Deformation Control of Carburized Gear Heat Treatment

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The heat treatment deformation of carburized gear directly affects the accuracy, strength, noise and life of the gear. Even if the gear grinding process is added after the carburizing heat treatment, the deformation will still reduce the precision level of the gear. There are many factors that affect the deformation of carburizing heat treatment, and only by controlling various factors can the deformation be controlled to a small extent. Controlling gear deformation must also be solved in the whole process of manufacturing gears.

1. The influence of gear material metallurgical factors on deformation The test shows that the higher the hardenability of steel, the greater the deformation. When the core hardness is higher than 40HRC, the deformation will increase significantly. Therefore, there are certain requirements on the hardenability of steel. The narrower the hardenability zone, the more stable the deformation. The steel mill is required to provide “low and stable deformation” steel. The A1/N content ratio is controlled within the range of 1 to 2.5, which can narrow the hardenability band and reduce deformation. In addition, the box segregation and band structure of the material affect the uneven deformation and uneven carburization of the gear spline hole.

2. The effect of preliminary heat treatment on gear deformation. Excessive normalizing hardness, mixed crystal, large amount of sorbite or Widmanstat will increase the deformation of the inner hole, so temperature control normalizing or isothermal annealing should be used to treat forgings.

3. The effect of carburizing process on deformation The uniformity of temperature, the uniformity of the carburized layer, and the uniformity of the cooling medium temperature all affect the deformation of the gear. At the same time, the higher the carburizing temperature, the thicker the carburized layer and the lower the oil temperature. The gear deforms greatly. Therefore, it is necessary to improve the equipment, optimize the process, and improve the quality of gear heat treatment.

4. The effect of quenching on deformation Quenching cooling behavior is the most important factor affecting gear deformation. Hot oil quenching has less deformation than cold oil quenching, and is generally controlled at 100°C±120°C. The cooling capacity of oil is also crucial to deformation. Stirring methods all affect the deformation. The disk gears quenched by the upper quenching press, according to the deformation of various gears, adjust the parameters of the quenching press to reduce the deformation, adjust the pressure of the inner and outer die and the expansion block and the spraying of each section The amount of oil and the upper work surface are used to control the deformation.

5. The clamping method and the purpose of the fixture make the workpiece heating and cooling uniform, and the carburized layer of each part of the workpiece is uniform to reduce the uneven thermal stress and the uneven structural stress to reduce deformation. The clamping method can be changed, and the plate parts are perpendicular to the oil surface. , Shaft parts are installed vertically, using compensation washers, supporting washers, superimposed washers, etc., spline hole parts can be carburized mandrels, etc.

6. Coordination in mechanical processing:

First, master the heat treatment deformation law, move the position of the tolerance zone, and improve the product qualification rate.

Second, according to the law of deformation, the application of anti-deformation, shrinking end pre-expansion hole, improve the deformation qualification rate after quenching.

Third, the method of reserved processing amount is used for asymmetrical or uneven thickness parts, and then processed after heat treatment.

Fourth, after heat treatment, use a push knife to finish the spline hole, or electrolytically process the spline hole, or heat the mandrel after carburization for quenching, and then press out the mandrel to ensure the size of the spline hole to reduce deformation.

Editing by Baccata

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