ASTM D3520 Quenching Time of Heat-Treating Fluids (Magnetic Quenchometer Method)
Steel is used in numerous applications because it is hard and strong. For steel to achieve these properties, it must be heated to a high temperature and cooled at the appropriate rate – the cooling rate helps determine the hardness characteristics of the final product. To control the cooling rate, the hot fabricated metal is placed in a quenching fluid and allowed to cool. This test determines the cooling rate provided by the sample quenching fluid. It uses a Magnetic Quenchometer with a nickel ball which becomes magnetic below a certain temperature (354ºC – its Curie Point).
The sample quenching fluid is placed in a stainless steel beaker in the quenchometer. A nickel ball is heated in a furnace to 885ºC, and dropped into the sample. The ball entering the fluid triggers a timer to start, and when the ball becomes magnetic, it turns the timer off. The time that elapses between the ball entering the fluid, and the oil reaching 354ºC, is reported as the quench time.
This method is considered obsolete by ASTM.
Note: This test is still offered by Petro-Lubricant Testing Laboratories as a service to our clients.