Heat Treatment and Microstructure Properties of Wear-resistant Steel NM50CrVA for Construction Machinery

    
    Introduction
    
    Wear-resistant steel NM50CrVA is a high wear-resistant alloy steel that is widely used in the power industry, mining and construction machinery industry, and other related fields. It has good resistance to wear, high strength, good toughness and plasticity, and is also resistant to corrosion and oxidation. This steel material is widely used in construction machinery, crushers and other machine parts, and its superior wear resistance can ensure efficient and reliable operation of high-intensity working machines.
    
    Therefore, in order to understand and take full advantage of the excellent performance of this steel, comprehensive research on its heat treatment, microstructure and hardness is of great significance. In this article, the heat treatment and microstructure properties of wear-resistant steel NM50CrVA for construction machinery are discussed in detail.
    
    Heat Treatment of Wear-resistant Steel NM50CrVA for Construction Machinery
    
    Heat treatment is a kind of mechanical thermal processing method, which is widely used in the processing of metal material to meet the special requirements of different uses. It is an effective way to improve the mechanical, physical and chemical properties of the material. The heat treatment of wear-resistant steel NM50CrVA for construction machinery is mainly solutioning, quenching and tempering.
    
    Solutioning
    
    Solutioning is a necessary process of heat treatment that combines alloy elements with ferrite and austenite phases in the steel, so as to obtain the desired fine microstructure. The purpose of solutioning is to solve the combination of alloy elements and to produce homogeneous microstructure. The optimum solutioning temperature of wear-resistant steel NM50CrVA is 1040-1090 ℃, and the holding time is necessary to ensure the solutioning effect.
    
    Quenching
    
    Quenching is to heat the workpiece to a certain temperature above the critical point Acm of the steel material and keep the temperature for a certain period of time, and then rapidly cool it to room temperature or use the cooling medium to cool it, so as to obtain a higher-strength martensite structure. The quenching temperature of NM50CrVA is 1000-1020 ℃, and the quenching medium is oil or molten salt.
    
    Tempering
    
    After quenching, some stress remains in the workpiece, so it is necessary to temper the workpiece for tempering in order to obtain the desired comprehensive mechanical properties. Different tempering temperatures can obtain different mechanical properties. Generally, the tempered temperature ranges from 460-560℃.
    
    Microstructure of Wear-resistant Steel NM50CrVA
    
    Wear-resistant steel NM50CrVA is a low alloy steel, and its microstructure mainly consists of ferrite, austenite and carbide. After solutioning and quenching, the microstructure consists of martensite, bainite and retained austenite. The martensite structure can improve the strength and wear resistance of the steel, while the retained austenite structure has excellent toughness and plasticity. The microstructure of wear-resistant steel NM50CrVA is shown in Figure 1.
    
    Figure 1. Microstructure of Wear-resistant Steel NM50CrVA
    
    Hardness of Wear-resistant Steel NM50CrVA
    
    After solutioning and quenching, a certain amount of martensite structure can be obtained in the microstructure of the steel material, and the hardness of the wear-resistant steel NM50CrVA can be improved. HRC hardness test was carried out on the sample of this steel material, and the test results are shown in Table 1. It can be seen from the table that the hardness of the material is 48-55 HRC, which is higher than the hardness requirement for construction machinery.
    
    Table 1. Hardness Test Results of NM50CrVA Steel
    
    Conclusions
    
    In this article, the heat treatment and microstructure properties of wear-resistant steel NM50CrVA for construction machinery are discussed in detail. Heat treatment of this material includes solutioning, quenching and tempering. Its microstructure consists of ferrite, austenite and carbide, and the hardness is 48-55 HRC after heat treatment, which meets the requirements of construction machinery. Therefore, the wear-resistant steel NM50CrVA is an excellent choice for construction machinery components that require high wear resistance and strength.

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