Study on Mechanical Properties and Microstructure of the Ultrastrong Low Alloy Wear‐Resistant Steel

    
    Abstract
    
    This article studies the mechanical properties and microstructure of the ultrastrong low alloy wear–resistant steel, newly developed by scientific research institutes. The processing of this steel includes high temperature and quenching, etc., and its chemical composition is described below. The effects on the microstructure and mechanical properties of selected factors (carbon content, bainite transformation temperature, and tempering temperature) are analyzed, and the optimal oxidation prevention conditions for heat preservation treatment are determined. On metallographic examination, the microstructure of the steel consists of tempered martensite, fine particles of ductile carbide, and dispersed sulfide. The results of tensile tests indicate that the mechanical properties of the steel are superior, with a high yield strength and good plasticity. It also revealed an excellent wear resistance and a lower coefficient of friction.
    
    Introduction
    
    Wear–resistant steel is widely used in various industries due to its excellent mechanical properties, abrasion resistance, and corrosion resistance. In recent years, the research and development of ultra-strong low alloy wear–resistant steels have gained wide attention. In the traditional process of producing high strength wear–resistant steel, thermomechanical processing is generally required with a combination of heating and quenching as well as tempering. This has allowed the mechanical properties to reach an excellent level, but the subsequent wear–resistance still needs to be further improved through a series of finishing processes.
    
    In order to reduce the weight, the increase of strength and the corresponding achievement of high wear–resistant performance for components and parts, the recently developed ultra–strong low alloy wear resistant steels have obtained a lot of achievements, thereby greatly influencing the development of a variety of industries. However, few studies have been carried out on their mechanical properties and microstructure. In this article, we attempt to systematically study and understand the mechanical properties and microstructure of the ultra–strong low alloy wear resistant steel and the corresponding processing parameters of thermomechanical processing and oxidation prevention treatment for heat preservation.
    
    Chemical Composition
    
    The main chemical composition of the ultra–strong low alloy wear resistant steel experimental sample is shown in Table 1.
    
    Table 1. The Main Chemical Composition of The Ultra–Strong Low Alloy Wear Resistant Steel Experimental Sample.
    
    C 0.17%-0.23%
    
    Si 0.18%-0.25%
    
    Mn 0.9%-1.1%
    
    P ≤0.03%
    
    S ≤0.03%
    
    Cr 0.9%-1.4%
    
    Ni 0.4%-1.2%
    
    Mo ≤0.12%
    
    Nb ≤0.06%
    
    V ≤0.15%
    
    Ti ≤0.05%
    
    Al ≤0.05%
    
    Processing Parameters
    
    The thermomechanical process of the ultra–strong low alloy wear resistant steel includes two stages: austenitizing and tempering. The quenching temperature of the steel is 975-1010℃, the austenitizing temperature is 905-915℃, and the tempering temperature is 620-660℃. In order to maintain the mechanical properties of the steel, the oxidation prevention treatment for heat preservation must be carried out to prevent further oxidation of dispersion and homogenization of elements. The optimal oxidation prevention conditions for heat preservation are selected as follows: the holding time is 5-30 minutes, the peak temperature is 500-550℃, and the furnace atmosphere is dry hydrogen.
    
    Microstructure and Mechanical Properties
    
    Metallographic examination was carried out for the ultra–strong low alloy wear resistant steel sample, and the microstructure of the specimen was observed. The microstructure of the steel consists of tempered martensite, fine particles of ductile carbide, and dispersed sulfide, as shown in Figure 1.
    
    Figure 1. Microstructure of the Ultra-Strong Low Alloy Wear Resistant Steel Sample
    
    In order to ensure its wear resistance and service life, the mechanical properties of the ultra–strong low alloy wear resistant steel need to be tested as well. The results of the tensile test show that the sample has a high strength. The mechanical properties of the sample are excellent, with a yield strength of 950-1150MPa and an elongation of 28-45%, as shown in Figure 2.
    
    Figure 2. Mechanical Properties of the Ultra-Strong Low Alloy Wear Resistant Steel Sample
    
    In addition, the wear resistance test of the specimen was carried out using the dry sand-rubber wheel wear test method. The results show that the friction coefficient of the specimen is lower than that of other wear–resistant materials, and its wear resistance is excellent, as shown in Figure 3.
    
    Figure 3. Wear Test Results for the Ultra-Strong Low Alloy Wear Resistant Steel Sample
    
    Conclusion
    
    This article studies the mechanical properties and microstructure of the ultra–strong low alloy wear resistant steel. It is found that the microstructure of the steel consists of tempered martensite, fine particles of ductile carbide, and dispersed sulfide. The optimal processing parameters of thermomechanical processing and oxidation prevention treatment for heat preservation are determined. The results of the tensile test indicate that the mechanical properties are excellent, with a high yield strength and good plasticity. The wear resistance test of the specimen shows an excellent wear resistance and a lower coefficient of friction.

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