GB479777A - Improvements relating to the production of molten metal - Google Patents

Abstract

479,777. Metal-melting furnaces. HENLEY EXTRUSION MACHINE CO., Ltd., and DUNSHEATH, P. Aug. 14, 1936, No. 22443. [Class 51 (ii)] A furnace 1 for melting metals in a non-oxidizing atmosphere is charged with ingots 2 through 1 a lock chamber 10 having inner and outer doors 3, 11, the air which enters the chamber 10 when the outer door is opened, being, before the inner door is opened, ejected and replaced by non-oxidizing gas. In the form shown in Fig. 1, the non-oxidizing gas is admitted at 18 and escapes at 13, an igniter 14 being provided so that completion' of the scavenging of the chamber 10 is indicated by ignition of the escaping gas. Entry of air past the operating-rod 17 of the door 3 is prevented by maintaining a trickle supply of gas through a pipe 15. In cases where the lock chamber is at a dangerously high temperature, it is placed in communication with an evacuating device or scavenged by inert gas before the non-oxidizing gas is supplied. Fig. 2 shows a construction in which the action of opening the outer door 11 automatically actuates a valve 20 to connect the chamber 10 to an evacuating plant, the non-oxidizing gas being automatically delivered, when the pressure has fallen to a predetermined degree, through a spring-loaded valve 30. Incorporated in this valve is a small needle valve which maintains a trickle supply through pipe 36 to the housing 16 of the rod 17 and through pipe 35 to the interior of the lock chamber 10. To minimize the effect of any explosion that may occur, the doors 3, 11 are fitted with insets 37 of mechanically weak material. The non- oxidizing gas employed in the melting chamber preferably consists of a mixture of an oxidereducing gas and a commercial inert gas which has been pre-treated by being subjected to high temperature and/or an ionizing electric discharge. Specifications 458,089 and 478,278 are referred to.