1. Causes of Cracks
The causes of cracks in the side plate of the elastic arm of excavator include air bubbles, slag inclusion and small cracks in the original welding seam itself. When the excavator is working under overload, small cracks will occur in the original welding seam and gradually expand. When welding, cracks will occur because the function of the welding rod is not consistent with that of the plate.
Because of the large volume of the elastic arm of the excavator, it is difficult to choose reliable and effective heating and insulation measures. After welding, the hardening zone of the base metal around the weld can not be completely removed, which leads to the decrease of the weld strength, the greater vibration impact during the excavator operation, and the uneven stress at the weld makes the weld crack.
2. Repair methods
Pre-welding preparation: Use hand grinding wheel to clean the oil stain, paint and rust at the crack of the original weld. The cracks in the weld seam are gouged out by air planer, and then the main body of the side plate is gouged out, and the hardened zone of the base metal previously welded is removed and cleaned. After planing and cutting, the incision is polished flat with a corner grinding wheel (the inner interface is polished with a V-shaped groove). After cleaning and pink inspection, it is acknowledged that all cracks have been found and cleaned up.
According to the existing maintenance conditions, the 5mm type E5015 (J507) or E5016 (J506) electrodes are selected, baked at 350 (?) for 2 hours, then kept at 100 (?) to avoid moisture absorption of the electrodes. The welding current is 190-230A. Because the side plate of excavator is thicker.
Before welding, the welding parts should be preheated to 150-250 C. During the welding process, segmented, symmetrical and retrogressive welding method can be used; during the cooling process, hammer should be used continuously to knock on the weld metal to eliminate the stress; while welding at the corner of the side plate, in order to avoid and landing arc defects, continuous welding should be applied to improve the stress condition of the joint.
After welding, spatters, welding slag and welding nodules should be completely eradicated, and the remaining height of the weld should not exceed 2.5 mm. It is not allowed to have cracks and other defects when checking the weld by magnetic particle inspection.
3. Anti-corrosion Measures for Weld Seam
The weld seam is completely polished, rusted and coated with anti-rust paint. In the excavation site, for the existing corrosion welds, the actual situation of the excavation can be selected to remove rust by craftsmanship. The defect is that the worker's labor intensity is greater, the labor cost is higher, and the acid pickling method can also be used to remove rust.
That is to say, organic acid is the main base, with corrosion inhibitor, surfactant, rust remover, rust inhibitor and film-forming agent and other composite materials, to prepare acid pickling solution with functions of rust removing, rust-proof and primer. The purpose of rust removing and rust-proof is achieved by cleaning.
The above information is that our long arm excavator is organized and released. We hope to help you with our website: http://www.rbaras.com!