PWHT ( Stress Relieves) ASTM A 537 class 1

[sadminto6]

Hello, I have a Question :
After we perform PWHT (stress relieve annealing),is there any decrease of tensile strenght of material, if yes ,how many percent decrease? Thanks
Note :
Material : ASTM A-537 class 1, stress relieve temperature @ 595º (ref ASME –III div. 2) :Equipment : Spheical Tank, Thickness :40 mm

 

[metengr]

The Class 1 steel is supplied normalized based on the SA material specification. Assuming a subcritical PWHT because of welding or possibly to remove forming strains, there should be no appreciable drop in the base metal tensile properties. The regions effected will be the base metal HAZ and weld metal, or where forming strains were concentrated, which will soften but still remain above the minimum tensile properties for SA 537.

Keep in mind, the code only requires the minimum tensile properties are met, and typically the approved material specifications when subjected to sub-critical heat treatments (like PWHT or thermal to remove forming strains), end up still exceeding the minimum requirements.

 

[metengr]

One point to add is that multiple PWHT cycles, where time at temperature extends beyond the hour/inch minimum because of anticipated repeat weld repairs or due to fabrication constraints with heat treatment cycles can result in reduced tensile properties or effect notch toughness behavior. This is why the Code will require qualification of a WPS having multiple or time-extended PWHT cycles to evaluate the change in tensile and notch toughness properties.

 

[sadminto6]

Thanks for your replied