Investigation of the decay kinetics of austenite with continuous cooling K76F steel for wide-gauge railway rails

A.I. Babachenko, A.A. Kononenko, A.M. Khulin
2018 Fundamental and applied problems of ferrous metallurgy  
The aim of the work is to study the kinetics of decomposition of supercooled austenite with continuous cooling of steel for railway rails with a high content of manganese and micro-alloyed vanadium. The relevance of the work is the need to determine the possibility of producing rails from K76 F steel according to foreign standards, in particular EN 13674-1-2011. During the research, a thermo-kinetic diagram was constructed with different cooling rates for samples of K76F steel heated by the
more » ... ing mode for quenching the rails in an induction unit at the heat treatment site at Azovstal Iron and Steel Works. Dilatometric studies have shown that when samples are heated at a rate of 300С/min in steel for railway rails, polymorphic  -transformation begins at temperature 7350С (Ас1), ends at 7600С (Ас3). It is established that the temperatures of the beginning and completion of the formation of ferrite, perlite and bainite decrease with increasing cooling rate. With an increase in the rate of cooling, the morphology changes and the dispersion of perlite increases - from the middle plate of frequent perlite to highly dispersed sorbitol structures and quenching troostite. It was concluded that in the studied steel grade K76F with 0.80%С, 0.25%Si, 0.97%Mn, 0.055%V, it is impossible to achieve hardness above 400НВ without the formation of bainite. For the manufacture of high-strength rails of category R400HT EN 13674-1-2011, it is necessary to create steel of a new chemical composition. It is shown that it is possible to develop grounded reinforcing heat treatment mode and to increase the operational reliability of rails by defining critical points and studying the kinetics of decomposition of supercooled austenite with continuous cooling of steel.
doi:10.52150/2522-9117-2018-32-317-327 fatcat:6q7gt6i44nczzay27ac2xkcium