QUENCHING TIME OF HEAT TREATING FLUIDS: ASTM D3520
EXPLANATION
This method covers a procedure for making a comparative evaluation of the quenching speed characteristics of petroleum fluids used in quenching of metals by means of the magnetic quenchometer. A comparison method for evaluation of the quenching speed characteristics of petroleum fluids used in quenching of metals is Test Method ASTM D6200. A comparison method for testing the hardenability of steel is Test Method A 255. Although this test method has been found useful for some water-based fluids, the statistical significance of the test has been established only by round robin testing of petroleum based fluids.
This test method provides a measure of changes in oil chemistry due to contamination, base oil degradation, and additive drag-out during use. This test measures changes in the quenching speed characteristics of petroleum fluids at the high temperature 354° C. The test method does not reliably predict metallurgical performance. Results from this test method provide a measure of quenching speed (cooling rate) from approximately 885° C - 354° C, and are not directly proportional to hardness obtainable on metals quenched therein as many other factors are involved in the quenching process in actual plant operation with production parts.
TEST SUMMARY
This test method determines the time for cooling a chromized nickel ball from approximately 885° C to approximately 354° C when quenched in 200 mL of test fluid in a metal beaker at 21 - 27° C. The quenching time is recorded by a digital timer which is energized by a photoelectric cell from light produced by the ball at 885° C, and which is stopped when the ball becomes magnetic (Curie point, approximately 354° C), and is attracted by a magnet to the side of the beaker, tripping a relay to stop the timer. Test Method ASTM D6200 describes the equipment and the procedure for characterizing the time-temperature performance of a quenching oil through the entire cooling process.
TEST PRECISION
Repeatability: 5%
Reproducibility: 9%
The values are means of quench time in seconds.
This method has no bias because the value of the quenching speed can be defined only in terms of this test method.
