Describing the effect of tempering on hysteresis curves of 54SiCr6 spring steel by the effective field model

Abstract

Hysteresis loops of a ferromagnetic material containing internal stresses due to heat treatment are investigated. The 54SiCr6 spring steel was quenched and tempered in the 300–740°C range. At temperatures from 300 to 500°C changes in hysteresis curves can be described with a very good accuracy by the effective field model found previously for steels under stress due to direct mechanical loading. The effective field due to tempering had a similar shape with that by direct application of external compressive stress. In the range 300–500°C the effective field changes linearly with the tempering temperature. These magnetic results are in correspondence with other works showing that in this temperature range the internal stress decreases by more than two orders of magnitude. At temperatures above 500°C the change of magnetic properties is not monotonous because of influence of different factors—the spheroidization and the coarsening of the cementite, followed by recovery and recrystallization above 600°C.