Effect of holding time variations on mechanical properties and microstructures of medium manganese steel

The heat treatment cycle went through 2 stages, the heating from room temperature to 700 °C with a holding time of 3 hours, then raised again to a temperature of 1000 °C with variations in holding time for 1 hour, 2 hours, and 3 hours followed by quenching of 3% NaCl solution. The results showed that the heat treatment was followed by quenching the 3% NaCl solution, produces a higher hardness value at a holding time of 1 hour and further decreases at a longer holding time. The highest hardness value reached 255 BHN at a detention time of 1 hour, while the lowest hardness value reached 241 BHN at a holding time of 3 hours. The highest impact value of 105 Joules resulted in heat treatment with a holding time of 2 hours followed by rapid cooling of 3% NaCl solution. In contrast, the lowest impact value reached 100 Joules at a holding time of 3 hours. Medium manganese steel has brittleness and little ductility. The microstructure shows that the insoluble carbide dispersed at the grain boundaries and within the grains affects the high hardness value of medium manganese steel.