As for  non-magnetic  stainless steel  topic. Generally it is correct. But it is not exactly true . According to our cong shine experience and experiment, The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a relative magnetic permeability of 1.

 Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1.  But  it is difficult to achieve 100% AUSTENITIC STAINLESS STEEL . There is always a small amount of ferrite or martensites in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels is in the order of 1.05 – 1.1. So it is Composition effects on the magnetic permeability of austenitic stainless steels

 Regard to  the magnetic permeability of austenitic steels it is also changed during processing in some situation. For example,Cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.

In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004.

Martensitic, ferritic, duplex and precipitation hardening steels are magnetic