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Impurity Segregation in Stainless Steel Bar

thread330-462291

Impurity Segregation in Stainless Steel Bar

Impurity Segregation in Stainless Steel Bar

(OP)
We are managing weldability risks in orbital welding of small Ø tubing, specifically the effects of sulphur on autogenous orbital welding. For those of you familiar with ASME BPE-97, you will know that this is a base metal sulphur matching exercise. 1" 304LSS bar will be machined at one end to a profile matching a ½" OD x 0.049" wall tube, also 304L.

The question is about sulphur distribution as a function of bar radius: how much variation can we expect from core to OD, and should we be very precise about where we sample for chemical analysis?

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

RE: Impurity Segregation in Stainless Steel Bar

If material was re-melted, no much variation is expected cross bar diameter. At the most there possibly have some variations from the top and bottom of ingot(s) before processed to 1'' bar.
If arc-melted, I expect higher S in the middle of ingot/electrode, especially in those locations with pipes and large porosities.

RE: Impurity Segregation in Stainless Steel Bar

Can you find bar with the correct S level?
The segregation is going to be a function of both the melting method and the amount of cold reduction.
If this has been heavily cold worked then the variations will be very slight. And you are taking out the center where the most segregation will be.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

RE: Impurity Segregation in Stainless Steel Bar

Don't you do the boring of the bar before welding it to a tube? Just out of curiosity, what is the variation you expect from a thickness of 1.2 to 1.6mm? As a user, I know that valve manufacturers maintain higher limit of sulfur content and weld the matching tube spools at their manufacturing unit and claim that as the welding is done in controlled conditions, things are ok and we just accept it.

RE: Impurity Segregation in Stainless Steel Bar

At 0.03% max sulfur you should not have any welding problems. We do autogenous laser welding on 304L deep drawn thin wall parts by the millions without any problems. Is orbital welding particularly sensitive to sulfur?

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