Microstructure and properties of NM400 high-strength low-alloy wear-resistant steel

NM400 high-strength low-alloy wear-resistant steel is a kind of alloy steel which has superior performance and high strength. After special process treatment, its toughness and plasticity index are significantly improved. The alloy steel has excellent properties such as wear resistance, fatigue strength, impact toughness, good thermal conductivity and low temperature toughness. Its superior microstructure and excellent properties make it widely used in engineering machinery, mining machinery, agricultural machinery, petroleum machinery, metallurgical machinery and other industries.
    
NM400 steel is a kind of tempered and normalized bainite steel. After strict quenching tempering and secondary tempering, the microstructure of NM400 steel consists of fine tempered bainite and martensite, with a large amount of carbides around ferrite nodules. The steel has good mechanical properties and oxidation resistance, and good performance in wear resistance.
    
The microstructure of NM400 steel is shown in Figure 1. It can be seen from the figure that after quenching, it is a microstructure of tempered bainite and martensite. The microstructure is uniform, the grain size is fine, and the carbides are evenly distributed and well-distributed. The chemical composition of the steel is shown in Table 1.
    
Table 1. Chemical composition of NM400 steel (% by weight)
    | C: | 0.26-0.70 |
    | Si: | 0.18-0.50 |
    | Mn: | 1.50-2.90 |
    | P: | 0.030 max |
    | S: | 0.030 max |
    | Cr: | 2.00-3.50 |
    | Ni: | ≤ 0.010 |
    | Mo: | ≤ 0.10 |
    | B: | ≤ 0.0025 |
    
The mechanical properties of NM400 high-strength wear-resistant steel are excellent, with a yield strength of more than 700 MPa, an ultimate tensile strength of more than 830 MPa, a bisplate-90 hardness of up to 400 HB and more than 2.5 times the impact toughness of ordinary steel. The wear resistance is greatly improved due to the formation of a large amount of carbides around ferrite and austenite. With the characteristic of wear resistance, fatigue strength, impact toughness and thermal conductivity, NM400 is widely used in engineering machinery and mining machinery, such as bulldozer, loader, crane and excavator, especially at working sites with high wear and severe impact conditions.
    
In summary, NM400 high-strength low-Alloy wear-resistant steel has excellent microstructure, mechanical properties and oxidation resistance, and its wear resistance is 2-3 times that of ordinary steel. Due to its special properties, NM400 steel is widely used in engineering machinery and mining machinery. The combination of excellent properties and excellent wear resistance makes it an indispensable material.

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