AISI H10 sıcak iş takım çeliğinin mekanik özelliklerine temperleme ve yaşlanma işlemlerinin etkisi

Abstract

The effect of tempering on AISI H10 hot work tool steel  Dynamic strain aging behavior of AISI H10 hot work tool steel  Analysis of microstructure and mechanical properties Figure A. Change in mechanical properties of H10 hot work tool steel at different tempering times and dynamic strain aging behaviorPurpose: This study aims to investigate the changes in the microstructure and mechanical properties of AISI H10 hot work tool steel which is used in many fields of the industry as a result of different tempering times and dynamic strain aging based on optimum tempering time. Theory and Methods:Austenitization and tempering processes were carried out to examine the structural change of AISI H10 hot work tool steel. The experimental steel was quenched after austenitizing treatment at the specified temperature and then tempered at different times. After the process, microstructure and mechanical properties of the material were examined and optimum tempering time was selected for the dynamic strain aging process. Dynamic strain aging was performed at different test temperatures for a determined deformation rate. Results:Increasing the tempering time at 550 °C from 10 minutes to 2 hours resulted in a gradual increase in hardness.The highest hardness was obtained as 393 Hv1 in samples tempered for 2 hours. This is due to the presence of finer precipitates particles in the samples. However, the lowest hardness value was obtained as 290 Hv1 in the samples tempered for 15 hours due to the presence of coarse precipitate particles. According to hot tensile test results which were obtained for the samples tempered at 550 °C for 2 hours, the strength values showed a decrease in the test temperature range of 25-400 °C, however the strength values increased when the test temperature was rised from 200 °C to 300 °C. This indicated that dynamic strain aging takes place in the tempered samples. Conclusion:Dynamic strain ageing and secondary hardening occur in the AISI H10 hot work tool steel under tempered condition which showed an increase in YS and UTS at temperatures 300°C and 400°C corresponding to dynamic strain ageing region. It was also noticed that elongation remained constant as the testing temperature increased from 25 °C to 400 °C. Above 400 °C, tempered samples showed a sharp decrease in strength but a slight increase in elongation. It can be concluded that mechanical properties of AISI H10 hot work tool steel become so poor under tempered condition after tensile testing above 400 °C.