Bethlehem Steel Corporation

Angelo R Borzillo

Herbert E Townsend

Louis K Allegra

Paik W Shin

Theodore E Torok

James B Horton

This invention relates to an aluminum-zinc alloy coated ferrous product whose coating is highly ductile, and to the method whereby such improved coating ductility may be realized. The process is characterized by the steps of thermally treating the aluminum-zinc alloy coated product by heating to a temperature between about 200.degree. F. (93.degree. C.) and 800.degree. F. (427.degree. C.) and holding for a period of time to effect metallurgical structure changes, among them being the precipitation of a second phase incoherent with the matrix, followed by slow cooling to at least 400.degree. F. (205.degree. C.). The resulting product is characterized by an aluminum-zinc alloy coating with a hardness no greater than about 115 VHN, and preferably no greater than about 110 VHN.

Method of improving the ductility of the coating of an aluminum-zinc

This invention relates to an aluminum-zinc alloy coated ferrous base product which exhibits improved atmospheric corrosion resistance, and to the process whereby such improved corrosion resistance may be realized. The process is characterized by the steps of heating such coated product to a temperature within the single phase region for the composition corresponding to the aluminum and zinc of said coating, defined as .alpha. in the FIGURE in the accompanying drawing, preferably at a temperature between about 650.degree. F. (343.degree. C.) to 750.degree. F. (399.degree. C.), for a period of time to solution treat the aluminum-zinc alloy coating overlay, and cooling slowly to at least 350.degree. F. (177.degree. C.). The resulting product is characterized by improved atmospheric corrosion resistance as a result of the combination of an aluminum-zinc alloy coating overlay having a structure comprised of a fine dispersion of beta-zinc within a matrix of alpha-aluminum, and a thin intermetallic layer interposed between said overlay and said ferrous base.

Method of producing an aluminum-zinc alloy coated ferrous product to

Large steel products such as structural sections, castings, forgings and machined sections are coated with a smooth, adherent, bright metallic coating comprised of 25 to 85% aluminum, silicon in an amount of 0.7% or more by weight of the amount of aluminum and the balance substantially zinc without the occurrence of detrimental exothermic reactions of the coating medium with the base metal.

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Norristown, PA, United States of America

Angelo R Borzillo