Engineering machinery slewing bearing may not work properly due to manufacturing quality problems such as material porosity or interlayer, uneven hardness and depth of the quenched hard layer on the raceway, or certain external reasons. For raceway peeling, it is necessary to make a correct judgment first. Peeling is generally not easily visible externally.
When the host is loaded and rotates, there is a "clack-clack" sound at the raceway, the rotating speed is uneven or a certain direction speed decreases significantly accompanied by slight vibration; the temperature rise or current of the rotating motor is too high; the keyway of the rotating motor is crushed due to coupling with the hydraulic coupling or coupling joint. After peeling occurs, it must be repaired in a timely manner. Otherwise, the peeling area will expand, resulting in the scrapping of the entire slewing bearing.
The reason for the broken teeth of the slewing ring may be the quality problems of the gear mother material (such as sand eyes, interlayers, etc., which significantly weaken the gear's bending resistance); hard objects such as stones or steel bars are embedded in the gear meshing position during use, causing local bending stress to increase and fracture. The repair method is local welding repair or tooth-inlay repair. The method of local welding repair is as follows: first, grind the residual crack matrix of the damaged area with a hand-held grinding wheel, and clean it with gasoline (engine oil); preheat the area with a welding torch, and when it reaches a certain temperature, use a medium carbon steel welding rod to push-weld the prototype of the teeth at the damaged area of the gear, making it 1-2mm higher than the tooth surface; select an experienced machine repair fitter to inspect the tooth shape using a tooth profile template until the tooth shape meets the requirements. When a whole tooth of the slewing ring is damaged, it can be cut along the tooth root, then file the tooth root into a certain shape. Then, cut a tooth from a similar scrapped slewing ring, process it into a shape corresponding to the mother material, and put it into the slot, using a tooth profile template for positioning. This ensures the consistency of tooth pitch, and use double-thread pliers for added clamping. Weld the low carbon steel around the teeth. Finally, use files and other tools to smooth the weld, ensuring stable gear meshing.
Remove the rollers or steel balls in the slewing bearing to separate the inner and outer rings; then use gasoline to clean the raceway; then use a grinding machine to carefully remove the hardened layer that has been cracked around the peeling area and flatten the bottom of the peeling. Preheat the area needing welding repair with a welding cutting torch, and use a medium carbon steel welding rod for welding (the welding rod must be dried before use and used immediately after drying, making the weld slightly higher than the surface of the raceway by 1-2mm); if the peeling depth or area is large, the welding should be divided into layers and segments, and the temperature of the base material should not be too high to avoid deformation. This prevents rapid cooling and welding cracks. After welding, take immediate insulation measures to gradually cool it down. After cooling, use a grinding machine to level the welded repair layer, making it slightly higher than the raceway surface. Use oilstone or metallographic emery cloth to gradually polish the surface of the welded repair layer to make it consistent with the height of the normal raceway surface. Use a corresponding original curvature template for inspection until it meets the requirements. Clean the raceway and rollers (steel balls) with gasoline, apply lubricating grease, and assemble them into one to complete. After following the above method, the raceway of the slewing bearing of equipment such as tower cranes can work normally after long-term use.