The Basics of TIG and MIG Welding

TIG and MIG welding custom sheet metal fabrication prototypesTIG and MIG welding are two of the most common arc welding processes. But what exactly do these abbreviations mean?

To better understand the two terms, let’s start by defining what arc welding is.

Arc welding is one of the several fusion methods for joining metals. Usually, two metals are brought together and intense heat applied at the point where they join causing metal at this joint to melt and intermix either directly or with an intermediate filler metal. As the joint cools, it solidifies creating a metallurgical bond. These bonds, having been created by mixing the two metals, will potentially have the same strength properties of the parent metals. Arc welding is therefore different from non-fusion processes such as soldering and brazing in which the physical and mechanical properties of bonds formed at joints don’t duplicate the properties of the parent metals.

Tungsten Inert Gas (TIG) welding

Tungsten Inert Gas welding also commonly known as Gas Tungsten Arc Welding (GTAW) uses a non-consumable tungsten or alloy of tungsten as the electrode. A filler metal may or may not be used.

Tungsten is used because among pure metals it has the highest melting point (3,422°C). The name TIG actually comes from the tungsten electrode and the inert gas (usually argon or helium) surrounding this tungsten. TIG welding is predominantly used in magnesium, stainless steel, copper, and titanium and can also be used for two dissimilar metals. It is also handy for tricky welds such as S-Curves or when welding around things.

When performed by skilled operators, TIG welding can produce some of the highest quality welds. This is partly because of the greater control afforded to the operator. All material used in the process must also be very clean and free of oil, moisture, and dirt. The level of heat applied must be high enough for greater penetration and thus stronger welds.

Special requirements for aluminum welding

For aluminum welding, the tungsten should be either pure tungsten or zirconium tungsten and must be ball shaped at its end. Aluminum welding also requires A/C electricity from start to finish.

TIG welding certifications

GTAW welders have to sit and pass several TIG related courses. Basically, a TIG welding certificate indicates that one can perform production and maintenance on aluminum, mild steel and stainless steel; weld positions on corners, edges, and lap welds; read blueprints; understand different welding symbols; and pass GTAW welding tests in the future.

Metal Inert Gas (MIG) welding

Metal Inert Gas (MIG) welding also popular as Gas Metal Arc Welding (GMAW) is not very different from TIG welding except for the use of consumable tungsten in place of a non-consumable tungsten electrode. The consumable wire acts as the anode and the metal being welded becomes the cathode. An electric current is passed though the tungsten and onto the work-piece metal causing it to melt and join. There are four sub-categories of MIG welding namely; Spray, Pulse-sprayed, Short Circuiting, and Globular MIG. A major advantage of MIG welding is that it’s very easy to learn.

Special requirements for aluminum welding

While MIG welding is arguably simpler than TIG welding, you’ll still need basic welding knowledge even just for setting up the machinery. MIG welding also requires that the welding surface be very clean. Welding a dirty, rusty, painted or coated surface will usually result in a weak weld. For aluminum, thicker materials are the best. Welding out of position requires very highly skilled welders.

MIG welding is often the best for tack welding.

MIG welding certifications

Every MIG welder needs the GMAW or MIG 3G welding certificate. The certification qualifies a welder to work on vertical, horizontal and flat positions; 1G, 2G, and 3G positions; and 1F, 2F, and 3F positions.