Welding preheating process

　　Welding preheating is the process before high frequency welding or submerged-arc welding process for producing welded steel pipes. When the environment temperature is too low, welding preheating process is quite necessary. Besides, this process is widely applied for the weldments has large thickness, high strength level, hardening tendency, and good thermal conductivity.

　　In general, the welding preheating is applicapable in the welded seam areas or the whole steel pipes. For example, during the ERW Steel Pipes manufacturing process, the welding preheating process will be only applied in the welded seam areas.

　　The purpose of the welding preheating process is to reduce the cooling speed of the welded joints and preheating temperature. Welding preheating can reduce the cooling speed, but it will not influence the high temperature maintaining time. Therefore, in order to decreases the hardening tendency, applying welding preheating process to reduce the cooling rate is significant.

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