The normal temperature tension of the heat treated bainite Martian multiphase wear-resistant cast steel was carried out on the wdw-02a micro controlled universal testing machine, the strain rate was ht3s’, and the normal temperature impact was carried out by the zbc2452-b pendulum impact testing machine. The schematic diagram of the tensile and impact samples is shown in Figure 1; Hardness test shall be conducted with TH320 hardness tester; The microstructure was observed by optical microscope after being eroded with 4% nitric acid and alcohol; The microstructure was observed by Zeiss ultra55 scanning electron microscope equipped with EDs; The experimental steel was analyzed by dmax-rb XRD (Cu target). The working voltage was 40kV and the working current was 150mA; EBSD and AEs were performed on phi710 Auger electron spectrometer; After cutting the sheet, it is evenly polished and thinned on both sides, and then thinned with double spray solution to obtain TEM sample. The fine microstructure is observed by tecnaif20tem.
In the production of low-alloy high-strength wear-resistant steel, the effect of quenching process on the final properties of wear-resistant steel is very important. In bainite martensite multiphase steel, quenching and heat preservation process mainly affects the lath morphology, size and microstructure of martensite, so as to affect the mechanical properties. Therefore, we can improve the mechanical properties of wear-resistant steel by studying the martensite morphology and microstructure under different quenching and heat preservation process conditions and analyzing the influence law of microstructure on the mechanical properties after quenching.
In order to investigate the influence of quenching and heat preservation process on the mechanical properties and microstructure of experimental steel, four temperatures of 850 ° C, 900 ° C, 950 ° C and 1000 ° C were selected, which were kept for 1H and 2H respectively. The cooling mode of air cooling was adopted uniformly, and tempered at 300 ° C for 2 hours.
The influence trend of quenching and heat preservation process on mechanical properties is shown in Figure 2. It can be seen that at 850 ° C and 900 ° C, with the extension of quenching and holding time, the strength of the experimental steel increases, the strength is flat at 950 ° C, while the strength decreases at 1000 ° C, and the hardness and impact energy basically do not change with the quenching and holding time. Generally speaking, the quenching and holding time has little effect on the mechanical properties of the experimental steel. In terms of strength, when holding at 900 ° C for 2h, before the tensile strength and yield strength reach 1478mpa and 1233mpad50 ° C respectively, the strength is positively correlated with the quenching holding time at the same quenching holding temperature. When the heating temperature exceeds 950 ° C, the strength decreases with the change of temperature. At 1000 ° C, the strength of the experimental steel decreases with the extension of quenching and holding time. In terms of impact energy, when quenching at 850-900 ° C, the impact energy increases to 20.6j with the increase of heating temperature, and when quenching at 900-1000 ° C, the impact energy decreases significantly to 6.9j. In terms of hardness, quenching and heat preservation process has little effect.