Magnetic and magnetoacoustic testing parameters of the stressed–strained state of carbon steels that were subjected to a cold plastic deformation and annealing

A complex of magnetic and magnetoacoustic properties of cold-deformed and annealed (at different temperatures) steels with carbon contents of 0.2 (20 steel) and 0.7% (70 steel) was investigated. It was established that as the annealing temperature of these steels increases up to 700°C, the values of the parameters that are related to the intensity of irreversible magnetization-reversal processes monotonically increase. It is shown that the coercive force of 70 steel changes nonmonotonically under variations in the annealing conditions and cannot be a testing parameter. Among quasi-statically measured magnetic parameters for testing the annealing procedure, the residual induction and the coercivereturn induction can be used. The structural sensitivities of such parameters of the magnetoacoustic emission (MAE) as the amplitude, the fundamental frequency, and the field of the MAE maximum were investigated. It is shown that the MAE maximum amplitude and field correlate with the residual magnetic induction of the substance of the investigated steels and can be used in the diagnostics.