TIG Welding Topics
TIG Welding Systems
TIG Welding Aluminum (AC)
TIG Welding with DC
Pulsed TIG Welding
TIG Torches (Air vs. Water Cooled)
TIG Welding Safety
TIG Welding Problems
TIG Welding Definitions
GTAW: Gas Tungsten Arc Welding (aka: TIG Welding)
The American Welding Society classifies this process as Gas Tungsten Arc Welding, abbreviated GTAW. In the shop, most welders refer to it as TIG and some veterans may still call it HeliArc. I've even heard it called Atomic Welding because of it's use in nuclear applications. Whatever your preference, all of these terms refer to this highly-capable and precise welding process that can weld more metals and alloys than any other conventional type of arc welding.
TIG Welding Basics
TIG welding uses an electric arc welder to create a welding arc between the tungsten electrode in the torch and the work or "ground." Usually an inert shielding gas like Argon or Helium is used to shield the electrode and weld pool from the atmosphere. This gas flows through the torch during welding and is critical to the process because the atmosphere contains gases like oxygen, hydrogen and CO2 (carbon dioxide) that can cause problems like oxidation and porosity in the weld. TIG welding is considered a "clean" process because there's no flux or slag and no sparks or spatter generated by the process. For this reason, it's used in the most critical of applications like aerospace, tool & die, petro-chemical, bio-pharmaceutical and food processes. It's very aesthetic - which means it has a nice, consistent appearance so it lends itself well to any application where cosmetic appearance is important. Because it can weld so many materials - you see TIG used in almost every industry.
TIG welding Current & polarity
Most metals are welded using DC or direct current. Electrode negative or straight polarity us most common because it causes the least amount of erosion to the tungsten electrode - so it keeps a sharp point. Electrode positive or reverse polarity tends to heat and ball up the tungsten, even at low amperages - so it's not practical to use except for specialized applications. So, if you plan to weld steel, stainless, nickel, copper and even gold alloys - you need a DC welding machine with a proper "TIG Rig" to get the job done.
AC or alternating current is mainly used for welding white metals like aluminum and magnesium. That's because it alternates between EN and EP, which helps to provide oxide cleaning action that can hinder welding on these alloys. The reason? Both of these metals contain unique surface oxides that melt at a higher temperature than the base metal. Electrode positive creates a surface etching or cleaning action that helps to remove those surface oxides so you can form a weld puddle. EP does generate heat and balling of the tungsten, but the nature of alternating current reduces the erosion to a manageable level.
If you plan to weld all metals, you need use a welding machine that's capable of both AC and DC output. Sure, you can weld aluminum with DC - but it's a highly specialized process that requires ultra-pure helium and special techniques. That's an advanced topic for discussion elsewhere. Just keep in mind, it can be done.