Steel with electrically insulating hematite layer

摘要

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° 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.