Effects of heat treatment on the microstructure and mechanical properties of high speed steel roll

The effects of quenching temperature, cooling pattern, tempering temperature and tempering time on the microstructures and mechanical properties of high speed steel (HSS) roll have been investigated. The results show that the hardness increases as the quenching temperature increases under oil cooling when the quenching temperature is lower than 1050℃;while the hardness decreases as the quenching temperature increases when the quenching temperature exceeds 1100℃. Under the condition of salt bath ard air cooling, the effect of quenching temperature on the hardness is similar, but the queching temporature at which the highest hardness is obtained is higher than the one in oil quenching. When tempering temperature is lower that 350℃,the hardness of HSS has little change,while it will increase along with the increase of the tempering temperature when the temperature exceeds 475℃ and the highest hardness is obtained at 525℃, and the hardness will decrease as the tempering temperature continues to increase. Two time tempering has little effect on the hardness, three time tempering will decrease the hardness.The HSS roll with air cooling has lower hardenability, cracks are easy to be produced in oil cooling and the HSS roll quenched in salt bath has high hardenability,less cracks, high and homogeneous surface hardness and excellent wear resistance.