Stress releaved ASTM SB-163 Inconel 600 smls tube procedure

Date 06-11-2015 19:35

Here's a scenario. Company A is taking a .049" wall SB-163 Inconel 600 smls tube and stress relieving after forming into a serpetine at 1400deg F for an hour and could wind up being longer in the end. Also to bake off whatever residuals may be left on the tube once that process is complete. Company A then sends it to company B to have a machined fitting autogenously orbital welded on to the end of the tube. Fitting is a machined .049" wall SB-166 Inconel 600 bar stock that no stress relief or annealing will be done to it. Company B is qualifying the welding procedure to NAVSEA Tech Pub 248. Company B is using 2 pieces of untreated .049" SB-163 smls tube to qualify the procedure. Before everyone starts yelling at me for not providing enough information :lol:

, my only question is, In real life, wouldn't one want one of the tubes in the PQR qualification have the same stress relief as the formed serpentine in production done to it? I can only find in the tech pub where it speaks to stress relieving after the welding and that's what has to be done for the PQR also. Company C (End user) has not squawked this, but there's always that chance that they don't know all the low level details. Thoughts on this scenario please.

Thanks,
Kix

By js55

Date 06-11-2015 21:23

Kix,
Its an engineering decision. But IMO not necessary.
Think about it. This is done all of the time.
Wrought treating does not match forge treating which does not match castings, etc.
A106 B is essentially hot finished for large grain and Grade 6 333 is normalized for small grain size adnthey are welded together all of the time.
In some Codes HT matching is a requirement in some situations but it is not pervasive.
If the SR tube meets the design tensile (if it is engineered to do so), then I see no problem. With the information available.
The different HT conditions will not effect weldability.

By Kix

Date 06-12-2015 11:31

Thank you for the response. Per your point on if the SR tube meets the design tensile then there won't be a problem, how is one going to know if the material meets the designed tensile after an hour or 3 bake at 1400 degrees F and welding when there will be no testing of that scenario? In reading the rest of your post and coming from an engineering standpoint, if the material all by itself still meets min tensile requirements of the ASTM spec after SR, then the same material in it's original condition is ok to use in the PQR. I'm with you there. So I must assume that company A's engineer team has a way to compile the data that the SR of the production tubing will not effect it's min tensile. Then they were able to figure that it was still high enough that the autogenous weld and it's HAZ will not put it out of spec. Am I correct in saying that? One last thing that still has me scratching my head is that the PQR qualifications are in process to meet program schedule dates and rumor has it that company A still does not have a time at temp defined for the SR process. Now you guys can yell at me for not providing that information in the first post. ;-)

Thanks
Kix