Ltv Steel Company, Inc.

International Steel Group Inc.

Barry A Lauer

Richard J Blotzer

Jeffrey P Anderson

Gerald F Beatty

Ann M R Larson

John F Held

Jeffery P Anderson

John F Butler

Ann M Larson

A method of making electrical steel strip characterized by low core loss and high permeability in the rolling direction includes the steps of: hot rolling a slab of an electrical steel composition into a strip, hot band annealing in a temperature range effective to coarsen the grains sufficient to improve magnetic properties in a rolling direction of the strip, cold rolling, batch annealing in a temperature range effective to produce a batch annealed grain size of not greater than 40 &mgr;m and, preferably not greater than 20 &mgr;m, and temper rolling to provide the strip with a transfer surface roughness (Ra) of less than 49 &mgr;in. Electrical steel articles are manufactured from the steel strip upon final annealing. The electrical steel articles have a grain texture including a &lcub;110&rcub;<001> orientation and improved permeability in the rolling direction.

Electrical steel with improved magnetic properties in the rolling direction

The present invention is directed to a method of forming an electrically insulating layer on a steel article such as a stack of electrical steel laminations or an individual, unstacked electrical steel lamination, comprising exposing the article to an oxidation atmosphere, and to a temperature (such as at least about 800&deg; F.) for a time sufficient to form on the article an electrically insulating layer comprising hematite. The hematite layer is effective to provide the article with a surface resistivity characterized by an F-amp value of not greater than about 0.85 at a test pressure of 50 psi and a transfer surface roughness of about 10 microinches (Ra). Also featured is a steel article having the electrically insulating layer formed thereon.

Steel with electrically insulating hematite layer

The present invention is directed to a method of forming an electrically insulating layer on a steel article such as a stack of electrical steel laminations or an individual, unstacked electrical steel lamination, comprising exposing the article to an oxidation atmosphere, and to a temperature (such as at least about 800&deg; F.) for a time sufficient to form on the article an electrically insulating layer comprising hematite. The hematite layer is effective to provide the article with a surface resistivity characterized by an F-amp value of not greater than about 0.85 at a test pressure of 50 psi and a transfer surface roughness of about 10 micro inches (Ra). Also featured is a steel article having the electrically insulating layer formed thereon.

Batch annealed, semi-processed and fully processed motor lamination steels are made by processes which subject a slab having a particular ultra low carbon composition (less than 0.01%) to steps which include hot rolling a slab into a strip and coiling the strip. This is followed by the sequential steps of preferably annealing the strip in coil form, cold rolling the strip and batch annealing the strip in coil form. The strip is flattened by a temper rolling or leveling process. The flattening step reduces the thickness of the strip by an amount ranging from greater than 0% to not greater than 1.0% to provide the strip with a permeability when stress relief annealed of at least 2500 Gauss/Oersted.

Process of making electrical steels

A method of making electrical steel strip characterized by low core loss, high permeability and good cleanliness includes producing a slab having a composition consisting essentially of (% by weight): up to 0.02 C, 0.20-1.35 Si, 0.10-0.45 Al, 0.10-1.0 Mn, up to 0.015 S, up to 0.006 N, up to 0.07 Sb, up to 0.12 Sn, and the balance being substantially iron. The slab is hot rolled into a strip with a finishing temperature in the ferrite region. The strip is coiled at a temperature less than 1200.degree. F. and, preferably, less than 1000.degree. F. The strip which has not been subjected to an annealing operation after the coiling is subjected to cold rolling. The strip is then batch annealed and temper rolled.

Process of making electrical steels having good cleanliness and magnetic

Batch annealed, semi-processed and fully processed motor lamination steels are made by processes which subject a slab having an ultra low carbon composition (less than 0.01%) to at least the following steps: hot rolling with an austenite finishing temperature, coiling at a temperature ranging from 1300.degree.-1450.degree. F., and light temper rolling (less than 1.0% reduction) or leveling; reheating at a temperature less than 2300.degree. F., hot rolling with a ferrite finishing temperature, coiling at a temperature less than 1200.degree. F., and light temper rolling or leveling; or hot rolling with a ferrite finishing temperature, coiling at a temperature ranging from 1100.degree.-1350.degree. F. without a subsequent hot band anneal, and light temper rolling or leveling.

The toughness of vanadium and niobium microalloyed medium carbon bar steels is significantly improved by a controlled addition of aluminum in a range of from about 0.05 to 0.11 percent. Forged parts combining high strength and hardness properties with improved toughness can be made from the new bar steel without the need of heat treatment.

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Macedonia, OH, United States of America

Barry A Lauer