Armco Steel Corporation

Robert P Dunkle

John R McClelland

John H Burger

A batch-type method of annealing large coils of silicon steel for magnetic purposes in an annealing furance of the type comprising an outer enclosure surrounding an insulated heating chamber in which the coils are supported, the furnace being capable of subjecting the coils both to a desired atmosphere and a vacuum. The method comprises the steps of locating the coils to be annealed in the furnace heating chamber; drawing and holding a vacuum within the outer enclosure and heating chamber to remove air therefrom; backfilling with a desired non-oxidizing annealing atmosphere; circulating the annealing atmosphere through the outer enclosure and heating chamber; heating the coils to a temperature of about 2200.degree.F. (1204.degree.C.) and soaking the coils at temperature with continued annealing atmosphere circulation; subjecting the coils to an initial, slow, unassisted cooling step down to about 1700.degree.F. (927.degree.C.); subjecting the coils to an intermediate cooling step down to about 1225.degree.F. (663.degree.C) with the furnace fans on and the furnace bungs closed; subjecting the coils to a final fast cooling step down to about 250.degree.F. (121.degree.C.) with the furnace fans on and the furnace bungs open; drawing and holding a vacuum within the outer enclosure and heating chamber to remove the annealing atmosphere therefrom; backfilling with nitrogen and removing the coils from the furnace. When the silicon steel for magnetic purposes is to have a cube-on-edge orientation and contains Aln as the grain growth inhibitor, the coils may be held at 1200.degree.F. (649.degree.C.) for about 6 hours prior to heating them to 2200.degree.F. (1204.degree.C.) and the soaking step.

Method of annealing oriented silicon steel

In an annealing furnace of the type comprising an outer enclosure surrounding an insulated heating chamber and wherein the bottom of the heating chamber comprises a metallic coil carrying car having one or more base plates upon which the coils of metal to be annealed are supported and having electrical heating elements beneath the base plates, improved means for supporting the one or more base plates on the coil carrying car. The support means for each base plate comprises a plurality of refractory blocks mounted on the upper surface of the car and upon which the base plate rests. The refractory blocks are so arranged as to accommodate the heating elements beneath the base plate and to permit the circulation of an atmosphere thereabout, while at the same time affording maximum support for the base plate.

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Kittanning, PA, United States of America

Robert P Dunkle