Identical Heat Numbers from several MTR's

[Zeberoff]

I am dealing with an MTR for pipe from COMCO supplier. There is confusion about the associated heat numbers. The mill has provided several MTR's with identical heat numbers showing up in separate MTR's each having slightly different compositions for both product and heat analysis. Also in the MTR are additional heat numbers that are not relevant to our tag number for the PO.
So I have two questions:

1) If the heat number traces the original cast (heat) or roll (product), how can the composition vary? For instance, wt.% carbon for heat # X = 0.13 in MTR2, and wt.% carbon for heat # X = 0.15 on MTR3. Is there an acceptable variance I should be aware of according to a standard or rule of thumb.
2) Does the mill provide multiple MTR's for the same heat number to represent different sections of pipe?

Thank you!

 

[BillPSU]

I would direct the questions back to your supplier and wait for the interesting explanation.

Bill

 

[stanweld]

You also need to address the requirements of the material Specification and whether one or both of the MTR's heat analyses was based on product analysis. Finally, was the MTR provided by the mill (steel manufacturer) or the Warehouse suppier, importer or exporter?

 

[LittleInch]

See also

http://www.eng-tips.com/viewthread.cfm?qid=349456

, which has a similar issue.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Zeberoff]

Thank you all for the replies. The matter has been resolved as I made a slight error and noticed that the composition values for heat analysis was the same while the product analysis varied, which makes sense.

LittleInch, your link was very useful! - stanweld, you replied to the thread in this link and made a comment with regard to sulfur content: "There is no way that the sulfur contents could be so disparate". This concerns me a bit, as the sulfur content is 0.003 wt% in the MTR I am reviewing. We specify that it shall be less than 0.015%. What common manufacturing practice is used to reduce the sulfur content to such a low level? - I would like to follow up with our Warehouse supplier with this question. Thanks!

 

[stanweld]

Low sulfur steels which have < .005% S are readily available. If you specify S < .015% you can easily get S < .010%. If one has a heat analysis showing .003% S and it is true, there is no way that the same heat will have .015% S. Such disparity, would be indicative of major problems with the chemical analysis, itself, or other error, either intensional or unintensional.