Bulletin of the Polish Academy of Sciences: Technical Sciences

Abstract

of acoustic emission during heat treatment processes show that this method is the source of relevant information about the phenomena occurring in the processed material [6,7,11,12]. Measurement of acoustic emission signals is performed using the passive method. The apparatus used has no influence on the tested object. Registered signals are related only to the acoustic effects occurring in the material under study [13]. Sources of acoustic emission in metals are [3,5,[14][15][16][17][18][19][20][21]: dislocation motion due to plastic deformation, formation of twins, phase transitions of the displacive type, micro and macro cracks. Acoustic emission is a method of obtaining new information about phenomena occurring during phase changes. The applied research techniques may be used in the industry to test large samples in the future. Monitoring of heat treatment processes is vitally important for the utility values of finished industrial products. By tracking the breakdown kinetics of supercooled austenite, processes can be regulated and improved. New solutions and technologies in this aspect are still being searched for. MATERIALS AND METHODS Research materialThe samples were prepared from 27MnCrB5-2 steel. Samples were taken and prepared from one steel rod. Cylindrical specimens with diameters of 22 mm and height of 25 mm were made. The chemical composition of 27MnCrB5-2 steel is presented in Table 1.The steel subjected to the tests is used in the automotive industry for fasteners of machine parts. The fasteners are heat treated to improve the properties of the material from which they are made. During the tests, the continuous cooling process was performed on the samples.