| 摘要 |
966,435. Making composite tubes; drawing tubes; welding by pressure. STAHL-UND ROHRENWERK REISHOLZ G.m.b.H. Oct. 5, 1962 [Oct. 5, 1961], No. 37744/62. Headings B3A, B3P and B3R. A method of making seamless ferrous hollow bodies coated with ferritic or austenitic corrosion resistant steel or other corrosion resistant metal, particularly tubes, by hot pressing of a double tube comprising a main tube and a lining tube over a mandrel on a drawing or thrust frame, characterized in that for the reduction and cleaning of the tube surfaces to be joined a gaseous reducing medium is passed through a ring-shaped gap between the main tube and the coating tube at the treatment temperature before the hot pressing. One end of an austenitic lining tube 3 supported by and welded at each end to an unalloyed steel strengthening tube 4 is positioned in and welded to an annular groove 2 of a conically shaped weld plate 1. A ferrtic outer tube 5 having an internal diameter greater than the outside diameter of the tube 3 is slid over the tubes and welded to the plate 1. The air gap so produced is closed at the open end by a heat deformable ring 7 welded to the tubes 3, 5. The assembly is heated to drawing temperature and a reducing medium, e.g. hydrogen is passed through a number of vent holes 8 in the ring into the space and out through vent holes 9 in the plate 1 to remove surface impurities. The assembly is subsequently positioned on a drawing mandrel and drawn through a ring to press and weld the tubes together. After heat treatment the ends are sawn off and the strengthening tube removed. To facilitate separation of the tubes 3 and 4 the contact faces are coated with an oxide coating. Wire having a thickness equal to the width of the air gap may be spirally wound about the austenitic tube 3 to facilitate positioning of the outer tube 5. External coatings can be similarly produced by pressing an austenitic tube strengthened by an outer tube on to an inner tube. |
