Nitronic 50 Corrosion 2

[metalguesser]

Friends,

We have a situation in which, we have welded SS 2205 (UNS S2205) grade duplex steel to Nitronic 50 (UNS S20910) grade of steel. The whole unit was then subjected to a corrosion test per ASTM A923 and we have observed extensive pitting corrosion on the Nitronic side of the weld. My question to the forum is; (1) Is it common to weld duplex 2205 to Nitronic 50 and if so (2) What are the precautions to be taken and what PWHT needs to be carried out, especially because of the high Vanadium (0.10 to 0.30%)present in Nitronic (3) what other tests are recommended to make sure the weld is of good quality and strength over and above the standard ASME Sec IX tests?

Thanking y'all in anticipation,

Best regards,

 

[SJones]

Review the title of ASTM A923. Then review Note 4 of the same standard. On the basis that Nitronic 50 is NOT a "duplex ferritic/austenitic stainless steel," would it lead to the conclusion that subjecting it to a ferric chloride test, particularly in a dissimilar weld, is not really the best idea?

"Good quality and strength" can be ascertained by the standard nondestructive and destructive testing applied correctly to the weld and individually to the distinct materials, e.g. it probably wouldn't be of any use to perform a point count phase balance measurement on the Nitronic 50 side of the weld. If "good quality" is taken to include corrosion performance in the intended service environment, then the corrosion testing would have to be of an appropriate type using an appropriate environment.

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.

 

[EdStainless]

What weld filler did you use?
So you did a 923, that means that you cut out a sections and tested it with freshly ground surfaces, right? What was the test temp? The one used for 'as welded 2205'?

Was the pitting in the weld or 209 HAZ?

The only PWHT that you could do is a full solution anneal.
Look at some micros and see if you formed secondary phases in the 209. You may need to watch weld practice and heat input more closely.

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P.E. Metallurgy, Plymouth Tube

 

[metalguesser]

Thanks SJones and EdStainless for the response. I shall revert back with the information.

Best regards,