Schemes of deformation strengthening for dies from steel with regulated austenitic transformation during exploitation

Abstract

Krugljakow O., Medvediev M. Konovodov D., Huba R. Schemes of deformation strengthening for dies from steel with regulated austenitic transformation during exploitation

The most heat-resistant conventional ferrite-pearlite-based stamping steels with carbide and mixed hardening reduce their strength when heated above 650-700°C, which leads to rapid tool failure. Using heat-resistant austenitic steels and alloys does not solve the problem. In fact, at high temperatures, these are sometimes stronger than ferrite-class steels. This can sometimes make tools last longer. However, these steels can crack easily, are difficult to machine, and are expensive and in short supply. Stamp steels with controlled austenitic transformation during exploitation are a new and only class of tool steels characterized by the phenomenon of retention of hot strain hardening (hot hardening). The degree of hot work hardening in steel obtained after austenitizing at 1150 °C followed by cyclic deformation at 450 °C increases with further cyclic deformation at 700-850 °C. Austenitizing at 1150 °C, holding and pre-deformation at 450 °C, followed by cooling to room temperature and rapid heating to a deformation temperature of 750 °C stabilizes the hot metal state and contributes to maximum steel hardening at 700-850 °C Taking into account of the stabilisation of the hot hardening, two technological schemes of deformation strengthening of extrusion dies have been proposed in this paper, which ensure their high operational stability. Quantitative dependencies have been established between the change in die dimensions and the heating or cooling temperature. The dependencies obtained in this work enable the design of the initial dimensions of the extrusion tool, taking into account the peculiarities of phase transformations in steels with controlled austenitic transformation during exploitation.