In daily life, welding technology is mainly applied to metal base materials. Arc welding, argon arc welding, CO2 welding, oxygen-acetylene welding, laser welding, electroslag pressure welding, and other non-metal materials are commonly used. Welding is also possible. There are more than 40 kinds of metal welding methods, which are mainly divided into three major categories: welding, pressure welding and brazing. Let ’s take a look with Chengdu welding machine equipment manufacturer Xiaobian:
Fusion welding: It is a method of heating the workpiece interface to a molten state during the welding process and completing welding without applying pressure. During fusion welding, the heat source rapidly heats and melts the interface between the two workpieces to be welded to form a molten pool. The molten pool moves forward with the heat source and forms a continuous weld after cooling to connect the two workpieces into one.
During the welding process, if the atmosphere is in direct contact with the hot pool, oxygen in the atmosphere will oxidize metals and various alloy elements. Nitrogen, water vapor, etc. in the atmosphere enter the molten pool, and defects such as pores, slag inclusions, and cracks are formed in the weld during subsequent cooling, which deteriorates the quality and performance of the weld.
Pressure welding: Under pressure conditions, the two workpieces are bonded in the solid state to achieve atomic bonding, also known as solid state welding. The common pressure welding process is resistance butt welding. When the current passes through the connection end of the two workpieces, the temperature rises because of the large resistance. When heated to a plastic state, the connection becomes a whole under the action of axial pressure.
A common feature of various pressure welding methods is the application of pressure during the welding process without the addition of filler materials. Most pressure welding methods, such as diffusion welding, high frequency welding, and cold welding, do not have a melting process, so there is no problem with the burning of beneficial alloy elements and the intrusion of harmful elements into the weld, such as welding, which simplifies the welding process. Improved welding safety and health conditions. At the same time, because the heating temperature is lower than welding and the heating time is short, the heat affected zone is small. Many materials that are difficult to weld by fusion welding can often be welded by pressure welding into high-quality joints with the same strength as the base metal.
Brazing: the use of a metal material with a lower melting point than the workpiece as the brazing material, heating the workpiece and the solder to a temperature higher than the melting point of the solder, lower than the melting point of the workpiece, using a liquid solder to wet the workpiece, filling the interface gap and the workpiece A method for achieving mutual diffusion between atoms and thus welding.
The seam formed between two connected objects during welding is called a weld. Both sides of the weld seam will be subjected to welding heat during welding, and the structure and properties will change. This area is called the heat affected zone. Due to different welding materials and welding currents during welding, overheating, embrittlement, hardening or softening may occur in the weld and heat affected zone after welding, which also reduces the performance of the weldment and deteriorates the weldability. This requires adjustment of welding conditions. Pre-heating of the weldment interface before welding, heat preservation during welding, and post-weld heat treatment can improve the welding quality of the weldment.