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# New help in understanding a specification

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## New help in understanding a specification

(OP)
Spec. = the relative magnetic permeablity shall be determined and shall not exceed 2.0 (air - 1.0)

AMS-QQ-S-763 (also referenced) says: shall show a magnetic permeability not higher than 1.02 at 200 oersteds (air equal to 1.00)

Mill Test Report for 304 Stainless steel says:
DC perm feebly magnetic material
Perm x 1000
----------------------------------
HM Oersted = 200.0 (A/M = 915.49)   Permeability = 1.02000

I am assuming air = 1.0 at 200.0 oersteds and the material per the MTR is exactly at the spec.  However, the "Perm x 1000" has me concerned.

### RE: New help in understanding a specification

aggie
this may be a bit late but:

304 stainless steel is austenitic which is non magnetic:
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=Q304A
- as opposed to martensitic stainless which is magnetic.  The above link does actually say that it is "slightly magnetic when cold worked", but they mean it will be barely noticeable.  At 200 Oersted the permeability of mild steel is about 1100 (cast steel is a bit less), I think 304 would never get above about 1.1.  It is really all or nothing, if you place a magnet next to the steel it will be completely obvious if it is non-magnetic stainless or not, there is nothing in between.

As to the meaning of "Perm x 1000", I don't understand it either but I would ignore it.

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