GB515331A - Improvements in, or relating to, annealing and other heat-treatment furnaces - Google Patents

Abstract

515,331. Metal-heating furnaces. BIRMINGHAM ELECTRIC FURNACES, Ltd. LOBLEY, A. G., and ROBIETTE, A. G. E. June 18, 1938, No. 18122. [Class 51 (ii)] The hearth of a bright annealing furnace having a removable heating hood or bell is formed of a porous refractory, and arrangements are provided for forcing gas through the material of the hearth for removing moisture or occluded gases which may act detrimentally on the metal. The purging gas may be that used as a protective atmosphere in the furnace. In the arrangement shown, pipes a, e for the supply and exhaust respectively of a protective gas extend vertically through the hearth f and open into the space beneath the hood h, and other exhaust pipes g are connected at points on a circle to the underside of the hearth. The pipes e and g lead to a common exhaust main, the latter through a moisture trap i. In starting up the furnace, either initially or after it has been standing idle, the offtake e is closed and gas supplied through the intake a is exhausted through the porous hearth and the pipes g, while for normal working the offtake e is opened and the pipes g are closed or left open as may be desired. In a modification a single exhaust pipe for the protective gas is connected to a chamber beneath the hearth which is supported on a perforated plate. A fan d may be provided to circulate the furnace atmosphere.