Nippon Steel Corporation

Hiroyuki Hasegawa

Kazuo Fujita

Teruyuki Wakatsuki

Takeshi Hioki

Yasushi Horiuchi

Akira Inagaki

Toshihiro Ishibashi

Yasushi Takeshima

Masao Kurokawa

Hiroaki Hadano

Yoshimi Toriyama

Suguru Yoshida

Hirokazu Sugiyama

Hironori Satoh

Kouichi Yamamoto

A 590 MPa-class rolled steel shape of high strength and excellent toughness for use as a building structural member and a method of producing the high-tensile rolled steel shape are provided. Strength optimization by an alloy that elevates hardenability, texture refinement obtained by fine dispersion of Ti oxides and TiN owing to Ti addition, precipitation strengthening by Cu addition, and formation of a fine bainite texture by temperature-controlled rolling, cooling control and the like enable a high-strength, high-toughness rolled steel shape of high-strength and excellent toughness having mechanical properties of a tensile strength of not less than 590 MPa, a yield strength or 0.2% proof strength of not less than 440 MPa and a Charpy impact absorption energy at 0&deg; C. of not less than 47 J, and method of producing the same.

High-strength, high-toughness rolled shape steel and method of producing the same

An apparatus for cooling thin-webbed H-beam steel includes means for forcibly spray cooling the flanges of the H-beam in intermediate and final hot rolling zones. The cooling is based upon tracking information with respect to predetermined positions along the length of the H-beam. A plurality of flow quantity control blocks are disposed in parallel with each having a three way valve having a water supply side port, a nozzle side port, and a water drain port. A plurality of on-off valves connect the nozzle side port to nozzles in a nozzle group to select nozzles based upon the flange width of the H-beam. A variable throttle mechanism maintains pressure loss at the water drain side equal to pressure loss at the nozzle side. Switching of the three way valve of one flow quantity control block can be carried out without affecting other flow quantity control blocks.

Apparatus for cooling thin-webbed H-beam steel

A thin-webbed H-beam steel having a web thinner that flanges is produced by forcibly water cooling the outer surface of the flanges during an intermediate hot rolling prior to a final hot rolling by cooling to less than 700.degree. C., interrupting the cooling to return the temperature to greater than 700.degree. C., and repeating the cooling and interrupting in order to refine the microstructure of the surface of the flanges to a predetermined depth from the surface; final-hot rolling the intermediate-hot rolled H-beam steel; and forcibly water cooling the flanges of the final-hot rolled H-beam steel in a manner such that the web does not wave during this forcible water cooling, and such that upon completion of the forcible water cooling, thermal stress, generated in the web during air cooling to room temperature, does not exceed the buckling strength of the web.

Process for producing thin-webbed H-beam steel

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Sakai, Japan

Hiroyuki Hasegawa