Effect of Cooling Mode on Microstructure and Mechanical Properties of Medium Carbon Low Alloy Steel ZG35Cr2NiMoVTi

The development of medium carbon low alloy steel ZG35Cr2NiMoVTi used for shaft and gear parts of heavy machinery and automobile industry has made great progress in recent years. The application of ZG35Cr2NiMoVTi requires an appropriate cooling rate to obtain an optimal combination of microstructure and mechanical properties. This article focuses on the investigation of the effect of air cooling, water cooling and oil cooling on the microstructure and mechanical properties of ZG35Cr2NiMoVTi.
    
Microstructural examination and mechanical properties testing is conducted on ZG35Cr2NiMoVTi samples heat-treated by different cooling modes during quenching treatment. The experimental results are compared and analyzed in terms of hardness, tensile strength and impact toughness.
    
Shows the microstructure of the ZG35Cr2NiMoVTi samples quenched by air, water and oil cooling. Compared with air cooling and oil cooling, water cooling shows that the samples present uniform austenite grains, less non-uniformly distributed locations and higher hardness. As the cooling rate of water cooling is greater than that of air cooling and oil cooling, it can promote the transformation of austenite to martensite. In addition, the continuous cooling can quickly quench the sample, making it easier to form a net-like martensite lattice and gain higher hardness.
    
Shows the comparison of the mechanical properties of the samples. Comparing the quenching samples of the three cooling modes, it can be found that the hardness, tensile strength, and impact toughness of ZG35Cr2NiMoVTi after water cooling are higher than those of the sample after air cooling and oil cooling. It shows that there is a certain relationship between the cooling rate and the mechanical properties of ZG35Cr2NiMoVTi.
    
In conclusion, this study indicates that the microstructure and mechanical properties of ZG35Cr2NiMoVTi will vary with different cooling modes during quenching, and water cooling exhibits the best results. This selection of cooling rate can not only obtain satisfactory hardness, tensile strength and impact toughness, but also improve the work performance and service life of ZG35Cr2NiMoVTi parts. Therefore, it is recommended that medium carbon low alloy steel ZG35Cr2NiMoVTi be cooled by water quenching during heat treatment.

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