GB1219967A - Improvements in the processing of strip metal - Google Patents

Abstract

1,219,967. Straightening; tensioning; rolling; altering physical properties. HEAD WRIGHTSON & CO. Ltd. 21 July, 1969 [30 April, 1968], No. 20450/68. Headings B3E, B3M and B3V. A method of cold processing metal strip, e.g. hot-dipped galvanized strip, comprises passing the strip through a first processing stage in which the strip is subjected to surface compression by rolling whilst under tension, passing the strip through a second processing stage in which it is stretched by the application of tension, isolating the tensions applied to the strip in the two sections by passing it through a bridle roll set intermediate the two sections and which applies forward tension to the strip in the first stage and back tension to the strip in the second stage and adjusting the tensions in the two sections so as to flatten the strip to achieve a required balance between surface hardening and stretching of the strip to eliminate the formation of Luder lines. Apparatus for carrying out the method comprises first, second and third sets of driven bridle rolls, namely 1, 2; 3, 4 and 5, 6, 7, 8 respectively (Fig. 1). Rolls 5-8 run faster than rolls 3, 4 which run faster than rolls 1, 2. A floating roll 10 is positioned in a loop of the strip between rolls 2 and 3 to bend and plastically strain the strip. The strip may pass from roll 4 and be stretched by the third set of bridle rolls 5-8 or a series of bending rolls may be interposed to bend the strip in alternate directions which decreases the tension required between rolls 4 and 5-8. In another embodiment the strip passes over a first set of driven bridle rolls 301-303 (Fig. 3) and thence to undriven backing rolls 311, 312 and 313, 314 provided with float rolls 315 and 316 respectively. From a second set of bridle rolls 304, 305 the strip passes to a third set of driven tension bridle rolls 306-310. In a further embodiment, a pair of superimposed float rolls 414, 415 supported by an undriven steady roll 413 is used (Fig. 4, not shown). Alternatively, an ordinary rolling mill 609, 610 is used between the bridle rolls 601, 602 and 603, 604 (Fig. 5). On leaving the bridle rolls 603, 604 and before entering the final set of driven bridle rolls 605-608 the strip passes through a series of flexing rolls 611, 612, 613.