GB752687A - Improvements in the manufacture of sintered iron bodies - Google Patents

Abstract

752,687. Powder metallurgy. HUSQVARNA VAPENFABRIKS AKTIEBOLAG. May 3, 1954 [May 2,1953], No. 12863/54. Classes 83 (2) and 83 (4). A method of making porous iron bodies, particularly driving bands for projectiles, comprises compacting iron powder to a density of 4.9- 5.9 grams per c.c., presintering preferably at 850-950‹ C., repressing to a density of 5.4- 6.2 grams per c.c. and resintering, preferably at 1200-1250‹ C for 2-3 hours. Electrolytic iron powder having an apparent density of not more than 2.7 and preferably between 2.3 and 2.6 grams per c.c. is used. It preferably contains less than 0.1 per cent carbon, less than 0.05 per cent silicon and less than 0.15 per cent of metals which form difficultly reducible oxides. If the powder has an apparent density in excess of 2.7 grams per c.c. it is heat-treated in a reducing or inert atmosphere and the resulting agglomerated particles crushed or ground. The initial compacting will be at 1.5-2.5 tons per sq. cm. and the second pressing at 2-3 tons per sq. cm. and both sintering treatments take place in hydrogen or an inert gas. After the final sintering the bands are given a phosphate treatment or are impregnated with paraffin to increase their resistance to corrosion and in order to reduce their coefficient of friction they may be treated with steam or dipped in molten sulphur to form a thin sulphide layer. The finished bands are mounted in the circumferential grooves in the shells by an hydraulic press, the pressure being kept below 40-50 kilograms per sq. mm. in order not to close the pores and they are then brought to final size by machining.