GB1394197A - Annealing furnace and method for its operation - Google Patents

Abstract

1394197 Continuous heat treatment furnaces ALLEGHENY LUDLUM INDUSTRIES Inc 15 Sept 1972 [17 Sept 1971] 42878/72 Heading F4B [Also in Division C7] A continuous furnace for the heat treatment of silicon steel coils C on trucks 40 comprises an elongate structure divided into heating zones 8, 10, 12 and (14, Fig. 1B) and cooling zones 16, 26, 28 (30, Figs. 1B, 1C) and 31, a sealable entrance vestibule 4 and a similar discharge vestibule 20, a sealable intermediate transfer station 180, connections to vacuum pumps 160, 190 and 191 from zone 8, vestibule 4 and vestibule 20 respectively, and pipes 116, 118 supplying reconditioned atmosphere gas (hydrogen) to jets 120 at the discharge end of the furnace. Purging nitrogen may be supplied via controlled inlets 144 to the vestibules, which have controlled outlets 152 to the atmosphere. Hydrogen may also be supplied to the transfer station 180 through line 119 and valve 187 and to the vestibules through lines 142 and 116 and manifolds 144. A line 132 with valve 181 connects zone 8 with the other heating zones. Atmosphere gas withdrawn through headers 112 and 170 is returned to the reconditioner 110 where contaminants are removed and the gas is cooled. Headers 121 and 125 in the cooling sections are also used to withdraw atmosphere gas which is returned to roof jets 74 from coolers 122 and 126. A container 138 replaces hydrogen lost by leakage. Heating elements in the form of molybdenum rods (58, Figs. 2 and 3) are mounted on the walls in the heating sections and the refractory on said walls is gradually narrowed in the cooling sections until in the last of these it is nil. The coil carrying truck 40, Fig. 9, comprises lower layers of refractory 82, 84 with an upper layer formed with radiation tunnels 86 about the level of the heating elements, surmounted by silicon carbide tiles 90 and a hearth plate 92 of low carbon steel with a coating of alumina. In these layers a vertical hole (94, Fig. 10) in line with the centre coil opening 104 communicates with the radial radiation tunnels 86. A tube 95 carries a thermocouple 96 extending to a plug-in point 97 below the truck. The trucks are impelled by the piston-rod 44 of an hydraulic motor 42 outside the vestibule 4 and by similar piston-rods 44<SP>1</SP> of motors 42<SP>1</SP> located adjacent the transfer section 180.