Argon arc welding argon shielded welding. Argon arc shielding gas is introduced around arc welding to isolate the air from the welding zone and prevent the welding zone from oxidation. According to the difference of covered electrode, argon arc welding can be divided into two types: melting argon arc welding and non-melting argon arc welding. 1. Working principle and characteristics of non-melting argon arc welding. Non-melting electrode argon arc welding is that the arc burns between the non-melting electrode (generally tungsten electrode) and the workpiece, and inert gas (generally argon gas) which does not react with the metal flows around the welding arc to form a protective gas cover, so that the tungsten tip, the arc, the molten pool and the metal at high temperature do not contact with air, which can prevent oxidation and absorb harmful gases. So as to form a dense welded joint with excellent mechanical properties. 2. Working principle and characteristics of 2.MIG welding: the welding wire is fed through the wire wheel, and the conductive nozzle conducts electricity, so that an arc is generated between the base metal and the welding wire, so that the welding wire and the base metal are melted, and the arc and the molten metal are welded with inert gas argon. Different from TIG welding: one is that the welding wire is used as the electrode, which is continuously melted and filled into the molten pool, and then condensed to form a weld; The other is protective gas. With the application of MIG welding technology, shielding gas has developed from a single argon gas to a variety of mixed gases, such as argon-rich shielding gas with Ar 80%+CO220%. Usually the former is called MIG and the latter is called MAG. Judging from its operation mode, semi-automatic MIG welding and argon-rich gas shielded welding are the most widely used at present, followed by automatic MIG welding. Compared with TIG welding, MIG welding has the following characteristics. (1) has high efficiency because of its high current density, concentrated heat, high deposition rate and fast welding speed. In addition, it is easy to arc. (2) Protection needs to be strengthened. Due to strong arc and heavy smoke, protection should be strengthened.