On the efficiency of application of magnetic and electrical parameters for nondestructive testing of crystal-lattice microdistortions in heat-treated carbon steels

The effect of crystal-lattice microdistortions that characterize residual stresses in heat-treated steels that contain 0.36, 0.62, and 0.75% carbon on their magnetic characteristics, in particular, magnetic Barkhausen noise parameters, electrical resistivity, and elastic wave propagation velocity, which was determined by the electromagnetic acoustic transformation (EMAT) method, was studied. The coercive force and number of Barkhausen jumps for hardened steels are shown to correlate, to a great extent, with the average grain size rather than with crystal-lattice mirodistortions. Crystal-lattice microdistortions induced in steels upon hardening from different temperatures correlate adequately with the root-mean-square magnetic Barkhausen noise (RMS BN) voltage. When estimating crystallattice microdistortions in articles made from carbon steels subjected to marquenching and subsequent tempering, the combined use of the coercive force (for steels after low- and medium-temperature tempering) and RMS BN voltage (for steels after high-temperature tempering) is most efficient. Such parameters as the number of Barkhausen jumps, electrical resistivity, and elastic wave propagation velocity are less sensitive to changes in crystal-lattice microdistortions (CLMs) in heat-treated carbon steels.