GB1236205A - Improvements in or relating to abrading - Google Patents

Abstract

1,236,205. Blasting; making seamless tubes; drawing. ABRASIVE DEVELOPMENTS Ltd. 11 Oct., 1968 [17 Aug., 1967], No. 37915/67. Headings B3A, B3D and B3P. In the production of weldless tubes by drawing a tubular blank the internal surface of the bore of the blank is abraded, prior to drawing, with a slurry of abrasive and liquid propelled along the bore by compressed gas to produce a surface finish of 30-80 microinches. The abrading removes scale and provides pockets to retain lubricant to facilitate drawing. Preferably the external surface of the tubular blank is similarly abraded. A tubular blank 10, e.g. 100 feet long and with an internal bore diameter of 3 inches, is supported so that it slopes at least 2 degrees to the horizontal. At the upper end of the blank is air and slurry supply means 11 and at the lower end of the blank are a deceleration chamber 12 and a separator 13. The supply means 11 is mounted on a stand 25 and comprises a nozzle 15, mounted in a body 20, and a Venturi-shaped mixing chamber 17; flanges 21, 18 on the body 20 and chamber 17 are held against the ends of a tube 16 by rings 22, 19 and tie rods 23. Compressed air is supplied through a tube 14 to the nozzle 15. The tube 16 has a slurry entry 24. The upper end 26 of the blank abuts a ring seal 27 in a recess 28 in the end of the chamber 17, means being provided for drawing the end 26 and the chamber 17 together. The deceleration chamber 12 comprises an elongated tube having a bore of greater crosssectional area than the bore of the blank; the diameter of the tube may be 9 inches. The blank passes through an end plate 30 having a rubber seal 31 to prevent or substantially restrict the entry of air into the right-hand end of the chamber. The left-hand end of the chamber communicates with the separator 13. The separator 13 is a cyclone 32. Separated air leaves through a central outlet 33. A supply pipe 34 enables the system to be topped up with liquid, e.g. water, when requested. A pump 35 carried by the cyclone draws slurry from the bottom of the cyclone and delivers it through a pipe 37, 38, 39 to the slurry entry 24. For treating the bore of a blank having an internal diameter of 1 to 3 inches, the abrasive may be 60 mesh Bauxilite, or a mixture of 40- 80 mesh or 60-100 mesh. The abrasive is 20- 40%, preferably 30%, by volume of the slurry. The slurry is fed to the entry at 60-70 p.s.i. and 350-400 gallons/min. Air is supplied to the nozzle 15 at 1000-1300 cubic feet/minute and 80-100 p.s.i. or higher. The air accelerates the slurry to a speed of approximately 450 feet/ second in the bore of the blank so that the flow is turbulent. The air may be supplied in pulses by means of a valve 40; the pulses may be regular or there may be different on-and-off periods and these periods may be varied during the treatment of a single blank. Alternatively the conditions of treatment may be so arranged that the system is unstable without use of the valve 40 so that the pulsations are automatically introduced. A modified supply means, Fig. 4 (not shown), comprises members 41, 42 with a gap 43 through which slurry enters, from an annular space 44 between the members and an outer tube.