| With the rapid growth of the demand for plastic products,the mold industry develops rapidly,and the performance requirements for plastic mold steel are higher and higher.Compared with the imported commercial Gritz XPM plastic mold steel,this paper studied the new plastic mold steel 35 CrMnSiMoNi developed independently.In this paper studied the influence of different heat treatment processes on the microstructure and properties between the two steels,compared and analyzed the mechanical properties and corrosion resistance of the two steels.The results show:After quenching at different temperatures,the microstructure of the Gritz XPM steel is mainly composed of lath martensite and retained austenite.With the increase of quenching temperature,the impact toughness of the material increases gradually,the hardness increases firstly and then decreases.The mechanical properties of the material are better after quenching at 960°C.After quenching treatment,the impact toughness and hardness gradually decrease with the increase of tempering temperature.The comprehensive performance of the material is better when the tempering temperature is 250°C.The microstructure of 35 CrMnSiMoNi steel consists mainly of bainite and retained austenite after normalizing at different temperatures.The bainite has two types,including lath and granular.With the increase of normalizing temperature,the number of granular bainite decreases,the number of lath bainite increases,and the microstructure coarsens.As the normalizing temperature rises,the hardness,tensile strength and impact toughness of the material increase firstly and then decrease.After 920°C normalizing treatment,the material has good comprehensive performance,the specific performance is tensile strength of 1934.8Mpa,section shrinkage of 12.81%,elongation of 4.33%,hardness of 54.4HRC and impact toughness of 36.7J.35 CrMnSiMoNi steel after normalizing and tempering at different temperatures,the hardness and tensile strength decrease gradually,the elongation and section shrinkage gradually increase,the impact toughness firstly increases and then decreases.The impact toughness reaches the maximum value of 37 J after the tempering temperature at 250°C,and the material has better comprehensive performance.After isothermal quenching at different temperatures,the microstructure of 35 CrMnSiMoNi steel is mainly composed of bainite,retained austenite and a small amount of martensite.The bainite in the microstructure has two shapes: lath and granular.With the increase of isothermal quenching temperature,there is a tendency about the bainite in the microstructure from lath or needle to granular.With the increase of isothermal quenching temperature,the tensile strength and hardness firstly decrease and then increase.The section shrinkage,elongation and impact toughness increase firstly and then decrease.The mechanical properties of the material get better after isothermal quenching at 370°C.The microstructure of 35 CrMnSiMoNi steel is composed of lath martensite and retained austenite after quenching treatment.With the increase of quenching temperature,the tensile strength of the experimental material increases gradually,and the elongation rate,shrinkage rate,impact toughness increase firstly and then decrease,the hardness gradually decreases.The experimental material has better mechanical properties after quenching at 960°C.After the Q&P process,the microstructure of 35 CrMnSiMoNi steel is mainly composed of martensite,bainite and retained austenite.With the increase of quenching temperature(QT),the hardness,the elongation,section shrinkage firstly increase and then decrease,and the impact toughness gradually decreases.The tensile strength reaches a maximum value of 2209.2Mpa after salt bath quenching at 200°C,and the mechanical properties of the material are good.Compared with the Gritz XPM steel,the 35 CrMnSiMoNi steel has higher hardness after different heat treatment processes.The hardness range of different media after cooling is 54.0HRC~56.7HRC.The higher hardness is beneficial to improve the wear resistance of the plastic mold.After air cooling treatment,35 CrMnSiMoNi steel has a high impact toughness of 42.2J,but this value is lower than the impact toughness of Gritz XPM steel after cooling with medium;Corrosion test results show,when the corrosion time is less than 200 h,the corrosion rates of the two steels are little difference.When the temperature is between 200h~250h,the corrosion rate of 35 CrMnSiMoNi steel is slightly higher than that of Gritz XPM steel.When the corrosion time is higher than 250 h,the corrosion rate of 35 CrMnSiMoNi steel is higher than that of Gritz XPM steel. |
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