Research on Production Technology of 450HBW Grade Quenched and Tempered Wear-resistant Steel

    
    Abstract
    
    This article analyzes the properties and experimental research of 450HBW grade quenched and tempered wear-resistant steel, introduces the characteristics and composition of 450HBW steel, summarizes the quenching and tempering process, and studies the surface hardness, mechanism and influence of quenching and tempering. Finally, it summarizes the advantages and key points of quenching and tempering in production technology of 450HBW grade wear-resistant steel.
    
    Introduction
    
    450HBW grade quenched and tempered wear-resistant steel is an alloy steel with high hardness and good wear resistance, mainly used in mining, drilling and excavation tools, as well as mining machinery parts. 450HBW steel is usually used in the quenched and tempered condition, and the hardness is up to 480HBW.
    
    450HBW wear-resistant steel has good comprehensive properties, a wide range of applications, and has the highest hardness values among all wear-resistant steels. 450HBW steel has low alloy elements, excellent welding performance and low heat sensitivity.
    
    Therefore, correct quenching and tempering of 450HBW grade wear-resistant steel is critical to achieve its full performance.In order to make the wear-resistant steel fully play its due role, the hardness and performance after quenching and tempering need to be thoroughly studied.
    
    Material Properties
    
    The 450HBW grade of steel is a multi-element alloy steel that includes Chromium, Molybdenum, Carbon, Manganese, Sulphur, and Phosphorous. Its composition is typically as follows (wt%):
    
    C: 0.28 - 0.40
    Si: 0.40 max
    Mn: 0.30 - 0.60
    P: 0.035 max
    S: 0.035 max
    Cr: 1.20 - 1.50
    Mo: 0.45 - 0.60
    
    This steel is in the annealed condition and has a hardness of ≤350HBW. The goal of heat treatment is to achieve a desired level of wear resistance and toughness through an appropriate quenching and tempering cycle.
    
    Quenching and Temperment Process
    
    In order to further improve the wear resistance and toughness of the steel, it is necessary to quench and temper it. Quenching is the rapid cooling of the steel after its austenization to obtain a certain level of hardness, while tempering is the secondary heating of the quenched steel to a specific temperature to produce a desired level of toughness.
    
    The quenching and tempering process of the 450HBW grade steel should be strictly controlled according to the specific parameters of the product. Generally, the temperature of the austenization should be 850~870℃, and the holding time should be more than 1 hour. The cooling speed after quenching should not be too fast to avoid cracking. Generally, the cooling media used is water or oil, and the cooling rate needs to be controlled in the range of 5~ 70℃/s.
    
    After quenching, the tempering temperature should be 500~600℃. The tempering time should be determined according to the size of the steel, but generally it should not exceed 28 hours. After tempering, the surface hardness should reach 450~480HBW.
    
    Surface Hardness & Mechanism
    
    The surface hardness of 450HBW wear-resistant steel after quenching and tempering is 450~480HBW. The wear resistance, toughness and impact resistance of the steel all depend on its surface hardness.
    
    Quenching and tempering of 450HBW grade wear-resistant steel can form martensite and secondary carbides, which are dispersed and distributed in martensite. These martensite and secondary carbides can improve the wear resistance of the steel.
    
    At the same time, a small amount of retained austenite can be formed during the quenching and tempering process, which can improve the impact resistance of steel.
    
    Influence of Quenching and Temperment
    
    The quenching and tempering process will affect the microstructure and distribution of carbide in the steel. The uneven distribution of carbide will reduce the wear resistance of the steel.
    
    At the same time, the residual austenite remaining after quenching affects the hardness and fracture toughness of the steel. Excessive retained austenite reduces the hardness of steel and increases the fracture toughness.
    
    If the quenching and tempering process is not optimized, it will cause too large or small hardness, which will greatly reduce the performance of the steel and the service life of the parts. Thus, it is necessary to optimize the quenching and tempering process parameters to ensure that the hardness of the steel remains within the specified range.
    
    Advantages & Key Points
    
    The quenching and tempering process of 450HBW grade wear-resistant steel has some significant advantages that can improve the performance of the steel:
    
    1. Quenching and tempering can form martensite and secondary carbides, disperse and distribute them in martensite, and make their distribution more uniform, which can greatly improve the wear resistance and impact resistance of the steel.
    
    2. Quenching and tempering can also form a small amount of retained austenite. Although this has the effect of lowering the hardness and toughness of the steel, it also increases the fracture toughness of the steel and improves its impact resistance.
    
    The key points of quenching and tempering for 450HBW grade wear-resistant steel should be paid attention to:
    
    1. Choose the appropriate austenitizing temperature and holding time. Generally, the austenitizing temperature should not be higher than 870℃ and the holding time should not be less than 1 hour.
    
    2. Pay attention to the controlling of cooling rate and number of cooling processes during the quenching process in order to avoid cracking due to quenching.
    
    3. Select the appropriate tempering temperature and time to ensure that the hardness of the steel is between 450~480HBW.
    
    Conclusion
    
    This article mainly discusses the quenching and tempering process and its influence in the production technology of 450HBW grade wear-resistant steel. The content includes its material properties, quenching and temperment process, surface hardness, mechanism, influence and advantages.
    
    The quenching and tempering process of 450HBW grade wear-resistant steel should pay attention to the austenitizing temperature and the quenching cooling rate and select the appropriate tempering temperature and time. In order to make the steel fully play its due role, the hardness and performance of the product after quenching and tempering need to be thoroughly studied.

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