Post weld heat treatment 2

[chimpchoker123]

What is the recommended temperature to PWHT below a materials tempering temperature? Some opinions have it as -20c below tempering temperature, others say 50 degrees below tempering temperature, suspect incorrect PWHT may result in poor charpy values ie to low.

 

[metengr]

chimpchoker123;
Typically, the PWHT temperature should be below the original tempering temperature of the metal to avoid softening or reducing the desired strength level from the original specified heat treatment. If the PWHT is too low, you will not achieve the desired ductility and notch toughness.

I normally use original tempering temperature – 50 deg F for electric resistance heaters or furnace controlled PWHT. If a torch is used, I specify original tempering temperature -100 deg F.

 

[MikeMet]

Because you don't know the calibration of the furnace that was used to perform the original tempering I recommend you stay 100 deg. F below the tempering temperature listed on the CMTR. Typically a good heat treat vendor should hold a +/- 25 deg. F on the original temper temp if done correctly, but you never know. If mechanical properties are critical, stay 100 deg. F below and soak longer.