Development of quenched and tempered wear-resistant steel for bulldozer bucket

    
    With the rapid development of earthmoving machinery, the demands for bulldozer buckets are getting higher and higher. In particular, increasing attention is paid to the requirements of longer working life, higher efficiency and better impact resistance of bulldozer buckets. Various advanced wear-resistant steel plates are available on the market, but these steel plates show different levels of wear resistance in diesel-powered bulldozers with different speed, load, working environment and type specified on the market. It is necessary to further improve the wear performance of bulldozer buckets by using quenched and tempered wear-resistant steel plates.
    
    Quenching and Tempering Wear-Resistant Steel (QTWR) is a kind of wear-resistant steel developed from high-strength steel. Its wear-resistant performance is obviously improved after proper quenching and tempering. The microstructure of QTWR steel is homogeneous bainite or martensite, and the hard carbide precipitates uniformly on the matrix, that is, QTWR has excellent wear resistance. Therefore, QTWR steel is the best choice for bulldozers with various environmental and operating parameters.
    
    At present, the common thicknesses of QTWR steel plates used in bulldozer buckets range from 8mm to 150mm. It is composed of a variety of low carbon alloy particles and components, such as C, Si, Mn, Ni, Cr, Mo, Ti and Nb. The tensile strength, yield strength, elongation and impact energy of QTWR steel can reach more than 1100MPa, 700MPa and 15%, respectively. In addition, the wear resistance of QTWR steel is significantly improved by quenching and tempering. Usually the hardness of QTWR steel can reach 470-530HB.
    
    The quenching and tempering process of QTWR steel starts with a rough annealing of the steel plate. During the process of rough annealing, the temperature of the steel plate rises gradually at a specific rate. This process not only eliminates the internal stress of the plate, but also reduces the hardness and strength of the plate, which is beneficial to the uniformity of heat treatment. After the rough annealing, the steel plate is quenched and tempered at high temperature. The tempering process is uniform and low-temperature tempering is used to ensure the quenching effect of the steel plate.
    
    
    
    Fig 1. Quenching and tempering process of QTWR steel
    
    In order to improve the wear resistance of QTWR steel, the mechanochemical method of adding vanadium carbide particles to the steel plate can be adopted. In the mechanochemical method, the surface of the steel plate is sprayed with live vanadium carbide particles, so that the surface of the steel plate is covered with a layer of vanadium carbide particles, which can increase the hardness and heat resistance of the steel plate. This method can significantly improve the wear resistance of steel plate, and make the service life of bulldozer bucket 30% longer than the conventional quenched and tempered steel plate.
    
    In conclusion, the quenched and tempered wear-resistant steel plate is the best choice for the development of bulldozer buckets. It has excellent wear resistance, high strength and good impact resistance. In order to further improve the wear resistance and service life of the bulldozer bucket, the mechanochemical method of adding vanadium carbide particles can be adopted. The newly developed quenched and tempered wear-resistant steel plate not only meets the requirements of modern bulldozers, but also meets the needs of more efficient and economical construction.

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