The boom of truck crane is the most important load-bearing component, which must be replaced or repaired after deformation, but it is not cost-effective, expensive to buy and inconvenient to transport for a long time. In order to save cost and time, welding repair can be carried out according to the actual situation on site. After the boom is repaired, the technical parameters of the crane must be met. Therefore, choosing a reasonable repair process is the key to repair the boom. How to achieve the goal economically and quickly? Let's talk about how to realize it in combination with our actual work.
1, the shape and material of the deformed boom must be known first in the selection of materials for repairing the boom by welding. Generally speaking, the telescopic boom of truck crane is composed of many box welded plates. The cross section of each arm is mostly rectangular, pentagonal and polygonal. The length of this arm frame is continuously variable and has great bending strength. Boom is the most important load-bearing component of truck crane, and the material selection of box boom must meet the requirements of crane bending strength index. The working level of truck crane, that is, the working level of metal structure is A 1-A6. When designing, the metal structure and mechanical parts should have sufficient strength, rigidity and buckling resistance. The type of steel used for suspenders is not lower than Q235-B. Therefore, when selecting welding materials, we directly choose 16Mn, that is, the thickness of Q345 steel plate is 8mm. In order to explain the rationality of selecting 16Mn steel plate, the chemical composition table 1 and physical properties 2 of 16Mn steel plate were analyzed.
It is known that 8mm 16Mn steel plate has good weldability and the yield strength is 345. Therefore, when choosing this steel plate as welding material, it can completely meet the requirements of strength, stiffness and buckling resistance of the boom.
2. Prepare the deformed part before welding, and handle and clean it before welding. After removing the deformed boom, use a gas cutting machine to cut off the deformed parts of the groove plate and web plate. As shown on the right, polish the rest of the boom to remove surface paint and all kinds of stolen goods. Put the cut boom on an oil press for shaping and straightening, and fix it on the platform with clips. Cut the weldments with the same size from the prepared 8mm 16Mn steel plate, edge the steel plate with a grinder, and then press it into the same shape as the cutting part of the original boom on an oil press.
3. The welding methods are mainly butt welding and manual arc welding. The welding method is single-sided welding and double-sided molding. When welding, make sure that the penetration is easy to process. Because the material thickness is greater than 6mm, manual arc welding groove is needed. For flexible and convenient application, manual mechanical grinder or angle grinder is generally used to groove, and the angle of V-groove is 35-500. In order to make the weld shape better, reduce the deformation of steel plate after welding, increase the welding depth, and control the splicing gap between plates within 2mm. Manual arc welding is more suitable for covered electrode. According to the brand of steel, alkaline covered electrode E50 16 and E50 15 covered electrode should be selected, baked at 300-350℃ 1 hour and placed at 10-65438+. ZXG3-300 DC arc welding machine is preferred.
Welding: The welding parameters are shown in the table. The welding method and process specification adopted ensure the hardness of the weld, and the deformation after welding should be reduced as much as possible. If the angle changes after welding, the weld should be padded and pressed with a heavy hammer. After the boom was recovered and the original machine was installed successfully, it passed the test under 1 10 static load 125 static load, meeting the requirements of crane appraisal and acceptance, and meeting the technical requirements after delivery. Everything is normal after use. More relevant knowledge can be found in China Hoisting Network.