Magnetostriction and Magnetization of Common High Strength Steels

Some common high strength steels possess enough magnetostriction to serve as the active material in sensors, e.g. torque sensors, while simultaneously performing their usual structural role. The magnetization and magnetostriction of six common high strength steels have been measured as a function of stress. Measurements were made in a hydraulic load frame at compressive stresses of -1, -50, -100, and -150 MPa with fields up to 135 kA/m (1700 Oe). With two exceptions, all of the samples displayed ldquonormalrdquo strain-field curves. The exceptions were Maraging 300 steel whose magnetostriction was continuing to increase with stress even at -150 MPa and an SAE 4130 steel that showed an ldquoinverted V rdquo shape. B-H curves of all of the samples showed some small dependencies on stress but were otherwise unremarkable. The saturation magnetostrictions (muS = 1 times 10^-6) and saturation magnetization (tesla) were: AerMet 100 [30 muS, 1.68 T]; HP 9-4-20 [23 muS, 1.68 T]; SAE 4130 [10 muS, 1.81 T]; Maraging 300 [32 muS (at -150 MPa), 1.67 T]; SAE 4340 [5 muS, 1.58 T]; SAE 9310 (heat treatment I) [10 muS, 1.77 T]; and SAE 9310 (heat treatment II) [12 muS, 1.82 T]. Details of the heat treatments are given.