Intense Hardening of Optimal Hardenability Steels Saves Alloy Elements, Energy, Improves Service Life of Machine Components and Makes Environment Cleaner

摘要

Manufacturing steels of optimal chemical composition, combined with intensive quenching, is an important step to save essential alloy elements and make the environment cleaner. As a rule, alloy steels are hardened in oils or high concentration polymers to prevent crack formation during quenching. However, slow cooling in oils requires more alloy elements to provide the needed surface hardness and hardenability. To provide an optimal hardened layer and optimal residual stress distribution in machine components after intensive cooling, chemical composition of steel must be properly optimized. High compressive residual stresses and high cooling rate within the martensite range result in additional strengthening of a material. Both high compressive residual stresses at the surface of steel parts and additional strengthening (superstrengthening) increase significantly their service life and save expensive alloy elements. After intensive quenching machine components, made of optimal hardenability steels, provide the following benefits: (1) high compressive residual stresses at the surface of steel parts are formed; (2) the superstrengthening phenomenon in the surface layers take place; (3) mechanical properties of material at the core of steel parts are significantly improved due to high cooling rate during intensive cooling; (4) crack formation decreases due to compressive residual stresses at the surface and low tensile residual stresses at the core where material is softer. (5) distortion of steel parts decreases because the core does not swell. All of these factors increase service life of machine components, save energy and improve environment condition in heat treating industry. These important problems are widely discussed in the plenary lecture and appropriate results of computer simulations of technological processes are provided.