Jfe Steel Corporation

Kawasaki Steel Corporation

Kazuhiko Shiotani

Keniti Amano

Fumimaru Kawabata

Kimihiro Nishimura

Tatsumi Kimura

Akio Ohmori

Toshiyuki Hoshino

Yasuyoshi Yamane

Itaru Samusawa

Italu Samusawa

Yasuyashi Yamane

Yasuto Inohara

A steel material of the disclosure has a chemical composition containing, in mass %: 0.03% to 0.3% C; 0.03% to 1.0% Si; 0.1% to 2.0% Mn; 0.003% to 0.03% P; 0.005% or less S; 0.005% to 0.1% Al; 0.005% to 0.5% Cu; 0.01% to 0.5% Sb; and 0.005% to 0.5% Ni, with a balance being Fe and incidental impurities. Thus, the steel material has excellent alcohol-induced pitting corrosion resistance and alcohol-induced SCC resistance, and can be used for large structures with no need for coating, inhibitor addition, or the like by improving the pitting corrosion resistance and SCC resistance of the steel material itself.

Steel material having excellent alcohol-induced pitting corrosion resistance and alcohol-induced SCC resistance

A stress corrosion crack test method for evaluating the stress corrosion crack susceptibility of a steel material in alcohol. The method includes filling a cell containing a uniaxial tensile test piece of the steel material with an alcohol solution containing carboxylic acid: 0.1 mmol/L or more and less than 40 mmol/L, chloride ions: 0.05 mg/L or more and less than 300 mg/L, and water: 0.1 vol. % or more and less than 5 vol. %. Additionally, the method includes applying a fluctuating stress at a frequency of 2.0&#xd7;10Hz or more and 2.0&#xd7;10Hz or less to the uniaxial tensile test piece in the tensile direction. The maximum stress being equal to or more than the yield strength and less than the tensile strength at a test solution temperature, and the minimum stress being 0% or more and 90% or less of the yield strength.

Stress corrosion crack test method in alcohol environment

A steel material excellent in weathering resistance by defining the chemical ingredients in the steel each to a predetermined range and setting an ingredient parameter formula in accordance with the working circumstance thereby reducing the flow rust and, particularly, forming stable rust with good protective property even in a salty circumstance such as in coast districts is provided. Further, also considering the amount of A type inclusions and B type inclusions according to JIS G 0555, a steel material of excellent earthquake proofness and weathering proofness also including weld heat affect zone is provided.

Method of manufacturing corrosion resistant steel materials

Steel is obtained which comprises by wt %, C: 0.001-0.025%, Si: not more than 0.60%, Mn: 0.10-3.00%, P: 0.005-0.030%, S: not more than 0.01%, Al: not more than 0.10%, Cu: 0.1-1.5%, Ni: 0.1-6.0%, B: 0.0001-0.0050%, and the balance being Fe and inevitable impurities; since the steel contains C and P in small contents, stable amorphous rusts are formed on the surface thereof at an early stage; and steel simultaneously realizes excellent weather resistance, material weldability and toughness particularly in an environment such as a seashore district and the like where salt is present in a large amount.

Weatherable steel material

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.

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Okayama, Japan

Kazuhiko Shiotani