According to the forming mechanism of the grinding and deteriorating layer on the FAG bearing working surface, the main factors affecting the grinding and deteriorating layer are the grinding heat and the grinding force. The following analysis of the cause of the failure of FAG bearings.
FAG bearing heat of grinding In the FAG bearing grinding process, the grinding wheel and the workpiece contact area consume a lot of energy, generate a lot of grinding heat, resulting in a local high temperature in the grinding area. The instantaneous temperature in the experimental conditions can be deduced, calculated or applied by the infrared heat transfer method and the thermocouple heat transfer theoretical formula. It can be found that the instantaneous temperature in the grinding zone can be as high as 1000 to 1500°C in 0.1 to 0.001 ms. Such an instantaneous high temperature is sufficient to cause high-temperature oxidation, high-temperature tempering, amorphous structure, secondary quenching, and some burn-cracking and other changes in the surface layer at a certain depth of the working surface.
(1) High temperature tempered layer
The instantaneous high temperature in the grinding zone allows the surface to be heated to a certain depth (10 to 100 nm) above the temperature at which the workpiece is tempered. In the case where the austenitizing temperature is not reached, as the heating temperature is increased, the surface of the layer will generate a re-tempering or high-temperature tempering corresponding to the heating temperature, and the hardness will also decrease. The higher the heating temperature, the greater the reduction in hardness.
(2) Surface oxide layer
The surface of the steel under the effect of transient high temperatures reacts with oxygen in the air and rises to a thin (20-30 nm) thin layer of iron oxide. It is worth noting that the thickness of the oxide layer corresponds to the total thickness of the surface grinding degraded layer. This shows that the oxide thickness is directly related to the grinding process and is an important symbol of grinding quality.
(3) Amorphous tissue layer
When the instantaneous high temperature in the grinding zone causes the surface of the workpiece to reach a molten state, the molten metal molecular flow is uniformly applied to the working surface and cooled by the base metal at an extremely rapid rate to form an extremely thin layer of amorphous material. Organization level. It has high hardness and toughness, but it is only about 10nm and it is easily removed in precision grinding.
(4) Grinding crack
Secondary quench burns will change the surface layer stress. The secondary quench zone is under pressure, and there is maximum tensile stress in the material under the high temperature temper zone. This is where the crack core is most likely to occur. Cracks propagate most easily along the original austenite grain boundaries. Severe burns can cause cracks in the entire grinding surface (mostly cracking) resulting in scrapped parts.
(5) Second layer quenched layer
When the instantaneous high temperature in the grinding zone heats the surface layer of the workpiece above the austenitizing temperature (Ac1), the austenitized structure of the layer is re-quenched into a martensitic structure during subsequent cooling. All parts that have secondary quenched burns must have a very low hardness and high temperature tempering layer under the secondary quenching layer.
FAG bearing heat of grinding In the FAG bearing grinding process, the grinding wheel and the workpiece contact area consume a lot of energy, generate a lot of grinding heat, resulting in a local high temperature in the grinding area. The instantaneous temperature in the experimental conditions can be deduced, calculated or applied by the infrared heat transfer method and the thermocouple heat transfer theoretical formula. It can be found that the instantaneous temperature in the grinding zone can be as high as 1000 to 1500°C in 0.1 to 0.001 ms. Such an instantaneous high temperature is sufficient to cause high-temperature oxidation, high-temperature tempering, amorphous structure, secondary quenching, and some burn-cracking and other changes in the surface layer at a certain depth of the working surface.
(1) High temperature tempered layer
The instantaneous high temperature in the grinding zone allows the surface to be heated to a certain depth (10 to 100 nm) above the temperature at which the workpiece is tempered. In the case where the austenitizing temperature is not reached, as the heating temperature is increased, the surface of the layer will generate a re-tempering or high-temperature tempering corresponding to the heating temperature, and the hardness will also decrease. The higher the heating temperature, the greater the reduction in hardness.
(2) Surface oxide layer
The surface of the steel under the effect of transient high temperatures reacts with oxygen in the air and rises to a thin (20-30 nm) thin layer of iron oxide. It is worth noting that the thickness of the oxide layer corresponds to the total thickness of the surface grinding degraded layer. This shows that the oxide thickness is directly related to the grinding process and is an important symbol of grinding quality.
(3) Amorphous tissue layer
When the instantaneous high temperature in the grinding zone causes the surface of the workpiece to reach a molten state, the molten metal molecular flow is uniformly applied to the working surface and cooled by the base metal at an extremely rapid rate to form an extremely thin layer of amorphous material. Organization level. It has high hardness and toughness, but it is only about 10nm and it is easily removed in precision grinding.
(4) Grinding crack
Secondary quench burns will change the surface layer stress. The secondary quench zone is under pressure, and there is maximum tensile stress in the material under the high temperature temper zone. This is where the crack core is most likely to occur. Cracks propagate most easily along the original austenite grain boundaries. Severe burns can cause cracks in the entire grinding surface (mostly cracking) resulting in scrapped parts.
(5) Second layer quenched layer
When the instantaneous high temperature in the grinding zone heats the surface layer of the workpiece above the austenitizing temperature (Ac1), the austenitized structure of the layer is re-quenched into a martensitic structure during subsequent cooling. All parts that have secondary quenched burns must have a very low hardness and high temperature tempering layer under the secondary quenching layer.
Intelligent Weighing Cabinet,Full Touch Screen Control Weighing Cabinet,10 Door Intelligent Grid Cabinet,Weighing Intelligent Cabinet
Jiangsu Xicang Intelligent Technology Co., Ltd. , https://www.xciwarehousing.com