Tempering and PWHT
Tempering and PWHT
(OP)
We welded some SA333 Gr.6 pipe and subsequently performed post weld heat treatment at 1100F per UCS-56. The actual temperature maxed out at just under 1175F. The material test reports for the material show that it was tempered at a minimum temperature of 1050F. We have a customer that is saying we must provide new test results for the mechanical properties on the MTR because the PWHT temperature was higher than the tempering temperature. I have never heard of this before and it doesn't make sense to me. I've looked through Sections II, VIII Div.1 and IX and cannot find supporting evidence for either side. Can anyone help me?
thanks.
thanks.





RE: Tempering and PWHT
No, this is not the case. ASME code rules for PWHT are based on establishing a minimum ductility and strength level. Tempering at lower temperature does provide increased strength above the minimum but ASME does not give credit for increased strength above the minimum requirement in the material specification. So, your customer is incorrect in their assumption.
RE: Tempering and PWHT
RE: Tempering and PWHT
Can you demonstrate that your PQR test coupon underwent the same heat treatments? If so, they might buy that off as proof enough.
RE: Tempering and PWHT
If material is manufactured to an SA specification with no specified tempering temperature in the specification other than what is agreed upon as suitable (review SA 333) why would I need to void this material or conduct mechanical property tests for an MTR?
Nowhere is there mentioned in ASME Code where if a lower tempering temperature is selected to gain higher strength that I need to conduct mechanical property tests.
In this case, a slightly lower temper was selected. The UTS for the plate will be much higher than the minimum specified. Again, one cannot take credit for this and the PWHT temperature that was used was selected based on current rules in UCS-56.
RE: Tempering and PWHT
So guess what - suitable reheat temperature does not mean much in this case, does it?
RE: Tempering and PWHT
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Tempering and PWHT
Were such specs agreed upon during or before the issue of the PO?
RE: Tempering and PWHT
It might mean something if the purchaser's technical specification has detailed the requirement. It might also mean something if the responsible engineer deems it to be outside of the specified PWHT temperature range as per QW-407.2. Naturally, if it is not addressed in any supplementary way, and the purchaser maintains the requirement, then the purchaser would pay for the privilege.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Tempering and PWHT
Lets see, maybe I can present it this way. In SA 333, heat treatment shall be by one of the options in 4.2.1 - normalization OR normalization followed by reheating to an agreed upon tempering temperature.
I do not believe that this reheat temperature is used other than to establish some form of stress relief. If the user is concerned with welding and PWHT, they should have specified a higher agreed upon reheat temperature.
Of course the end user can do what they wish at their cost.
RE: Tempering and PWHT
My solution is simply to avoid a problem by tempering as high as possible and PWHT 50-100F below that. I have still to come to grips with a P-1 to P-5 weld. PWHT for the P-5 sake certainly abrogates the P-1 CMTR properties. What do you do in this case? I recommend a design or process change for critical components.
RE: Tempering and PWHT
and often 1175*F +/-25*F
it has always been our contention that as long as a pwht cycle per ucs-56 was maintained and we did not go above 1200*F we were fine
Now if you got the temp into the normalizing range, then yes, new tests are required.
But at 1175 not required
RE: Tempering and PWHT
Agreed.
.
No design or process change is required. For a P1 to P5 weld, the lower alloy base metal will dictate PWHT requirements OR you butter the P-No 5 base metal side with B3 filler metal composition, PWHT the buttered P-No 5 base material, and finish the weld with B3 to carbon steel and perform a final PWHT at lower temperature for the P-No 1 base material. The Code rules are flexible.
RE: Tempering and PWHT
309 butter (heavy pass) to c.s. and proceed with pwht
then weld on the SS section
yep...flexible
RE: Tempering and PWHT
RE: Tempering and PWHT
We simply prohibit welding carbon steel to P91 alloy and use a transition P-5A or P-4 part.
RE: Tempering and PWHT
RE: Tempering and PWHT
RE: Tempering and PWHT