PWHT of L-80 13Cr

[nottoobright]

Hello Everyone,

I need to weld a ring onto the surface an L-80 13Cr Sumitomo casing. There is a pre-weld heat treatment required and also a PWHT (post weld heat treatment). Can anyone explain the procedure and some of the science behind the PWHT.
If it's any help, the end product is a sand control screen for sour service.

Appreciate the help!

 

[metengr]

Preheat, which involves heating the base material in the region of the weld prior to welding, is used to slow the cooling rate of the base material during welding to reduce the formation of hardened base material within the weld region and thermal stresses from the local heat of welding. Preheat can be applied locally or the entire component can be preheated, it depends on thickness, material and size of the component.

Post weld heat treatment (PWHT) is performed after welding to soften or temper the hardened material in the weld region and to reduce residual stresses caused by weld shrinkage. PWHT can also be applied locally or the entire component can be subject to PWHT. That is about it.

 

[EdStainless]

I'll just add that in 9Cr and 13Cr alloys the PWHT is critical.
If you do it wrong you will sacrifice corrosion resistance, strength, and toughness.
Pay close attention to how it will be done.

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Plymouth Tube

 

[nottoobright]

Thank you metengr and EdStainless.
Is there a standard for this PWHT? We will be outsourcing the heat treatment but this company has asked us to provide the procedure. Some research and we've found around 630 celsius for 5 minutes but this is too vague.

 

[metengr]

The PWHT temperature for this martensitic 12-14%Cr alloy will be based on ensuring the weld region (weld metal and base metal heat affected zone) is below a specified maximum hardness. This material is supplied in a quenched and tempered heat treated condition.

For starters, I would use API 5CT as a guide because this alloy is manufactured to this standard. You want to PWHT the weld region at or near the original material specification tempering temperature because the hardness is specified as a maximum.

First, you need to develop a welding procedure specification, which you did not mention and should be required. The preheat and PWHT will be part of the welding procedure development. If you are unfamiliar with this, seek professional help to work with a company that can develop this for you.

 

[nottoobright]

Sound advice. Thank you.