At the pipeline prefabrication production or construction site, post heat treatment and post welding heat treatment(PWHT) are often encountered. Which one should be used and what is the difference between them?

Although post heat treatment is also a post weld heating and holding time, it is not the same as post weld heat treatment. They has some difference.The first is their purposes are different. The post heat treatment is to eliminate hydrogen, and the post weld heat treatment is to eliminate welding residual stress and improve the structure and performance of the joint. In the case of heat treatment immediately after welding, it also has the function of hydrogen elimination, so it can be exempted from hydrogen elimination.

Prefabrication pipeline

Second, the heating temperature is different. The heating temperature of PWHT is at least 400 ℃, and the temperature of PWHT is 200-350 ℃.

Third,Measures after heat preservation are different,post heat treatment is to cover with heat preservation cotton and let it cool to room temperature slowly. Post weld heat treatment is to let it cool to room temperature in still air when come out from furnace.

Pipeline prefabrication products

At last,the heating time is different too.Post heat treatment request min 30 minutes.PWHT request longer heating time.

After you are familiar with the concepts, functions, and purposes of post-heat and post-weld heat treatment, as well as the processing methods, you can clearly understand the differences.As professional supplier of pipeline prefabrication and weldment, Hebei HaiHao Group accept all kinds welding works.Welcome your inquiry.Email:sales@haihaogroup.com