Cold worked austenitic s/steels will contain some "strain induced" martensite which as making steel partially "ferrus magnetic" can also reduce corrosion resistance.

Annealing is required to reduce permeability of components after final machining, rolling or welding and is necessary for components used in applications where magnetic fields must be kept to a minimum.

Process - Anneal at 1025c/1050c - suitable top soak followed by rapid cooling.