The Influence of Heat Treatment on the Propagation Velocity of Shear Waves in Steel Bars

Abstract

The paper discusses the possibility of assessing changes in the speed of an ultrasonic wave in bars of steel 45 for different types of heat treatment. The diameter of the rods is 14 mm, the length of the working part is 20 cm. An electromagnetic-acoustic method of input and reception of transverse waves of axial polarization based on a transducer is used for structuroscopy. The wave velocity was measured by the method of multiple reflections over the cross section of the bar. In addition to the delivery status, heat treatment was performed on 8 bar samples in the following modes: annealing at 850 ° С, normalization at 850 ° С, quenching from 850 ° С in oil, tempering at 200 ° С, 400 ° С, 450 ° С, 500 ° C, 600 ° C. The results of a change in the shear wave velocity in bars under all heat treatment conditions are presented. To increase the accuracy of determining the shear wave velocity, the diameters of the rods were measured with a step of 1 cm along the entire length. The velocity of the transverse wave in the rods after annealing was 3240 m/s, and after quenching, 3170 m/s. The states of delivery and after normalization show the same shear wave velocity of 3230 m/s. The obtained experimental data show that annealing increases the shear wave propagation velocity in the bar by 70 m / s relative to quenching without tempering. With an increase in tempering temperature, an increase in the shear wave propagation velocity relative to the quenched state is observed, reaching an increase of 65 m/s to 3235 m/s at a temperature of 600 ° C.