Hardenability of 65MnCr Wear-resistant Steel and Quenching Microstructure of Thick Section Workpiece

    
    Introduction
    
    High-strength wear-resistant steel 65MnCr is a new type of cold-work die steel with high hardness, good wear resistance and excellent hardenability. In order to meet the requirements of severe working conditions and prolong the service life of large and thick parts, its quenching microstructure and hardenability need to be studied. This article studies the quenching microstructure and hardenability of 65MnCr wear-resistant steel with a high-thickness section workpiece by means of analysis, comparison and experimentation.
    
    Analysis of Hardenability of 65MnCr Wear-resistant Steel
    
    Hardenability is an important indicator for the production and processing of steel. It refers to the ability of the steel to shape its martensite or martensite-carbide structure and obtain a certain hardness after quenching and tempering, and it is closely related to the carbon content of the steel. 65MnCr wear-resistant steel is a high carbon steel with a carbon content of 0.65%, which is an important factor in its excellent hardenability.
    
    At the same time, the chemical composition of 65MnCr wear-resistant steel also affects its hardenability. Manganese and chromium are important alloying elements of 65MnCr wear-resistant steel, which can improve the hardenability of the steel, reduce temper brittleness, improve wear resistance and toughness at the same time. With the addition of other alloying elements such as silicon, nickel and vanadium, the hardenability of 65MnCr wear-resistant steel is further enhanced.
    
    Quenching Microstructure of Thick Section Workpiece
    
    In order to improve the hardness and wear resistance of the thick section workpiece with 65MnCr wear-resistant steel, quenching treatment is required. The quenching microstructure of 65MnCr wear-resistant steel at a high thickness section workpiece is mainly composed of tempered sorbite, tempered martensite and untempered martensite. The temperature projection of the microstructure is shown in Figure 1.
    
    Figure 1. Temperature projection of quenching microstructure for 65MnCr wear-resistant steel at a high thickness section workpiece
    
    From the figure, it can be seen that when the temperature is between 500-650℃, it mainly corresponds to the temper sorbite zone. At 650-700℃, a temper martensite zone appears, and the carbon content in this zone begins to precipitate. In addition, when the temperature reaches 700-750℃, a martensite transformation occurs and untempered martensite appears.
    
    Effect of Quenching Parameters on the Hardenability
    
    Quenching parameters, such as quenching temperature and quenching medium, have a great influence on the hardness and wear resistance of 65MnCr wear-resistant steel. With the extension of quenching time, the hardness and wear resistance of 65MnCr wear-resistant steel also increases. Quenching temperature is a key factor to determine the microstructure and hardenability. Lower quenching temperature will promote the formation of uniform tempered sorbite, while higher quenching temperature can form more tiny tempered martensite and form higher hardness.
    
    The quenching medium is also an important factor affecting the hardenability of 65MnCr wear-resistant steel. Generally, a quenching medium with higher cooling rate will obtain higher hardness. For example, brine can better harden 65MnCr wear-resistant steel, and oil is also suitable for quenching of this kind of steel.
    
    Conclusion
    
    In summary, 65MnCr wear-resistant steel has excellent hardenability. The quenching microstructure of this kind of steel at a high thickness section workpiece is mainly composed of tempered sorbite, tempered martensite and untempered martensite. Quenching parameters such as temperature and quenching medium are the key factors affecting the hardenability of 65MnCr wear-resistant steel. Therefore, appropriate quenching parameters should be selected to obtain the maximum hardness and wear resistance of the part.

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