Estimation of Heat Flux Transients During Quench Hardening of Steel Probes Using IHCP-Phase Transformation Coupled Model

The steel/quenchant interfacial heat flux was estimated for cylindrical steel probes using a phase transformation model coupled with the inverse heat conduction problem (IHCP). Cylindrical steel probes having diameters of 25 and 50mm with a length of 30mm were made from medium and high carbon steels (AISI 1045 and 52100). The probes were quenched in mineral and neem oils. The cooling curves at the centre and near the surface of steel probes were recorded. The near-surface cooling curve was used as a reference temperature data in the IHCP algorithm for the estimation of surface heat flux, whereas the cooling curve at the centre was used as the Dirichlet boundary condition in an axisymmetric model of probe. The effect of phase transformation was indicated by a kink and rise in the heat flux for the diffusion-based phase transformations. For the martensitic transformation, the inversion of heat flux to a negative value was observed around the start of martensite transformation temperature (M_S). The increase in the section thickness of the probe from 25 to 50mm decreased the magnitude of heat flux due to the increase in the thermal resistance and the amount of phase transformation.

Keywords: Quenching; IHCP; Phase transformation; Heat flux