316L high purity seamless tubing SF 1

[DECLAN SHEEHAN]

316L high purity seamless tubing SF4 internal polish.
Orbital welded
Material grades 1.4404 versus 1.4435.
Any experience with mixing both grades in the same piping spool and any issues with orbitally fusion welding these grads.

 

[EdStainless]

It is mostly trace elements that govern weld fluidity and penetration, I don't believe that the differences in the bulk chem will have any impact.
Small differences in S and O (among others) will have the major impact.
So your spec allows both grades???

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P.E. Metallurgy, Plymouth Tube

 

Too low overall S causes inconsistent penetration. Too large a difference between base metals can cause the arc to deviate to one side. Whatever you do, have sulphur analysis done on both base metals so you can make an assessment of weldability. Oxygen is also a factor, though less critical than sulphur.

Google 'heat to heat variation' and 'Marangoni effect'. There is an ASME code BPE, for biopharmaceutical tubing. ASTM A270 was written specifically for stainless tubing and recognizes the sulphur issue in supplementary requirement S2.

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"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[WKTaylor]

DS...

Ever consider using aircraft-grade hydraulic quality/drawn 321-Ann or -1/8H CRES tubing per AMS5557 or AMS5896?

Regards, Wil Taylor

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