| 摘要 |
PURPOSE:To reduce the process for producing a multiple clad steel pipe by fitting a core material into a blank material for a base pipe to form a blank material for a fitted pipe, maintaining the boundary surface of the blank materials with each other in a vacuum state and subjecting the blank materials to diffusion joining thereby bonding metallurgically the entire boundary surface. CONSTITUTION:A columner ceramic core material 6 consisting of silicon nitride and an outside carbon steel pipe 7 which is open at both ends are oppositely superposed and fitted to an inside stainless steel pipe 2 which is open at both ends in ordinary temp., low temp. and high temp. states and are restored to the ordinary temp. to make these pipes mechanically tight, by which a short-sized and tightly fitted blank pipe material 8 having a set wall thickness is obtd. The blank material is put into an electron beam welding device 9 and is maintained in a vacuum state. Carbon steel seal discs 10, 10 having the same diameter as the outside diameter of the pipe 7 are pressed to both ends 11, 11 of the pipe material 8 and the assembly is put into a diffusion joining device 14 and is subjected to diffusion joining in a gaseous argon atmosphere to join 15 metallurgically the boundary surface 13 of the respective blank materials 2, 7 and thereafter end materials 17, 17' are removed by cutting. The core material 6' is removed by drawing to form a composite pipe block 18' which is drawn and the triple clad steel pipe 19 having a long size is botd. |
