When we use small excavators, there may be various unexpected failures, such as the boom failure of excavators. Next, I will introduce the solution to the boom failure of small excavator.
Check the welding position of the boom side plate of the small excavator to see if there are any cracks caused by corrosion. At this time, the paint layer on the surface needs to be scraped off or polished clean. When observing, use a small hammer to tap the weld gently, and use a magnifying glass to see if necessary.
1. Causes of cracks
The main reason for the cracks on the side plate of the boom of small excavator is that the original weld has bubbles, slag inclusions or cracks with a smile. When the excavator works under overload, the original weld will have tiny cracks and will show signs of slowly expanding.
During welding, the performance of welding rod and plate is not in conformity, which leads to cracks. Because the boom of small excavator is large, it is difficult to adopt reliable and effective heating and heat preservation method, and the base metal hardening area around the weld cannot be completely removed after welding. This leads to a decrease in the strength of the weld.
In the process of excavator operation, the impact force of vibration is relatively large, which leads to the uneven hand of the welding seam and the cracking of the welding seam.
2. Introduction to repair methods
Preparation before welding: use the hand grinding wheel to clean the oil stain and especially the rust on the original welding crack. Then the weld crack is planed and cut to the body of the side plate by the bubble machine, and the hardened area of the previous welding base metal is reasonably clean. Then, after planing and cutting, use the angle grinding wheel to polish the incision flat. It is recommended that the inner interface be polished into a V-shaped groove. After cleaning, check that all the cracks of penguin man have been found and are clear.
According to the current maintenance conditions, E5015 (J507) or E5016 (j506) electrode of Φ 5mm type is selected to be baked at 350 ℃ for 2 hours, and then the temperature of 100 ℃ is used for heat preservation to prevent the electrode from moisture absorption failure. The welding current is 190-230a.
Because the thickness of the side plates of excavators is large after all, the welding parts should be preheated to 150-250 degrees before welding. In the welding of the sheet, the welding methods such as sectioning, symmetry, retrogression can be used. In the process of weld cooling, it is necessary to knock the position of weld metal with hammer continuously to eliminate stress. In addition, when welding at the corner of the side plate, in order to avoid the defect of arc welding, it is better to carry out continuous welding operation to improve the stress condition of the joint.
After welding, all spatter, welding slag and weld beading shall be completely removed, and the residual height of the weld shall not be greater than 2.5mm. Cracks are not allowed when magnetic particle inspection is conducted for welds.
3. Measures to prevent weld corrosion
After the weld is thoroughly polished and derusted, the coating is required to take antirust measures. In the excavation construction site, for the existing rusty welds, manual derusting can be selected according to the actual situation, but this disadvantage is that the labor intensity and cost of labor will be relatively large, and the labor cost will be high.
It can also be treated by the way of acid cleaning. Organic acid is used as the main base, with corrosion inhibitor, surfactant, rust remover, rust inhibitor and film-forming agent, etc., which are in line with the materials. The acid cleaning solution with the functions of rust removal, rust prevention and primer can be prepared to achieve the perfect purpose of cleaning, rust removal and rust prevention.
In addition, in the process of using small excavators, we also need to pay attention to the fact that excavators need to be frequently parked in clean and dry environment, and it is better to keep good ventilation and timely remove corrosive gas and moisture.