Stainless steel as ferromagnetic or non/paramagnetic

[abdulbadii]

TL;DR Summary

this stainless steel ferromagnetic while that one is non/paramagnetic ?

Why is this stainless steel ferromagnetic while that one is non/paramagnetic, how's each proportion of them and what's its key difference that'd determines such the distinction?

 

[DaveC426913]

What has your research on the subject turned up? What are your ideas on the subject?

 

[Baluncore]

Martensitic, duplex and ferritic stainless steels are magnetic, while austenitic stainless steel is usually non-magnetic.
https://en.wikipedia.org/wiki/Stainless_steel#Magnetism

Fridge magnets work on the stainless steel used to make "white goods" because it is martensitic.

If you cut or grind stainless steel, it will often change its local magnetic properties.

 

[Astronuc]

Martensitic, duplex and ferritic stainless steels are magnetic, while austenitic stainless steel is usually non-magnetic.

Martensitic and ferritic stainless steels have bct/bcc and bcc crystal structure, respectively, while duplex, as the term implies, has two crystal structures, which could be ferritic-martensitic (F/M), austenitic-ferritic, or austenitic-martensitic. Non-magnetic austenitic stainless steel (usually with a fair amount of Ni and Mn, which are austenite stabilizers) has an fcc crystal structure. The more bcc in an fcc matrix, the more magnetic a stainless steel.

The significance of stainless is the Cr content, which allows a steel to become stainless through the formation of a stable chromia (Cr₂O₃) film on the surface, which prevents or retards further oxidation/corrosion.