Welded 316L part, NACE MR0175 Compliancy

[mforoutanfar]

Hi everyone.

Sorry if this looks like a duplicate subject; I know there are lots of other threads regarding NACE MR0175, welding and PWHT requirements, but I couldn't find a clear answer to my problem in any of them.

Here's the deal: we are manufacturing 316L thermowells which are to be compliant with NACE MR0175. The raw materials are NACE certified, but they need to go through some fabrication procedures such as welding and turning.

As for welding, the standard only states that the hardness of weldment, HAZ, etc. needs to be lower than 22 HRC and that the carbon content needs to be < 0.03%. But it doesn't say (as it does with martensitic stainless steels, which need to go through a PWHT at 621 deg. C) how to achieve this hardness value. Is it enough to conduct a sample section test as instructed by ISO 15156, after our as-usual PWHT?

Also, will the turning induce any non-negligible cold work on the part? How about tapping?

Thanks!

 

[mforoutanfar]

Double also, does the whole part needs to be NACE compliant or just the wetted sections?

 

[SJones]

Austenitic stainless steels are not usually subject to PWHT, hence ISO 15156 doesn't really need to address it since the PWHT would have to be a solution anneal or anneal anyway. It just becomes a question of qualifying the welding procedure with a hardness test as directed. You will note that A.1.5.3 of Part 3 regards turning and threading as normal machining operations with no restrictions. As to how much of the part needs to comply with ISO 15156, that would be down to the end user to specify.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[mforoutanfar]

Thank you so much for your answer SJones.

So, if the hardness test of the sample(s) turn out to be OK, there will be NO need for solution annealing the whole part again, right?

 

[rustbuster]

I worked in a sour facility in the 90's. During start-up we had numerous 316L to A333 Gr. 6 thermowell welds fail due to stress corrosion cracking. We changed them all to allow for PWHT. I don't recall what material was used but will try to find out.