GB1248794A - Bonded aluminum/steel composites and method of making same - Google Patents

Abstract

1,248,794. Making composite bodies; welding by pressure and fusion. E. I. DU PONT DE NEMOURS & CO. 2 Jan., 1969 [3 Jan., 1968], No. 214/69. Headings B3A and B3R. A bonded composite comprises a layer of aluminium, i.e. pure aluminium and aluminium base alloys containing at least 85% by weight aluminium, bonded to a layer of steel, i.e. carbon steel and alloy steels containing less than 5% alloying elements, by a wavy bond formation. The aluminium and steel have yield strengths before bonding of up to 17,000 p.s.i. and up to 60,000 p.s.i. respectively, and the layers are bonded over at least 90% of the interface by a substantially diffusionless metallurgical wavy bond comprising at least 70% direct aluminium to steel bonding, the remainder being periodically spaced discrete regions of solidified melt separated by direct bonding. The layers are arranged at less than 5 degrees prior to detonation of an explosive for explosive welding, the collision velocity is 2500-3400 metres/sec. and the impact angle is 14-25 degrees. The collision velocity is the velocity with which the line or region of collision travels along the layers and the impact angle is the angle between the layers on collision. The aluminium layer may be fully or partially annealed or hardened and the steel layer may be normalized or annealed and the layers may be parallel and spaced or at an angle of less than 5 degrees. Aluminium layers may be clad on both sides of steel layers simultaneously or separately or a layer of aluminium may be bonded to one side of a steel layer according to the invention and a stainless steel layer is bonded to the other side of the steel layer. Alternatively an aluminium base alloy whose yield strength exceeds 17,000 p.s.i. may be bonded to the other side of the aluminium layer by explosion or roll bonding. The aluminium and steel layers may be such as to produce products in plate, sheet, strip, rod, bar or tubing form and the product may be for fusion welded transition joints in structures and electrical systems, e.g. in aluminium reduction cells or in ship or railway car construction aluminium components being welded to the aluminium layers and steel components to the steel layers. In examples an aluminium plate is arranged spaced from and parallel to and at 2 degrees to a steel plate, an explosive comprising ammonium nitrate, trinitrotoluene and sodium chloride is provided on the aluminium sheet and initiated at the centre of one edge. Extension pieces are tack-welded to the edge of the aluminium sheet to extend the explosive layer. The direct bonding varies from 75- 98%. To produce a three-layer composite a steel layer and two aluminium layers are vertically arranged with explosive on the aluminium layers simultaneously initiated.