Is Inconel 625 tubes the work hardening of tube material? 1

[mechengineer]

Hi experts,

As per API 660, A.4.4.2,
"Where work hardening of the tube material during rolling could result in the potential for environmental
cracking, a strength-welded tube-to-tubesheet joint should be applied, and a light expansion (1 % to 3 % wall
reduction) should be applied (as per A4.4.1) if crevice corrosion from the shell side fluid is a concern".
Is Inconel 625 tubes the work hardening of tube material?

Thanks

 

[Dhurjati Sen]

Even if the Inconel is work hardened, its crystal structure being FCC, is not much of a concern.

DHURJATI SEN
Kolkata, India

 

[mechengineer]

@ Dhurjati Sen,
Did you mean that the thickness reduction can be 5% to 8% by heavy expaded as per API 660 Table 6 for Inconel 625 tubes ?

Regards,

 

[EdStainless]

What tubing spec are you using?
Which strength level of 625 are you using? (there are two options)
Why would you have tubes that are cold worked?
But in general it doesn't matter with a Ni alloy like 625.
Even lightly cold worked the material will still have tensile elongations over 30%.
And its cracking resistance is very high.

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P.E. Metallurgy, consulting work welcomed

 

[mechengineer]

@EdStainless,
Tube material: SB-444 N06625 Gr. 2
Tube shett material: SB-443 UNS 06625.
Yield stress at 40 deg.C is 274979.1 kPa.
Yes, if we take the tensile elongation as the judgement whether the material is working hardning or not, that will make me confident.
Thanks,

 

[Krausen]

Your cold working parameter is tube wall thickness reduction from roller expansion, is it not? Either way, I don't believe this is a concern with Inconel 625 tubes, as others state above. The cold work hardening clauses in API660 are geared mostly to ferritic/austenitic SS material (including Duplex SS) as I understand.