Duplex stainless weldment failures
Duplex stainless weldment failures
(OP)
My company provides equipment in a variety of corrosion-resistant alloys.
We have done duplex in the past and had a few more mechanical failures (cracking) particularly around HAZs. Even with greatly reduced stress limits we couldn't stay out of trouble.
I have a few areas of focus to get back on track:
1) Design of the weldments for duplex welding heat control. Do certain weld joints lend to worse HAZ phase imbalance.
2) We generally use ASME BPVC allowable stress limits for design. Is this standard practice, and if so, are there cases where we shouldn't?
3) We subcontract welding. Many weld shops "have a procedure for that". What are key questions / criteria to get past the "we can do that" promise to actual success?
I realize these are loaded questions, so I'll take what I can get.
Thanks,
We have done duplex in the past and had a few more mechanical failures (cracking) particularly around HAZs. Even with greatly reduced stress limits we couldn't stay out of trouble.
I have a few areas of focus to get back on track:
1) Design of the weldments for duplex welding heat control. Do certain weld joints lend to worse HAZ phase imbalance.
2) We generally use ASME BPVC allowable stress limits for design. Is this standard practice, and if so, are there cases where we shouldn't?
3) We subcontract welding. Many weld shops "have a procedure for that". What are key questions / criteria to get past the "we can do that" promise to actual success?
I realize these are loaded questions, so I'll take what I can get.
Thanks,
RE: Duplex stainless weldment failures
Are the welds tested for austenite:ferrite ratio?
Are they tested for detrimental intermetallics? (such as A923)
What about pitting corrosion resistance?
While these things are somewhat related they are each important.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Duplex stainless weldment failures
http://www.iso3834.org/welding-fabricator-certific...
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Duplex stainless weldment failures
API RP 582 was completely revamped in 2016 to include some pretty tight welding requirements, restrictions, and procedure qualification requirements for DSS. Familiarize yourself with that document, and ask your vendors to do the same.
RE: Duplex stainless weldment failures
Austenite:ferrite is not required per piece.
A923 is called out in some cases. Not all.
Pitting corrosion resistance is not required unless our customer requires it. I don't recall seeing this before.
We don't really. We avoid working with dirt floor operations but that's obviously not enough and what I'm trying to develop. ISO 3834 is worth a look - does it contain information specific to duplex?
Good tip, thanks. My copy is 2009 edition, so I will update.
RE: Duplex stainless weldment failures
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Duplex stainless weldment failures
IMOA publishes a duplex fabrication handbook.
https://www.imoa.info/molybdenum-media-centre/down...
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Duplex stainless weldment failures
RE: Duplex stainless weldment failures
RE: Duplex stainless weldment failures
Cracking during service.
I also got clarification that we did get Ferrite count and intermetallics tested with our work.
Has anyone found the need to reduce stress limits below ASME allowables?
RE: Duplex stainless weldment failures
Are there weld geometries that you would do in a 300 series that you would avoid in a duplex? If so, why?
RE: Duplex stainless weldment failures
RE: Duplex stainless weldment failures
S31803 is too wide of a chemistry, that is why it has been superseded.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube