The self-lubricating bearing has a wide operating temperature, sufficient solid lubricating material content, uniform release, good self-lubricating performance and occlusion, and can effectively protect the journal to achieve the purpose of long-lasting use. It is suitable for operation in the environment of high temperature, low speed, heavy load, dust, water shower and shock vibration, and can be widely used in the rolling and sliding bearing parts of mining machinery, metallurgy, petroleum, chemical industry, food, textile, papermaking, printing and dyeing and other mechanical equipment.

The molten aluminum produced by the aluminum electrolytic tank is sucked out by vacuum lifting ladle and poured into the mixing furnace, and after proportioning and slag removal, it flows into the aluminum ingot casting machine for casting and molding, and the formed solid is called aluminum ingot, and the aluminum ingot produced is stacked by the stacker. In order to improve production efficiency, aluminum ingots must be cooled with a large amount of cooling water before molding, and during the cooling process, the huge heat energy of the molten aluminum is released into the cooling water, producing scorching water vapor. The bearing of the casting machine is in the high temperature and water vapor environment, and many of the bearings are grease lubricated, and the added grease will melt and overflow in a short time due to high temperature, which is difficult to maintain, and the surface hygiene of the equipment is also difficult to wipe. Then there are steel structure bearings in the scorching, humid environment is easy to corrode and rust, the failure rate is very high, the equipment maintenance cost is high, the equipment operation is often troubled by the following two problems.

It is difficult to achieve high temperature continuous operation in oil supply operation, and the ingot pulling, spindle moving, spindle splicing, spindle turning and other devices of the casting machine are installed in the unit shell, and each rotating bearing is designed with a grease nozzle facility for regular injection of lubricating grease. And the whole machine has more than 30 oil injection points, long-term operation and maintenance can not realize this cumbersome oil injection operation, so we have to hold a thin oil pot to pour on the outside of the bearing sleeve in operation, and the lubricating oil is difficult to enter the friction pair of the bearing, and most of the bearings are in a state of friction.

The ambient temperature is high, the grease lubrication is not suitable for the molybdenum disulfide grease used in the rolling bearing of the casting machine is considered to be able to withstand high temperature grease, we know that its base oil is petroleum products, plus a small amount of high-temperature resistant molybdenum disulfide additives, its temperature resistance limit is 120 °C. It is measured that the working temperature of the casting machine bearing can reach 200 °C, which has far exceeded the temperature resistance limit of the grease. Under such high temperature conditions, the base oil in the grease will be thinned and gradually evaporated, and the remaining carbon slag, molybdenum disulfide and dust will be mixed into solid blocks and solidified on the cage of the rolling bearing, which not only loses its lubricating effect, but also hinders the normal operation of the rolling bearing and wears out quickly, and it will have to be shut down for up to 2 weeks, and the bearing will be removed for cleaning and replacing with new grease.

1. Wear and tear condition:
The abnormal wear of bearings caused by two major problems in the operation of aluminum ingot casting equipment bearings is more serious. Taking the ingot pulling mechanism of an aluminum enterprise as an example, the average service life of the bearing is 2 months, and the inner ring of 5mm is worn through when the wear is serious, so that the equipment can not continue to operate.
Wear is uneven. The reason is that the original design of the oil feeding method can not be realized, so it has to be poured thin oil on the outside of the bearing in operation, a small amount can be burned into the bearing, the wear is smaller, and it can be seen from the table that more than 50% of the shafts and sleeves are not lubricated, but are in a dry friction state to produce strong adhesive wear. This wear quickly increases the clearance between the shaft and the sleeve, making it easier for dust to enter, creating a vicious circle.

Second, the selection of oil-free self-lubricating bearings:
In order to solve the lubrication problems of high temperature, low speed, heavy load, large dust, water flushing and shock and vibration in mechanical equipment, oil-free self-lubricating bearings are selected.
1. The structure of the bearing: The self-lubricating bearing is to develop holes arranged in an orderly manner on the metal friction surface of the bearing matrix, and embed molybdenum disulfide, graphite, etc. to make composite self-lubricating blocks embedded in the metal sleeve, and the composite bearing is made of solid lubricant friction area of 25-65%. The solid self-lubricating block can operate normally at a high temperature of 280°C. However, due to its low mechanical strength, weak bearing capacity, and easy to deform, it can be inhibited by inlaying it in the metal hole groove, forming a metal part that plays a bearing role, and a self-lubricating block plays a lubricating role. The lubrication mechanism of this self-lubricating bearing is that in the process of sliding friction between the shaft and the sleeve, a part of the molecule of the self-lubricating material is transferred to the metal surface of the shaft, filling the tiny non-plane, and forming a layer of relatively stable solid lubricating film, resulting in the grinding between the solid lubricating film and preventing the adhesion and wear of the shaft and the sleeve. This rational combination combines the complementary advantages of copper alloy and non-metallic anti-friction materials, and is especially suitable for use under the special working conditions of oil-free, high temperature, high load, low speed, anti-fouling, anti-corrosion, strong radiation environment, and under the special working conditions that can not be lubricated at all.
2. The ratio of the self-lubricating block to the surface area of the self-lubricating block is related to the running speed and compressive strength, and the running speed is low; The compressive 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 ingot trolley walking wheel bearing is about 25%, the lubrication of the rotating shaft bearing of the ingot pulling mechanism should be sufficient, the bearing strength is not large, and the area occupied by the self-lubricating block is about 65%.
3. The technical requirements for the bushing material The bushing should be made of alloy copper, and the bushing should have a high hardness, generally heat treated, and its hardness should not be less than HRC45.
4. Geometry and inlay requirements of self-lubricating block. The shape of the self-lubricating block is cylindrical and rectangular, and the self-lubrication can be cylindrical according to the size of the occupied area, and the reverse can be rectangular. Whatever the shape, it must be firmly inlaid to prevent it from falling off during operation.
5. The linear expansion coefficient of the self-lubricating block is about 10 times that of steel in the matching clearance value of the bushing and the shaft. In order to adapt to the temperature change of the bearing, the gap between the shaft and the bushing is increased from 0.032~0.15mm to 0.45~0.5mm from the original four-stage dynamic fit (D4/dc4) of metal parts. The self-lubricating block protrudes the bushing metal 0.2~0.4mm on one side of the friction pair. This results in sufficient lubrication during the initial break-in period of bearing operation, reducing the consumption of power for power dragging.
6. Advantages of oil-free self-lubricating bearings:
a. No oil lubrication or less oil lubrication, suitable for places where oil cannot be refueled or it is difficult to refuel, and can be used without maintenance or less maintenance.
b. Good wear resistance, small friction coefficient and long service life.
c. It has an appropriate amount of elastoplasticity, which can distribute the stress on a wide contact surface and improve the bearing capacity.
d. The static and dynamic friction coefficients are similar, which can eliminate crawling at low speed, so as to ensure the working accuracy of the machinery.
e. It can reduce vibration, reduce noise, prevent pollution, and improve working conditions.
f. In the process of operation, the transfer film can be formed, which plays a role in protecting the grinding shaft, and there is no bite to the shaft.
g. The hardness requirements for the grinding shaft are low, and the unconditioned shaft can be used, which reduces the machining difficulty of related parts.
h. Thin-walled structure, light weight, can reduce mechanical volume.
i. The bushing material is brass, which can be used in corrosive media.

Through the practice of an aluminum enterprise, the casting machine bearing has been changed to an oil-free self-lubricating bearing, which has been used continuously for 15 months, and is still running, and the clearance of the shaft and bushing is generally not more than 1mm, and it is expected to be used for another 12 months, which significantly exceeds the original service life (2 months). Oil-free self-lubricating bearings can not only be used well in aluminum ingot casting machines, but also can be adapted to the movement amplitude in oil-free, high temperature, high load, low speed, anti-fouling, anti-corrosion, strong radiation environment, as well as equipment under special working conditions that can not be lubricated at all in water or other solutions.