Inland Steel Company

Richard A Nickola

Shashi B Agarwal

Brian A Sok

A cold rolled solid solution iron-aluminum diffusion alloy foil and a method of making the foil are described. The foil has good room temperature formability and high temperature oxidation and corrosion resistance with useful electrical and magnetic properties and is adapted for use as a tool wrap, as an electrical steel, and as a support for a catalyst after a coating of spine-like aluminum oxide whiskers is grown on the surface thereof. The foil is made by hot-dip aluminum coating a titanium stabilized low carbon steel strip, cold rolling the aluminum coated strip to effect between about a 40 and 99 percent reduction in thickness, and diffusion heating the cold rolled aluminum coated steel strip to form a solid solution iron-aluminum diffusion alloy foil containing between about 2 and 12 wt. % aluminum. In a modified form the cold rolled aluminum coated steel is heated in a dry nitrogen containing atmosphere to form an aluminum nitride-containing surface film which has increased resistance to attack by acidic solutions. As a further modification, the foil product is subjected to additional cold rolling to create strain in the foil and the strained foil is heated to cause the crystal size in the foil to be substantially increased.

Diffusion alloy steel foil

Coatings of a powdered protective metallic material or refractory material and mixtures thereof are formed on a ferrous metal strip as a wet film dispersion in a resin binder composition of a synthetic organic resin and a volatile organic solvent compatible with said resin, and the coated strip is heated to effect curing said resin binder and forming a flexible non-tacky dry film. The metal strip having the cured dry film containing powdered protective metallic material can be subjected to varying heat treatments to provide a wide range of protective coatings having improved surface properties, including iron-protective metal diffusion alloy coatings, such as iron-aluminum diffusion alloy coatings having a surface concentration of aluminum between about 8 and 10 wt. percent aluminum, which have improved high temperature oxidation resistance after being severely strained during fabrication at room temperature.

Powder metal and/or refractory coated ferrous metals

A solid solution iron-aluminum diffusion alloy coated steel strip is formed by hot-dip aluminum coating a cold rolled low alloy low carbon steel strip preferably having all the carbon in the steel combined with titanium by hot-dip aluminum coating the steel strip and subjecting the aluminum coated low alloy steel strip to a controlled diffusion heat treatment in a non-oxidizing atmosphere for a period and at a temperature which avoids significantly increasing the grain size of the steel, and which effects diffusion of the hot-dip aluminum coating into the steel to establish a critical surface concentration of aluminum in the iron-aluminum diffusion alloy coating of at least about 8 wt. percent and below an aluminum surface concentration which results in crazing and cracking of the diffusion alloy coating when the diffusion alloy coated strip is fabricated at room temperature. A solid solution iron-aluminum diffusion alloy coated titanium containing low carbon steel strip having an aluminum surface concentration between about 8 and about 10 wt. percent does not exhibit objectionable crazing and cracking of the diffusion alloy coating when the coated steel is severely strained during fabrication at room temperature and has good high temperature oxidation resistance when the diffusion alloy coated steel strip is exposed to oxidizing gasses having temperatures between about 816.degree. C. (1500.degree. F.) and 982.degree. C. (1800.degree. F.) after being severely strained at room temperature.

Diffusion treated hot-dip aluminum coated steel

A ferrous metal strip is provided with a wet film coating of a powder metal, powder refractory material or a mixture thereof dispersed in a resin binder composition formed of a synthetic organic resin and a volatile solvent, followed by heating the coated strip to remove the solvent and cure the organic resin. The metal strip with the cured resin-powder flexible non-tacky coating can be subjected to varying heat treatments to provide a wide range of protective coatings having improved surface properties. The formability properties of the cured resin-powder coating is further improved by applying a surface coating of a dry lubricant, such as molybdenum disulfide or graphite, as a dry powder or as a dispersion in a fluid vehicle.

Powder metal and/or refractory coated ferrous metal

A low-titanium alloy steel foil having a cold rolled metallic aluminum hot-dip coated surface which is adapted for growing a thick surface coating of spine-like whiskers of aluminum oxide suitable for retaining a coating of a metallic catalyst, which is formable at room temperature without annealing, and which exhibits good resistance to oxidation at temperatures up to 1149.degree. C. (2100.degree. F.).

Aluminum coated low-alloy steel foil

Coatings of a powdered protective metallic material or refractory material and mixtures thereof are formed on a ferrous metal strip as a wet film dispersion in a resin binder composition of a synthetic organic resin and a volatile organic solvent compatible with said resin, and the coated strip is heated to effect curing said resin binder and forming a flexible non-tacky dry film. The metal strip having the cured dry film containing powdered protective metallic material can be subjected to varying heat treatments to provide a wide range of protective coatings having improved surface properties, including iron-protective metal diffusion alloy coatings, such as iron-aluminum diffusion alloy coatings having a surface concentration of aluminum between about 8 and about 10 wt. percent aluminum, which have improved high temperature oxidation resistance after being severely strained during fabrication at room temperature.

Diffusion treated hot-dip aluminum coated steel and method of treating

A process of hot-dip coating a strip of cold rolled low carbon steel having as an essential alloying element at least one strong oxide forming metal, such as titanium, aluminum, silicon or chromium or a combination thereof, to overcome the difficulty of uniformly hot-dip coating such steels with aluminum and other protective metals on a Sendzimir-type hot-dip coating line wherein the steel strip is thoroughly cleaned by washing in an alkaline cleaning solution, brushing and drying to remove metallic particles and non-metallic contaminants, forming a dry film coating on a clean dry surface of the strip of a higher fatty acid amide having from 8 to 18 carbon atoms, heating said strip to a temperature sufficient to completely volatilize said amide film coating, passing said strip through a heating zone containing a reducing atmosphere in which the strip is heated to a temperature of at least about 704.degree. C. (1300.degree. F.), cooling said strip in a reducing atmosphere to about the temperature of a molten aluminum hot-dip coating bath, and passing said strip through said hot-dip coating bath. The amide coated steel strip has excellent corrosion resistance when stored in coiled form and is adapted for uniform hot-dip coating with aluminum on a Sendzimir-type hot-dip coating line.

Hot-dip metallic coatings on low carbon alloy steel

A method of providing sintered and diffused metal coatings of finely divided metallic material on a metal base, such as a steel strip or panel, by forming a molten film of one or more higher fatty acid amides having a carbon chain length from about 8 to 18 carbon atoms on a clean surface of the metal base which is preferably heated to a temperature above the melting point of the fatty acid amide film, applying uniformly on the molten amide film an amount of a finely divided metallic material, such as powdered Monel metal or nickel, in excess of that which settles into the film and is held thereby and removing the excess metal powder after the amide film has solidified, and heat treating the metal base having the coating of amide and metal powder thereon in a non-oxidizing reducing atmosphere at a temperature and for a period sufficient to effect bonding of said finely divided metallic material with each other and with said metal base to form a uniform firmly adherent metal coating. The metal base with the finely divided metallic material on the surface thereof can be compacted by rolling, either before or after heat treating, and thereafter annealed as required. The resulting coatings are porous coatings having a large surface area where no compacting is effected and are dense impervious coatings when compacted to effect a 60 percent reduction in the thickness of the base.

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Highland, IN, United States of America

Richard A Nickola