1) Fusion welding

During the fusion welding process, if the atmosphere comes into direct contact with a high-temperature molten pool, the oxygen in the atmosphere will oxidize metals and various alloy elements. Nitrogen, water vapor, and other substances in the atmosphere enter the molten pool, and during the subsequent cooling process, defects such as pores, slag inclusions, and cracks are formed in the weld seam, deteriorating the quality and performance of the weld seam.

In order to improve welding quality, various protection methods have been developed. For example, gas shielded arc welding uses gases such as argon and carbon dioxide to isolate the atmosphere, in order to protect the arc and molten pool rate during welding; For example, when welding steel, adding titanium iron powder with high oxygen affinity to the electrode coating for deoxygenation can protect the beneficial elements such as manganese and silicon in the electrode from oxidation and entering the molten pool. After cooling, high-quality welds can be obtained.

2) Pressure welding

Pressure welding is the process of achieving atomic bonding between two workpieces in a solid state under pressure conditions, also known as solid-state welding. The commonly used pressure welding process is resistance butt welding. When the current passes through the connecting end of two workpieces, the temperature increases due to the high resistance. When heated to a plastic state, it is connected under axial pressure to form a whole.

The common feature of various pressure welding methods is to apply pressure during the welding process without adding filler material. Most pressure welding methods, such as diffusion welding, high-frequency welding, and cold pressure welding, do not have a melting process, so there is no problem of beneficial alloy element burning and harmful element intrusion into the weld seam, which simplifies the welding process and improves welding safety and hygiene conditions. Meanwhile, due to the lower heating temperature and shorter heating time compared to fusion welding, the heat affected zone is small. Many materials that are difficult to weld with fusion welding can often be welded into high-quality joints with the same strength as the base material using pressure welding.

3) Brazing