Self-lubricating bearings have a wide temperature range, sufficient solid lubricant content, uniform release, good self-lubricating properties and occlusion, which can effectively protect the journal and achieve long-lasting use. It is suitable for operation in high temperature, low speed, heavy load, large dust, water shower and impact vibration. It can be widely used in the rolling of mining machinery, metallurgy, petroleum, chemical, food, textile, paper, printing and dyeing machinery and equipment. And sliding bearing parts.
The aluminum liquid produced by the aluminum electrolysis cell is sucked out by vacuum lifting and poured into the mixing furnace. After the ratio and slag removal, it flows into the aluminum ingot casting machine for casting, and the formed solid is called aluminum ingot, and the produced aluminum is produced. The ingots are stacked by a stacker. In order to improve production efficiency, the aluminum ingot must be cooled with a large amount of cooling water before molding, and the huge heat of the aluminum liquid is released into the cooling water during the cooling process to generate hot water vapor. Casting machine bearings are in high temperature and water vapor environment. Many bearings are greased. The added grease will be melted and discharged due to high temperature in a short time. Maintenance and maintenance are difficult, and the surface of the equipment is difficult to clean. Further, the steel structure bearing is easy to corrode and rust in a hot and humid environment, the failure rate is very high, the equipment maintenance cost is high, and the equipment operation is often troubled by the following two problems.
It is difficult to realize high-temperature continuous operation of the oil supply operation. The ingot, ingot, ingot, and ingot are installed in the unit casing. Each rotating bearing is designed with a grease fitting that periodically injects grease. Remove the housing and use a grease gun to pressurize the grease. And the whole machine has more than 30 oil filling points. The long-term operation and maintenance can not achieve this cumbersome oil filling operation. It is only necessary to hold the thin oil pot and pour it on the outside of the running bearing sleeve. It is difficult for the lubricating oil to enter the friction pair of the bearing. Some of the bearings are in a frictional state.
High ambient temperature, grease lubrication is not suitable for the current casting machine rolling bearing used in the molybdenum disulfide grease is considered to be resistant to high temperature grease, we know that its base oil is a petroleum product, add a small amount of high temperature resistant molybdenum disulfide additive, its temperature limit That is 120 ° C. According to the test, the working temperature of the casting machine bearing can reach 200 °C, which has far exceeded the temperature limit of grease. Under such high temperature conditions, the base oil in the grease will become thinner and gradually evaporate, and the remaining carbon residue, molybdenum disulfide and dust will be mixed into a solid block to solidify on the cage of the rolling bearing, which not only loses its lubricating effect, It also hinders the normal operation of the rolling bearing and wears out quickly. It takes up to 2 weeks to stop, and removes the bearing to clean the grease.
First, the wear situation
The abnormal wear of the bearing caused by the two major problems in the operation of the bearing of the aluminum ingot casting equipment is more serious. Taking an aluminum alloy drawing mechanism as an example, the average service life of the bearing is 2 months. When the wear is serious, the inner ring of 5 mm is worn through, so that the equipment cannot continue to operate.
Wear is uneven. The reason is that the original design can not be achieved by the oil supply method. It is only necessary to smear the thin oil outside the bearing in operation, and a small amount can be leached into the bearing, and the wear is small. It can also be seen from the table that more than 50% of the shaft and the sleeve are not Lubricated, but in the dry friction state produces strong adhesive wear. This wear quickly increases the play gap between the shaft and the sleeve, so that dust is more accessible and causes a vicious circle.
Second, the choice of oil-free self-lubricating bearings
In order to solve the lubrication problems of high temperature, low speed, heavy load, large dust, water shower and impact vibration in mechanical equipment, oil-free self-lubricating bearings are selected.
1. Construction of the bearing The self-lubricating bearing is to develop a well-ordered hole in the metal friction surface of the bearing base, and embed molybdenum disulfide, graphite, etc. to form a composite self-lubricating block embedded in the metal sleeve to make a composite. Bearings, solid lubricants have a friction area of ​​25-65%. The solid self-lubricating block can work normally at a high temperature of 280 °C. However, due to its low mechanical strength, weak bearing capacity and easy deformation, it can be suppressed by inserting it in the metal hole groove, forming a metal part to bear the bearing function and lubricating the self-lubricating block. The lubrication mechanism of the self-lubricating bearing is that during the sliding friction between the shaft and the sleeve, a part of the self-lubricating material molecules is transferred to the metal surface of the shaft to fill the micro-non-planar surface and form a stable solid lubricating film. , causing the grinding between the solid lubricating film to prevent the adhesive wear of the shaft and the sleeve. This combination of rationality combines the complementary advantages of copper alloys and non-metal wear-reducing materials, and is particularly suitable for motion-free environments in oil-free, high-temperature, high-load, low-speed, anti-fouling, anti-corrosive, and strong radiation environments, and It is used under special working conditions where water or other solution is infiltrated and no grease can be added at all.
2. The area occupied by the self-lubricating block is related to the running speed and bearing strength, and the running speed is low; the bearing strength is large, and the area occupied by the metal should be larger. For example, the area occupied by the self-lubricating block of the traveling wheel bearing of the ingot car is about 25%, the lubrication of the shaft bearing of the pulling mechanism is sufficient, the bearing strength is not large, and the area occupied by the self-lubricating block is about 65%.
3. Technical requirements for bushing materials Bushings shall be made of alloyed copper. The bushings shall have a high hardness and shall generally be heat treated with a hardness not less than HRC45.
4. Self-lubricating block geometry and inlay requirements. The self-lubricating block has two shapes of a column shape and a rectangular shape, and the self-lubrication can adopt a column shape according to the occupied area, and a rectangle can be used instead. No matter what shape must be set in order to prevent it from falling off during operation.
5. The clearance value of the bushing and the shaft The linear expansion coefficient of the self-lubricating block is about 10 times that of steel. In order to adapt to the bearing temperature change, the gap between the shaft and the bushing is increased from the original four-stage dynamic matching (D4/dc4) of 0.032 to 0.15 mm to 0.45 to 0.5 mm. The self-lubricating block protrudes from the bushing metal by 0.2 to 0.4 mm on the side of the friction pair. This will be fully lubricated during the initial running-in period of the bearing operation, reducing the power consumption of the power drag.
6. Advantages of oil-free self-lubricating bearings:
a. No oil lubrication or less oil lubrication, suitable for places that cannot be refueled or difficult to refuel. It can be used without maintenance or less maintenance.
b. Good wear resistance, low friction coefficient and long service life.
c. There is an appropriate amount of elastoplasticity, which can distribute the stress on the wider contact surface and improve the bearing capacity of the bearing.
d. The static friction coefficient is similar, which can eliminate the creep at low speed, thus ensuring the working precision of the machine.
e. It can reduce vibration, reduce noise, prevent pollution and improve working conditions.
f. The transfer film can be formed during the operation to protect the grinding shaft and not bite the shaft.
g. The hardness of the grinding shaft is low, and the unconditioned shaft can be used, which reduces the processing difficulty of the relevant parts.
h. Thin wall structure, light weight, can reduce the mechanical volume.
i. The bushing is made of brass and can be used in corrosive media.
Through the practice of an aluminum enterprise, the casting machine bearing has been changed to oil-free self-lubricating bearing. It has been used continuously for 15 months and is still in operation. The gap between the shaft and the bushing is generally less than 1mm. It is expected to be used for another 12 months. More than the original service life (2 months). Oil-free self-lubricating bearings can be used not only in aluminum ingot casting machines, but also in oil-free, high-temperature, high-load, low-speed, anti-fouling, anti-corrosion, and strong radiation environments, as well as in water. Or equipment under special working conditions in which the solution is infiltrated and cannot be greased at all. Such bearings have a wide spread value.
At present, most of the bearings used in various machinery industries are balls, needles and the like, but a small number of self-lubricating bearings have been used. It is believed that in the near future, lubricating bearings will become the dominant bearing.
The following are the application features and advantages of some self-lubricating bearings:
1. No oil lubrication or less oil lubrication, suitable for places that cannot be refueled or difficult to refuel. It can be used without maintenance or less maintenance.
2. Good wear resistance, low friction coefficient and long service life.
3. With proper elastoplasticity, the stress can be distributed over a wide contact surface to improve the bearing capacity of the bearing.
4. The static friction coefficient is similar, which can eliminate the creep at low speed, thus ensuring the working precision of the machine.
5. It can reduce vibration, reduce noise, prevent pollution and improve working conditions.
6. The transfer film can be formed during the operation to protect the grinding shaft without biting.
7. For the hardness requirement of the grinding shaft, the shaft without the quenching and tempering can be used, which reduces the processing difficulty of the related parts.
8. Thin wall structure, light weight, can reduce the mechanical volume.
9. The back of the steel can be plated with various metals and can be used in corrosive media. It has been widely used in sliding parts of various machinery, such as printing machines, textile machines, tobacco machinery, micro-motors, automobiles, motorcycles and agricultural machinery. and many more.
The aluminum liquid produced by the aluminum electrolysis cell is sucked out by vacuum lifting and poured into the mixing furnace. After the ratio and slag removal, it flows into the aluminum ingot casting machine for casting, and the formed solid is called aluminum ingot, and the produced aluminum is produced. The ingots are stacked by a stacker. In order to improve production efficiency, the aluminum ingot must be cooled with a large amount of cooling water before molding, and the huge heat of the aluminum liquid is released into the cooling water during the cooling process to generate hot water vapor. Casting machine bearings are in high temperature and water vapor environment. Many bearings are greased. The added grease will be melted and discharged due to high temperature in a short time. Maintenance and maintenance are difficult, and the surface of the equipment is difficult to clean. Further, the steel structure bearing is easy to corrode and rust in a hot and humid environment, the failure rate is very high, the equipment maintenance cost is high, and the equipment operation is often troubled by the following two problems.
It is difficult to realize high-temperature continuous operation of the oil supply operation. The ingot, ingot, ingot, and ingot are installed in the unit casing. Each rotating bearing is designed with a grease fitting that periodically injects grease. Remove the housing and use a grease gun to pressurize the grease. And the whole machine has more than 30 oil filling points. The long-term operation and maintenance can not achieve this cumbersome oil filling operation. It is only necessary to hold the thin oil pot and pour it on the outside of the running bearing sleeve. It is difficult for the lubricating oil to enter the friction pair of the bearing. Some of the bearings are in a frictional state.
High ambient temperature, grease lubrication is not suitable for the current casting machine rolling bearing used in the molybdenum disulfide grease is considered to be resistant to high temperature grease, we know that its base oil is a petroleum product, add a small amount of high temperature resistant molybdenum disulfide additive, its temperature limit That is 120 ° C. According to the test, the working temperature of the casting machine bearing can reach 200 °C, which has far exceeded the temperature limit of grease. Under such high temperature conditions, the base oil in the grease will become thinner and gradually evaporate, and the remaining carbon residue, molybdenum disulfide and dust will be mixed into a solid block to solidify on the cage of the rolling bearing, which not only loses its lubricating effect, It also hinders the normal operation of the rolling bearing and wears out quickly. It takes up to 2 weeks to stop, and removes the bearing to clean the grease.
First, the wear situation
The abnormal wear of the bearing caused by the two major problems in the operation of the bearing of the aluminum ingot casting equipment is more serious. Taking an aluminum alloy drawing mechanism as an example, the average service life of the bearing is 2 months. When the wear is serious, the inner ring of 5 mm is worn through, so that the equipment cannot continue to operate.
Wear is uneven. The reason is that the original design can not be achieved by the oil supply method. It is only necessary to smear the thin oil outside the bearing in operation, and a small amount can be leached into the bearing, and the wear is small. It can also be seen from the table that more than 50% of the shaft and the sleeve are not Lubricated, but in the dry friction state produces strong adhesive wear. This wear quickly increases the play gap between the shaft and the sleeve, so that dust is more accessible and causes a vicious circle.
Second, the choice of oil-free self-lubricating bearings
In order to solve the lubrication problems of high temperature, low speed, heavy load, large dust, water shower and impact vibration in mechanical equipment, oil-free self-lubricating bearings are selected.
1. Construction of the bearing The self-lubricating bearing is to develop a well-ordered hole in the metal friction surface of the bearing base, and embed molybdenum disulfide, graphite, etc. to form a composite self-lubricating block embedded in the metal sleeve to make a composite. Bearings, solid lubricants have a friction area of ​​25-65%. The solid self-lubricating block can work normally at a high temperature of 280 °C. However, due to its low mechanical strength, weak bearing capacity and easy deformation, it can be suppressed by inserting it in the metal hole groove, forming a metal part to bear the bearing function and lubricating the self-lubricating block. The lubrication mechanism of the self-lubricating bearing is that during the sliding friction between the shaft and the sleeve, a part of the self-lubricating material molecules is transferred to the metal surface of the shaft to fill the micro-non-planar surface and form a stable solid lubricating film. , causing the grinding between the solid lubricating film to prevent the adhesive wear of the shaft and the sleeve. This combination of rationality combines the complementary advantages of copper alloys and non-metal wear-reducing materials, and is particularly suitable for motion-free environments in oil-free, high-temperature, high-load, low-speed, anti-fouling, anti-corrosive, and strong radiation environments, and It is used under special working conditions where water or other solution is infiltrated and no grease can be added at all.
2. The area occupied by the self-lubricating block is related to the running speed and bearing strength, and the running speed is low; the bearing strength is large, and the area occupied by the metal should be larger. For example, the area occupied by the self-lubricating block of the traveling wheel bearing of the ingot car is about 25%, the lubrication of the shaft bearing of the pulling mechanism is sufficient, the bearing strength is not large, and the area occupied by the self-lubricating block is about 65%.
3. Technical requirements for bushing materials Bushings shall be made of alloyed copper. The bushings shall have a high hardness and shall generally be heat treated with a hardness not less than HRC45.
4. Self-lubricating block geometry and inlay requirements. The self-lubricating block has two shapes of a column shape and a rectangular shape, and the self-lubrication can adopt a column shape according to the occupied area, and a rectangle can be used instead. No matter what shape must be set in order to prevent it from falling off during operation.
5. The clearance value of the bushing and the shaft The linear expansion coefficient of the self-lubricating block is about 10 times that of steel. In order to adapt to the bearing temperature change, the gap between the shaft and the bushing is increased from the original four-stage dynamic matching (D4/dc4) of 0.032 to 0.15 mm to 0.45 to 0.5 mm. The self-lubricating block protrudes from the bushing metal by 0.2 to 0.4 mm on the side of the friction pair. This will be fully lubricated during the initial running-in period of the bearing operation, reducing the power consumption of the power drag.
6. Advantages of oil-free self-lubricating bearings:
a. No oil lubrication or less oil lubrication, suitable for places that cannot be refueled or difficult to refuel. It can be used without maintenance or less maintenance.
b. Good wear resistance, low friction coefficient and long service life.
c. There is an appropriate amount of elastoplasticity, which can distribute the stress on the wider contact surface and improve the bearing capacity of the bearing.
d. The static friction coefficient is similar, which can eliminate the creep at low speed, thus ensuring the working precision of the machine.
e. It can reduce vibration, reduce noise, prevent pollution and improve working conditions.
f. The transfer film can be formed during the operation to protect the grinding shaft and not bite the shaft.
g. The hardness of the grinding shaft is low, and the unconditioned shaft can be used, which reduces the processing difficulty of the relevant parts.
h. Thin wall structure, light weight, can reduce the mechanical volume.
i. The bushing is made of brass and can be used in corrosive media.
Through the practice of an aluminum enterprise, the casting machine bearing has been changed to oil-free self-lubricating bearing. It has been used continuously for 15 months and is still in operation. The gap between the shaft and the bushing is generally less than 1mm. It is expected to be used for another 12 months. More than the original service life (2 months). Oil-free self-lubricating bearings can be used not only in aluminum ingot casting machines, but also in oil-free, high-temperature, high-load, low-speed, anti-fouling, anti-corrosion, and strong radiation environments, as well as in water. Or equipment under special working conditions in which the solution is infiltrated and cannot be greased at all. Such bearings have a wide spread value.
At present, most of the bearings used in various machinery industries are balls, needles and the like, but a small number of self-lubricating bearings have been used. It is believed that in the near future, lubricating bearings will become the dominant bearing.
The following are the application features and advantages of some self-lubricating bearings:
1. No oil lubrication or less oil lubrication, suitable for places that cannot be refueled or difficult to refuel. It can be used without maintenance or less maintenance.
2. Good wear resistance, low friction coefficient and long service life.
3. With proper elastoplasticity, the stress can be distributed over a wide contact surface to improve the bearing capacity of the bearing.
4. The static friction coefficient is similar, which can eliminate the creep at low speed, thus ensuring the working precision of the machine.
5. It can reduce vibration, reduce noise, prevent pollution and improve working conditions.
6. The transfer film can be formed during the operation to protect the grinding shaft without biting.
7. For the hardness requirement of the grinding shaft, the shaft without the quenching and tempering can be used, which reduces the processing difficulty of the related parts.
8. Thin wall structure, light weight, can reduce the mechanical volume.
9. The back of the steel can be plated with various metals and can be used in corrosive media. It has been widely used in sliding parts of various machinery, such as printing machines, textile machines, tobacco machinery, micro-motors, automobiles, motorcycles and agricultural machinery. and many more.
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