GB646469A - Process and equipment for producing sheet and strip by die-stretching - Google Patents

Abstract

646,469. Wire-drawing. OROWAN, E. Jan. 19, 1948, No. 1528. [Class 83 (iv)] Metal strip is reduced by advancing the stock through a die, applying tension to the strip by keeping the speed of travel of the stock entering to a constant fraction of the speed of the stock leaving the die and reducing the separation between the lips of the die while the first portion of the stock is passing until the pressure on the lips reaches a predetermined value and then maintaining the separation constant. The tension of the strip on the entry side should preferably exceed 40 per cent of the yield stress. The strip 5 to be reduced is fed from a coiler drum 4, round a tension roll 7 through a pass between die members 27, 28, round a tension roll 11 and finally on to a coiler drum 13. The tension rolls are geared together and driven so that the strip on the entry side of the die is under a tension not far from its yield stress. Further reduction may be obtained by returning the strip through the die from the coiler 13 to the coiler 4, the roll 7 then being driven at a higher speed than the roll 11. The die comprises upper and lower members 27, 28 of steel, metal carbides or other hard material supported in holders 30, 29, the upper holder being adjustable by screw means 31. The upper die member may be capable of flexing slightly within its holder and may be given a sufficient camber by means of screws 33 as to bring the edges into parallelism during working. Correct adjustment of the die is necessary in order to avoid an extension of the work taking place outside the die or an excessive die pressure. This adjustment is facilitated by an electrical strain gauge meter in association with the screw means 31. In operation, the strip is moved through the die and the die lips are then closed up until the required pressure is obtained, after which the die opening remains fixed. Cooling liquid is circulated through bores 34, 35 in the die holders or through the dies themselves or alternatively the dies are cooled by sprays or by being immersed in a liquid. The strip may be brought to its final gauge by a light drawing pass with little or no back tension.