Verfahren zur Herstellung von Verbundrohren

1,168,265. Welding by pressure. E. I. DU PONT DE NEMOUR & CO. 8 Feb., 1967 [10 Feb., 1966], No. 6056/67. Heading B3R. In bonding two or more metal tubes, the tubes are coaxially arranged with a space between the or each pair of tubes, the inner tube is filled with liquid, the outer tube is surrounded by an explosive having a detonation velocity of at least 1200 m.p.s. and less than 120% of the sonic velocity of the metal having the highest sonic velocity and the explosive is initiated at a location along the length of the outer tube such that, at that location, initiation is substantially simultaneous around the tube periphery in a plane perpendicular to the axis of the tube. An inner metal tube 1, Fig. 1, is arranged coaxially inside an outer metal tube 2, the uniform space 3 therebetween being maintained by wrapping tape around the ends of tube 1 or by annular plugs at both ends of the tubes. Tube 1 is filled with water 5 and sealed by plugs 4, 6 of rubber and the assembly is positioned inside a cardboard or plywood cylinder 7 with a detonating explosive 8 filling the space between the assembly and cylinder 7. An electric blasting cap 9 wrapped in explosive 11 is provided for initiating the explosive 8. On initiation of the explosive 8 the detonation front passed down the explosive and the tube 2 is propelled inwards progressively to bond to the tube 1. In a modification metal tubes 1, 2, Fig. 2, are arranged with an annular spacer 17 and a metal support tube 13 is arranged within tube 1, annular spacers 15, 16 providing a liquid filled space 14 between tubes 1 and 13. Plugs 4, 6 retain the liquid 5 in the tube 1 and plug 4 rests on the base of container 7, an annular spacer 18 supporting the explosive 8 and maintaining the assembly coaxial with wall of container 7. A blasting cap 9 is located at the centre of an inverted dished layer 19 of explosive extending over the plug 6. The bonds obtained are substantially rectilinear with an alloy layer at the interface or preferably a wavy bond zone is obtained which may have pockets of alloy. In examples the outer and inner tubes are respectively: mild steel, brass; mild steel, titanium; stainless steel, mild steel; mild steel, stainless steel; titanium, mild steel; titanium, stainless steel; stainless steel, nickel; mild steel, "Hastelloy" (Registered Trade Mark); "Hastelloy" (Registered Trade Mark), mild steel; mild steel, "Inconel" (Registered Trade Mark); "Inconel" (Registered Trade Mark), mild steel; mild