Monitoring the Physicomechanical Properties of 40X Steel on the Basis of the Limiting Magnetic Hysteresis Loop

Abstract

The mechanical properties (strength σ_u, yield point σ_0.2, relative elongation ψ; and hardness HB and HRC) of 40X steel depend monotonically on the tempering temperature T_te after quenching and are closely correlated. Their relationships are described by linear regression equations. The corresponding correlation coefficients and computational errors are determined. The coercive force H_c of 40X steel is not clearly related to its physicomechanical properties over the whole range of T_te. However, magnetic analysis of the structure of 40X steel may be based on an algorithm that employs Hc and the ratio of the residual magnetization to the saturation magnetization. The results given by this algorithm depend uniquely on T_te over its practical range and are highly sensitive to change in the physicomechanical properties of 40X steel.