Abstract
The influence of the heating mode of samples of constructional cemented steels 20ХН3А, 20ХГНР and 15ХГН2ТА on the value of austenite grain after high-temperature isothermal aging at 1000 °С is studied. It is shown that the heating of steels at a rate of 1.2–3.0 °C / min in the phase-transformation interval stabilizes the grain structure of the steels and leads to a slowing down of the kinetics of the growth of austenite grains during prolonged high-temperature aging, which makes it possible to increase the temperature of the chemical-thermal treatment of steels. It is concluded that the stabilization of the grain structure of steels is associated with the formation of segregation of impurity atoms and particles at grain boundaries with high-angle disorientation during slow heating, which prevents migration of grain boundaries in the process of prolonged high-temperature aging. A high-temperature chemical-thermal treatment of a batch of billets from steel 20ХН3А under experimental conditions with stepwise heating in the phase-transformation interval provided a qualitative fine-grained structure of the cemented layer.
Highlights
Вместе с тем применение стандартных сталей для высокотемпературной цементации в значительной степени сдерживается ростом аустенитного зерна в упрочненном слое и сердцевине зубчатых колес, что сопровождается понижением их ударной вязкости и сопротивления уста лостному разрушению
It is shown that the heating of steels at a rate of 1.2–3.0 °C / min in the phase-transformation interval stabilizes the grain structure of the steels and leads to a slowing down of the kinetics of the growth of austenite grains during prolonged high-temperature aging, which makes it possible to increase the temperature of the chemical-thermal treatment of steels
It is concluded that the stabilization of the grain structure of steels is associated with the formation of segregation of impurity atoms and particles at grain boundaries with high-angle disorientation during slow heating, which prevents migration of grain boundaries in the process of prolonged high-temperature aging
Summary
Вместе с тем применение стандартных сталей для высокотемпературной цементации в значительной степени сдерживается ростом аустенитного зерна в упрочненном слое и сердцевине зубчатых колес, что сопровождается понижением их ударной вязкости и сопротивления уста лостному разрушению. 2. Микроструктуры сталей 20ХН3А (а) и 20ХГНР (b) после предварительной термической обработки (нормализация и высокий отпуск) При этом в сталях 20ХН3А, 20ХГНР и 15ХГН2ТА формируется разнозернистая структура со средним размером зерна 95, 128 и 91 мкм соответственно.
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