GB280382A - Method of making hollow iron bars - Google Patents

Abstract

280,382. Wheelwright, T. S. Dec. 7, 1926. Pipes and tubes.-In a method of manufacture of hollow iron bars for stay bolts &c. comprising bundling weldable metal round a hollow metal core, packing the core with refractory material, heating the bundle to a welding temperature, rolling it to desired size and removing the refractory core, torsion of the bundle and distortion of the axial hole is avoided in the rolling operation by the provision of polygonal or non-circular passes. In the arrangement of Fig. 1 the metal bars C are bundled between the hollow metal core B and an outer tube A, and in Fig. 2 the bars are packed between the core B and two semi-cylindrical metal sheets D, the whole being bound together by wire E. In another arrangement, Fig. 3, flat bars F are set to polygonal outline and the space between them is packed with bars C round the core B and the whole secured by wire binding. E, whilst in a further arrangement the bars are merely bundled round the core and bound with wire. Any suitable refractory material may be employed for packing the core for example silica sand, soapstone, graphite, carborundum sand, zircon sand, or electrically sintered alumina or magnesia. Twisting of the bar during rolling is prevented by employing polygonal passes H and the bar J is fed in with its flats in the same planes as the flats of the pass; a larger number of passes is used to minimize distortion, sixteen or twenty being preferred, and the last pass K is round to give the bar its final form. The refractory filling G is removed from the finished bar M, Fig. 7, by revolving the bar in a lathe and advancing in the bore a metal tube N connected to a compressed air supply.