Is Post Weld Heat Treatment for dismilar materials required?

[SukhpalSingh]

Did I need to perform the post weld heat treatment for weled dismilar materials (low alloy steel and stainless steel) which were welded by EN NiCr3 electrode? and Where can I find the subject in the literature?

 

[metengr]

The requirement for PWHT of DMW's and similar base material welds is either by a construction code, standard or by client request based on expected service conditions.

Typically my simple view is if either of the base materials being joined can be hardened by heat treatment or air cooling than PWHT should be considered regardless of filler metal.

Look up PWHT of steels and you will find lots of information and guidance.

 

[EdStainless]

IF the steel is hardenable, yes you do. If you check hardness in the HAZ or near weld and it is higher than the base metal you would want to PWHT. Now doing it without damaging the SS can be a trick.
This is why some people will put a Ni alloy pass on the CS (buttering) and then PWHT, and then weld to the SS.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

Unfortunately, blanket statements can lead one into trouble. Thickness of the base material plays an important role just like hardening in deciding the need for PWHT. Many carbon and low alloy steels which can harden by cooling can be welded with no PWHT because below a certain thickness, tempering or softening will occur from weld passes in multi-pass welds with adequate preheat. There is nothing easy about this and one size does not fit all. Refer to recognized codes and standards for information regarding preheat and the need for PWHT.

 

[weldstan]

When Codes are not absolute with regard to PWHT, the service and or repair geometries should dictate the need when using nickel base alloy weld filler metals. As metengr stated, there are methods of welding that can be used to assure sound welds without PWHT.