Monel Carbon Content

[BLaroux]

I'm wondering how a 0.05% decrease in carbon content would beneficially affect the properties of Monel 400. I realize carbon additions generally increase strength while decresing ductility, but somehow I doubt the reason for lower carbon in the situation below has anything to do with improving ductility. Perhaps a corrosion, welding, or physical property issue?

We have a customer that is asking for Class A Monel 400 made to QQ-N-281 Add. 2, Interim Change 1. (for fasteners & other misc. small parts) Although QQ-N-281 Add. 2 is commonly specified, this "Interim Change 1" is very obscure and difficult to obtain. The primary difference we can acertain is that the max. carbon limitation for Class A Monel is 0.15% instead of the previous 0.2%. I'm looking for anything that might help to explain why this was done.

Thanks!

 

[metengr]

I have a suggestion, go to the source of information. Contact the folks below, I know several of the individuals that participate on ASME B&PV Code material activities, they are knowledgeable on Ni base alloys.

http://www.specialmetals.com/

 

[kenvlach]

QQ-N-281D NICKEL-COPPER ALLOY BAR, ROD, PLATE, SHEET, STRIP, WIRE, FORGINGS, AND STRUCTURAL AND SPECIAL SHAPED SECTIONS,
Revision D Interim Amendment 1, and
Revision D Amendment 2
are freely available at ASSIST:

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=50916

I see no language lowering the carbon limit. But, a possible reason for doing so is usage in a hydrogen-containing atmosphere -- don't want internal formation of CH₄ gas!

 

[BLaroux]

Thanks Kenvlach, we have both of those amendments, what I speak of is apparenlty called "Interim Change 1 to Amendment 2 of QQ-N-281D". Our information handing service has never even heard of it, but our customer is supposed to be getting it for us.

On the bright side it looks like a decent portion of Monel heats fall under the 0.15 limit by chance, but either way this requirement is obscure and material with certs will be unobtanium.

The methane gas idea is interesting... I have heard of Monel being used in such services. (Its just too bad that this service is fresh-water at ambient temperature. I'm starting to wonder where our customer is getting this stuff...)

 

[JamesCKelly]

Very often the mill can re-certify the material, that it meets your particular spec, for the distributor who is handling it. Since most Monel 400 has the carbon you want this should be quite possible. The QA guy at the distributor can handle it. Try Corrosion Materials, Baker, Louisiana.