GB558382A - Improvements in or relating to electric induction furnaces - Google Patents

Abstract

558,382. Moulding metal powder. BIRMINGHAM ELECTRIC FURNACES. Ltd., and ROBIETTE, A. G. E. Oct. 20, 1943, No. 17240. [Class 87 (ii)] [Also in Group XI] An induction furnace suitable for sintering compacts of powdered metal or alloy 16 adapted afterwards to be formed into piston rings, comprises a vertical heating chamber 1, a vertical cooling chamber 2, and a gas-tight transverse chamber 3 to which non-oxidizing or reducing gas is supplied through a pipe 4 to fill both chambers. The lower part of chamber 1 is surrounded by a refractory sleeve 5 with an inductor coil 8, and the upper part by a water- or air-cooled jacket 7. A similar cooling jacket 9 is provided around the upper part of chamber 2. The compacts 16 are carried by refractory insulating moulds or spacers 10 which are fed into the lower end of chamber 1 by rotary table 11, plunger 13, and reciprocating slide 12. A reciprocating arm 15 transfers each spacer 10, as it reaches the top, to chamber 2, and a cooled spacer is removed at the bottom of chamber 2 by plunger 14. Each mould has a peripheral part 17, and tapered crown 18 co-operating with the recessed base 19 of the adjacent mould. A high frequency current of 500-2,000,000 cycles may be used, or a low frequency current of 25-100 cycles with a magnetic core. Instead of feeding non-oxidizing gas, the metal powder may be mixed with a metal hydride which decomposes to produce the required atmosphere. The compacts may be subjected to pressure during the heat treatment. The heating and/or cooling may be controlled by extending the coil 8 and varying the spacing of the turns, or the controlled cooling may be effected by a graduated resistance element at the discharge end of the inductor coil, terminating in a water or air cooled zone.