Reval® – Magnetic properties of stainless steel
Ferritic, martensitic, duplex and the standard precipitation hardening stainless steels are usually referred to as “magnetic” in that a normal magnet will stick to them. Austenitic stainless steel in the annealed condition is non-magnetic. However if an austenitic grade is on the lean side, i.e. has a low range of nickel, or if it has been cold worked, it can become sufficiently magnetic for a normal sized magnet to stick to it. In particular small diameter bars that have been bright drawn can exhibit a strong pull on a magnet.
Magnetism can vary in a bar, with the thread of a thread rolled bar being magnetic but the still smooth shaft being non-magnetic. If bars are bent to a high degree, the bend area can become magnetic.
If non-magnetism is crucial, for example reinforcing bar in concrete for particular applications, this must be established at the enquiry stage. A general figure for the grade can then be given, or a sample can be checked by a UKAS approved test house to establish its relative magnetic permeability.