Abstract: A set of design methods suitable for the vacuum chamber of a square electron beam melting furnace is proposed to address the difficulties in selecting the wall thickness and reinforcing ribs. The method first confirms the furnace material for the vacuum chamber, and arranges reinforcing ribs according to the hole positions such as flanges, openings and exhaust holes, and calculates the wall thickness. Taking the rectangular reinforcing ribs as example, the calculation methods for the wall thickness, the maximum bending moment of the plate between the reinforcing ribs, inertia moment, section modulus in bending and shear stress on the neutral layer during bending of the square vacuum chamber under conditions of bearing water pressure and air pressure were discusses in detail. Finally, the as-designed vacuum chamber of the electron beam melting furnace was validated through simulation experiments. The results indicate that the stress of the vacuum chamber of the as-designed electron beam melting furnace under water and gas load conditions is within 35 MPa, which is lower than the allowable stress of the material. The calculation results of this method are highly consistent with the simulation results, it can meet the design requirements of vacuum chambers similar to square electron beam melting furnaces.

Key words: electron beam melting furnace, square vacuum chamber, section modulus in bending, vacuum selection