GB1001135A - Open coil annealing - Google Patents

Abstract

In an open-coil annealing process the strip is coiled with a separator between convolutions, the separator being formed by a central wire round which is helically wound an outer wire at a pitch sufficient to provide passages for the circulation ofthe heat-treatment atmosphere. The separator remains in place during the annealing operation and is subsequently removed. Preferably the diameter of the outer wire is at least as great as that of central wire, while a pitch of three or four turns per inch is exemplified. The central wire may <PICT:1001135/C6-C7/1> <PICT:1001135/C6-C7/2> initially be harder than the outer wire, the separator being annealed after its formation. In the apparatus shown in Fig. 1, strip from tight-wound coil C on turntable 2 is rewound together with separator 12 from reel 10 into open coil C1 on turntable 4. The coil is then annealed in the furnace of Fig. 2, hot gas being circulated by fan 12, after which the separator is removed. This may be carried out on the apparatus of Fig. 1, the separator being removed by boom 6.ALSO:A separator for use in the open-coil annealing of metal strips consists of a central wire having helically wound round it a second wire at a pitch sufficient to provide passages for the circulation of the treatment atmosphere. The central wire is preferably harder than the central wire, while the latter preferably has a diameter at least as great as that of the former. A pitch of three or four turns per inch is exemplified. The wires may be of low carbon steel, the inner being hard drawn and the outer in the annealed condition, or stainless steel may be used.