Effect of quench probe material and section size on cooling severity

Simulation of heat transfer during quenching was carried out using finite difference heat transfer based SolidCast software. Copper, Inconel 600, Nickel, Silver and Type 304 stainless steel were chosen as quench probe material and were of cylindrical geometry with a length to diameter ratio of 5.  Simulations were carried out at different combinations of heat transfer coefficient (500 to 10000 W/m²K) and quench probe diameter (0.25 to 5”). Temperature at the geometric centre of the probe was estimated and plotted against time. From the temperature – time curve the average cooling rate was determined by taking linear portion of the curve. Simulation results indicate that there is a critical diameter above which increase in cooling rate at the centre of probe is negligible for a material even with a quench medium having a very high severity of cooling. A simple quantitative model which correlates probe material, section size and cooling severity of quench media was proposed. The results of the model is independent of characteristics of quench probe used in assessment of cooling severity and could be used effectively for selection of quenchants during heat treatment.

Keywords: Probe material; section size; cooling curve; heat transfer coefficient; quench severity