| 摘要 |
1,196,562. Welded joints. HITACHI Ltd. 8 Feb., 1968 [17 Feb., 1967], No. 6350/68. Heading F2G. [Also in Divisions B3 and F4] In a welded joint between a tube 28, Fig. 3, and a tube plate 22, the tube 28 is inserted in a countersunk hole 26 in the plate 22 with its end flush with the base of the tapered portion of the hole and weld metal 30 is deposited on the tube end and on the tapered wall of the hole and is finished to provide a smooth converging inlet to the tube. The width b of the entrance is 1À1 to 2 times the outer diameter c of the tube 28. The depth a of the tapered portion is at least one fourth of the outer diameter c of the tube. The weld deposit is either nickel based, e.g. 15% Cr, 50% Ni, 35% Fe; or 70-76% Ni, 13-17% Cr, 6-12% Fe, 0À5-2% Mo, 1-3À5% Mn, 0À015% max. S, 0À75% max. Si, 0À1% max. C with or without 2-3% Nb or is an austenitic steel, e.g. a Ni, Mn or Co steel, or a stainless steel such as 18% Cr, 8% Ni; 25% Cr, 35% Ni or 25% Cr, 20% Ni. The plate 22 is of mild steel and the tubes may be of low-alloy steel containing, e.g. 0À5% Mo; 1% Mo; or 2¢% Cr, 0À1% Mo. Welding is effected in a plurality of passes using an argon shielded tungsten arc. The tube is expanded into the hole prior to welding and the weld is shaped by machining. In a heat exchanger, the fluid outlet ends of U tubes 12, Fig. 2, project from the tube plate 10 and are externally welded and the fluid inlet ends are joined by welds 16 to the tube plate 10 as described above. |
