Method and apparatus for double vacuum production of steel
AssigneeA. Finkl & Sons Co.
InventorsCharles W. Finkl, Guy A. Brada, Algirdas A. Underys
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Abstract
A method and apparatus for producing high quality steel having less than about 1 ppm H, 50 ppm N, 25 ppm O and 0.005 S which includes subjection to vacuum, gas purging, and alternating current heating arcs, followed by shrouded pouring into sealed ingot molds to form a VAR electrode which is subsequently remelted under a very low absolute vacuum and re-solidified.
Claims25
In a method of producing high quality steel having low gas, sulphur and inclusion contents, the method comprising the steps of
- subjecting a heat of steel in a container to the simultaneous application of a vacuum and a purging fluid which proceeds from a lower portion of the heat to an upper portion of the heat whereby portions of the heat remote from the surface are brought to the surface where they are exposed to the vacuum,
- subjecting the heat to an electric heating arc under vacuum,
- solidifying the heat to form an electrode, and
- remelting the electrode in a low absolute pressure environment to form an ingot in a cuprous crucible,
- said ingot having low O,H,N contents and a very low sulphur content.
In a method of producing high quality steel having final gas contents on the order of about less than 1 ppm H, less than about 0.80 ppm N, less than about 25 ppm O and less than about 0.003 sulphur, method comprising the steps of
- making up a heat of steel in an electric arc furnace,
- tapping the heat into a treatment receptacle,
- subjecting the heat to the simultaneous action of a vacuum on the order of about 1 mm. Hg or below and a purging gas which is bubbled upwardly through the lower portion of the receptacle until the sulphur is reduced to a low level,
- bottom pouring the low gas, low sulphur molten steel into an ingot mold under an inert atmosphere,
- solidifying the steel to form an ingot,
- converting the ingot into a remeltable electrode, said conversion including the step of removing scale from the ingot following solidification,
- remelting the electrode in a copper crucible under an operating pressure of less than about 100 microns Hg, and
- solidifying the remelted electrode to form an ingot having less than about 1 ppm H, less than about 80 ppm N, less than about 25 ppm N and less than about 0.003 sulphur.
A system for producing high quality steel, said system including
- means for preparing a melt of low phosphorous, low sulphur steel,
- means for further processing the melt gas levels on the order of about 2 ppm H, 80 ppm N, 30 ppm O and 0.03, or below, S,
- means for pouring the processed melt a protective atmosphere into an ingot mold,
- means for converting the ingot which solidifies in the ingot mold to a remeltable electrode, and
- means for remelting the electrode under a low absolute pressure to produce a steel having less than about 1 ppm H, less than about 50 ppm N, less than about 25 ppm O, and less than about 0.005 S, characterized by a fine grain and by a substantially inclusion and dendritic-free microstructure.
A method of producing lens quality steel having a minimum of deleterious inclusions, a near isotropic microstructure and not over 0.005 S, 1 ppm H, 30 ppm O, and 50 ppm N which includes the steps of
- subjecting a heat of molten steel in the simultaneous action of a vacuum, purging gas and electric heating arc to form a VAR electrode, and
- thereafter vacuum arc remelting the electrode to form a product having not over 0.005 S, 1 ppm H, 30 ppm O and 50 ppm N.
Dependencies are inferred from the claim text.