Study on grinding burn and crack of hard tooth surface of cylindrical gear

For the finish machining of hardened cylindrical gears, gear grinding technology is a common choice at present. On the premise of ensuring quality, how to improve production efficiency is a factor that production organizers and implementers need to consider.

For the grinding process of cylindrical gear hard tooth surface, one of the common machining defects is the grinding burn and grinding crack of cylindrical gear tooth surface. During grinding, due to the instantaneous high temperature in the grinding area (900 ℃ ~ 1500 ℃), the surface structure of cylindrical gear changes locally, and oxidation discoloration is formed on some surfaces. This phenomenon is called grinding burn. At the same time, the metallographic structure of the tooth surface material of the cylindrical gear may also change, and the surface microhardness will change accordingly, accompanied by residual stress. When the internal stress in the surface exceeds the fracture limit of the material, cracks and grinding cracks will appear.

Grinding burns destroy the tooth surface structure of cylindrical gears, and grinding cracks seriously reduce the fatigue limit of cylindrical gears. Grinding burns and grinding cracks greatly affect the service performance and service life of cylindrical gears. Grinding burn will reduce the mechanical properties of the cylindrical gear tooth surface. It will prematurely produce pitting, peeling and other phenomena in the later product use process, and then pollute the lubrication system of the cylindrical gear transmission, resulting in the failure of the whole transmission system and even the bearing. Once grinding cracks occur, they are generally difficult to eliminate. For some important cylindrical gear products, they can only be scrapped.

Grinding burn and grinding crack of hard tooth surface of cylindrical gear are related to the following factors.

(1) previous process: heat treatment index factors after hardening of cylindrical gear tooth surface. Grinding burns and grinding cracks will occur when the tooth surface hardness is too high and there are carbon reticulates in carburized and quenched cylindrical gears. The heat treatment process must be well controlled.

(2) preparation before gear grinding: select appropriate grinding wheel according to the products to be processed and ground, including grinding wheel body material, grinding wheel hardness, grinding wheel particle size, grinding wheel air hole, etc; At the same time, it is also necessary to select the appropriate type of grinding fluid and coolant flow, which must be prepared before cylindrical gear grinding.

In view of these factors, there have been many relevant studies. ZHY gear focuses on how to control the influence of some factors in the machining process and improve the production efficiency without cylindrical gear grinding burns and grinding cracks.

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