In Re Inland Steel Company

265 F.3d 1354, 60 U.S.P.Q. 2d (BNA) 1396, 2001 U.S. App. LEXIS 20589
CourtCourt of Appeals for the Federal Circuit
DecidedSeptember 19, 2001
Docket00-1143
StatusPublished
Cited by13 cases

This text of 265 F.3d 1354 (In Re Inland Steel Company) is published on Counsel Stack Legal Research, covering Court of Appeals for the Federal Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
In Re Inland Steel Company, 265 F.3d 1354, 60 U.S.P.Q. 2d (BNA) 1396, 2001 U.S. App. LEXIS 20589 (Fed. Cir. 2001).

Opinion

*1356 BRYSON, Circuit Judge.

On reexamination of a patent owned by Inland Steel Company, the Patent and Trademark Office rejected all the claims of Inland’s U.S. Patent No. 4,421,574 (“the '574 patent”) as obvious under 35 U.S.C. § 103. Inland has appealed with respect to nine of the claims. We affirm.

I

The '574 patent issued in 1983. In 1991, Inland sued USX Corporation and LTV Steel Company, Inc., alleging infringement of the '574 patent. While that lawsuit was pending, USX and LTV filed requests for reexamination of the '574 patent. The Patent and Trademark Office granted those requests, and the district court stayed further proceedings pending the outcome of the reexamination proceeding.

Following the reexamination, the examiner rejected all claims of the '574 patent as either anticipated or obvious. After the final rejection, Inland cancelled claims 1-8 and appealed the rejection of the remaining claims, claims 9-17, to the Board of Patent Appeals and Interferences. The Board sustained the examiner’s rejections under 35 U.S.C. § 103 based on a variety of prior art combinations, including U.S. Patent No. 4,390,378 (“Rastogi”) and U.S. Patent No. 4,204,890 (“Irie”).

The appealed claims are directed to a method of producing cold-rolled electrical steel that has improved magnetic properties. Electrical steel is designed to carry magnetic flux in electrical products such as motors and transformers. Three magnetic properties that are commonly used to grade electrical steel are core loss (a measure of the steel’s loss of energy within the electrical core), permeability (a measure of the steel’s capacity to carry magnetic flux), and magnetic induction (which is directly proportional to permeability). Producers of electrical steel strive to obtain compositions that exhibit low core loss and high permeability.

In general, cold-rolled steel is produced by forming molten steel into thick slabs and then converting the slabs into thinner strips by a series of hot-rolling steps (rolling at an elevated temperature). The thin strips are then cooled to room temperature and reduced to nearly their final thickness by a series of cold-rolling steps (rolling at room temperature).

During the processing that follows hot rolling, the steel strip is conventionally subjected to an annealing operation in which the steel is heated and then slowly cooled. That annealing step may be performed either (1) between the hot-rolling, and cold-rolling steps, (2) between stages of multiple cold-rolling steps, or (3) after the completion of cold-rolling. Annealing that is performed between the hot-rolling and cold-rolling steps is called hot-band annealing.

The prior art taught that adding silicon and aluminum to the steel mixture improved the steel’s magnetic properties. However, adding silicon and aluminum had the disadvantage that an annealing step designed to eliminate carbon in the steel (the “decarburizing anneal”) would cause an undesirable layer containing oxides of silicon and aluminum to form near the surface of the steel. That layer reduced the improvements in magnetic properties otherwise obtained from the addition of silicon and aluminum.

The '574 patent addressed that problem by proposing the addition of antimony during the preparation of electrical steel. The addition of antimony, according to the patent, causes an antimony-enriched layer to form adjacent to the surface of the metal, which reduces the depth of the oxidation layer, thus improving the magnetic properties of the steel.

*1357 Representative claim 9 of the '574 patent recites a process for using antimony in making electrical steel:

9. A method for producing a cold rolled, temper rolled strip of electrical steel containing silicon and aluminum and which will suppress the formation of an internal oxidation layer containing oxides of silicon and aluminum adjacent the surface of said cold rolled steel strip during subsequent deearburizing after temper rolling, said method comprising the steps of:
providing a steel composition consisting essentially of, in wt.%:
carbon: up to 0.06,
manganese: 0.20-0.75,
silicon: 0.15-2.50,
aluminum: 0.15-0.50,
phosphorus: 0.12 max.,
sulfur: 0.02 max.,
antimony: 0.02-0.10 wt.%,
iron: essentially the balance,
hot rolling said steel into a strip; coiling said strip at an elevated temperature and then cooling the coiled strip;
cold rolling said strip;
annealing said strip after said cold rolling step, at a strip temperature which forms an antimony enriched layer at, and immediately adjacent, the surface of said strip;
there being no annealing step after said hot rolling step and prior to the completion of cold-rolling;
and temper rolling said strip after annealing;
there being no substantial reduction in the carbon content of said steel in any of said steps through said temper rolling step.

Claim 9 and the claims that depend from it preclude any annealing step during the period after hot rolling but before the completion of cold rolling. By excluding annealing during that time, the claimed process minimizes antimony depletion, thus preserving the antimony-enriched layer that inhibits the formation of the oxidation layer. See '574 patent, col. 2, 11. 60-68.

The primary reference on which the examiner and the Board relied was the Ras-togi patent, which was also assigned to Inland. Rastogi’s claim 1 recites:

I. In a method for producing cold rolled steel strip for use in electric motor core laminations, the steps of:
providing a steel consisting essentially of the following composition in wt.% before cold rolling:
carbon: 0.05 max.
manganese: 0.50-0.70
silicon: 0.85-1.05
aluminum: 0.20-0.30
phosphorus: 0.08 max.
sulfur: 0.02 max.
iron: essentially the balance;
hot rolling said steel into steel strip; coiling said hot rolled steel strip while the steel is at a coiling temperature in the range 1250-1400'F. (682-760"C.) and then allowing said coiled strip to cool;
cold rolling said steel strip;
continuously annealing said steel strip at a strip temperature in the range 1250-1400 ~F.

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Bluebook (online)
265 F.3d 1354, 60 U.S.P.Q. 2d (BNA) 1396, 2001 U.S. App. LEXIS 20589, Counsel Stack Legal Research, https://law.counselstack.com/opinion/in-re-inland-steel-company-cafc-2001.