7 processes for producing forged steel gears

2024-08-14 13:22:52

With the development of modern technology, there is an increasing demand for the quality of Gear forgings, and as the main basic component of the automotive industry, the quality of gears directly affects the noise, smoothness, and service life of automobiles. So, in order to achieve the dual goals of quality and noise, and to achieve efficient production, what are the seven processes of gear machining?

1. Forging blanks: Currently, hot forging is still a widely used blank forging process for automotive gear parts. In recent years, cross wedge rolling technology has been widely promoted in shaft machining. This technology is particularly suitable for making complex stepped shaft blanks. It not only has high precision and small post-processing allowance, but also has high production efficiency.

2. Normalization: After forging the blank, some factories choose to normalize, and some companies choose annealing. The purpose of normalizing and annealing is to refine the grain size and homogenize the distribution of carbides, and remove the internal stress of the material. However, due to the slightly faster cooling rate of normalizing than annealing, the normalized structure is finer and its mechanical properties are also improved. In addition, external cooling of the normalizing furnace does not occupy equipment and has high productivity, so normalizing is used as much as possible instead of annealing in production. Adopting isothermal normalizing to ensure stable and reliable product quality.

3. Rough machining: Rough machining of the outer circle and end face of gears can be done on ordinary lathes or CNC lathes. Due to the heat treatment of the workpiece after rough machining, there is usually a margin of 3-5 millimeters left for easy precision machining to * * * size in the future.

4. Quenching and tempering heat treatment: Due to different working conditions of gear forgings, the surface hardness after heat treatment is also different. However, the hardness of gears after quenching is generally above HRC45. For example, automotive gears often use 20CrMnTi steel as the gear material due to high stress and frequent impact. 20CrMnTi steel has high mechanical properties, and the surface hardness after quenching can reach HRC58-62, and the core hardness is HRC30-45, in order to improve wear resistance and fatigue resistance.

5. Precision machining: Precision machining the outer circle and end face of the gear, machining the dimensions to the size requirements specified in the drawing. If further grinding is required, a margin of 0.2-0.3 millimeters should be left to facilitate grinding and achieve higher precision requirements.

6. Gear making: Gear hobbing machines or hobbing machines are often used to machine tooth surfaces. Although adjustment and maintenance are convenient, low efficiency may occur in large-scale production. With the development of coating technology, it is very convenient to re coat the rolling cutters and cutting edges after grinding. Coated tools can significantly improve their service life, generally by more than 90%, effectively reducing the number of tool changes and grinding time, and achieving significant benefits.

7. Tooth surface grinding: The quality requirements for gear forgings are becoming increasingly high, and the requirements for variable speed noise are becoming lower and lower. To achieve the dual goals of quality and noise, higher precision gear machining is required. For gears produced in large quantities, grinding remains an effective precision machining method. Generally used for processing quenched tooth surfaces, it has strong correction ability for pre grinding process errors and can achieve high accuracy. The tooth surface roughness can be as small as R0.63-0.16 microns.