Simulation and analysis of welding scheme for new gate flange of vacuum vessel

Gate flange is a key component of a super vacuum vessel with a diameter of 17m, and its stiffness characteristics directly affect the sealing effect and stability of vacuum vessel. A new type of flange structure is put forward in this paper, which is difficult to manufacture, consume more materials, and has poor structural rigidity in the traditional form of super vacuum vessel. The new flange welding process will have a greater impact on its structural strength, through the finite element simulation of the door flange two kinds of welding program, and after welding stress and deformation were analyzed, so as to select the welding scheme ii. The maximum residual deformation after welding was 18.3mm, and the maximum residual stresses of two welds were 210 and 270MPa, respectively.

A vertical super large vacuum vessel with a diameter of 17m is mainly used in the space environment simulation test of large spacecraft, which belongs to special pressure vessel equipment. The gate flange is the key component of super vacuum vessel, which can realize the butt joint and vacuum seal between the head and the cylinder. At present, there is no specific design standard for vacuum vessel, and its design is usually referenced to the pressure vessel design standard. Pressure vessel design standards used in two categories: one is designed according to norms, known as the "conventional design"; the other is designed according to stress analysis, known as "analysis and design."". No matter which design standard, no specific specification for the gate flange structure of the vacuum vessel was made. Usually, the traditional form of the vacuum container door flange for high Jinghou flange, need not only the weight of large forging, and the overall stiffness is poor. With the increase of vacuum vessel diameter of the cylinder, the door flange manufacturing more and more difficult, the cost of materials also increased; on the other hand, the door flange and the head of the housing due to the structural discontinuity, under external pressure and poor stiffness, stiffness of the door flange will directly affect the vacuum effect the structure and stability of seal. Therefore, it is urgent to design a high stiffness and lightweight portal flange structure for large vacuum vessels.

In addition, due to the large size of the large vacuum vessel, the welding stress and deformation control of the welding between the gate flange and the head are very important. The heating of the spot heat source in the welding process will lead to uneven temperature field in the weldment, which will cause uneven expansion and contraction of the weld metal and its adjacent base metal, thus resulting in welding residual stress. The residual stress will cause the residual deformation of the workpiece, which is irreversible. For the gate flange, the welding residual deformation will directly affect the welding process and sealing. Therefore, the vacuum technology network believes that it is necessary to simulate and analyze the welding scheme of the gate flange of the super vacuum vessel.

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