How to Repair Excavator Slewing Bearing

During the operation of the excavator, the slewing bearing has to bear a large impact load. When the excavator is tilted, the stress state is even more unfavorable. Generally, when the excavator runs for about 350,000 hours, the slewing bearing of the excavator may be crushed or broken, and the tooth profile wear and broken teeth at the junction of the two halves of the ring gear are particularly serious. Practice has proved that using insert welding to repair the slewing bearing is simple and fast, and can ensure the performance of the whole machine.

1. Preparation before welding

(1) According to the damage of the ring gear, determine the position of the fixing hole and the damaged segment to be replaced, and then cut off the segment of the tooth to be replaced by gas cutting.

(2) According to the part of the ring gear that needs to be repaired, process and make inserts, or cut out a section of relatively good gear teeth from the corresponding part of another old ring gear under the condition of ensuring the pitch, and gas cut out the joint groove shape.

(3) Determine the position of the fixing hole of the insert, and drill the hole to fix it on the corresponding part of the ring gear. Note that the accuracy of the position of the fixing hole must be ensured.

(4) In order to ensure that the weld has high strength and can withstand large shock and vibration, the junction 507 electrode with a diameter of Φ4 mm is selected, and the electrode should be baked at 250-350 °C for 1 h before use.

(5) AX3500 DC arc welding machine is used for welding with DC reverse connection method, and the current is 130-140 A.

2. Welding process

(1) Preheat before welding, use 2 large gas torches to heat the welding surface to about 200 ℃.

(2) Using the tempering weld bead method, the latter weld has a tempering effect on the previous weld, which is beneficial to eliminate the hardened structure produced by the previous weld.

(3) Due to the large groove, when welding the first weld, it should be welded slightly thinner to reduce the fusion width and reduce the carbon content of the steel. When welding, the electrode is tilted forward by about 15° and moves forward in a straight line. When closing the arc, pay attention to filling the arc crater to avoid arc crater cracks. After welding, use a pointed hammer to quickly hammer the weld and both sides to relax the stress until dense pitting appears on the weld. Continue welding when the weld seam cools down to about 200°C.

(4) After the first weld, the welding method of each weld is the same as that of the first weld. The welding rod can be slightly placed. In order to avoid air holes, do not place too much.

(5) In order to eliminate the hardened structure and stress after welding, heat the weld seam and both sides to about 600-650 ℃ with an oxyacetylene flame, keep it warm for 20 minutes, and then cover the weld seam with asbestos, slaked lime powder or dry sand to make it Cool slowly to room temperature.

(6) Grind the weld seam with a polishing wheel, and the ring gear repair is completed.

The above is a detailed introduction to the repair method of the slewing bearing of the excavator. In order to ensure the performance of the whole machine during use, it is necessary to choose a simpler and faster repair method.