COLD RESISTANCE AND MECHANICAL PROPERTIES OF HIGH-STRENGTH MEDIUM ALLOY STEEL DEPENDING ON THE TECHNOLOGY OF CAST BILLETS PRODUCTION

Experimental data on influence of conditions of high-strength steel crystallization on its mechanical properties are given in the work. Special attention is paid to the cold resistance as to the most important indicator of operation properties of the responsible products defining reliability and operability of a cast final product. Serial curves of impact strength, work of crack development and percent of fibration are given depending on test temperature. The possibility of increase in cold resistance of the cast alloyed steel is shown depending on casting technology: in a volume sandy form (control casting), in a thin-walled form with the ceramic layer and compulsory cooling with air-and-water mix differentiated on height (with external cooling) and in the same form with input of microrefrigerators when filling liquid steel (with complex impact). According to the research results it was established that the impact strength of the experimental metal obtained at complex impact on the hardened metal is higher in all studied temperature interval. Distinctive feature is smoother change nature of impact strength of experimental metal and lack of sharp reduction of this indicator for control samples. Change of work of crack development also depends on conditions of crystallization and cooling of casting metal. Serial curves have shown that tested metal has smaller tendency to fragile destruction (higher cold resistance). Similar dependences are received during the research of break fibration.