Machinery & Energetics

On the basis of complex analytic and experimental studies of processes of crystallization from liquid state and recrystallization basic physical-chemical and phase parameters of structural steels, containing up to 0,4 wt.% C; 3% Si, Mn and Cr; 0,035% N; 0,3% V, were defined and qualitative regularities of their influence were established. These regularities give possibility to forecast analytically chemical compositions and conditions of heat treatment of castings and forgings of structural steels with required combination of casting and mechanical properties, hardenability, fatigue strength, cold resistance, toughness of destruction, abrasive wear resistance, heat stability and stability to reverse temper brittleness. The results of investigations implemented have shown, that low- and medium-alloy by manganese, silicon, and chromium structural steels in combination with nitride-vanadium hardening possess essential potential of physical-mechanical properties, which is realized at complex optimization of their chemical composition, deoxidization, types and conditions of heat treatment. The influence of these factors is so extreme and ambiguous that can be effectively optimized only by machine experiment of determined dependencies, presenting themselves as theoretical basis of computer metallography of structural steels. Study of many structural steels shows, that computer elaboration of their chemical composition, conditions of deoxidization and heat treatment ensure the creation new class of cost - efficient alloy steels with unique combination of strength, plastic and exploitation properties. Some examples of optimum heat treatment regimes of castings and forgings for a achieving such properties are presented.

structural steel, chemical composition, heat treatment, mechanical properties, hardenability, fatigue strength, cold resistance, toughness of destruction, abrasive wear resistance