Dissimilar weld , CS to SS, Ferrite test details

By Harikrishnan Date 04-16-2015 07:56

Hi All,

We are about to run a PQR for Carbon Steel to Stainless Steel based on AWS D1.6 with E309L-16 electrode. May I know your kind guidance regarding the requirements for Ferrite Test values for the final weld? Any code clause pertaining to this subject? Please advise.

Thanking for your valuable time and looking forward to hear from you,

Best regards,

Hari

By 803056

Date 04-16-2015 12:51

I recommend using a joint detail consisting of a double V-groove weld. Weld from the first side, back gouge by grinding, and back weld the second side.

If you elect to use backing, it should consist of the same stainless alloy being joined to the carbon steel. If you do use carbon steel backing, against my suggestion, make sure the root bead is convex. Concave root beads have a strong tendency to crack.

Best regards - Al

By js55

Date 04-20-2015 20:25

Does D1.6 really require ferrite testing for a dissimilar between SS and CS?
The logic of this escapes me.

By 803056

Date 04-22-2015 21:32

Not that I am aware of.

Al

By ssbn727 (*****)

Date 04-22-2015 23:14

He must be thinking of Duplex... Btw Al, I got it today so thank you my friend!

Respectfully,
Henry

By js55

Date 04-23-2015 13:33

Henry,
Interesting thought. A 309 weld in a dissimilar application will actually yield a duplex microstructure. 312 is in essence a duplex filler.
But whereas for most ferrite testing it is performed to verify enough to prevent microfissuring, for duplex it is performed to verify a compliant duplex balance(using the EFN instead of the FN).
Of course, technically speaking if you have any ferrite AT ALL its a duplex microstructure. I'm not sure there is an actual definition of duplex pertaining to ferrite content. Its kind of loosy goosy as far as I know. If the alloy is intended to combine strength and resistance to SCC through controlled balances of ferrite and austenite then it is a duplex alloy. We all know what a duplex alloy is, but I don't think it is actually written anywhere.