Metal welding, according to the characteristics of its process is divided into welding, pressure welding and brazing three major categories.

In the process of welding, if the atmosphere is directly in contact with the molten pool of high temperature, oxygen in the atmosphere will oxidize metal and various alloying elements. The nitrogen and water vapour in the atmosphere enter the molten pool, and the defects such as blowhole, slag and crack in the weld can be formed in the subsequent cooling process, which deteriorates the weld quality and performance.

In order to improve the welding quality, various protection methods have been studied. For example, gas shielded arc welding is the use of argon, carbon dioxide and other gases to isolate the atmosphere, in order to protect the arc and molten pool rate of welding, such as steel welding, in the electrode skin to add oxygen affinity to the titanium iron powder for deoxidation, you can protect the useful elements manganese, silicon, etc. from oxidation into the molten pool, cooling to obtain high-quality weld.