Electrode for overlay welding

[PAN]

Vessel material is 2.25Cr-1Mo-V steel (base metal) + Type 347 S.S. (weld overlay). The design temperature is 454 C.

In my understanding, the use of Type 309Cb is recommended for the first layer of overlay welding in API RP 582. The addition of columbium to weld metal improves its high temperature performance.

However, some manufacturers propose to use Type 309L for the first layer.

Please comment about the advantage and disadvantage of use 309L instead of 309Cb.

 

[rnd2]

http://www.weldwell.co.nz/products/electrodes/stainless_steel/stainles1.htm#PHRS347

 

[metengr]

The columbium addition ties up the carbon and avoids the formation of harmful chromium carbides that results in lower creep rupture strengths.

 

[weldtek]

You are correct in saying that RP 582 lists 309Cb as the consumable to be used for the first layer of a weld overlay on carbon or low alloy steels. See Appendix B. However, many fabricators have experienced that finding 309Cb is not easy, especially in some forms, while 309L is available off the shelf in all forms of consumables.