Study of the influence of cryogene processing on the characteristics of structure formation and fatigue resistance of 38KHN3MFA steel after preliminary thermal hardening

Abstract

The purpose of the work is to study the influence of complex heat treatment on the peculiarities of the formation of the structure and properties of carbon steel alloyed with chromium, nickel, molybdenum and vanadium. Currently, carbon alloy steels (38CrNi3MoV, 65Cr3SiMoV, 80Cr3MoV) containing chromium, molybdenum, nickel, vanadium and other expensive chemical elements are used for the production of various metallurgical and machine-building products (rolling rolls, rulers, piercing mandrels, parts of power equipment). However, the wear resistance of finished products made of specified steels in harsh operating conditions (significant cyclic loads and elevated temperatures) is insufficient in practice. One of the methods of effective influence on the improvement of the operational resistance of alloyed carbon steels may be the use of cryogenic treatment after preliminary thermal hardening. The results of studies of the effect and duration of cryogenic treatment on the features of structure formation, microhardness, hardness, and wear resistance of 38CrNi3MoV steel previously subjected to thermal hardening are presented. It was established that the duration of exposure of 38CrNi3MoV steel in liquid nitrogen should be at least 1.0 hours, which allows to achieve an increase in microhardness and wear resistance by 12 % and 17.4 %, respectively. The obtained results allow us to state that the use of cryogenic treatment at the final stage of thermal hardening will ensure an increase in the operational durability of products of special purpose, which are made of 38CrNi3MoV steel. The developed method can be recommended for the industrial implementation of the technology of complex heat treatment of carbon steels with increased wear resistance, which additionally contain chromium, nickel, molybdenum and vanadium.