Stainless steel laser welding machine heat treatment after welding

In the laser welding process of stainless steel, the welding thickness is 0.2--8mm, the width is 0.5-1.8m, high, medium and low carbon steel and stainless steel, and the welding speed is 1-10m/min. Generally, post-weld heat treatment is required, especially for martensitic and ferritic stainless steels. Choosing the correct pre-weld preheating and post-weld treatment is a necessary condition to ensure the welding quality of laser welding machines. How to conduct post-weld heat treatment of stainless steel?

 
Laser welding is an efficient and precise welding method that uses a high-energy-density laser beam as a heat source for welding. The effect of post-weld heat treatment on the tensile strength and creep limit of stainless steel is related to the heat treatment temperature and holding time. The effect of post-weld heat treatment on the impact toughness of stainless steel varies with different steel types. The post-weld heat treatment process of stainless steel generally adopts high temperature tempering or normalizing plus high temperature tempering:

1. Normalizing and high temperature tempering
 
Gas welded joints are heat treated by normalizing and high temperature tempering. This is because the grains in the gas weld and heat-affected zone are coarse, and the grains need to be refined, so normalizing treatment is adopted.
 
2. Single high temperature tempering
 
However, single normalizing cannot eliminate residual stress, so high temperature tempering is required to eliminate stress. Single medium temperature tempering is only suitable for assembly welding of large ordinary low-carbon steel vessels assembled on site, and its purpose is to achieve local elimination of residual stress and dehydrogenation. In most cases, a single high temperature temper is used. Heat treatment heating and cooling should not be too fast, and the inner and outer walls are uniform.

 
Post-weld heat treatment can eliminate the residual stress of stainless steel relaxation welding; stabilize the shape and size of the structure, reduce deformation; improve the plasticity of the weld metal; improve fatigue strength; improve stress corrosion resistance; prevent delayed cracks, etc., so stainless steel after welding Heat treatment is very important.

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