Allowable Impurities in ASTM A276, Stainless Steel

[tbq]

I have rejected parts for material composition.
The material requirement for purchasing was to ASTM A276. The certification for the chemical composition also lists
Mo (.235), Cu (.249), Co (.201) which are not listed as allowable within the ASTM A276, table 1.(Other Elements)

Questions:
Is there any tolerance on the extra elements?
Is there any ASTM guideline which may allow use of this material?

I have heard from my purchasing group the following:
1 - Now a days the equipment to analyse the composition is so much better and these impurities are normal.
2 - If it's not one of the critical 8 elements, we should not worry about it.

I simply want to complete further research before I even think of accepting these parts as usable.

 

[metengr]

5. Chemical Composition
5.1 The steel shall conform to the requirements for chemical
composition specified in Table 1.

5.2 Methods and practices relating to chemical analysis
required by this specification shall be in accordance with Test
Methods, Practices, and Terminology A 751.

Now, you need to review ASTM A 751 -
Look at Paragraph 7.
7. Unspecified Elements (Note 4)
7.1 Reporting analyses of unspecified elements is permitted.
NOTE 4—All commercial metals contain small amounts of various
elements in addition to those which are specified. It is neither practical nor
necessary to specify limits for every unspecified element that might be
present, despite the fact that the presence of many of these elements is
often routinely determined by the producer.

You now have your answer.

 

[redpicker]

What metengr said.

To add, you don't mention which grade you are dealing with. Specifically, some of the grades have specific limits for Molybdenum, which 0.235 may or may not conform to. But, from what metengr posted, if speficic limits are not shown, then you are dealing with an unspecified element.

For the austenitic grades, these residual levels of Mo, Cu and Co are normal and not a problem. I always assumed they come from the high nickel scrap used and it would be expensive and not very useful to try and get these levels any lower.

I disagree with the first part of point 1, above (it sounds a bit condescending to me). The equipment used today isn't any better (as far as accuacy is concerned) than that used 25 years ago or, for that matter, the wet analytical methods used 50 years ago and that these levels of residual were present (and often reported) in these alloys for quite some time. But, they are correct in that, depending on the alloy, these levels are normal and if an element is not specified, it is (by definition) an unspecified element and no limits apply.

Yeah, what metengr said.

rp

 

[EdStainless]

As long as they have not added enough of any unspecified element in order to qualify the material as another alloy then they are deemed acceptable.
Unless you have your own specification that your supplier has acknowledged and it limits these elements then this material is perfectly acceptable.

There is more Cu in SS today than 30 years ago. But the Mo and Co are about the same (we have done surveys of old MTRs).


= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[JoeyV87]

EdStainless -

There's a good reason for that - have you tried getting rid of it?

 

[EdStainless]

The Cu? There is no means to remove it, you can only dilute it. And to dilute it you have to use very clean virgin materials.
This would be heats with no scrap, and that is more than double the standard metal value.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[tbq]

Thank for your input.

**redpicker, I didn't mean to be condescending. And I learn things everyday, thanks.

The material in question is 304(UNS S30400)
Thanks again, I'll get a copy of the ASTM A751 straight away.

Thank you all for your inputs.