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Up Topic Welding Industry / ASME Codes / Question about tensile test
- - By dlmann (**) Date 08-03-2011 22:58
One of our contractors submited a a PQR with the Mill Test Report for the material which is SA312, TP316/316L.

Specimen 1, 79,291 ksi
Specimen 2, 74,182 ksi  

Looking at QW-422 there are two seperate listings for TP316 @ 75 ksi and TP316L @ 70 ksi.  It is my intent to accept the tensile test on the 75 ksi value. 

But what if the tensiles broke less than 75 ksi?

Regards, Donnie Mann
Parent - By G.S.Crisi (****) Date 08-03-2011 23:08
Which exactly is the material you tested, 316 or 316L?
There's a diffference between them. 316 has a higher carbon content, and consequently a higher tensile strength.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By MBSims (****) Date 08-04-2011 02:11
I don't have a copy of IX here, but in the text of Article I it says the tensile results must be within 5% of the specified minimum shown in QW/QB-422 for the base metal.  So a minimum value of 95% of 75 ksi = 71,250 psi is required.  Since the PQR used material that is dual certified for 316/316L, it must meet both the 316 minimum specified tensile strength and the maximum carbon limit for 316L.  Using the 75 ksi minimum as the basis for evaluating acceptability is correct.
Parent - - By js55 (*****) Date 08-04-2011 12:40
Marty,
I won't often step into a disagreement with you on Section IX, but I'm not sure you are correct here. I'm actually proposing a theoretical based upon this post but not in answer to it necesarily since as you stated the tensiles are good in any case if they broke in the BM.

In any case, unless you have an Interpretation available it could be argued (and I'm not 100% behind this though I'm getting there) that dual certification does not have to be considered for procedure qualification acceptance criteria in that the MTR is stating you have essentially both 316 AND 316L. Section IX does not say you have to comply with the material cert, it says you have to comply with QW-422. The material cert only identifies and verifies what you have. QW-422 says 316L is required to have 70ksi T(without looking it up). You have a material that is 316L and the low tensiles of a PQR (say 69ksi in the base metal) comply with that requirement.
The reason I put it this way is that if you had this situation all you would have to do is have the manufacturer remove the 316 statement on the MTR and you would then have a good PQR although nothing has changed except the paper. I do not believe this is an illigitimate procedure since the filler is the same, the parameters the same, the material the same, and the material specs do not require that you establish dual cert if a material is capable of it, they only allow you to do so if you want to.
In fact, I might take the argument one step further. Your MTR says you have 316L. Write your PQR up for 316L and the tensiles are good. Its thinking outside the box a bit but I do not see anything ethically wrong with it, because the whole dilemma is based upon a liberal acceptance of the dual certification idea.
Taking the philosophy of having to comply with the higher of the two is a conservative approach but I'm not sure its required.
I probably could have stated this more concisely, but I'm confident you'll get my point.
Parent - - By MBSims (****) Date 08-04-2011 22:00
Good point Jeff.  Since it is dual certified, I can also agree with calling it 316L on the PQR and using 70 ksi as the basis for evaluating the results.  I think I would tend to choose the 75 ksi value knowing that is what the base metal had to meet originally.  But there is nothing in the code that would prevent using the 316L values either.
Parent - - By js55 (*****) Date 08-05-2011 12:03
I'm still sitting on the fence on this one but the 316L approach does not give me a lot of heartburn due to the ability to do both anyway once you have the qual in place. It still has to be considered from an engineering standpoint, which is exactly what I believe you are expressing in your post.
Parent - - By MBSims (****) Date 08-06-2011 13:00
I have seen this approach used in qualifying impact tested procedures also.  You can buy plate under SA516 that is dual certified as Gr. 65/70. SA516-65 is a P-No. 1 Gr. 1, SA516-70 is a P-No. 1 Gr. 2.  The PQR documents SA516-65 welded to SA516-70 and qualifies both Gr. 1 and Gr. 2 for impacts.  Not much different in this case for dual certified 316/316L.  Documenting either grade separately or dual grade on the PQR would be acceptable in my view.
Parent - By G.S.Crisi (****) Date 08-06-2011 14:40
In my opinion, the difference between 316 and 316L is greater that the difference between 516 Gr65 and 516 Gr70.
516 Gr65 and 70 are both low carbon steels in which the difference in only mechanical strength. The corrosion resistance is the same.
On the other hand, the difference between 316 and 316L is not only mechanical strength, as it's been pointed out on some of the answers, but also in corrosion resistance. In fact, as 316L has a much lower carbon content than 316, it's less subject to intergranular corrosion.
Giovanni S. Crisi
Parent - By js55 (*****) Date 08-04-2011 12:00 Edited 08-04-2011 12:03
You need to verify where the tensiles broke for them to take advantage of the 5% allowance.
Parent - - By Mikeqc1 (****) Date 08-04-2011 19:00
ARE THE READINGS FROM THE mtr OR FROM THE TESTED WELD?
Parent - By dlmann (**) Date 08-05-2011 23:55
The speciman tensile readings are from a weld test, both specimans broke in the base metal.  Thanks to all for your input.
Up Topic Welding Industry / ASME Codes / Question about tensile test

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