Effect of Normalizing Temperature on Microstructure and Properties of Overlay Welding Layer of NM360 Wear-resistant Stee

The overlay welding layer of NM360 wear-resistant steel is a key component of the wear-resistant parts of mechanical equipment, which has a great influence on its performance. Therefore, the microstructure and properties of the overlay welding layer are important factors in determining the service life and service performance of the wear-resistant parts. The normalizing temperature of the overlay welding layer of NM360 wear-resistant steel has a great influence on the microstructure and performance of the overlay welding layer. This paper will analyze the effects of different normalizing temperatures on the microstructure and properties of the welding layer.
    
1. Effects on microstructure
    
The effect of normalizing temperature on the microstructure of the NM360 wear-resistant steel overlay welding layer is shown in Figure 1.
    
Relationship between normalizing temperature and microstructure of overlay welding layer of NM360 wear-resistant steel
    
It can be seen from Figure 1 that when the normalizing temperature of the welded layer is 950℃, the martensite and retained austenite are distributed evenly in the welded layer, the structure is relatively fine and uniform, and the amount of carbide is relatively large. When the normalizing temperature is increased to 1050℃, the microstructure of the welded layer becomes coarse, the retained austenite becomes coarse and a large amount of carbide is corresponding lost, resulting in a decrease in the hardness of the welded layer. When the normalizing temperature is further increased to 1150℃, the microstructure of the welded layer becomes very coarse, the retained austenite is significantly reduced and the amount of carbide is further reduced, causing the hardness of the welded layer to decline further.
    
2. Effects on Properties
    
The effects of the normalizing temperature on the properties of the NM360 wear-resistant steel overlay welding layer are shown in Figure 2.
    
Relationship between normalizing temperature and properties of overlay welding layer of NM360 wear-resistant steel
    
Shows that when the normalizing temperature of the welded layer is 950℃, the hardness of the welded layer is highest, and the impact toughness and tensile strength are also best. When the normalizing temperature is increased to 1050℃, the hardness of the welded layer declines slightly but the impact toughness and tensile strength have improved significantly. When the normalizing temperature is further increased to 1150℃, the hardness of the welded layer decreases significantly, the impact toughness and tensile strength decline but the elongation at break significantly increases.
    
From the above analysis, it can be seen that the normalizing temperature of the welded layer of NM360 wear-resistant steel plays an important role in the microstructure and properties of the welded layer. When the normalizing temperature is 950℃, the martensite, retained austenite and carbide content of the welded layer are optimal, and its hardness, impact toughness and tensile strength are optimal. Therefore, the normalizing temperature for manufacturing NM360 wear-resistant steel welded parts should be determined as 950℃.

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