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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Excavators Loaders can be of two types: 1- Backhoe Loaders, and 2- Wheel Loaders.

Backhoe

A backhoe, also called a rear actor or back actor, is a piece of excavating equipment consisting of a digging bucket on the end of an articulated arm (also called a stick or dipper). Modern backhoes are powered by hydraulics. They are typically mounted on the back of a tractor or front loader. (Similar attachments for skid loaders are still called backhoes even though they are mounted on the front of the vehicle). A backhoe attached to a swiveling cab on top of tracks is called an excavator.

Backhoe Loader

Backhoe loader, also called a Loader backhoe, is an engineering vehicle, which consists of a tractor, front shovelucket and small backhoe in the rear. Due to its relatively small size and versatility, backhoe loaders are very common in urban engineering and small construction projects such as building a small house, fixing city roads etc.

A common backhoe-loader. The backhoe is on the right, the bucket/blade on the left. Invented in Burlington, Iowa in 1957 the Backhoe loader (note: this needs checking – may have been invented in the UK by Joseph Cyril Bamford, founder of JCB) is probably the most common variation of the classic farm tractor. As the name implies, it has a loader assembly on the front and a backhoe on the back. When both the loader and the backhoe are permanently attached it is almost never called a tractor, not generally used for towing and usually does not have a PTO. When the backhoe is permanently attached, the machine usually has a seat that can swivel to the rear to face the hoe controls. Removable backhoe attachments almost always have a separate seat on the attachment itself.




Backhoe-loaders are very common and can be used for a wide variety of tasks: construction, small demolitions, light transportation of building materials, powering building equipment, digging holes/excavating, breaking asphalt, and paving roads. The backhoe bucket can often be replaced with other tools such as a breaker for smashing concrete and rock. Some loader buckets have a retractable bottom, enabling it to empty its load more quickly and efficiently.
Retractable-bottom loader buckets are also often used for grading and scratching off sand. The front assembly may be a removable attachment or permanently mounted. Often the bucket can be replaced with other devices or tools. The backhoe loader must be equipped with a tool coupler in order to mount different attachments to the loader. A tool coupler consists of two hydraulic cylinders on the end of the loader arm assembly which can expand and retract allowing different tools to be attached to the unit.

Their relatively small frame and precise control make backhoe-loaders very useful and common in urban engineering projects such as construction and repairs in areas too small for larger equipment. Their versatility and compact size makes them one of the most popular urban construction vehicles.

WHEEL LOADERS

Wheel Loader is a Front end loading machine. Wheel loader dig and as well as do secondary loading. Wheel loaders which do only secondary loading are called Pay Loaders.

The Wheel loaders are classified according to there bucket size and operating weight. The bucket size ranges from 1 cum upwards. The Wheel loaders can be tyre mounted or track mounted. The more popular version being tyres.

The Wheel loaders are very versatile and can be engaged in construction works, ranging from road work, plant loading, hopper and wagon feeding, stevedoring and mineface excavation.

A Wheel loader typically has semiautomatic or autometic transmition with autometic gear sifting. The power train will include engine, transmition, related propellar shaftes and powered axles at both front and rear.

A typical hydrolic curcuit for implimentation will include fixed/variable displacement pumps, controll valves, and actuators for boom, arm and bucket operation. Normally the steering curcuit is kept separate from the impliment curcuit.

The linkages are 2 types:
1- Paralallo bar and
2- Z bar

Autolevelling mechanism is also inbuilt in some of the loaders.

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