Nippon Steel Corporation

Mitsubishi Jukogyo Kabushiki Kaisha

Hidesato Mabuchi

Riki Okamoto

Manabu Takahashi

Akihiro Uenishi

Yukihisa Kuriyama

Osamu Kawano

Yasuharu Sakuma

Yuzo Takahashi

Junichi Wakita

Yukio Tomita

Akira Usami

Koji Tanabe

Yoshikazu Yamada

Katsumi Kurebayashi

Naoki Saito

Hiroshi Kondo

Ryuichiro Ebara

Katsutoshi Hashima

Masuo Matsumoto

Syuji Aihara

Kazuhide Yamauchi

The object of the present invention is to provide high-strength steel sheets exhibiting high impact energy absorption properties, as steel sheets to be used for shaping and working into such parts to front side members which absorb impact energy upon collision, as well as a method for their production. The high-strength steel sheets of the invention which exhibit high impact energy absorption properties are press formable high-strength steel sheets with high flow stress during dynamic deformation characterized in that the microstructure of the steel sheets in their final form is a composite microstructure of a mixture of ferrite and/or bainite, either of which is the dominant phase, and a third phase including retained austenite at a volume fraction between 3% and 50%, wherein the difference between the static tensile strength as when deformed in a strain rate range of 5&times;10 &tilde;5&times;10 (l/s) after pre-deformation at an equivalent strain of greater than 0% and less than or equal to 10%, and the dynamic tensile strength &sgr;d when deformed at a strain rate of 5&times;10 &tilde;5&times;10 (l/sec) after the pre-deformation, i.e. &sgr;d&minus;&sgr;s, is at least 60 MPa, and the work hardening coefficient between 5% and 10% of a strain is at least 0.130.

High-strength steel sheet highly resistant to dynamic deformation and excellent in workability and process for the production thereof

The object of the present invention is to provide high-strength steel sheets exhibiting high impact energy absorption properties, as steel materials, to be used for shaping and working into such parts as front side members of automobiles which absorb impact energy upon collision, as well as a method for their production. The high-strength steel sheets of the invention which exhibit high impact energy absorption properties are high-strength steel sheets with high flow stress during dynamic deformation characterized in that the microstructure of the steel sheets in their final form is a composite microstructure of a mixture of ferrite and/or bainite, either of which is the dominant phase, and a third phase including retained austenite at a volume fraction between 3% and 50%, wherein the average value &sgr;dyn (MPa) of the flow stress in the range of 3&tilde;10% of equivalent strain when deformed in a strain rate range of 5&times;10,&tilde;5&times;10,(1/sec) after pre-deformation of greater than 0% and less than or equal to 10% of equivalent strain, satisfies the inequality: &sgr;dyn&gE;0.766&times;TS&plus;250 as expressed in terms of the maximum stress TS (MPa) in the static tensile test as measured in a strain rate range of 5&times;10,&tilde;5&times;10,(1/s) without deformation, and the work hardening coefficient between 1% and 5% of a strain is at least 0.080.

High-strength steel plate having high dynamic deformation resistance and method of manufacturing the same

Welded joint of high fatigue strength

The present invention has an object to provide a steel for a chimney or a gas duct, which is excellent in pitting resistance and rust adhesion in a corrosive environment caused by combustion waste gas in a plant in which the combustion of natural gas occurs. Pitting resistance and rust adhesion are remarkably improved in the steel of the present invention which steel is prepared by using a 5% Cr steel as the base, while reducing an impurity sulfur to not more than 0.010 wt. %, adding titanium within a range of 0.005 to 0.05 wt. %, and further adding nickel alone within a range of 1.0 to 2.5 wt. %, or adding molybdenum alone within a range of 0.10 to 1.0 wt. %, or adding in combination therewith trace amount of copper or molybdenum within a range of 0.10 to 1.0 wt. %.

Steel for chimney or gas duct, excellent in pitting resistance and rust

Growing community of inventors

Oita, Japan

Hidesato Mabuchi