When inspecting the rusty cracks of the welding seam of the side plate of the excavating arm, it is necessary to scrape or polish the surface paint and rust of the welding seam. When observing, lightly hit the welding seam with a small hammer, and use a magnifying glass to observe if necessary.
1. Causes of cracks
Reasons for cracks in the side plate of the excavating arm: include bubbles, slag inclusions and micro cracks in the original weld itself. When the excavator is overloaded, the original weld will produce micro cracks and slowly expand: welding rod Cracks caused by inconsistency with the performance of the plate: Due to the large size of the excavating arm, it is difficult to adopt reliable and effective heating and heat preservation measures. After welding, the hardened area of the base material around the weld cannot be completely removed, resulting in a decrease in the strength of the weld: Excavator During the operation, the vibration and impact are relatively large, and the uneven force at the welding seam causes the welding seam to crack.
2. Repair method
Preparations before welding: remove the oil, paint, rust, etc. from the cracks of the original weld with a hand grinding wheel. Gouging away the weld cracks with gouging machine, gouging to the body of the side plate, and clear the hardened area of the base material welded in the past. After planing, use a corner grinding wheel to smooth the cut (the inner interface is polished to form a V-shaped groove). After cleaning and pink inspection, confirm that all the cracks have been found and removed.
According to the existing maintenance conditions, choose the Φ5mm electrode type E5015 (J507) or E5016 (J506), bake it at 350 ℃ for 2 hours, and then keep it at 100 ℃ to prevent the electrode from absorbing moisture, and take it as needed; welding current 190～ 230A. Due to the large thickness of the side plate of the excavator, the welded part should be preheated to 150～250℃ before welding; in the welding process, the welding can be performed in sections, symmetrical, and backward; it should be used continuously during the cooling process of the weld The hand hammer strikes the weld metal to eliminate stress; when welding at the corners of the side plate, in order to avoid arc defects, continuous welding is recommended to improve the stress condition of the joint.
After welding, completely remove spatter, welding slag and weld bead, etc., and the welding seam shall not exceed 2.5 mm in height. Magnetic particle inspection is carried out on the weld, and no defects such as cracks are allowed.
3. Measures to prevent weld corrosion
Thoroughly sand the weld, remove rust and apply anti-rust paint. In the excavation construction site, for the existing rusty welds, manual rust removal can be selected based on the actual situation. The disadvantage is that the labor intensity of the workers is relatively high and the labor cost is high; the pickling method can also be used, that is, organic acid The main base is equipped with composite materials such as corrosion inhibitor, surface activator, rust remover, rust inhibitor and film forming agent, and it is formulated into a pickling solution with rust removal, rust prevention and primer functions. Derusting and anti-rust purposes.
In addition, during use, care should be taken to keep the excavator in a clean and dry environment, maintain good ventilation, and remove corrosive gases and moisture in time.