Effects of quench rate and impact test temperature on the toughness and microstructure of H13

摘要

The NADCA Die Materials Specification and Heat Treatment Task Groups reached several conclusions based on this project. ·Conducting the CVN impact toughness test at elevated temperatures did increase the measured toughness values. However, it did not significantly improve the ability of the test to separate high-toughness and low-toughness steel. The elevated temperature impact testing did not help to differentiate between heat treatment quench rates. The additional variables and costs associated with the elevated temperature impact test were determined to be undesirable as a standard NADCA test protocol. ·A Charpy test methodology based upon testing five individual specimens and reporting the average result of three specimens after dropping the high and low values was found to significantly reduce the average standard deviation of CVN data. ·The CVN impact toughness of premium quality H13 was found to increase with increasing quench rates. However, based upon the limited data resulting from this investigation, there is no clear justification for altering the current NADCA minimum recommended quench rate of 50°F/min. ·The degree of intergranular carbide precipitation did not correlate with the impact toughness of commercially heat-treated steel in the range of 50°F/min to 120°F/min.