PREDICTION OF THE STRUCTURAL STATE OF THE WORKING LAYER OF LARGE-SIZE ROLLS DURING THERMAL HARDENING
Keywords:structure, cooling, rolling rolls, alloy steels, phase transformations, thermokinetic diagrams
Problem statement. High-carbon steels, which are additionally alloyed with chromium, molybdenum, and vanadium, are used during the production of large-sized rolling rolls for hot deformation. Rolling rolls are subjected to significant loads during operation, so they must have sufficient hardness and resistance to wear. Steels of the type 65Cr3SiMoV, 80Cr3MoV, 80Cr5MoV have recently been used for the production of hot-formed rolling rolls, but despite this, their resistance to wear in harsh operating conditions is insufficient. There is no information in the literature about the peculiarities of the austenite decay kinetics of the specified rolled steels, therefore, this direction requires appropriate comprehensive research. Purpose. Development of a methodology for predicting the structural state of the working layer of large rolling rolls in the process of thermal strengthening of high-carbon alloy steels, taking into account the determining parameters of the manufacturing technology. Results. A methodology for modeling phase-structural transformations in the process of continuous cooling of high-carbon alloy steels was developed. For steels 65Cr3SiMoV, 80Cr3MoV, 80Cr5MoV were constructed thermokinetic diagrams and on their basis, the peculiarities of the formation of the structural state of the working layer of large rolling rolls (support, working) during thermal hardening were investigated. It has been established that the method of hardening by volumetric heating of support rolls made of 65Cr3SiMoV steel ensures the formation of a bainite structure over the entire normalized depth of their working layer. For working rolls made of 80Cr3MoV and 80Cr5MoV steels, the most effective method is hardening with differentiated heating, while in the latter case continuous cooling should be carried out at a slower speed.
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