ASTM D6200 Determination of Cooling Characteristics of Quenching Oils by Cooling Curve Analysis
Quenching oils immerse very hot metals to cool them at a controlled rate without thermal gradients or crystallization. This allows cooling steel to achieve maximum hardness without weak spots. When quenching oils age, their effectiveness may decrease due to viscosity changes and the formation of sludge. This test determines the cooling profiles of quenching oils when hot metal is immersed. It is appropriate for new oils or service oils.
A metal heat probe is placed in a furnace and allowed to come to the initial test temperature (850oC). It is then transferred to the quenching oil sample and the profile of its cooling is recorded. Reported is the maximum cooling rate, and the temperature at which it occurs, and the time it takes to reach 600oC, 400oC and 200oC.