Question

the combination of which gas is generally used in the gas welding which are effective on small scale
and the process to form that gas ​

Answer 1

Argon is the common shielding gas, widely used as the base for the more specialized gas mixes. Carbon dioxide is the least expensive shielding gas, providing deep penetration, however it negatively affects the stability of the arc and enhances the molten metal's tendency to create droplets (spatter)

Shielding gases for GTAW are pure. Normally, an argon-rich mixture with either oxygen or carbon dioxide as the minor gas component is used forwelding carbon steels, while a helium and argon mixture is used to weld aluminum, stainless steel, and other nonferrous metals.