| 摘要 |
<p>A bottom plate (61) in the form of a thick aluminum plate, a top plate (62), a first side plate (63), a second side plate (64), a third side plate (65), and a fourth side plate (66) are assembled along four sides and welded together by the TIG method; thus, a pressure resistant casing (22) is constructed as a rectangular parallelepiped box. During TIG welding between the top plate (62) and the first side plate (63), the end surface of the top plate (62) in which a cavity (72) is recessed is abutted against the main surface of the first side plate (63) in which a positioning section (71) is projectingly formed. The edge of the cavity (72) of the top plate (62) is butted against the positioning section (71), and a fillet weld (75) is formed in a corner defined by the top plate (62) and the positioning section (71) by the TIG welding method. Since the heat capacities of the top plate cavity and the positioning section are small, a fillet weld can be formed even if an aluminum plate of high heat conductivity is used. Since a fillet weld closes a slit defined between the contact surfaces, it is possible for the pressure resistant casing to maintain vacuum performance, etc.</p> |
