Magnetic characteristics of ferromagnetic stainless steels

The magnetic characteristics of two representatives of martensitic and one of ferritic stainless steels, i.e. SUS 403, TAF, and SUS 405, were investigated in connection with development of high-temperature and nuclear resistive sensors. The test pieces were machined out from rod materials and heat-treated in an argon atmosphere. They were placed in an electric furnace, and their magnetic characteristics were measured at room temperature and elevated temperatures. The examined characteristics were of initial magnetization curve, hystersis loop, AC permeability, Curie point, and inverse magnetostriction. The martensitic stainless steels show somewhat semihard characteristics (H_c: 5 to 15 Oe) and the ferritic one is rather soft (H_c; 2 to 5 Oe). The Curie point ranges from 720 to 750°C. The magnetization is about 15000 G at a field strength of 100 Oe. A large inverse magnetostriction is observed in SUS 403 and SUS 405. Their magnetic characteristics were observed to change with heat treatment