Welding Dissimilar Metals

[zmazim]

Hey guys,

I have an ASTM A333 Gr. 6, seamless, with 3mm SS 316/316L overlay pipe to be welded to an ASTM A403 WP 316/316L reducer tee. Now as per my understanding, I shouldn't face any problems welding the two metals together. However, what would be a proposed methodology? And what filler metal should be used?

Thanks

 

[metengr]

Assuming you have a full penetration weld joining the pipe to the reducer tee, I would suggest the following;

1. For joining the pipe base material (A 333 Gr 6) to the 316/316L stainless tee base material, use 309 filler metal.

2. Once the A 333 Grade 6 base material has been fully welded to 316/316L stainless base material, you can switch to 316 filler metal to complete the remaining weld joint between the overlay and 316/316L tee base material.

The above can be optimized based on pipe OD and wall thickness, which you did not provide.

 

[zmazim]

Oh sorry the header is NPS 8", and the tee is NPS 6". I do have several welds to do though, that's just one of them. What do you recommend for optimizing in general?

 

[metengr]

Selection of the welding process. Also, perform a liquid penetrant test after welding.

 

[zmazim]

Thank you so much.

 

[Ripz]

Agree with metengr's welding procedures. But why not radiograph instead?

 

[Ripz]

Quick question, for my curiosity, why do you have a carbon steel pipe with a Stainless Steel overlay? Is an internal component for a vessel, or underwater or something?

 

[wegm]

zmazim,
I agree with metengr's recommended practice though I would like to highlight that the 316 filler metal shall be used to finish up the welding if the welding overlay of CS pipe has been externally performed. Otherwise, if it has been internally performed, you shall finsih up the welding using 309 filler metal while you can do root welding using 316 filler metal. Moreover, please note that the 309 filler metal is generally recommended for dissimilar welding (CS to SS) for normal temperatures whereas for higher temperatures (above 370 deg C) nickel based consumable like ErNiCr-3 is suggested so as to avoid cracking. Please have a look here:
Dissimilar metal welding, SS to CS
regards
wegm

 

[zmazim]

Ripz, the pipes will be radiographed as well. The overlay is because this is a highly corrosive environment.

wegm, the welding is actually internally performed, so this means I should start with the 316 root weld? As for the working temperature, it is 100 degC so I wouldn't worry about the filler.

Thank you guys.

 

[Ripz]

zmazim, is your 316 Overlay on the inside or outside?

Basically you weld 316L to 316L with 316L

and

Carbon Steel(A333 Grade 6) to 316L with 309 L.