Steel products having superior weathering, method of producing t

Details Steel products having superior weathering, method of producing t Steel products having superior weathering, method of producing t

1999-01-06

2000-05-30

Willis, Prince

Metal treatment

Process of modifying or maintaining internal physical...

Processes of coating utilizing a reactive composition which...

148284, 148287, 4284722, C23C 880

Patent

active

060687126

ABSTRACT:
The invention provides a steel product having superior weathering which is coated with a rust layer containing 50 or more weight % of non-crystalline rust, a method of producing the steel product, and a method of forming weathering protective rust on a material surface of the steel product. A material of a steel product is placed in an atmosphere in which the dew point is kept constant and the temperature of the steel product material is repeatedly varied between a temperature range of 5.degree. C. or more higher than the dew point and a temperature range of 5.degree. C. or more lower than the dew point. Weathering protective rust is thereby formed on the material surface of the steel product and a steel product having superior weathering is obtained. Preferably, the atmosphere contains 15 to 50 volume % of oxygen gas, and the temperature of the steel product is varied at a rising rate of 0.1 to 2.degree. C./minute and a lowering rate of 0.01 to 2.degree. C./minute. Alternatively, a desired steel product can also be obtained by placing a material of the steel product in an atmosphere containing 15 to 50 volume % of oxygen gas, keeping constant the dew point in the atmosphere, and keeping the temperature of the steel product material in the atmosphere at a certain value in a temperature range between a temperature 5.degree. C. lower than the dew point and a temperature 20.degree. C. lower than the dew point; or by placing a material of the steel product in an atmosphere containing 15 to 50 volume % of oxygen gas, and forming and keeping a water film with a thickness not more than 500 .mu.m but not less than 50 .mu.m on a material surface of the steel product.

REFERENCES:
patent: 3877977 (1975-04-01), Watanabe et al.
patent: 4094670 (1978-06-01), Bruno et al.
patent: 4448612 (1984-05-01), Ebert et al.
patent: 5407492 (1995-04-01), Ohmi et al.
ASM Handbook, Formerly Ninth Edition, Metals Handbook, vol. 13, Corrosio, pp. 516-521 and 1305-1306, Sep. 1987.

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