Gas quenching of steels -- an analysis of the effects of gas composition and of steel T types - 4140 and 304.

The CHTE quench probe system was modified to test quenching performance of a variety of different gases at atmospheric pressure. The tests were performed with 4140 and 304 steel in Argon, Helium, and Air at varying velocities. The heat transfer coefficients were calculated using Newtonian cooling analyses. The experimental results showed that helium produced the highest heat transfer coefficients, followed by air and argon. The highest heat transfer coefficient obtained was around 200W/m?K for helium using two fans and the lowest heat transfer coefficient obtained was around 30W/m?K for stagnant argon. The data for the 4140 steel showed a dip in the cooling rate and, therefore, the calculated heat transfer coefficient vs temperature but not for 304. This dip was explained as being due to heat that is released as Austernite transformed to Bainite and Pearlite in this temperature range