GB585165A - Improvements in or relating to cold processing strip metal - Google Patents

Abstract

585,165. Altering physical structure. DAVY & UNITED ENGINEERING CO., Ltd. May 17, 1944, No. 9469. Convention date, Aug. 12, 1943. [Classes 83 (ii) and 83 (iv)] Making strip ; cold-rolling; stretching.-In a method and apparatus for hardening and tempering wide thin metal strip by cold working, the strip is wound partially round parallel drag and pull rolls whereof the pull roll is driven at a higher peripheral speed than the drag roll to stretch the intervening strip beyond its elastic limit, the unsupported length of strip between the rolls being short in comparison with its width to prevent longitudinal guttering. The method is applicable to elastic metal such as steel, aluminium and copper and reference is made to low carbon tin plate which is rendered suitable for both can bodies and tops and to stock for auto-' mobile bodies, furniture and stainless steel panels. In one form of mill, the strip S, Fig. 3; is drawn from a coil box 24 by tensioning rolls 20, 21 from which it passes to the drag roll D and the pull roll P to stretch the intervening portion S<1>. Working rolls 1, 2 are arranged adjacent the stretching rolls to cold-roll the strip before and after stretching, with a reduction of about one half of one per cent, in order to roughen or p anish the strip, which then passes to tensioning rolls 22, 23 and then to a coiling drum 29. The unsupported length of strip between the tensioning rolls is not greater than its width for tin plate, but may be increased for thicker strip and the tension is sufficient to produce an elongation up to about seven per cent. The strip is guided initially through the mill by fibre &c. rolls 25, 28, which are subsequently removed from contact therewith, and by guides 26, 27, 31 ... 33, the latter being moved into the position shown by a hydraulic cylinder 36 and then withdrawn to the dotted position so that if the strip should break during stretching, the broken end will not be directed between the rolls 2, P. A roll 37 is maintained by a hydraulic cylinder 38 in the dotted line position to direct the end of the strip between rolls 1, D and is then moved to the full line position, and further guides 34, 35 direct the strip to roll 23. The rolls D, Pare at a fixed distance apart, but the rolls 1, 2 are adjustable by screw-down mechanism. Roll P is driven by an electric motor and roll D by a separate motor which, after the strip has been fed through, acts as a regenerative brake to maintain a peripheral speed difference of the rolls constant within one-tenth of one per cent. Rolls 20, 21 are driven by separate electric motors which also act as regenerative brakes to apply tension to the strip during working, rolls 22, 23 are driven by separate motors to apply constant tension and rolls 1, 2 are driven by friction only. Due to the lower pressures required as compared with tempering by rolling, the mill is stated to work at a speed of three thousand feet per minute or higher. The rolls D, P may be driven by a single motor and coupled by gearing which gives the required speed difference or these rolls may be driven through a differential gear whose casing is rotated by a separate motor whose speed is variable to give the required difference. In modifications of the mill, the strip S may pass round two drag rolls D, D<1>, Fig. 8, and two pull rolls P, P<1> these rolls being arranged in staggered relation as shown or all in one vertical plane, the rolls D, D <1> rotating at the same speed and the rolls P, P <1> at the same speed which is greater than that of the drag rolls. The double drag and pull rolls may be arranged as shown in Fig. 9, or alternatively single drag and pull rolls F, P, Fig. 10, may be arranged horizontally but spaced further apart, the portion S<1> of the strip under tension being supported by an idle roll 55. The Specification as open to inspection under Sect. 91 refers to U.S.A. Specification 1,776,444. This subject-matter does not appear in the Specification as accepted.