The manufacture of gear and rack needs specific materials. The manufacturing process of gear and rack includes forging, cutting and heat treatment. When selecting materials, attention should be paid to the technological properties of materials. Facing the process performance of materials, we can improve it by changing the process procedures and heat treatment methods.

What materials should be selected for gear rack? It is necessary to understand the form of industrial development in our country, combine the resources and production conditions in our country, proceed from the reality, and comprehensively consider the problems of mechanical performance, technological performance and economy. Only reasonable selection of materials can guarantee the quality of rack, reduce the cost of products, and improve the market competitiveness.

In order to meet the mechanical properties of materials, the mechanical properties of materials include strength, hardness, plasticity and toughness, reflecting the characteristics of materials in use. When the gears are meshed, there is contact stress at the contact point of the tooth surface, and there is the maximum bending stress at the root of the tooth, which may cause the strength failure of the tooth surface or the tooth body. Each point of the tooth surface has relative sliding, which will produce wear. The main failure forms of gears are pitting, gluing, plastic deformation and fracture. Therefore, the gear material is required to have high bending fatigue strength and contact fatigue strength, sufficient hardness and wear resistance of the tooth surface, and certain strength and toughness of the core. For example, when determining the hardness of the big and small gears, it should be noted that the hardness of the tooth surface of the small gear is 30-50hbs higher than that of the big gear, because the load times of the small gear are more than that of the big gear, and the tooth root of the small gear is thinner, and the strength is lower than that of the big gear. In order to make the teeth of the two gears close to equal strength, the tooth surface of the small gear is harder than that of the big gear. On the other hand, the material brand is determined according to the performance of the material. The mechanical properties or hardness of materials should be defined, and then we can achieve the required hardness range through different heat treatment processes, so as to give different mechanical properties to materials. If the material is 40Cr alloy steel gear, when 840-860c oil quenching and 540-620c tempering, the tempering hardness can reach 28-32hrc, which can improve the structure and improve the comprehensive mechanical properties; when 860-880c oil quenching and 240-280c tempering, the hardness can reach 46-51hrc, then the surface wear resistance of the steel is good, the core toughness is good, and the deformation is small; When the nitriding temperature is 500-560c and the nitriding layer is 0.15-0.6mm, the hardness can reach 52-54HRC, so the steel has high surface hardness, high wear resistance, high fatigue strength, high corrosion resistance and scuffing resistance, and the deformation is very small; after electroplating or surface alloying, the friction performance of gear working surface can be improved and the corrosion resistance can be improved

On the other hand, the material brand is determined according to the performance of the material. The mechanical properties or hardness of materials should be defined, and then we can achieve the required hardness range through different heat treatment processes, so as to give different mechanical properties to materials. If the material is 40Cr alloy steel gear, when 840-860c oil quenching and 540-620c tempering, the tempering hardness can reach 28-32hrc, which can improve the structure and improve the comprehensive mechanical properties; when 860-880c oil quenching and 240-280c tempering, the hardness can reach 46-51hrc, then the surface wear resistance of the steel is good, the core toughness is good, and the deformation is small; when 500-560c nitriding treatment and nitriding layer is 0.15-0.6mm, the hardness can reach 52-54HRC, Therefore, the steel has high surface hardness, high wear resistance, high fatigue strength, high corrosion resistance and scuffing resistance with minimal deformation. After plating or surface alloying, the friction performance of gear working surface can be improved and the corrosion resistance can be improved