High Mn content on ASTM A351-2003 grade CD4MCu

[msmedesign]

I have received a valve casting per ASTM A351-2003 grade CD4MCu. I performed Positive Identfication Inspection (PMI) and found all the elements meets the ASTM specification with exception of Mn%. Instead of max 1% Mn material that I received has Mn 1.5 % - 2%. Manganise should improve the mechanical strength of the cating but, I am not sure if it will effect the chemical resistance of the material or the macro structure of the material.
As a note: forged grade F51 has 2% Mn.

 

[metengr]

msmedesign;
Regardless, you have a nonconformance of the valve material per ASTM A 351 that must be dispositioned before use. Did you or can you obtain a material test report for the valve body material? If not, I would try to obtain a small sample from a noncritical location on the valve body for chemical analysis to verify the PMI results. I have seen where PMI results were not totally correct and further chemical analysis was required.

 

[EdStainless]

How did you do your PMI? If this was a field instrument then you don't really know what the Mn is. You need to have a real lab analysis done to verify the chemistry. You also have to remember the tolerance on the chemistry. A product chemistry has an additional deviation allowed outside of the spec range.
As far as your concern, I am not too worried about the Mn level itself. My concern would be realted to the overall austenite/ferrite balance and checking to make sure that it correct.

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