SHIELDING GASES FOR WELDING

摘要

Welding processes will typically result in melting of the metals at the weld interface before cooling back to room temperature. At high temperatures approaching melting point and in a molten state, the metal atoms are very reactive and can quickly combine with any willing and able gas molecules floating around near the surface to form reaction products that are usually detrimental to the weld. And hence the use of shielding gases during welding - their primary goal is to shield the molten metal. As far as pure shielding goes, the two most commonly used inert gases are Argon and Helium, and are used extensively in practically all welding processes where molten metal is exposed including arc/plasma welding and laser welding. Electron beam welding is an exception since it is performed in vacuum environment. Resistance welding is also an exception where the melt is not exposed and hence does not typically employ any shielding gases, except under unusual circumstances discussed later.