Evaluation of the Hardening Capacity of Low-Alloyed Steels Quenched by HPGQ in Vacuum Furnaces

Abstract

The technology of High Pressure Gas Quenching (HPGQ) in modern vacuum furnaces has already reached the level of 20 to 25 bar pressure and up to 80 m/s gas flow velocity. By using primarily nitrogen (N2) it is possible to quench also low-alloyed steels, and to compete, in some cases successfully, with oil quenching. This depends basically on the hardenability of the steel and on the cross-section thickness of the quenched workpiece. The present work explains experimental testing of steels' hardenability when gas quenching is applied. For determination and vizualization of the hardening capacity of steels quenched by HPGQ, a computer aided method has been developed for axially symmetric workpieces of any complex shape, to show at a glance the complete hardness distribution on longitudinal section. An included database of relevant steel grades and possible gas quenching parameters enables to choose another steel grade and/or other quenching parameters, and see on the display another relevant hardness distribution, without performing additional experiments.