Presence of Cu in SS 316L

[franklin55]

We have procured SS 316L pipe (4" Sch. 160)for our Urea plant. We have now tested some random lengths of the pipe and the result of one of them is as follows:
Cr = 16.78 %
Mn =1.39 %
Mo = 2.19 %
Ni = 10.59 %
Cu = 0.8 %
Fe = 68.25 %

The above composition seems perfect except the presence of Copper. Can anyone advise if the presence of Cu is acceptable?
Please note that the alloy analyzer cannot detect Carbon therefore the reading of Carbon is not given.

Regards

 

[SJones]

JL Seagull you need to look further along footnote B to Table 1 in A312. Look at the second sentence regarding ellipses (...) and then look at the copper column for TP316L where there happens to be an ellipsis. If there is no compositional requirement (for requirement read restriction), and one doesn't even have to analyse and report copper, would that change your view on how much copper is allowed?

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[rneill]

Sjones,

Which edition of A312 have you got? In my 2002 copy, Note B just says "Maximum, unless otherwise noted" but it doesn't say anything about what the ellipses per se actually mean (either none at all, or no restriction).

This is kind of bugging me so I tried calling ASTM this afternoon and got passed around a couple of people, none of whom knew what I was asking about nor had an answer.

I consulted with a couple of materials engineers I know and received the response that unless a numeric value is listed, there is no minimum or maximum to the element. The element is shown because a single table is being used for a number of different grades and some of the grades have that element controlled so there has to be a column for it. For other grades, where the element is "unspecified" no numeric value is listed.

I'd be as keen as everyone else to find a proper definition of the ellipses somewhere in one of the ASTM standards ...

 

[SJones]

I am quoting from the 2009 version of A312.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JLSeagull]

My copy is 2005 and worded as rneill described. Time for an update.

 

[rneill]

Likewise, time for an update on my ASTM standards as well.

 

[franklin55]

Deciding not to to take risk at critical application, we have rejected the pipe with Cu traces and the supplier is going to replace by pipe from another manufacturer.

 

[BigInch]

What did the mill/supplier say about why that copper content is there?

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

http://virtualpipeline.spaces.live.com/

 

[micalbrch]

Good question. We should have asked that two days ago.

 

[EdStainless]

If an element is not listed then it should not be deliberately added.
My guess is that this is from poor scrap segregation.
I am not so worried about the Cu as I am the possibility of Zn, Sn and other metals.

The ellipses technically means: this is from A941:
ellipsis, n—in a tabular entry, three periods (...) that indicate that there is no requirement.

Cu does help corrosion resistance is some cases (H2SO4), and it hurts in others.
This level of Cu can make welding more difficult, more prone to discoloration and porosity.

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