Determination of vacuum isothermal gas quenching process parameters for Cr12MoV molds

Abstract

To determine the vacuum isothermal gas-quenching process for Cr12MoV automotive stamping die inserts, vacuum isothermal gas-quenching experiments were first carried out on die-steel specimens using a VGQ-150-10 high-pressure, high-velocity gas-cooled vacuum furnace. The process parameters that produced the best combination of mechanical properties after gas quenching were identified. These parameters, however, cannot be applied directly to die inserts, because the workpiece cooling rate cannot be set directly on the control panel of a vacuum gas-quenching furnace, and the cooling rate of a die during gas quenching is affected by the furnace load and the internal spatial configuration. Therefore, a finite-element model of vacuum gas quenching in this furnace was established to simulate the gas flow field in the furnace and the temperature and stress fields in the workpiece. The model was validated by comparing the simulated and measured cooling curves of the specimens. The validated model was then used to simulate vacuum gas quenching of die inserts. The results show that, when a single die insert is loaded, the gas-quenching pressure must be increased to 12 bar for the die cavity to achieve a quenching effect similar to that obtained for the specimen. When four die inserts are loaded, the pressure must be increased to 15 bar to obtain a similar effect.