Abstract: To address the electron beam welding process requirements for complex workpieces in the nuclear industry, this paper proposes a design scheme for a local vacuum electron beam welding machine. It elaborates in detail the overall structural design framework of the equipment and constructs a local vacuum system composed of a main chamber (welding chamber), an auxiliary chamber, an electron gun chamber, and a transition chamber. Regarding the sealing structure, an innovative "positive-negative pressure synergistic drive" inflatable sealing system was proposed. By combining positive pressure inside the airbag with negative pressure outside, the contact pressure at the sealing interface was significantly enhanced. This was further integrated with a dual-airbag series arrangement and a vacuum barrier mechanism in the transition chamber, forming a multi-protection sealing structure that effectively addressed the challenge of maintaining a high vacuum in the local vacuum chamber under dynamic operating conditions. Experimental results showed that the vacuum level and the time to reach it for each vacuum chamber meet the design specifications. The effectiveness of the local vacuum technology is further verified through testing key indicators such as operating vacuum, ultimate vacuum, and pressure rise rate. The proposed positive-negative pressure synergistic sealing structure and the collaborative operation mode of the main and auxiliary chambers provide an engineering-applicable solution for local vacuum electron beam welding of complex workpieces, such as those with long dimensions and open ends, in the nuclear industry.

Key words: electron beam welding machine, local vacuum, positive-negative pressure synergistic sealing, main and auxiliary chamber collaboration