Q235/20# Steel Towing Bracket Leg Welding Sequence Optimization and Experimental Study

The towing bracket legs are crucial for the fixation and support of the towing bracket, and their welding quality directly affects the safety and stability of the truck. One effective method for welding these components is argon arc welding, which provides a clean and controlled environment for the welding process. This technique utilizes an inert argon gas to shield the weld from contamination, reducing the risk of defects. Improper welding sequences can lead to welding defects such as residual stress concentration and severe deformation, which significantly impact the performance and service life of the towing bracket legs. Therefore, using argon arc welding can help ensure a high-quality weld, enhancing the overall durability and reliability of the towing bracket system. In this paper, five welding sequence schemes are designed to simulate the ABAQUS simulation of Q235/20# steel heterogeneous steel traction seat legs, and the residual stress, strain, and temperature field in the results are analyzed. The residual stress of the specific path is detected by x-ray diffraction method to ensure the accuracy and reliability of the simulation model. The optimal welding sequence scheme was applied to the experimental welding, and it was found that the simulated melt pool characteristics highly agreed with the actual welding melt pool characteristics. Analysis with a scanning electron microscope indicated that the microstructure of the weld joints in the heterogeneous steel was more compact and consistent than that in the homogeneous steel weld joints. No obvious porosity or crack defects caused by welding were found in either type of steel weld joint, and the composition and chemical elements showed gradient distribution to varying degrees. The microhardness curves of the two types of weld joints showed a consistent trend, with the highest hardness in the weld metal area of the 20# side. Performance tests, including dynamic tests and static lifting tests, showed no visible cracks or fractures in the towing bracket legs and the connector plate deformation within allowable limits. In conclusion, a welding strategy of “short to long, internal to external” was developed. The operation of this strategy is to first weld the shorter welds and the internal parts of the weldment to reduce heat input and control the temperature distribution of the joint, followed by the completion of longer welds and the external parts. The method described above is capable of notably decreasing residual stresses in the joint, which in turn helps to limit distortion during welding and boosts the overall mechanical strength of the joint.

Graphical Abstract