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MIG Welding vs. TIG Welding – A Complete Comparison

MIG WELDING VS. TIG WELDING – A COMPLETE COMPARISON

MIG (Metal Inert Gas) and TIG (Tungsten Inert Gas) welding are both methods of joining metals that employ shielding gas to protect the forming and solidifying joints from the atmosphere. These two processes differ in this manner from stick welding, where the burning flux surrounding the electrode provides a protective cloud over the weld area.

The three techniques are collectively known as arc welding and use the heat generated from electric arcs to liquefy metal. Stick welding is more formally called Shielded Metal Arc Welding, or SMAW, while MIG is known as Gas Metal Arc Welding or GMAW, and TIG is known as Gas Tungsten Arc Welding or GTAW. These three techniques progress toward more and more control and more and more precision, with corresponding increases in equipment costs. Stick welding is perhaps the crudest of the three but has tremendous application in structural steel work, heavy machinery fabrication, pipelining, construction equipment repair, digging/cutting tool resurfacing, and so on. A primary advantage of stick welding, besides its simplicity, is its usefulness in outdoor settings where the burning flux shielding is not disturbed by the wind.

This article briefly describes the distinction between the two inert gas welding methods, MIG Welder and TIG Welder.

MIG Welding

There is some historical discussion as to whether the “M” in MIG stands for Metal, as is commonly accepted, or Mechanized, which it truly is. In this mechanized process, the electrode is fed automatically into the weld pool as the welder holds down a trigger. The welder need only move the MIG gun along the joint and the MIG machine feeds the welding wire while dispensing an atmosphere of inert gas over it. Let off the trigger and the process stops. There is no smoke from burning flux, no slag covering the joint after it solidifies, and no need for the welder to manually feed the electrode into the puddle as it is consumed – three characteristics associated with stick welding.

Of course, there is some complicated setup involved. Welding wire is sold on spools and is created not only in a range of diameters but in a range of materials just as stick welding electrodes are. The rollers that feed the welding wire from the spool up to the gun must be sized according to the wire diameter as must the tip of the gun where the wire comes out. Softer metals such as aluminum do not feed well from the machine up to the gun and so require a separate attachment that locates the spool feeder closer to the gun itself. The welder needs to select an appropriate amperage (as with stick welding) as well as a feed rate based on the size of the weld and the thickness of the material. Most of this information is codified so as to provide a starting point.

The selection of shielding gas and its flow rate is also important. Different gas mixes are used for different metals. Flow rates are adjusted based on travel speed, among other factors, and some gas must continue to flow onto the joint after the welding has ceased to insure coverage as the metal solidifies. A major advantage of MIG welding over stick welding is the efficiency of material use. The MIG welder can theoretically weld continuously until the spool runs out; the stick welder must grab a new stick every few inches and clean the slag off at the restart. Those little stub ends that the stick welder must throw away, an inch or two each time, can add up to significant material waste over the course of many welds.

Some claim that MIG welding is the easiest of the three processes to learn: if you can caulk you can MIG, they say. While that may be true in terms of one less factor to deal with, that of manually feeding the filler metal into the joint, there is quite a lot of technique and knowledge that goes into executing a sound MIG weld, as pretty as the weld itself may be. In reality, there are four types of MIG processes: short-circuit transfer, spray transfer, pulsed spray-transfer, and globular transfer.

MIG welding is used to weld steel, stainless steel, and aluminum. Stainless steel usually requires a 90%/7.5%/2.5% helium/argon/carbon dioxide mix while straight argon or argon/helium blends are used for welding aluminum.

TIG Welding

The high melting point of tungsten allows it to produce an arc hot enough to melt steel without consuming itself. A separate filler rod is used to add material to the weld joint. TIG welding is thus a two-hand process and not mechanized, although a wire feeder may also be used. A footswitch is available to further complicate matters.

It is the footswitch that gives the welder minute control of what happens in the weld pool, or puddle. The amount of heat going into the metal can be varied by simply stepping on or letting off of the “gas,” controlling the amperage of the arc. This control allows for the joining of very thin metals—think beer can thin—without burn through. Likewise, with manual manipulation of the filler rod, the welder has very many variables under direct control. As with MIG, shielding gas flows out through the nozzle of the TIG torch. The torch itself requires cooling of some sort.

It is easy to understand why TIG is the most difficult of the three processes to learn. Tungsten electrodes need to be properly ground and maintained. Special techniques such as “walking the cup” may be employed to produce some strikingly beautiful welds. As with MIG welds, aesthetics only run skin deep. TIG welding is used to produce welds that are extremely clean, as might be appropriate to a piping system that handles highly purified chemicals.

TIG welding can be used to weld steel, stainless steel, aluminum, nickel alloys, magnesium, copper, brass, and bronze. Gas mixes similar to those used for MIG welding are employed.

Summary

This article presented a brief discussion of MIG and TIG welding. For more information on related products, consult our other guides or visit our specific welding equipment products.

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