welding SS347H (heat treatment required)? 1

[Eduardo1982]

Hey guys, I am going to weld SS 347H. As far as I know, this kind of alloy is prone to be a problem during service (probably SCC problem). Actually I have selected an electrode free of rutile (it was an advice I read on many papers) and I perform some tests (according to ASME IX - tensile, bend.. RT) all were good. However, some people told me to consider to perform heat treatment according to ASTM A480. I was checking the entire specification and in my understanding to austenitic H grades it could not be mandatory. I need your help guys, maybe you have had experience using this material.

 

[metengr]

First, what is the application for the 347H material in service? Thickness? There are applications where the 347H performs well in the as-welded condition with no stablization heat treatment after proper solution anneal. I have seen reheat cracking of 347H weldments because of welding heavy section thickness (1" or greater).

 

[weldstan]

347H can be welded without PWHT and in most cases is. I only know of one boiler manufacturer which requires PWHT.

 

[Eduardo1982]

Thanks guys. Ok I give more details.
This SS 347H Will be used for tank fabrication (bottom, Shells, top). Also for piping.
Material to be transported (molten salts).. temperature around 550 °C.

 

[metengr]

If the 347H has been subjected to a proper solution anneal stated in the mill test report, you don't need a stablization heat treatment for this application. Following proper welding technique, the as welded condition should be acceptable.

 

[weldstan]

Agree with metengr.

 

[Mateeng]

Just carious to know how about heavy sections and reheat cracking. I do understand reheat cracking may happen either in high service temperature or during PWHT. Any solution for 347H/347 reheat cracking. Thanks

 

[metengr]

To reduce the risk of cracking, an intermediate stress relief can be done when welding. I have seen problems with 347H welded headers that were 1" in thickness.

 

[Mateeng]

Thanks Metengr,
Any suggestion for intermediate stress relief temperature and time.

 

[Eduardo1982]

Ups.. I was checking and I am going to Weld 55 mm. thickness plates.. so any recommendations? in this case, as metengr said, an intermediate stress relief could be done while welding.. any suggestion of this process?

 

[metengr]

I would suggest welding with no stablization heat treatment or intermediate stress relief unless cracking becomes an issue related to constraint. See below page 8

http://www.metserve.co.za/pdf/al321.pdf

 

[Mateeng]

347H PWHT is prone to reheat cracking (RHC). In service also susceptible to same. ASME VIII Div. 1 UHA-A-10 recommend PWHT for 347 heavy sections. wonder which way to go. Also any repair also increase risk of RHC. To me perform FAU after welding. Perform PWHT. Perform FAUT after PWHT.
Any suggestion.

 

[metengr]

Mateeng
The approach you describe is an option. I would attempt to weld without and if cracking is an issue, remove the crack and repair using the recommended stress relief temperature below

https://www.onepetro.org/conference-paper/NACE-04640