GB671333A - Electrode type salt-bath furnace - Google Patents

Abstract

671,333. Electrode salt baths. HOLDEN, A. DE F. Sept. 2, 1948 [Sept. 9, 1947], No. 23133/48. Class 39(iii) An electrode-type salt bath furnace having a ceramic pot 20, Fig. 1, 2, for the molten salts has the greater part of the pot bottom covered by pools of metal acting as electrodes 28 that are liquid at the operating temperatures of the furnace, there being one or more refractory separating slabs 27 between the electrodes 28 and current conductors 29 extending from the pools to the exterior of the furnace. Metal containers 26 hold the molten metal 28. As shown, the current conductors 29 extend downwardly, within metal sleeves 29a, through an overhanging ledge 22 of the furnace so as to be heat-insulated from the molten bath. Alternatively, the conductors 29 may be solid or hollow extensions of the containers 26 extending horizontally through the furnace walls, any hollow extensions having at their outer ends an upward extension 77, Fig. 12, forming a well in which the fluid pressures may balance should the normally unmolten metal at the outer ends of these extensions become fused. Such horizontally extending current conductors are cooled within the furnace walls by cooling pipes or heat conductive sheets or jackets 64, to prevent by chilling molten salts from escaping from the furnace. The pools of molten metal are preferably such that each has a surface formed of an oxide of the metal and which is capable of reducing oxides of the work being treated. The refractory mass 21 of the furnace is surrounded by rammed refractory material 31 having an outer layer of insulating material 34 and the whole is enclosed in a heavy gauge steel plate shell 35. In addition a metallic shell 32 may be included between the rammed refractory, material 31 and the surrounding insulation 34. If the furnace is to operate at a lower voltage than would ordinarily be required, conductive bars may extend across and be spaced somewhat above the pools of metal in the furnace or, alternatively, an auxiliary electrode may extend upwardly into the salt mass from each pool of metal. These conductive bars or auxiliary electrodes are preferably of chrome iron or nickel iron alloys. Starting.-When shutting down the furnace, a pronged resistive unit is inserted into the bath such that a prong extends into each pool of metal. The furnace, when cold is thus initially heated by current flowing through the pronged resistance which is removed when the salt bath has become re-fused.