GB912384A - Method of and apparatus for annealing - Google Patents

Abstract

912,384. Annealing coiled strip in open form. WILSON, L. March 10, 1959 [May 7, 1958], No. 8193/59. Class 72. [Also in Group XII] In a process for annealing coils of strip in opened-lap form, by a hot gas, the coils of strip e.g. cold rolled steel are treated cyclically at a series of stations, by adding and removing coils at opposite ends of the series, heating to a predetermined temperature by forcing the gas vertically through the opened laps at an intermediate station, circulating gas in a closed path through one coil which has been heated and then one which has not, to cool the one and preheat the other, the coils being moved step-by-step whereby each is successively preheated, heated, soaked and cooled. As shown in plan, Fig. 2, rotary hearth H is supported by wheels on tracks between inner wall 2 and outer wall 1 of the furnace. The furnace space is divided into compartments by dividing walls 11-17 supported on the hearth. Open lapped coils are placed on a support unit S on carriage L which is run on rails 24 into purge chamber P closed by doors 20 and 22. The support unit is in the form of a grid having openings only below the open lapped coil, whereby the hot gas flows solely between the coil laps. An inert or deoxidizing gas is circulated through it to remove air and then door 20 opened to give access to station I on the hearth on to which it is lowered with support S by carriage L and hydraulic jack 55. The carriage is withdrawn, door 20 closed, and furnace gas circulated up through coil 66, driven through conduit 33 by a fan down through hot coil 65 at about 900‹ F., through passage 33 back to the bottom of coil 66 eventually equalizing the temperature of the two coils. After about 1 hour hearth H is rotated to bring each coil to the next station. Coil 67 at station II has gas circulated down through it, via passage 37, up through the coil at station VI and through a passage 36, while coil 68 at station II is heated by gas circulated by a fan up through the coil and back to an external heater A, where it contacts radiant tubes heated by gas or electricity, to bring it up to the annealing temperature of 1320‹ F. Coils 69 and 70 at stations IV and V are heated by the series circulation of gas up through coil 70 and down through coil 69 and back to a second external heater A1, thus providing a soaking time of 2 hours for which the coils are kept at the annealing temperature at these stations. Meanwhile coils 71 and 65 are cooled as described at stations VI and VII and coil 65 can then be unloaded by means of carriage L<SP>1</SP> which first moves it into the unloading chamber F through which cooled gas is circulated by fan 58, and then out of door 23. The finished coil is removed by hydraulic lifters 55. The hot gas passes upwards in one stage and downwards in the next to attain uniform heating of the coil. The stepby-step motion is achieved by an indexing control. The invention is equally applicable to a straight line or V-type furnace. Specifications 878,497 and 890,409 are referred to.