The effectiveness of hardening thermally improved steels in aqueous polymer solutions

© 2020, "Ore and Metals" Publishing house. All rights reserved. Results of study of hardening capacity and hardenability of steel products of 40H, 42HМFА, 47GТ and steel 45 after quenching in water, oil and aqueous solutions with different content of polymer are presented. High capacity for hardening of medium-carbon alloyed steels and ab-sence of cracks on parts of complex shape at quenching in 32.5% solution of polyalkylene glycol were revealed. The properties of structural steels after thermal improvement, which were cooled in various media during quenching, have been investigated. Advantages of application for quenching of aqueous solutions of polymers are shown. In comparison with oil, quenching in synthetic media provides higher hardness and reduces the content of non-artensitic conversion products in hardened steel. Influence of bainite obtained during quenching on toughness, threshold of cold brittleness and endurance of steels after thermal improvement is revealed. A color etching method was used to distinguish structural constituents in hardened steel. Fractograms of the fracture surface of standard sam-ples tested for impact bending at different temperatures are presented. Hereditary connection is established between initial structure of hardened steel with quality indices of surface hardened layer obtained during quenching with heating by high-frequency currents. Quenching in aqueous solutions of polyalkylene glycol allows to realize at maximum level resistance of high-yield steel to brittle destruction and its fatigue strength, as well as quenching throughout the section of metal production