National University of Science and Technology MISIS, Moscow, Russia

N. A. Chichenev, Dr. Eng., Prof., Dept. of Engineering of Technological Equipment, e-mail: chich38@mail.ru
A. O. Karfidov, Head of the Dept. of Engineering of Technological Equipment, e-mail: a.korf@mail.ru
M. V. Vasilyev, Senior Lecturer, Dept. of Engineering of Technological Equipment, e-mail: michailvasiliev91@gmail.com
O. N. Chicheneva, Cand. Eng., Associate Prof., Dept. of Computer-Aided Design and Engineering, e-mail: ch-grafika@mail.ru

The application of laser hardening of steels during heating without melting the surface is considered to improve the efficiency of the metal forming tool, including rolls of cold rolling mills and cold deformation dies. To describe the processes of laser hardening, it is proposed to use dimensionless parameters that have a clear physical meaning and take into account the technological parameters of laser heat treatment and the thermophysical characteristics of the processed metal: 1) the relative power of the laser radiation, equal to the ratio of the power of the laser radiation to the power of the heat flux, which can be diverted from the surface due to thermal conductivity deep into the metal without melting it; 2) the relative speed of movement of the laser beam, equal to the ratio of the speed of movement of the laser beam to the speed of propagation of the temperature front in this material; 3) the relative depth of the hardened layer, equal to the ratio of the depth of the hardened layer to the maximum possible theoretical value, which is achieved when the temperature on the surface of the metal reaches its melting temperature. Experimental data on laser processing of structural alloy steel of type 40KhN2MA are presented, on the basis of which graphs are constructed and empirical dependences of the relative depth of the quenching zone on the relative power of laser radiation and the relative speed of the laser beam are obtained. It is shown that the formulas obtained and the graphs given can also be applied to other grades of steels, since they use relative (dimensionless, generalized) values of laser radiation power and the speed of movement of the laser beam.

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