Is OES PMI required for dual certified 316/316L material?

[Dennis van Zanten]

Hi all,

Got an issue on which I can't seem to find a conclusive answer.
I work in the Oil/Gas industry and specifically in filtration.

Now the question, is it required to perform OES PMI (Optical Emission Spectrometry, to determine Carbon content) on dual certified Stainless Steel (316/316L) or will 'standard' XRF PMI suffice? The Material Test Report surely indicates dual certified 316/316L (looking at mechanical properties, tensile tests it is conform 316 and the carbon content is indeed lower than 0.03% like required for 316L).

I am not really familiar with metallurgy.

If anyone has an answer I would be thankful.
Best Regards,
Dennis van Zanten

 

[DSB123]

Why are you doubting the matyerial test Certificate? Dodgy Mill? Dodgy Supplier?

 

[Dennis van Zanten]

It is not that there is any doubt regarding Mill / Material Certificate, but it is an additional requirement by the customer to perform PMI on machined parts as well..

 

[metengr]

is it required to perform OES PMI (Optical Emission Spectrometry, to determine Carbon content) on dual certified Stainless Steel (316/316L) or will 'standard' XRF PMI suffice?

No, unless required by the owner contract specification or on the PO. Standard PMI will not provide accurate carbon content, which is what you need to determine if L (low carbon) is met.

 

[weldstan]

Your PMI is to assure that you actually have 316(L). Often 304 is mixed with 316 but stamped/certified as 316. You should ask the engineer whether you will need to check for carbon. Most often checking for C is not done to verify L grade, especially today when most 316 is made to the low C standard and dual certified. Checking for C is more important when requiring 'H' grades for high temp applications.

 

[EdStainless]

Was it ordered as 316L or dual cert?
If it was ordered as 316 and delivered as dual cert then you only have to show that it is 316.

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P.E. Metallurgy, Plymouth Tube

 

[pradipgoswami]

The requirement:-
The Material Test Report surely indicates dual certified 316/316L (looking at mechanical properties, tensile tests it is conform 316 and the [highlight #FCE94F]carbon content is indeed lower than 0.03% like required for 316L[/highlight].

XRF technique will detect all elements except "C". In order to detect if Carbon content is lower than 0.03% OES is the only feasible PMI technique.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[EdStainless]

You only need to try to prove that it is 316L if that is what was ordered.
If it was ordered as 316 straight grade or as either, then just showing that it meets 316 is adequate for the situation.

If it was ordered as 316L, then must test to show that it is actually 316L.

I always amazes me that people fret so over the chemistry, but how often do they bother puling new tensile tests?

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P.E. Metallurgy, Plymouth Tube

 

[moltenmetal]

Unless technology has improved greatly in the last few years, XRF will NOT "detect all elements except C". Many common "point and shoot" XRF machines are either blind or insensitive to all sorts of lighter elements, such that they have difficulty telling the difference between 304, 303 and 321 for instance. They are useful, though, for quantifying the MAJOR alloying constituents of many stainless steels.

Carbon content takes much more elaborate methods to quantify, and hence is NOT routinely done on the shop floor as part of a PMI program. Rather, it's done by sampling. Some of the methods (the ones likely to be most accurate) are actually destructive tests, i.e. requiring the removal of material, so not of much use in testing welds in the deposited state for example.

 

[Dennis van Zanten]

Hi all, and thanks for all the replies.
The material we buy is dual certified 316 stainless steel so it is according to both 316 and 316L specifications and mechanical strengths.

However we see a lot of (end) customers who require us to perform PMI (so not on the laddle, but on the product after machining).
However in a lot of PMI specs customers give they specify on 316 no Carbon content needs to be measured (XRF PMI) but on 316L they need to see the Carbon content measured (and therefore we need OES PMI. This, for us makes a huge difference because we have our own handheld XRF PMI device with which me measure, but if Carbon content needs to be measured we have to outsource this to a different company with OES Device.

You can imagine OES PMI (Outsourced) takes longer and is much more expensive.

For recent orders we decided to perform OES PMI (to be on the safe side), but I was wondering if dual certified 316 material needs to be handled as 316 or 316L, in other words do we need OES PMI (like for 316L) or is XRF PMI sufficient (like for 316).

Heard something that because our 316 material is always purchased dual certified we don't need OES PMI, because dual certified 316 material has the same mechanical properties as 316 (only slightly lower Carbon content).

Regards,
Dennis

 

[EdStainless]

Not really, if it is specified as 316, and you decide to order dual certified then you don't need C to show that it meets the 316 spec.
If your customer requires either 316L or dual cert then you would need to test for C.
If you are machining these wouldn't it be easier to send some chips to the lab for traditional combustion C analysis? It is a better test and you could get it done while you are still working on the part.

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P.E. Metallurgy, Plymouth Tube

 

[mk3223]

IMO, it's better to clarify with the Buyer for the actual testing required for the "L" (or "H") grade SS material. Of cause, the test isn't free,and has a cost associated with it. Also, it needs to confirm how many samples are required for the testing.
In the warehouse of the previous company, the staff performed in-house PMI, as the material received, for a certain percentage of the alloy and SS items. But, the shop MTR is acceptable for the carbon content of the "L" or "H" grade material, and no in-house PMI needed.

 

[CoCoE]

Dear Dennis van Zanten

It doesn't look like a mandatory test for me!
Note 2 says, "Carbon content shall be specified by the Owner's engineer"-> Is it specified? In either cases, we have nothing to do here.
Next note says "XRF or OES or WCA MAY BE used if some undefined other methods differ from Mill certificates"---->is there any such differences noticed from mill certificates?
If no, I think you don't need to do PMI.

Do you have any other requirements stating PMI shall be carried out as mandatory?

Coco