316/316L Dual cert

[awiniarski]

Hi everyone,

First time posting. I am a quality manager for a manufacturing shop, machine shop (cnc/sheet metal).

On to my question. We have been machining 316L bar and have had very little trouble up until recently. Our supplier gave us some 316/316L dual certified material. We had no idea how big of a problem this would cause. We have been experiencing work hardening, burning up tooling etc.

What has been the experience in the industry using the dual cert material in regards to machining. We tried to specifiy only 316L but our supplier is stating that the material meets both certs.

Just looking for some input on how to try and resolve this issue

Thank you and look forward to reading the forums more =)

 

[mrfailure]

You have no problem. From a compositional standpoint 316L will also dual cert to 316 because the 0.030% max carbon, the only difference in composition, is contained within the 0.08% max limit of 316. Thus, 316L will always dual cert to 316.

 

[awiniarski]

I understand this completely. The problem we are having is machining this new ''hybrid'' material. I am not sure how else to identify it. It work hardens very rapidly unlike the old 316L we used to get.

 

[monkeydog]

Can you look at the chemistry of the old "good" 316L and compare it to your new dual 316?

 

[mrfailure]

The different behavior sounds suspicious to me. For piece of mind, send a sample out to another independent lab for composition to make sure you have composition conforming to 316L. If it does, you can take this one step further and have that lab run a comparison of properties (chemistry, hardness, tensile) between work-hardening and non-work-hardening material.

 

[Jughandle]

If chemistry is okay, maybe the difference is in the processing. Check the rolling mill particulars.

 

[EdStainless]

My guess is that this material is softer than what you have had before, or at least from a different mill.
You issues are not related to the chemistry or the dual certification.

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P.E. Metallurgy, Plymouth Tube

 

[eril]

For dual certified material i.e 316/316L, mechanical properties of material will follow 316, however chemical prop. will be same as 316L.

 

[remetaper]

I suggest to verify the certificate: what is Sulphur content ??? Indipendently if 316 L or 316, if S% is very low ( < 0,01), machinability will be poor. On the contrary, if S% = 0,02-0,03 , machinability will good. Moreover, as EdStainless said, if the structure were a little bit harder and grain were fine,the machinability improves. Finally, verify the old certificates ( where you had no difficulties to machine) and compare to the last ones. Other evaluautions could be added ( such as Ni e N content, HB, Ferrite an so on ) but the first "look" is Sulphur. Surely, your Supplier didn't delivery Ca -treated grades ( such as Project70, Maxival, Prodec and similar)

 

[awiniarski]

Guys, thank you for all the input.

We requested strictly 316L from our supplier in the most recent purchase orders. Our delivery today came with 316/316L. Our investigation now takes a turn to see if this supplier is buying from the same distributor as our previous supplier was. I will also be taking a look at the Sulphur content thanks to Remetaper. The material delivered today contained .027% Sulphur.

Thanks again for all the input and I will update if I have any further questions. =)

 

[gtaw]

It could be that the purchaser originally specified 18/8 stainless steel. That being the case, type 303 could have been provided. Type 303 is also known as "free Machining" stainless steel that has a nominal chrome content of 18% and a nickel content of 8% within plus or minus tolerance. The free machining stainless has roughly 5 times the sulfur content of type 304, 316, or other members of the 18/8 austenitic stainless steel family. The high sulfur makes the stainless steel relatively easy to machine and the chips break up rather than producing long continuous ribbons.

A quick comparison of the chips from the "old" stainless steel to the "new' stainless steel should tell the story pretty quickly.


Best regards - Al