Dissimilar Welds - SS to CS 2

[iam42]

I need to weld a P1 material to a P1 material (Pipe), which is relatively straight forward, However, this joint is backed with a stainless steel nozzle, which in effect acts as a backing bar as the root is open. The root run actually holds the nozzle in place within the pipe. I am contemplating putting the first 2 passes in with a 309 consumable then completing the joint with Carbon Steel electrodes. Is this acceptable for B31.1 and B31.3 specs? I already have WPS's for P1 to P1 and P1 to P8. Would a new PQR need to be run? If a PQR is run should the SS backing bar be removed before sending to the Test House?

Any Help would be greatly appreciated.

Many thanks

 

[0707]

I don’t understand why you only weld the first two passes of SS nozzle with 309. I think it would be better to do all of the weld between SS nozzle and carbon steel pipe with 309 filler

Regards

luis

 

[21121956]

Hello everybody:

The two leading Austenitic stainless steel filler metal for dissimilar metal welding are E309L and E312. You should consider also, the possible use of E307 stick electrode.

 

[metengr]

Normally, you do not deposit a ferritic weld metal over an austenitic filler metal because of the effects of dilution and potential for cracks. I would stick with either E309 for the entire weld or Inconel if the weld is exposed to service temperatures at or above 800 deg F.

 

[iam42]

OK,

It looks like I will use a 309 Consumable to weld the butt, however, the CS parent material is 1" thick. If I weld this with 309, does it still require PWHT with respect to B31.1/3?

Mnay Thanks for all your help so far.

Ian

 

[metengr]

PWHT requirements are based on base metal thickness and composition, not weld metal.

 

[iam42]

metengr,

Thanks for you help,however, would it not be detrimental to PWHT the SS weld metal.

I was also wondering if the exception from B31 case 174 would apply to this joint.

Thanks

 

[metengr]

The E309 is more compatible in terms of reducing susceptibility to deleterious phase formation from exposure to PWHT of base metals.

B31 Code Case 174 highlights the discrepancies in PWHT mentality between ASME Section VIII, Div 1 and B31.1. AS you are aware, ASM Section VIII, Div 1 exempts P-No 1 base materials from PWHT up to 1.5" in thickness with the application of preheat.

Code Case 174, which was approved in 2003, places a number of specific conditions to be met prior to use, including impact testing. If you want to jump through all these hoops and the owner agrees to acceptance of the code case, go for it.

One of these days, my hope is to have consistency across ASME B&PV Code and ASME B31 Piping code regarding PWHT, and eliminate the "my domain" syndrome.