ã€Abstract】The process of using a symmetrical two-half plate to bend into a trough-shaped half-shell, and then using CO 2 gas shielded welding to weld a rectangular tube. Due to the reasonable selection of welding specifications, satisfactory results have been achieved.
A tooling requires a rectangular tube with a length of 20m. However, China's steel market only supplies profiles such as I-beam, channel steel and angle steel. It is difficult to buy rectangular steel, especially rectangular steel with large section size. Because it is a single piece production, we decided to use Q345 plate to weld into a rectangular tube.
Because Q345 steel contains certain alloying elements, the carbon equivalent value is 0.39%, which has a certain tendency to harden. It is easy to appear cold cracks when welding with large thick plates and too fast cooling rate. In addition, when welding large process parameters, the heat input is too large, which may cause thermal cracking in the weld or thermal strain embrittlement in the heat affected zone. From the point of view of the weldment structure, the length of the rectangular tube is relatively large, and it is a slender rod. It is extremely deformable and complicated in deformation during welding. Therefore, welding deformation control becomes a problem.
1. Determination of the welding scheme of rectangular tube group
In order to meet the strength requirements, the rectangular tube has a cross-section dimension of 300 mm × 200 mm and a plate thickness of 3 mm. The design requires distortion and parallelism and other deviations ≤ 1.2 mm, making the production technique more difficult. To this end, through investigation and research, the final determination of the use of sheet metal symmetrical two halves bent into a trough-shaped half shell, and then using CO 2 gas shielded welding and forming manufacturing process, as shown in Figure 1.
figure 1
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