Exemption of impact test for austenitic stainless base materials (ASME B31.3 para 323.2.2. (f)

[9bbong]

Dear Sirs,

Please explain exemption of impact test for austenitic stainless base materials according to ASME B31.3 para 323.2.2.(f).

Clause: Impact testing is not required for the following combinations of weld metals and design minimum temperatures:
(1) for austenitic stainless steel base materials having a carbon content not exceeding 0.10%, welded without filler metal, at design minimum temperatures of −101°C (−150°F) and higher

Question: If I ordered A358-316/316L Class 1 pipe, impact testing will be required or not at MDMT of -80°C.
I understand that Class 1 pipe shall be impact tested due to the manufacturing process by double welded employing filler metal in all passes.
And please clarify the detail meaning of filler metal.

Thanks for your reply in advance.

 

[metengr]

Filler metal versus no filler metal (autogenous) can be used to manufacture long seam welded pipe. Filler metal means metal of specific composition is being added to fill the weld joint. Whereas, autogenous welds are made with no filler metal added only local melting of the two base materials during welding.

The Code recognizes that with filler metal added to complete the weld joint impact testing, if required, must be performed on the weld metal itself. For autogenous welds, since there is no filler metal, impact exemptions apply directly for the base materials.

 

[EdStainless]

Often weld filler is designed to give higher residual ferrite numbers to improve resistance to hot cracking.
If the ferrite is too high then it can harm the low temperature toughness.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

and higher residual ferrite numbers means impact testing for low temperature service.

 

[9bbong]

Dear metengr & EdStainless,

Thnaks so much for replies. I will study the ferrite No with impact test. Have a nice Day!!