Welding dissimilar hardness 316L

[mjurek]

I have a question regarding welding two 316L (ASTM A479) parts together that have different hardness and slightly different chemical compositions.

The first has a UTS of 110ksi, yield of 75ksi.
Chemical Comp: C .014%, Si .62, Mn 1.37, P .027, S .017, Cr 16.83, Mo 2.01, Ni 11.14, Ti .125, Co .14, Cu .5, N .03

The second has a UTS of 75ksi, yield of 30-55ksi
Chemical Comp: C .0088%, Si .0945, Mn 1.25, P .032, S .0255, Cr 16.69, Mo 2.07, Ni 10.845, Ti .02, Co .259, Cu .3895, N .0509, Cb .012

The application is for pipe fittings per ASM B31.1, able to withstand 3000psi.

The second part is fabricated from round tube stock, which can be purchased to the yield 30-55ksi per our spec. The first part is fabricated from CD square bar stock, which increases it's strength. The 30-55 yield can be procured, however it's more difficult.

Are there any effects of welding these 2 parts together? This is a basic TIG weld.

Thank you.

 

[metengr]

Are there any effects of welding these 2 parts together? This is a basic TIG weld.

No,there should be no adverse conditions related to welding these base materials. Most Codes and Standards do not allow credit for higher strength for similar material grades, only the minimum strength is required to be met.

 

[EdStainless]

Makes me wonder why the first one has such a high strength?

The high S in the second one may be a little bothersome. Don't be surprised if you have some issues with inclusions or porosity.

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Plymouth Tube

 

[mjurek]

The first material has a higher strength due to cold-drawing the square bar stock.

We are worried about more porosity.

Thanks for both your responses.

 

[EdStainless]

Very clean and dry. I hate to say it but Acetone is the best way to clean. Keep it in small metal cans that are always closed.
And your Ar purge gas needs to be clean also. No rubber hoses. They will contribute a lot of oxygen and moisture to the process.

Does 31.1 allow the use of material in the as-cold-worked condition?

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Plymouth Tube