Welding New

7/29/2019 Welding New

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TIG welding

TIG is also referred to as GTAW (Gas Tungsten Arc Welding) and Heliarc. MIG also isreferred to as GMAW (Gas Metal Arc Welding).

TIG welding is also called Heliarc welding. Heliarc was the trade name given to theprocess by Linde's when it was introduced decades ago. The arc is started with a tungsten

electrode shielded by inert gas and filler rod is fed into the weld puddle separately. The gasshielding that is required to protect the molten metal from contamination and amperage aresupplied during the TIG welding operation.

TIG welding is a slower process than MIG, but it produces a more precise weld and can beused at lower amperages for thinner metal and can even be used on exotic metals. TIG

welding is a commonly used high quality welding process. TIG welding has become a

popular choice of welding processes when high quality, precision welding is required. TheTIG welding process requires more time to learn than MIG.

Characteristics of the TIG welding process

TIG:

Uses a non-consumable tungsten electrode during the welding process,

Uses a number of shielding gases including helium (He) and argon (Ar), Is easily applied to thin materials, Produces very high-quality, superior welds,

Welds can be made with or without filler metal, Provides precise control of welding variables (i.e. heat), Welding yields low distortion, Leaves no slag or splatter.

In TIG welding, an arc is formed between a non-consumable tungsten electrode and the

metal being welded. Gas is fed through the torch to shield the electrode and molten weldpool. If filler wire is used, it is added to the weld pool separately.

The illustration that follow provide a schematic showing how the TIG welding process works.


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The most common TIG welds are illustrated below. They include the:

butt joint, lap joint, T-joint, and Fillet weld.

The following illustration shows these TIG-welded joints:

The TIG welding process utilizes a number of shielding gases including:

argon

argon/helium, and helium

Argon is superior for welding metals. It operates at a higher arc voltage, makes the arc startmore easily, and is commonly used to weld mild steel, aluminum and titanium.

Helium is generally added to increase heat input (increase welding speed or weldpenetration) and is used for high speed welding of mild steel and titanium. Helium offers a

smaller heat affected zone and therefore, penetrates metals deeply. It also can increase thewelding speed up to 40%. Helium is also commonly used to weld stainless steel and copper.

The argon/helium combination gas is used for a hotter arc in welding aluminum andaluminum alloys. It is also used in automatic welding applications.


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Even though TIG is a commonly used welding process, there are a number of limitations.These include:

TIG requires greater welder dexterity than MIG or stick welding,

TIG yields lower deposition rates, TIG is more costly for welding thick metal sections.

MIG welding

Advantage Fabricated Metals performs a number ofwelding processes. The two mostcommon welding processes we use includeTIG, an acronym for Tungsten Inert Gas welding

and MIG, an acronym for Metal Inert Gas welding. TIG is also referred to as GTAW (GasTungsten Arc Welding) and Heliarc. MIG also is referred to as GMAW (Gas Metal ArcWelding). We also provideoxy-acetylene welding.

The "Metal" in Gas Metal Arc Welding refers to the wire that is used to start the arc. It isshielded by inert gas and the feeding wire also acts as the filler rod. MIG is fairly easy tolearn and use as it is a semi-automatic welding process.

Characteristics of the MIG welding process

MIG:

Uses a consumable wire electrode during the welding process that is fed from a

spool, Provides a uniform weld bead, Produces a slag-free weld bead,

Uses a shielding gas, usually argon, argon - 1 to 5% oxygen, argon - 3 to 25%

CO2 and a combination argon/helium gas,

Is considered a semi-automatic welding process, Allows welding in all positions,

Requires less operator skill than TIG welding, Allows long welds to be made without starts or stops, Needs little cleanup.

The illustration that follows provides a look at a typical MIG welding process showing an arcthat is formed between the wire electrode and the workpiece. During the MIG welding

process, the electrode melts within the arc and becomes deposited as filler material. Theshielding gas that is used prevents atmospheric contamination from atmosphericcontamination and protects the weld during solidification. The shielding gas also assists with

stabilizing the arc which provides a smooth transfer of metal from the weld wire to themolten weld pool.
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Versatility is the major benefit of the MIG welding process. It is capable of joining most

types of metals and it can be performed in most positions, even though flat horizontal is

most optimum.

The most common welds are illustrated below. They include the:

lap joint

butt joint T-joint, and the edge joint

MIG is used to weld many materials, and different gases are used to form the arc dependingon the materials to be welded together. An argon CO2 blend is normally used to weld mild

steel, aluminum, titanium, and alloy metals. Helium is used to weld mild steel and titanium

in high speed process and also copper and stainless steel. Carbon dioxide is most often usedto weld carbon and low alloy steels. Magnesium and cast iron are other metals commonly

welded used the MIG process.

Shielded Metal Arc Welding (SMAW) is frequently referred to as "stick" or "coveredelectrode" welding. Stick welding is among the most widely used welding processes.

The flux covering on the electrode melts during welding. This forms the gas and slag to

shield the arc and molten weld pool. The slag must be chipped off the weld bead afterwelding. The flux also provides a method of adding scavengers, deoxidizers, and alloyingelements to the weld metal.


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When an arc is struck between the metal rod (electrode) and the workpiece, both the rod

and workpiece surface melt to form a weld pool. Simultaneous melting of the flux coating onthe rod will form gas and slag which protects the weld pool from the surrounding

atmosphere. The slag will solidify and cool and must be chipped off the weld bead once theweld run is complete (or before the next weld pass is deposited).

The process allows only short lengths of weld to be produced before a new electrode needs

to be inserted in the holder. Weld penetration is low and the quality of the weld deposit ishighly dependent on the skill of the welder.

Process characteristics of Shielded Metal Arc Welding (SMAW/Stick)

SMAW welding:

Uses a electrode rod that is quickly consumed,

Uses equipment that is simple, inexpensive, and highly portable, Uses an electrode that provides and regulates its own flux, Provides all position flexibility,

Is less sensitive to wind or drafts, Yields a weld with a variable quality and appearance based on operator skill,


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During the SMAW welding process the arc is established, the flux coating on the rod

disintegrates and then forms a gas that shields the weld from the atmosphere. The slag thatis produced by the flux coating prevents the weld metal from oxidizing.

Equipment required to perform the SMAW welding process includes a constant current

power source that supplies the power to the consumable rod electrode.

The SMAW welding process typically is capable of producing three types of welded joints.They are:

Butt joint

Lap joint, T-joint, and Fillet weld.

The illustration below shows these four common welded joints.

Flux-coated electrodes are available in many core wire diameters and lengths. Matching theelectrode properties to the base materials as a general rule for choosing the type of

electrode. Available electrodes types include aluminum bronze, bronze, mild steel, nickel,and stainless steel.

Materials commonly welded using the SMAW process include mild steel, cast iron, andstainless steel.


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