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The processing technology requirements of high carbon steel tube bearings and gears involve multiple key links, including material selection, blank treatment, heat treatment, tooth profile processing, surface treatment and fine processing, etc.

1. Material selection

High-carbon steel, due to its high hardness and wear resistance, is often used to manufacture high-precision gears and bearings. For instance, alloy steels such as 20CrMnTi and 20CrMoH are common high-carbon steel materials, suitable for gears that require high wear resistance and high strength. In addition, carburized steel (such as 20CrMnTi) is widely used in automotive gears due to its high surface hardness (HRC58~62) and good core toughness (HRC30~45), which can meet the usage requirements under high-speed and heavy-load working conditions. For bearings, high-carbon steel (such as 40Cr) is also often used to manufacture shaft parts due to its excellent comprehensive mechanical properties.

2. Blank treatment

The blanks of high carbon steel tube bearings and gears are usually processed by forging or casting. Forging processes (such as hot die forging and cross wedge rolling) can improve the accuracy of the blank and reduce the machining allowance, and are suitable for complex stepped shaft parts. Casting is suitable for parts with complex shapes or small batch sizes. After the blank is forged, normalizing treatment is usually carried out to refine the grains, homogenize the structure and eliminate internal stress, preparing for subsequent processing. For carburized steel, after normalizing treatment, quenching and tempering treatment is still required to obtain tempered sorbite structure and improve the comprehensive mechanical properties of the material.

3. Heat treatment

Heat treatment is a key process in the processing of high carbon steel tube bearings and gears, mainly including normalizing, quenching and tempering, carburizing and quenching, surface quenching, etc.

Normalizing treatment: It is used to reduce hardness, improve machinability, and prepare for subsequent heat treatment. Normalizing has a finer microstructure than annealing, which helps improve product quality.

Quenching and tempering treatment: It is carried out after the rough machining of the gear blank to obtain a uniform and fine tempered sorbite structure, thereby enhancing the strength and toughness of the material.

Carburizing and quenching: It is suitable for gears that require high surface hardness and wear resistance, such as automotive gears. The carburizing temperature is usually 930℃, the quenching temperature is 780-800℃, and the tempering temperature is 180-200℃, in order to obtain a fine martensitic structure and good metallographic structure.

– Surface hardening: It is used to enhance the hardness of the tooth surface, such as high-frequency hardening (44~48HRC), to reduce friction and wear.

Tempering treatment: It is carried out after carburizing and quenching to reduce quenching stress and enhance the toughness and stability of the material.

4. Tooth profile processing

Tooth profile processing is the core link in the gear processing of high carbon steel tube. Common tooth profile processing methods include hobbing, shaping, shaving, grinding, etc.

– Gear hobbing: It is suitable for rough machining, with high efficiency, but the surface roughness is relatively poor. Gear hobbing machines are usually used in mass production.

– Gear shaping: It is suitable for the processing of internal teeth and external teeth affected by structural interference, with relatively high tooth profile accuracy.

– Shaving: It is used for fine processing to improve the accuracy of tooth profile and surface quality, and is suitable for gears with high requirements.

– Gear grinding: It is used for final finishing to enhance the accuracy and surface quality of the gear surface, and is suitable for high-precision gears.

– Honing: It is used to correct tooth profile errors and improve meshing performance.

5. Surface treatment and finishing

Surface quenching and carburizing: The hardness of the tooth surface is increased through carburizing or carburizing and nitriding. Then, through quenching and tempering treatment, the hardness of the tooth surface reaches 58 to 64HRC, and the core hardness is maintained at 30 to 45HRC.

– Surface quality treatment: The tooth surface undergoes grinding, polishing and other treatments to reduce surface roughness, minimize friction and wear, and enhance transmission efficiency.

– End face and journal processing: Finish the end face and journal to ensure their dimensional accuracy and surface roughness. High-precision CNC grinding machines are usually used.

– Chamfering and deburring: After processing, chamfer the top of the teeth and the end of the teeth to prevent damage from bumps.

6. Precision control and Inspection

The machining accuracy requirements of the high carbon steel tube gears are relatively high, involving multiple key parameters such as tooth profile accuracy, end face runout, radial runout, surface roughness, etc.

– Tooth profile accuracy: It is usually required to reach grade 6 to 7 accuracy to ensure the smoothness of gear movement and meshing performance.

– End face runout: It is required to be less than 0.03 to 0.05mm to ensure the axial positioning accuracy of the gear.

– Surface roughness: The tooth surface roughness is usually required to reach Ra=0.1 to 0.63μm to reduce friction and wear.

– Inspection: After processing is completed, multiple inspections are required, including tooth profile inspection, surface hardness inspection, dimensional inspection, etc., to ensure product quality.

7. Special process requirements

– Center hole processing: As a positioning reference, the accuracy of the center hole directly affects the processing quality of the gear. The depth of the central hole and the distance between the two central holes need to be strictly controlled to ensure the positioning accuracy.

Warm extrusion process: It is suitable for processing high-carbon steel materials, which can reduce deformation resistance and improve forming quality. It is suitable for materials that are difficult to process at room temperature.

– Superfinishing: It is used to improve the surface quality of gear journal, with a surface roughness that can reach Ra=0.1, to meet the requirements of high-precision transmission.

8. Summary

The processing technology requirements of high carbon steel tube bearings and gears involve multiple links such as material selection, blank treatment, heat treatment, tooth profile processing, surface treatment and fine processing. Each link needs to strictly control the process parameters to ensure the accuracy, surface quality and wear resistance of the gears. For instance, carburizing and quenching treatment is the key to enhancing the hardness of the tooth surface, while tooth profile processing methods such as hobbing, shaping, shaving and grinding determine the accuracy and surface quality of gears. In addition, the machining accuracy and inspection of the center hole are also important factors in ensuring the overall performance of the gears.

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