GB784619A - Improvements in or relating to cold shaping of steel - Google Patents

Abstract

784,619. Making pistons and cylinders. AMERICAN RADIATOR & STANDARD SANITARY CORPORATION. May 26, 1955 [May 27, 1954], No. 15185/55. Classes 83 (2) and 83 (4). A method of producing elongate hollow articles which are provided with very smooth accurately dimensioned surfaces comprises cold extruding a hollow blank to the size and shape of the finished article and thereafter axially straightening said blank and smoothing out any irregularities on the surfaces thereof by a series of cold working operations comprising engaging one surface of the side wall of the blank with an axially straight tool so that the blank assumes the axial alignment of the tool and thereafter ironing out the opposite surface of the blank side wall by applying pressure thereto in excess of the elastic limit of the metal while the first surface is temporarily deformed by said tool to thereby bring said wall into permanent axial alignment with said tool and to permanently smooth out the irregularities in the surface thereof. In an embodiment a stress relieved low carbon or mild steel blank is subjected to a pickling operation, then washed and given a phosphate treatment and finally coated with lubricant in readiness for the sizing and surface finishing operation. Apparatus for carrying out the method comprises a punch shoe 16 on which is rotatably supported a ram plate 18 carrying four punches 24. The punch assembly moves towards and away from a die assembly mounted on a lower die shoe 28 provided with spaced die rings 30 (Fig. 6) for receiving the lower end of a blank 10 and a pair of die supports 34 each carrying a die ring 40. The assembly includes stripper heads 46 and mechanism (not shown) for rotatably indexing the ram plate 18 to successively position the punches 24 first over the die ring 30 and then over the die support 34. The punches are accurately machined 0.005 to 0.025 inch greater than the inner diameter of the blank. In operation on downward movement of the punch assembly a punch will engage within the bore of a blank seated in the die rings 30 and will expand the blank as shown in Fig. 8 and remove any irregularities from the bore. The punch assembly is then raised and the ram plate rotated to position the blanks and punches over the die rings 40. A second pair of blanks are then positioned in the die rings 30 and the punch assembly is again lowered. The first blanks are driven through the die rings 40 and any irregularities are removed from their outer surfaces by cold working and their inner surfaces are compressed against the punches thereby relieving the stresses set up by the elastic deformation and permanently deforming the metal. Finally, on raising of the punch assembly the formed blanks are stripped from the punches and the cycle is repeated with the second pair of blanks. The blanks may have a non-circular cross-section and tapering side walls. Specifications 718,506 and 718,590 are referred to.