The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 27, 1976
Filed:
Sep. 02, 1975
John H Burger, Butler, PA (US);
John R McClelland, Butler, PA (US);
Robert P Dunkle, Kittanning, PA (US);
Armco Steel Corporation, Middletown, OH (US);
Abstract
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.