and improved power source technology.

Underwater welding techniques can be dangerous if proper procedures and equipment is not used. An underwater welder faces the potential risk from electric shocks and from nitrogen introduced into the bloodstream during exposure to air at increased pressure. Underwater welding safety measures include emergency air or gas supply, stand-by divers, and decompression chambers to avoid decompression sickness following rapid surfacing after saturation diving.

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