Sliding bearings refer to bearings that operate under sliding friction. Sliding bearings work smoothly, reliably, and without noise. It is generally used under low-speed and heavy-duty working conditions, or in operating parts where maintenance and lubrication are difficult. It is mainly divided into two categories: integral bearings and split bearings. The repair method can be selected according to the following classification:
Integral bearing
(1) When the bearing hole wears out, it is generally repaired by replacing the bearing and machining the bearing hole through boring, reaming, or scraping; Plastic deformation method can also be used to repair by shortening the bearing length and reducing the inner diameter.
(2) After the inner hole of a bearing without a bearing shell wears out, it can be repaired using the bushing method, which involves enlarging the bearing hole, pressing it into the machined bushing, and then trimming it according to the shaft neck to meet the fitting requirements.
Split type bearing
(1) Replacing the bearing shell generally requires replacing it with a new one under the following conditions:
Severe burn damage, large area of tile mouth burn damage, and deep wear cannot be saved by scraping and grinding and running in methods;
The bearing alloy of the tile lining is thinned to the maximum size;
The bearing shell is shattered or severely cracked;
Severe wear and tear, with excessive radial clearance that cannot be adjusted.
(2) Accidents of scratching or severe bonding (burning of tiles) of scraped bearings during operation are common.
(3) Adjusting the radial clearance of the bearing causes an increase in radial clearance due to wear, resulting in phenomena such as oil leakage, vibration, and accelerated wear.
(4) Reducing the contact angle and increasing the size of the oil wedge, as the running time increases, the wear of the bearing gradually increases, causing the journal to sink and the contact angle to increase, deteriorating the lubrication conditions and accelerating wear.
(5) Repair welding and overlay welding can be used to repair bearings that are worn, scratched, broken, or have other defects.
Use tools such as chisels and scrapers to clean the parts that need to be welded, ensuring that the surface is free of oil, residue, and impurities, and revealing the luster of the metal;
Choose the same material as the bearing as the welding rod and use gas welding to repair the bearing. The thickness of the welding layer is generally 2-3mm, and deeper defects can be repaired with multiple layers of welding;
When the welding area is large, the bottom of the bearing can be immersed in water for cooling, or intermittent operation can be carried out, leaving a cooling time;
After welding, it needs to be reworked. Local welding can be repaired by manual trimming and scraping, while larger welding areas can be machined on the machine tool
(6) Re casting the bearing liner is a very common repair method for sliding bearings that have suffered severe wear and failure, and repair welding or overlay welding can no longer meet the requirements. In this case, it is necessary to re cast the bearing alloy
Make preparations before pouring, including necessary tools, materials, and equipment, such as fixtures and plates for fixing bearing shells, bearing alloys of the same grade as required by the drawings, tin powder and tin rods for hanging tin, heating furnaces for melting bearing alloys, crucibles for holding bearing alloys, etc.
Before pouring, the old bearing alloy on the bearing shell should be melted off. It can be baked with a blowtorch or placed in a crucible for melting the alloy.
Check and correct the tile back to ensure that the inner surface of the tile back is free of oxides and appears silver gray; Make the geometric shape of the tile back meet the technical requirements; Expand the tile back before pouring to ensure that it fits well with the tile seat due to cooling shrinkage after pouring.
Clean, degrease, remove dirt, rust, and dry the bearing shell to keep it clean before tinning.
Tin plating involves applying a zinc chloride solution dissolved in hydrochloric acid onto the surface of the tile lining, and preheating the tile lining to 250-270 ℃; Apply a layer of zinc chloride solution evenly again, sprinkle some ammonium chloride powder and form a thin layer; File the tin bar or tin rod into powder with a file, evenly sprinkle it on the surface of the processed tile lining, and the tin will melt on it when heated, forming a thin, uniform, and shiny tin coating; If there are light yellow or black spots, it indicates poor quality and needs to be re hung.
Melting bearing alloys, including preheating of tile liners; Select and prepare bearing alloys; Melt the bearing alloy and sprinkle a layer of crushed charcoal blocks on the surface of the alloy, with a thickness of about 20mm, to reduce surface oxidation of the alloy. Pay attention to controlling the temperature, neither too high nor too low. Generally, the pouring temperature for tin based bearing alloy is 400-450 ℃, and the pouring temperature for lead based bearing alloy is 460-510 ℃.
Pour the bearing alloy and preheat the lining to 150-200 ℃ before pouring; The pouring speed should not be too fast, cannot be interrupted, and should be carried out continuously and evenly; The pouring temperature should not be too low to avoid the formation of sand holes; Pay attention to cleaning the slag and remove the charcoal and slag floating on the surface of the machine tool.
Quality inspection involves analyzing and determining defects through fracture surfaces. If the quality does not meet technical requirements, it cannot be used.
(7) Plastic deformation method can also be used for repairing bronze shaft sleeves or bearings, mainly including upsetting, compression, and correction methods.
The upsetting method involves centering a metal mold and a core rod, applying pressure on the upper mold to reduce the inner diameter of the shaft sleeve, and then adding its inner diameter.
The compression method installs the shaft sleeve into the mold, and under the action of pressure, the inner and outer diameters of the shaft sleeve are reduced through the mold. The reduced outer diameter is restored to its original size by metal spraying, and then processed to the required size.
The calibration method combines two half bearing shells together, fixes them, and applies pressure on a press to form an oval shape. Then, the joint surfaces of the half bearing shells are cut off to a certain thickness to reduce the inner and outer diameters of the bearing shells. The outer diameter is repaired by metal spraying and processed to the required size.
2025 April 4th Week Marginal Product Recommendation:
Material Specification Sheet–MG-6:
Material specification sheet – MG-6 is Ball and roller bearing steel according to EN ISO 683-17. Ball and roller bearing steel for balls and rollers of any dimension,rings and discs up to 30mm effective thickness.
