×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Duplex stainless weldment failures
4

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,

RE: Duplex stainless weldment failures

In duplex there are critical issues other than just heat input.
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

Quote:

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?

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

(OP)

Quote (EdStainless)

In duplex there are critical issues other than just heat input.
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.

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.

Quote (SJones)

3) How do you physically vet the subcontractors for their capabilities to successfully weld DSS/SDSS?
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?

Quote (DVWE)

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.
Good tip, thanks. My copy is 2009 edition, so I will update.

RE: Duplex stainless weldment failures

2
3) No. ISO 3834 deals with the quality requirements for welding as opposed to specific technical requirements for materials. It provides a framework for assessing the procedures and processes in place to consistently meet technical specification requirements. The actual technical specification is a different matter. API RP 582 is one guide from which a technical specification can be developed. AWS D10.18 is another, and there are others like the NiDI guide: https://www.nickelinstitute.org/en/TechnicalLibrar...

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

If you are welding duplex then every time there needs to a fixed procedure, documented welder qualification, including both A923 and ferrite measurements.
IMOA publishes a duplex fabrication handbook.
https://www.imoa.info/molybdenum-media-centre/down...

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Duplex stainless weldment failures

You need to determine the metallurgical cause(s) of the failures. It could be based on base material properties or on welding. Fully agree with Ed regarding welding procedure, welder qualification issues.

RE: Duplex stainless weldment failures

Duplex HAZs are relatively resistant to cracking during the fabrication process. Were your HAZ cracks during fabrictation or during service? The causes would be quite different depending on the time of occurance.

RE: Duplex stainless weldment failures

(OP)

Quote (CWEng)

Duplex HAZs are relatively resistant to cracking during the fabrication process. Were your HAZ cracks during fabrictation or during service? The causes would be quite different depending on the time of occurance.

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

(OP)
I do appreciate the info provided so far.

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

So if the cracks are in service, there is a good chance you either have a susceptible microstructure, an environment too aggressive for the Duplex, or a combination of stress/environment that exeeds the duplex capabilties. What do you know about the environemnts for your equipment?

RE: Duplex stainless weldment failures

And what duplex rages are we talking about, S32205?
S31803 is too wide of a chemistry, that is why it has been superseded.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper - Strategies to Secure Connected Cars with Firewalls
White-hat hackers have demonstrated gaining remote access to dashboard functions and transmissions of connected vehicles. That makes a firewall a vital component of a multilayered approach to vehicle security as well as overall vehicle safety and reliability. Learn strategies to secure with firewalls. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - What is Generative Design and Why Do You Need It?
Engineers are being asked to produce more sophisticated designs under a perfect storm of complexity, cost, and change management pressures. Generative design empowers automotive design teams to navigate this storm by employing automation, data re-use and synchronization, and framing design in the context of a full vehicle platform. Download Now
eBook - Simulation-Driven Design with SOLIDWORKS
Simulation-driven design can reduce the time and cost of product development. In this engineering.com eBook, we’ll explore how SOLIDWORKS users can access simulation-driven design through the SOLIDWORKS Simulation suite of analysis tools. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close