Welding or flange connection of 2.25Cr piping to 316 SS piping

[engineermat]

I have a super high pressure steam piping, which is 2.25Cr piping. It is going to be connected to a 316 SS Piping. We want to use welding or flange connection for these two different piping. The flow in the piping high pressure steam (959 DegF). We don't need to consider the galvanic corrosion for this condition since there is no electrolyte, right? These two piping can be welded or flanged, right?

Thanks.

 

[gr2vessels]

Right and Right. However, make sure to drain the pipe correctly during the outages.
cheers,
gr2vessels

 

[metengr]

Go with butt welded if 2" or greater OD (my design philosphy, anyway).

 

[strider6]

in my opinion you should consider the possibility of galvanic corrosion on the exteranl surface expecially if your pipe is located in a marine environments.
you can weld the two materials but a special care in the preparation and execution of the weld is necessary.
look at this article that cover your case:

Pay attention to dissimilar-metal welds.

http://www.nickelinstitute.org/inde...oc_id/3286/search_keyword/14018/method/1.html

a flange connection allow you to avoid all this problem.

hope this help
S.



Corrosion Protection & Corrosion Control

 

[engineermat]

Thanks.

How about the sensitization of 316 SS? The high pressure steam temperature is in the sensitization temperature range.

 

[metengr]

engineermat;
There is not much you can do to prevent sensitization in service with the 316 ss because you need high carbon content for creep strength. Why are you even using a dissimilar metal weld in the first place, especially if you are concerned about sensitization? I would use a 321H or 347H stainless for elevated temperature service.

 

[engineermat]

The client is worried about the leaking of flange connection of 2.25Cr and 316SS in this condition. That's the reason I want to use dissimilar metal weld.

 

[PAN]

engineermat,
What is your selected welding electrode?

 

[engineermat]

PAN,

We have not decide the welding process and filler metal. Any recommendation?

 

[PAN]

engineermat,

I agree with metengr's comment to consider 321H or 347H instead of 316 ss.

Regarding the welding electrode, for your high temperature service, I do not recommend to use filler metal type 309. You may find the detail in the paper of NiDl No. 14018 as mentioned by strider6.

 

[engineermat]

welding Process: SMAW
Filler metal: ENiCrFe3

Or

Welding Process: GTAW
Filler Metal: ENiCr-3

Any comments?

How about the preheat temperature, and interpass temperature?

If I use 1300F-1400F, is it ok?

Thanks.

 

[metengr]

engineermat;
For this dissimilar metal weld joint, I would first butter the 2.25%Cr-1%Mo side of the weld joint like you were welding P-No 5 A to itself. Use 1/4" thickness for the butter layer.

Once you have buttered the weld prep and performed the PWHT, you can join the 316 ss to the buttered 2.25% Cr- 1% Mo base material using Inconel, with no preheat and no PWHT. Keep the interpass below 350 deg F to minimize sensitization.

 

[MJCronin]

mat..

Consider posting in the "piping & fluid mechanics" forum..

What is your pipe size/temperature and pressure ?

Dissimilar metal welds have been used on tubes and smallbore piping, how big will this weld be ?

-MJC

 

[engineermat]

22"

959F

1751 psi(g)