nonmetallic inclusions in bar vs plate in 316L

[frank72]

here a recent discussion we had - are there more or less nonmetallic inclusion in a bar or in a plate visible when you are doing an evaluation assumed that the same melting procedure for the primary and secondary melting.

basically my point was that I would not expect a difference but a guy from a comany doing a lot of polishing told me that they are using more plate material for polished goods as they would see more defects ( or inclusions ) on finished products when using bar stock material.

if anybody knows a scientific examination i would bevery grateful.
regards
Frank

 

[metengr]

frank72;
Actually, it is not that simple of a comparison with inclusions in bar or plate if both are made from the same melting practice. Having performed a number of mill audits, what it boils down to me is ingot versus continuous cast steel processing. I would expect a difference in inclusion formation if the bar was originally produced from an ingot versus a continuous cast strand, given similar melting practices. However, can you be sure that the observation made in your OP was indeed of product forms made with similar melting practice and processing?

 

[mcguire]

There's virtually no ingot material made these days. Inclusions are mostly sulfides, left there intentionally (and unfortunately) for welding and machining benefits. Just look on the certification for S content and that will tell you the cleanliness.
Bar producers make a lot of free machining versions of 316, which would be loaded with sulfide inclusions. One would have a very good chance of getting some of this, even if you didn't specify it.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[frank72]

@metengr: thanks for you reply. up to now i did not think about continious casting vs ingot. I will try to follow up on this issue. may be this gives more infromation. what would you expect - more problems during polishing with materaial from ingot melting or from the continious casting. I assume continious casting gives less problems....

@mcquire: thanks for your support. we won't accept free machining qualities but I will check the sulfide contents of the mateial.

regards
frank

 

[EdStainless]

S levels well below FM levels are often used to improve weldability, and it causes more inclusions.

Amount of cold reduction is also a key as it contributes to breaking up the inclusions. They are still there but being smaller they are less noticeable.
One issue with bar is that the center never gets worked. Often there are serious stringer inclusions down the centerline.

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