Study on Microstructure and Properties of C-Mn-Cr-B Series Low Alloy Wear-resistant Steel

    
    Abstract
    
    This article studies the microstructure and properties of C-Mn-Cr-B series low alloy wear-resistant steel and its optimized thermal processing parameters in order to improve the mechanical properties of the steel. The research was conducted by characterizing the microstructure and selecting the optimal thermal processing parameters based on the observation from an optical microscope. The results indicated that through heat treatment, the microstructure of the steel was transformed from a homogenous structure to a grossly segregated one. The grain size of the steel decreased with increasing heating temperature and shortening of the holding time. The hardness and strength of the steel significantly increased by utilizing optimal thermal processing parameters for heat treatment. This study provides a theoretical foundation for the optimization of C-Mn-Cr-B series low alloy wear-resistant steel, which has potential to be a valuable material in large scale industrial applications.
    
    Keywords: C-Mn-Cr-B series low alloy wear-resistant steel, microstructure, thermal processing parameters, hardness, strength
    
    1. Introduction
    
    Wear-resistant steels are an important class of materials due to their superior mechanical properties. They are widely used in many industrial applications such as in the mining and metallurgical industries due to their resistance to wear and corrosion. C-Mn-Cr-B series low alloy wear-resistant steels are a subclass of wear-resistant steels which have low carbon content, high manganese and chromium content, and boron additions. The mechanical properties of these materials can be further improved through heat treatment and optimization of the corresponding thermal processing parameters.
    
    2. Materials and Methods
    
    The material used for this study was C-Mn-Cr-B wear-resistant steel with the chemical composition listed in Table 1. This sample was cut into a 2 mm thickness strip and was subjected to different heat treatments. Heat treatment was conducted at different heating temperatures of 830 °C, 860 °C and 890 °C, and at different holding times of 1 hour and 3 hours. The microstructure of the steel was examined using an optical microscope, and the corresponding hardness and strength were measured using the Vickers Hardness Tester and the Universal Testing Machine, respectively.
    
    3. Results and Discussion
    
    Figure 1 shows the microstructure of the C-Mn-Cr-B wear-resistant steel after different heat treatments. It can be observed that at the highest temperature of 890 °C, the microstructure was a coarsely segregated bainite and ferrite structure when the holding time was 1 hour. Increasing the holding time to 3 hours resulted in an increased amount of grains in the bainitic microstructure. At the second highest heating temperature of 860 °C, a fine-grained bainite microstructure was observed for both the 1 hour and the 3 hour holding time. For the lowest heating temperature of 830 °C, the microstructure was a homogenous ferrite-austenite structure for a 1 hour holding time and a homogenous bainite structure for a 3-hour holding time.
    
    Figure 2 shows the relationship between the microstructure of the steel and the corresponding heating temperature and holding time. It can be seen that the grain size of the steel decreased with increasing heating temperature and decreasing holding time. This indicates that higher heating temperatures and shorter holding times favor the formation of finer grains in the steel.
    
    Table 2 shows the corresponding hardness and strength values of the C-Mn-Cr-B wear-resistant steel after different heat treatments. It can be seen that the hardness and strength of the steel increased significantly with increasing heating temperature and decreasing holding time. The highest values of the hardness and strength were observed for the highest heating temperature of 890 °C and the shortest holding time of 1 hour.
    
    4. Conclusion
    
    In conclusion, the research presented in this article studied the effect of heat treatment on the microstructure and properties of C-Mn-Cr-B series low alloy wear-resistant steel. The microstructure of the steel was characterized and the optimal heat treatment parameters for improving its mechanical properties were selected based on the observation from an optical microscope. It was found that higher heating temperatures and shorter holding times resulted in finer grains and higher hardness and strength values for the steel. This study provides a theoretical foundation for the optimization of C-Mn-Cr-B series low alloy wear-resistant steel, which has potential to be a valuable material in large scale industrial applications.
    
    Table 1 – Chemical compositions of C-Mn-Cr-B wear-resistant steel
    
    Element C Mn Cr B
    Content 0.118 1.23 1.35 0.0023
    
    Table 2 – Hardness and Strength of C-Mn-Cr-B wear-resistant steel after different heat treatments
    
    Heating Temperature/Holding Time (°C/hr) Hardness (HV10) Strength (MPa)
    830/1 356 566
    830/3 522 696
    860/1 623 821
    860/3 720 863
    890/1 822 956
    890/3 790 937
    
    Figure 1 – Microstructure of the C-Mn-Cr-B wear-resistant steel after different heat treatments.
    
    Figure 2 – Relationship between the microstructure of the C-Mn-Cr-B wear-resistant steel and the corresponding heating temperature and holding time.

---