Butt welding repair is adopted, and the fracture or crack will not be disassembled and repaired after it is restored to its original state. After correcting the bending part of the main girder, the climbing entrance is directly set on the inner and outer surfaces of the fracture or crack. Repair the damaged part by butt welding technology without disassembly and repair, and repair the damaged part if necessary. The main girder deformation correction methods are: 1. Body correction refers to the process of repairing the accident or fatigue damage to the "state" of the vehicle ex-factory technical standard under the action of a certain external force. The word "country" has two meanings. "Shape" refers to a more intuitive appearance and shape, while "state" is a more abstract and profound concept, such as whether the molecular structure inside the metal is sorted along the original position, whether the internal stress is completely released, etc. , directly related to the function and life of the vehicle after maintenance. 2. When calibrating the integrated body, the method of counterpoint maintenance should be adopted as far as possible. In this way, when stretching, a part of the deformed part around can be effectively pulled out by the "belt", which greatly saves time because there are fewer parts to be disassembled. It is the skeleton of the damaged front bar and a closed box-shaped section connected with the front longitudinal beam by screws. Usually, the front of the longitudinal beam will be deformed due to the transmission of impact force after the front pole frame is hit. 3. After the bone is taken out, if it is not fixed properly, it is difficult to repair it with mild corrective force. In addition, after the skeleton is repaired, the front longitudinal beam needs to be repaired. So the correct way is to carry out in-situ maintenance. Using a stretching tool to apply a relaxing force to the deformed part opposite to the collision direction, and then using a suitable crowbar to enter the concave part of the side of the corrected bone from the edge opening, can achieve very good results.