Welding process specification for electric soldering iron
1) Fusion welding
Fusion welding is a method of heating the workpiece interface to a molten state during the welding process, and completing the welding without applying pressure. During fusion welding, the heat source rapidly heats and melts the interface between the two workpieces to be welded, forming a molten pool. The molten pool moves forward with the heat source and forms a continuous weld after cooling, connecting the two workpieces into one.
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
Brazing is a method of using metal materials with a lower melting point than the workpiece as brazing material, heating the workpiece and brazing material to a temperature higher than or lower than the melting point of the workpiece, wetting the workpiece with liquid brazing material, filling the interface gap, and achieving atomic diffusion with the workpiece, thereby achieving welding.
The joint formed during welding that connects two connected bodies is called a weld seam. The two sides of the weld seam are subjected to welding heat during welding, resulting in changes in microstructure and properties. This area is called the heat affected zone. During welding, due to differences in workpiece material, welding material, welding current, etc., overheating, embrittlement, hardening, or softening may occur in the weld seam and heat affected zone after welding, which can also lead to a decrease in the performance of the weldment and deteriorate its weldability. This requires adjusting the welding conditions. Preheating at the interface of the welded part before welding, insulation during welding, and post weld heat treatment can improve the welding quality of the welded part.
