What is the difference between post heating of weld and PWHT?

As supplier of piping goods,we often use post heating of weld and PWHT in production.What is the difference between them?

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In post heating, you raised the temperature of the weld joint to a predetermined temperature range (usually 250° C to 350° C) for a minimum period (usually 3 hours) before the weld cools down to room temperature. Post heating performed immediately before weld get cold when welding is completed or terminated any time in between. Post-heating is also known as a Dehydrogenation as it removes entrapped hydrogen from the weld. Post-heating is done to avoid delayed cracking in the weld.

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PWHT that is known as a post weld heat treatment is performed on the completed weld to relieve the stress from the weld joint. This will soften the heat affected zone and reduce the hardness of the weld.

Now you know what post heating and PWHT is,you can answer the difference between post heating and PWHT easily.In one word,post-heating is used to avoid delayed cracking, and PWHT is used to relieve the stress from the joint.

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Haihao Group could provide the piping goods with proper heat treatment methods.If you need related goods,email us to:sales@haihaogroup.com