Improvements in or relating to the production of decorative finishes on metal products

摘要

515,455. Altering physical structure. COOK, M., MACQUARIE, C., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. June 2, 1938, No. 16593. [Classes 83 (ii) and 83 (iv)] Making ornamental metalwork.-Copper and copper-rich alloys are provided with a decorative surface finish by severe cold working followed by high temperature annealing to increase the grain size and then etching. The cold working effects a reduction of at least 96 per cent., may be carried out in several stages, and the heat treatment is at 1,000‹ C. If intermediate annealing at 550‹ C. be adopted, the final reduction must be 85 per cent. and final annealing temperature 1,000‹ C. The intermediate and final temperatures may be 900 and 750‹ C. respectively. Thirty to 70 per cent of the reduction may be. by cross -'rolling with intermediate annealing at 500 to 600 C. and final at 750 to 850‹ C. In another modification employing cross-rolling the penultimate annealing temperature is 450‹ C. and the penultimate reduction is from 85 to 90 per cent. Only a part of the metal surface may be treated to increase the crystal size; the whole sheet, tube &c. being cold rolled to an extent just below that required to produce the increase, and the areas where large crystals are required are then further worked by hammering or pressing.