Post-heating is not a heat treatment, but also a slow cooling measure. The post-heating temperature is 200-300 degrees, some are just for slow cooling, and some are for hydrogen elimination. A certain post-heating temperature can make the hydrogen in the weld diffuse out, so as not to accumulate and produce cracks. The post-heat preservation time should be determined according to the thickness of the workpiece, generally not less than 0.5 hours.
There are many kinds of post-weld heat treatment, which are mainly divided into four types:
Post-weld heat treatment, such as stress relief annealing, is carried out below the lower transition temperature of 1, generally between 600 and 700, with the main purpose of eliminating welding residual stress.
2. Post-weld heat treatment above the upper transition temperature, such as normalizing, the temperature is between 950- 1 150, the grain is refined, the mechanical properties of the material are improved, and the temperature is around 1050, such as solid solution stabilization treatment of stainless steel, which improves the corrosion resistance of stainless steel. Especially the ability to resist intergranular corrosion. Another example is quenching. Different quenching processes can get different effects and improve the wear resistance and hardness of steel.
3. First, the heat treatment is carried out above the upper transition temperature, and then the heat treatment is carried out below the lower transition temperature. Such as normalizing tempering, quenching tempering, etc.
4. Post-weld heat treatment between upper and lower transition temperatures. Between 750 and 900, the practical effect of some materials strengthens recrystallization annealing and so on.
Want to know more, I suggest to find some books to read. It's not easy to go into too many details.
Everyone criticizes mistakes! thank you