FABRICATION WORK

"Fabricator" redirects here. For other uses, see Fabricator (disambiguation).

A typical steel fabrication shop

Fabrication, when used as an industrial term, applies to the building of machines, structures and other equipment, by cutting, shaping and assembling components made from raw materials. Small businesses that specialize in metal are called fab shops.

Fabrication comprises or overlaps with various metalworking specialties:

• Fabrication shops and machine shops have overlapping capabilities, but fabrication shops generally concentrate on the metal preparation aspects (such as sawing tubing to length or bending sheet metal or plate), welding, and assembly, whereas machine shops are more concerned with the machining of parts on machine tools. Firms that encompass both are also common.
• Blacksmithing has always involved fabrication, although it was not always called by that name.
• The products produced by welders, which are often referred to as weldments, are an example of fabrication.
• Boilermakers originally specialized in boilers, leading to their trade's name, but the term as used today has a broader meaning.
• Similarly, millwrights originally specialized in setting up grain mills and saw mills, but today they may be called upon for a broad range of fabrication work.
• Ironworkers, also known as steel erectors, also engage in fabrication. Often the fabrications for structural work begin as prefabricated segments in a fab shop, then are moved to the site by truck, rail, or barge, and finally are installed by erectors.

Contents  [hide] 1 Metal fabrication 1.1 Engineering 1.2 Raw materials 1.3 Cutting and burning 1.4 Forming 1.5 Machining 1.6 Welding 1.7 Final assembly 2 Specialties 3 See also

[edit]Metal fabrication

Metal fabrication is a value added process that involves the construction of machines and structures from various raw materials. A fab shop will bid on a job, usually based on the engineering drawings, and if awarded the contract will build the product.

Fabrication shops are employed by contractors, OEM's and VAR's. Typical projects include; loose parts, structural frames for buildings and heavy equipment, and hand railings and stairs for buildings.

[edit]Engineering

The fabricator may employ or contract out steel detailers to prepare shop drawings, if not provided by the customer, which the fabricating shop will use for manufacturing. Manufacturing engineers will program CNC machines as needed.

[edit]Raw materials

Standard raw materials used by metal fabricators are;

• plate metal
• formed and expanded metal
  
  • tube stock, CDSM
  • square stock
  • sectional metals (I beams, W beams, C-channel...)
• welding wire
• hardware
• castings
• fittings

[edit]Cutting and burning

The raw material has to be cut to size. This is done with a variety of tools.

The most common way to cut material is by Shearing (metalworking);

Special band saws designed for cutting metal have hardened blades and a feed mechanism for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but with a steel cutting abrasive disk. Cutting torches can cut very large sections of steel with little effort.

Burn tables are CNC cutting torches, usually natural gas powered. Plasma and laser cutting tables, and Water jet cutters, are also common. Plate steel is loaded on a table and the parts are cut out as programmed. The support table is made of a grid of bars that can be replaced. Some very expensive burn tables also include CNC punch capability, with a carousel of different punches and taps.Fabrication of structural steel by plasma and laser cutting introduces robots to move the cutting head in three dimensions around the material to be cut.

[edit]Forming

Hydraulic brake presses with v-dies are the most common method of forming metal. The cut plate is placed in the press and a v-shaped die is pressed a predetermined distance to bend the plate to the desired angle. Wing brakes and hand powered brakes are sometimes used.

Tube bending machines have specially shaped dies and mandrels to bend tubular sections without kinking them.

Rolling machines are used to form plate steel into a round section.

English Wheel or Wheeling Machines are used to form complex double curvature shapes using sheet metal.

[edit]Machining

Main article: machining

Fab shops will generally have a limited machining capability including; metal lathes, mills, magnetic based drills along with other portable metal working tools.

[edit]Welding

Main article: welding

Welding is the main focus of steel fabrication. The formed and machined parts will be assembled and tack welded into place then re-checked for accuracy. A fixture may be used to locate parts for welding if multiple weldments have been ordered.

The welder then completes welding per the engineering drawings, if welding is detailed, or per his own judgment if no welding details are provided.

Special precautions may be needed to prevent warping of the weldment due to heat. These may include re-designing the weldment to use less weld, welding in a staggered fashion, using a stout fixture, covering the weldment in sand during cooling, and straightening operations after welding.

Straightening of warped steel weldments is done with an Oxy-acetylene torch and is somewhat of an art. Heat is selectively applied to the steel in a slow, linear sweep. The steel will have a net contraction, upon cooling, in the direction of the sweep. A highly skilled welder can remove significant warpage using this technique.

Steel weldments are occasionally annealed in a low temperature oven to relieve residual stresses.

[edit]Final assembly

After the weldment has cooled it is generally sand blasted, primed and painted. Any additional manufacturing specified by the customer is then completed. The finished product is then inspected and shipped.

[edit]Specialties

Many fab shops have specialty processes which they develop or invest in, based on their customers needs and their expertise:

• brazing
• casting
• chipping
• drawing
• extrusion
• forging
• heat treatment
• hydroforming
• oven soldering
• plastic fabrication
• powder coating
• powder metallurgy
• punching
• shearing
• spinning
• English wheeling
• welding

And higher-level specializations such as:

• electrical
• hydraulics
• prototyping/machine design/technical drawing
• sub-contract manufacturing

[edit]See also

• Interchangeable parts
• Steel detailer

Categories: Fabrication (metal)

Quick Oxy-Acetylene Welding Introduction

OPERASI MENGGERUDI

Drilling Operations

The alignment between the headstock and tailstock of the lathe enables you to drill holes that are precisely centered in a cylindrical piece of stock. I tried doing this once with my drill press and vise before I had the lathe; it did not turn out too well.
Before you drill into the end of a workpiece you should first face the end as described in the facing operations section. The next step is to start the drill hole using a center drill - a stiff, stubby drill with a short tip. If you try to drill a hole without first center drilling, the drill will almost certainly wander off center, producing a hole that is oversized and misaligned. We hate that!
Center drills come in various sizes such as #00, #0, #1 - #5, etc. You can purchase sets of #1-#5 for under $5.00 on sale from several suppliers.

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Preparing to Drill

Before drilling you need to make sure that the drill chuck is firmly seated in the tailstock. With the chuck arbor loosely inserted in the tailstock bore, crank the tailstock bore out about 1/2". Lock the tailstock to the ways, then thrust the chuck firmly back towards the tailstock to firmly seat the arbor in the Morse taper of the tailstock. (The chuck is removed from the tailstock by cranking the tailstock ram back until the arbor is forced out).
Choose a center drill with a diameter similar to that of the hole that you intend to drill. Insert the center drill in the jaws of the tailstock chuck and tighten the chuck until the jaws just start to grip the drill. Since the goal is to make the drill as stiff as possible, you don't want it to extend very far from the tip of the jaws. Twist the drill to seat it and dislodge any metal chips or other crud that might keep the drill from seating properly. Now tighten the chuck. It's good practice to use 2 or 3 of the chuck key holes to ensure even tightening (but all three may be impossible to reach given the tight confines of the 7x10).
Slide the tailstock along the ways until the tip of the center drill is about 1/4" from the end of the workpiece and tighten the tailstock clamp nut. The locking lever for the tailstock ram should be just snug - not enough to impede the movement of the ram, but enough to ensure that the ram is as rigid as possible.
  

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Cutting Fluid

Unless I'm working with brass, I nearly always use a cutting fluid when drilling. Particularly with aluminum, which tends to grab the drill, this helps to ensure a smooth and accurate hole. I use Tap Magic brand cutting fluid but there are several other excellent brands available.
 
You only need a few drops at a time, so a small can should last for a long time. I use a small needle tipped bottle to apply fluid to the work. The bottle originally contained light oil & was obtained at Home Depot.

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Center Drilling

Turn on the lathe and set the speed to around 600 RPM. Use the tailstock crank to advance the drill slowly into the end of the workpiece and continue until the conical section of the center drill is about 3/4ths of the way into the workpiece. This is as far as you need to go with the center drill since its purpose is just to make a starter hole for the regular drill. Back the center drill out and stop the lathe.
 

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Drilling the Hole

Loosen the tailstock clamp nut and slide the tailstock back to the end of the ways. Remove the center drill from the chuck and insert a regular drill and tighten it down in the chuck. Slide the tailstock until the tip of the drill is about 1/4" from the workpiece and then lock the tailstock in place. Place a few drops of cutting fluid on the tip of the drill, then start the lathe and drill into the workpiece as before, at 400 to 600 RPM.

After advancing the drill about twice its diameter, back it out of the hole and use a brush to remove the metal chips from the tip of the drill. Add a few more drops of cutting fluid if necessary, then continue drilling, backing the drill out to remove chips about every 2 diameters of depth.

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Measuring Drilling Depth

Unless you are drilling completely through a fairly short workpiece you will generally need a way to measure the depth of the hole so that you can stop at the desired depth. One of the first accessories I made on the lathe is a simple depth gauge - just a small cylinder of brass with a locking screw which slides on a piece of 1/16" drill rod about 3" long. It's quite handy for checking the depth of holes. You can use a shop rule to set the brass slider to the desired depth and then lock it in place with the little set screw.

Another way to measure the depth is to use the graduated markings on the barrel of the tailstock. These are not easy to see, though.

If you need real accuracy, Varmint Al came up with a nifty idea to mount a 1" dial indicator on the tailstock. The tip of the DI touches a plastic plate that is mounted on the tailstock ram. The DI is bolted into a 1/4-20 hole drilled and tapped in the side of the tailstock. If you make this mod to your lathe, remove the ram from the tailstock before drilling the mounting hole for the DI to avoid drilling into the ram.

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Drilling Deep Holes, Blind Holes and Large Holes
In the world of metalwork, a "deep" hole is any hole more than about 3 times the drill diameter. A blind hole is one in which you are not drilling all the way through the workpiece; i.e. the bottom end is closed. The critical thing when drilling such holes is to frequently back the drill completely out of the hole to allow the chips to escape from the hole.  You need to do this repeatedly each time you advance the drill by about twice its diameter.  Failure to follow this procedure will cause the chips to bind in the hole, weld to the drill and create a hole with an uneven and rough diameter. Cutting fluid will also help to keep the chips from binding to the drill or the sides of the hole.
Large holes are relative to the size of the machine and for the mini-lathe, I consider a hole larger than 3/8" to be "large". If you try to drill a large hole, say 1/2" starting with a 1/2" drill, you may not get a nice clean hole because too much material is being removed at one time.  It is better to drill the hole in stages, starting, say, with a 5/16" drill, then a 3/8" and so forth, until you work up to the 1/2" drill for the final pass. This way, the large drill is removing only a small amount of material around the perimeter of the hole and will have a much easier job to do.

PLASMA CUTTING

Metal is necessary for many objects being built but due to its strength, a cutting system needed to be developed.Plasma cutting has been used for years to meet the needs of configuring metals into proper shapes. They are very prevalent in the automotive industry.

• Conceptually, a plasma cutter is extremely simple.
• Many factories working on military aircraft adopted a new method of welding that involved the use of an inert gas fed through an electric arc.
• The breakthrough discovery was that charging the gas with an electric current formed a barrier around the weld, which protected it from oxidation.
• This new method made for much cleaner lines at the joints and much sturdier construction.
• They figured out that they could boost temperatures by speeding up the flow of gas and shrinking the release hole.
• The new system could reach higher temperatures than any other commercial welder. In fact, at these high temperatures, the tool no longer acted as a welder. Instead, it worked like a saw, cutting through tough metals like a hot knife through butter.
• This introduction of the plasma arc revolutionized the speed, accuracy and types of cuts manufacturers could make in all types of metals
  A plasma cutter can pass through metals with little or no resistance thanks to the unique properties of plasma.
• If you boost a gas to extremely high temperatures, you get plasma.
• When the fast-moving electrons collide with other electrons and ions, they release vast amounts of energy. This energy is what gives plasma its unique status and unbelievable cutting power.
• Though cool plasma cannot be used to cut metals, it has tons of other useful applications.
• Plasma cutters come in all shapes and sizes. There are monstrous plasma cutters that use robotic arms to make precise incisions.
• Regardless of size, all plasma cutters function on the same principle and are constructed around roughly the same design.
• Plasma cutters work by sending a pressurized gas, such as nitrogen, argon, or oxygen, through a small channel.
• When you apply power to the negative electrode, and you touch the tip of the nozzle to the metal, the connection creates a circuit.
• As the inert gas passes through the channel, the spark heats the gas until it reaches the fourth state of matter. This reaction creates a stream of directed plasma, approximately 30,000 F (16,649 C) and moving at 20,000 feet per second (6,096 m/sec), that reduces metal to molten slag.
• The plasma itself conducts electrical current.
• The cycle of creating the arc is continuous as long as power is supplied to the electrode and the plasma stays in contact with the metal that is being cut.
• In order to ensure this contact, protect the cut from oxidation and regulate the unpredictable nature of plasma, the cutter nozzle has a second set of channels. These channels release a constant flow of shielding gas around the cutting area.
• The pressure of this gas flow effectively controls the radius of the plasma beam.
• Plasma cutters are now a staple of industry.
• They are used largely in custom auto shops as well as by car manufacturers to customize and create chassis and frames.
• Construction companies use plasma cutters in large-scale projects to cut and fabricate huge beams or metal-sheet goods.
• Locksmiths use plasma cutters to bore into safes and vaults when customers have been locked out.
• In the past, plasma cutters were prohibitively expensive and were used primarily for huge metal-cutting jobs.
• In recent years, the cost and size of plasma cutters have dropped considerably, making them available for more personal projects.
• This single tool gives artists the ability to bevel cuts, bore precise holes and cut in just about any way they can conceive.
• The plasma cutter is one of the most interesting and powerful tools developed in the 20th century. Using basic principles of physics to harness the fourth state of matter, the plasma cutter performs with nearly magical results.

To read the original article please click:

http://science.howstuffworks.com/plasma-cutter.htm

JENIS-JENIS KECACATAN KIMPALAN

Welding Defects

1. Introduction

Common weld defects include:

• i. Lack of fusion
• ii. Lack of penetration or excess penetration
• iii. Porosity
• iv. Inclusions
• v. Cracking
• vi. Undercut
• vii. Lamellar tearing

Any of these defects are potentially disastorous as they can all give rise to high stress intensities which may result in sudden unexpected failure below the design load or in the case of cyclic loading, failure after fewer load cycles than predicted.

2. Types of Defects
i and ii. - To achieve a good quality join it is essential that the fusion zone extends the full thickness of the sheets being joined. Thin sheet material can be joined with a single pass and a clean square edge will be a satisfactory basis for a join. However thicker material will normally need edges cut at a V angle and may need several passes to fill the V with weld metal. Where both sides are accessible one or more passes may be made along the reverse side to ensure the joint extends the full thickness of the metal.
Lack of fusion results from too little heat input and / or too rapid traverse of the welding torch (gas or electric).
Excess penetration arises from to high a heat input and / or too slow transverse of the welding torch (gas or electric). Excess penetration - burning through - is more of a problem with thin sheet as a higher level of skill is needed to balance heat input and torch traverse when welding thin metal.

ii. Porosity - This occurs when gases are trapped in the solidifying weld metal. These may arise from damp consumables or metal or, from dirt, particularly oil or grease, on the metal in the vicinity of the weld. This can be avoided by ensuring all consumables are stored in dry conditions and work is carefully cleaned and degreased prior to welding.

iv. Inclusions - These can occur when several runs are made along a V join when joining thick plate using flux cored or flux coated rods and the slag covering a run is not totally removed after every run before the following run.

v. Cracking - This can occur due just to thermal shrinkage or due to a combination of strain accompanying phase change and thermal shrinkage.
In the case of welded stiff frames, a combination of poor design and inappropriate procedure may result in high residual stresses and cracking.
Where alloy steels or steels with a carbon content greater than about 0.2% are being welded, self cooling may be rapid enough to cause some (brittle) martensite to form. This will easily develop cracks.
To prevent these problems a process of pre-heating in stages may be needed and after welding a slow controlled post cooling in stages will be required. This can greatly increase the cost of welded joins, but for high strength steels, such as those used in petrochemical plant and piping, there may well be no alternative.

Solidification Cracking
This is also called centreline or hot cracking. They are called hot cracks because they occur immediately after welds are completed and sometimes while the welds are being made. These defects, which are often caused by sulphur and phosphorus, are more likely to occur in higher carbon steels.
Solidification cracks are normally distinguishable from other types of cracks by the following features:

• they occur only in the weld metal - although the parent metal is almost always the source of the low melting point contaminants associated with the cracking
• they normally appear in straight lines along the centreline of the weld bead, but may occasionally appear as transverse cracking
• solidification cracks in the final crater may have a branching appearance
• as the cracks are 'open' they are visible to the naked eye

A schematic diagram of a centreline crack is shown below: 
 
On breaking open the weld the crack surface may have a blue appearance, showing the cracks formed while the metal was still hot. The cracks form at the solidification boundaries and are characteristically inter dendritic. There may be evidence of segregation associated with the solidification boundary. 
The main cause of solidification cracking is that the weld bead in the final stage of solidification has insufficient strength to withstand the contraction stresses generated as the weld pool solidifies. Factors which increase the risk include:

• insufficient weld bead size or inappropriate shape
• welding under excessive restraint
• material properties - such as a high impurity content or a relatively large shrinkage on solidification

Joint design can have an influence on the level of residual stresses. Large gaps between conponents will increase the strain on the solidifying weld metal, especially if the depth of penetration is small. Hence weld beads with a small depth to width ratio, such as is formed when bridging a large wide gap with a thin bead, will be more susceptible to solidification cracking.

In steels, cracking is associated with impurities, particularly sulphur and phosphorus and is promoted by carbon, whereas manganese and sulphur can help to reduce the risk. To minimise the risk of cracking, fillers with low carbon and impurity levels and a relatively high manganese content are preferred. As a general rule, for carbon manganese steels, the total sulphur and phosphorus content should be no greater than 0.06%. However when welding a highly restrained joint using high strength steels, a combined level below 0.03% might be needed.

Weld metal composition is dominated by the filler and as this is usually cleaner than the metal being welded, cracking is less likely with low dilution processes such as MMA and MIG. Parent metal composition becomes more important with autogenous welding techniques, such as TIG with no filler.

Avoiding Solidification Cracking
Apart from choice of material and filler, the main techniques for avoiding solidification cracking are:

• control the joint fit up to reduce the gaps
• clean off all contaminants before welding
• ensure that the welding sequence will not lead to a buildup of thermally induced stresses
• choose welding parameters to produce a weld bead with adequate depth to width ratio or with sufficient throat thickness (fillet weld) to ensure the bead has sufficient resistance to solidificatiuon stresses. Recommended minimum depth to width ratio is 0.5:1
• avoid producing too large a depth to width ratio which will encourage segregation and excessive transverse strains. As a rule, weld beads with a depth to width ratio exceeds 2:1 will be prone to solidification cracking
• avoid high welding speeds (at high current levels) which increase segregation and stress levels accross the weld bead
• at the run stop, ensure adequate filling of the crater to avoid an unfavourable concave shape

Hydrogen induced cracking (HIC) - also referred to as hydrogen cracking or hydrogen assisted cracking, can occur in steels during manufacture, during fabrication or during service. When HIC occurs as a result of welding, the cracks are in the heat affected zone (HAZ) or in the weld metal itself.

Four requirements for HIC to occur are:

• a) Hydrogen be present, this may come from moisture in any flux or from other sources. It is absorbed by the weld pool and diffuses int o the HAZ.
• b) A HAZ microstructure susceptible to hydrogen cracking.
• c) Tensile stresses act on the weld
• d) The assembly has cooled to close to ambient - less than 150^oC

HIC in the HAZ is often at the weld toe, but can be under the weld bead or at the weld root. In fillet welds cracks are normally parallel to the weld run but in butt welds cracks can be transverse to the welding direction.

vi Undercutting - In this case the thickness of one (or both) of the sheets is reduced at the toe of the weld. This is due to incorrect settings / procedure. There is already a stress concentration at the toe of the weld and any undercut will reduce the strength of the join.

vii Lamellar tearing - This is mainly a problem with low quality steels. It occurs in plate that has a low ductility in the through thickness direction, which is caused by non metallic inclusions, such as suphides and oxides that have been elongated during the rolling process. These inclusions mean that the plate can not tolerate the contraction stresses in the short transverse direction.
Lamellar tearing can occur in both fillet and butt welds, but the most vulnerable joints are 'T' and corner joints, where the fusion boundary is parallel to the rolling plane.
These problem can be overcome by using better quality steel, 'buttering' the weld area with a ductile material and possibly by redesigning the joint.

3. Detection
Visual Inspection
Prior to any welding, the materials should be visually inspected to see that they are clean, aligned correctly, machine settings, filler selection checked, etc.
As a first stage of inspection of all completed welds, visual inspected under good lighting should be carried out. A magnifying glass and straight edge may be used as a part of this process.

Undercutting can be detected with the naked eye and (provided there is access to the reverse side) excess penetration can often be visually detected.

Liquid Penetrant Inspection
Serious cases of surface cracking can be detected by the naked eye but for most cases some type of aid is needed and the use of dye penetrant methods are quite efficient when used by a trained operator.
This procedure is as follows:

• Clean the surface of the weld and the weld vicinity
• Spray the surface with a liquid dye that has good penetrating properties
• Carefully wipe all the die off the surface
• Spray the surface with a white powder
• Any cracks will have trapped some die which will weep out and discolour the white coating and be clearly visible

X - Ray Inspection
Sub-surface cracks and inclusions can be detected 'X' ray examination. This is expensive, but for safety critical joints - eg in submarines and nuclear power plants - 100% 'X' ray examination of welded joints will normally be carried out.

Ultrasonic Inspection
Surface and sub-surface defects can also be detected by ultrasonic inspection. This involves directing a high frequency sound beam through the base metal and weld on a predictable path. When the beam strikes a discontinuity some of it is reflected beck. This reflected beam is received and amplified and processed and from the time delay, the location of a flaw estimated.
Porosity, however, in the form of numerous gas bubbles causes a lot of low amplitude reflections which are difficult to separate from the background noise.
Results from any ultrasonic inspection require skilled interpretation.

Magnetic Particle Inspection
This process can be used to detect surface and slightly sub-surface cracks in ferro-magnetic materials (it can not therefore be used with austenitic stainless steels).
The process involves placing a probe on each side of the area to be inspected and passing a high current between them. This produces a magnetic flux at right angles to the flow of the current. When these lines of force meet a discontinuity, such as a longitudinal crack, they are diverted and leak through the surface, creating magnetic poles or points of attraction. A magnetic powder dusted onto the surface will cling to the leakage area more than elsewhere, indicating the location of any discontinuities.
This process may be carried out wet or dry, the wet process is more sensitive as finer particles may be used which can detect very small defects. Fluorescent powders can also be used to enhance sensitivity when used in conjunction with ultra violet illumination.

4. Repair
Any detected cracks must be ground out and the area re-welded to give the required profile and then the joint must be inspected again.

WELDING PROSES

Welding

Introduction  A weld occurs when pieces of metal are joined by causing the interface to melt and blend prior to solidifying as a uniform metal joint.   This process may be caused by heat, pressure or a combination of both.   When heat alone is used the process is called fusion welding. Pressure welding usually involves heating the surfaces to a plastic state and then forcing the metal together.   The heating can be by electric current of by friction resulting from moving one surface relative to the other. The methods and equipment used for welding metal are also associated with cutting metal.   There are a large number of welding and allied processes including the following. Welding Processs Gas Welding Arc Welding Brazing Soldering Resistance Welding Solid State Welding Other Welding Allied processes Adhesive Bonding Thermal Spraying Oxygen Cutting Thermal Cutting Arc Cutting Electron Beam Cutting Laser Cutting Calculation relating to welded joints can be found on webpage... Weld Stress Calculations Notes on drawing representations of welds can be found on webpage .. Drawing of Weld Symbols. Manual Metal Arc Welding Process Electric Arc welding is based on providing an electric circuit comprising the Electric current source the feed and return path, the electrode and the workpiece.  The arc welding process involves the creation of a suitable small gap between the electrode and the workpiece.   When the circuit is made a large current flows and an arc is formed between the electrode and the workpiece. The resulting high temperatures causing the workpiece and the electrode to melt    The electrode is consumable.   It includes metal for the weld, a coating which burns off to form gases which shield the weld from the air and flux which combines with the nitrides and oxide generated at the weld.   When the weld solidifies a crust is formed from the impurities created in the weld process (Slag).   This is easily chipped away. MIG & TIG Welding The Metal Inert Gas Process uses a consumable electrode of wire form and an inert gas shield of carbon dioxide when welding carbon steel..  The wire electrode provides a continuous feed of filler metal allowing welds of any length without stopping.   The inert gas shield eliminates slag and allows cleaner and stronger weld..   This process is used widely for automated welding using robots. The Tungsten Inert gas (TIG) system uses a non-consumable electrode of tungsten and also provides an inert gas shield of argon or helium. This process was orginally developed for welding magnesium and it is now used for welding aluminium, copper, stainless steel, and a wide range of other metals that are difficult to weld.  Consumable rods may be used depending on the type of weld and the thickness of weld. Welding process Designations The welding process designations provided below are based on BS EN ISO 4063 and are used when identifying welds to BS EN 22553 1 Arc welding 11 Metal-arc welding without gas protection. 111 Metal-arc welding with covered electrode. 112 Gravity arc welding with covered electrode. 113 Bare wire metal-arc welding. 114 Flux cored wire metal-arc welding. 115 Coated wire metal-arc welding. 118 Firecracker welding. 13 Gas-shielded metal-arc welding 131 MIG welding: metal-arc inert gas welding 135 MAG welding: metal-arc active gas welding 136 Flux-cored wire metal-arc welding with active gas shield 14 Gas-shielded welding with non-consumable electrode 141 TIG welding: tungsten inert gas arc welding 149 Atomic-hydrogen welding 15 Plasma arc welding 18 Other arc welding processes 181 Carbon-arc welding 185 Rotating arc welding 2 Resistance Welding 21 Spot welding 22 Seam welding 221 Lap seam welding 225 Seam welding with strip. 23 Projection welding 24 Flash welding 25 Resistance butt welding 29 Other resistance welding processes 291 HF (High-Frequency) resistance welding 3 Gas welding 31 Oxy-fuel gas welding 311 Oxy-acetylene welding 312 Oxy-propane welding 313 Oxy-hydrogen welding 32 Air-fuel gas welding 321 Air-acetylene welding 322 Air-propane welding 4 Pressure welding 41 Ultrasonic welding 42 Friction welding 43 Forge welding 44 Welding by high mechanical energy 441 Explosive welding 45 Diffusion welding 47 Gas pressure welding 48 Cold pressure welding. Other welding processes 71 Thermit welding 72 Electro-slag welding 73 Electro-gas welding 74 Induction welding 75 Light radiation welding 751 Laser beam welding 752 Arc image welding 753 Infrared welding 76 Electron beam welding 77 Percussion welding 78 Stud welding 781 Arc stud welding 782 Resistance stud welding