Partially alloyed galvanize product and method
AssigneeBethlehem Steel Corporation
InventorsGeorge M. Mino, Donald L. Dustin
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Abstract
A partially alloyed galvanized ferrous strand and a method for its production. The method is characterized by the steps of immersing a clean and oxide-free ferrous strand in a molten zinc galvanizing bath to produce on the strand a coating weight of between 0.2 and 0.5 oz. per square foot. After immersion, the zinc-coated ferrous strand is heat treated and cooled to produce a galvanized coating on said ferrous strand, which coating has a duplex structure characterized by an iron-zinc intermetallic layer consisting essentially of the zeta phase, an overlay of free zinc, and an average iron content between about 2 and less than 4% by weight.
Claims10
A process for producing an improved galvanized coating on a ferrous strand, which coating is characterized by an iron-zinc intermetallic layer consisting essentially of the zeta phase and a surface layer of free zinc, said process comprising:
- a. cleaning said ferrous strand to remove oxides therefrom,
- b. protecting said ferrous strand against reoxidation by the application of a flux to the oxide free surfaces of said strand,
- c. heating said ferrous strand to a temperature sufficient to dry said flux in situ without burning such flux off the said ferrous strand prior to its immersion in a galvanizing bath,
- d. immersing said heated and oxide free ferrous strand in a molten galvanizing bath containing at least 0.15% aluminum, by weight, balance essentially zinc maintained at a temperature of at least 900.degree. F (482.degree. C) to produce a coating on said ferrous strand of between 0.2 to 0.5 oz. per square foot of strand,
- e. subjecting said ferrous strand having such galvanized coating thereon to a controlled heat treatment at a temperature below the melting point of zinc for a period of time to promote the development of the zeta phase, wherein the average iron content of such galvanized coating is at least 2% but less than 4%, by weight, and
- f. cooling said galvanized coated ferrous strand.
Dependencies are inferred from the claim text.