Jfe Steel Corporation

Tokyo Institute of Technology

Shinji Ootsuka

Hiroyuki Masuoka

Hideyuki Takahashi

Masahiro Yoshida

Tatsuya Miyoshi

Katsuya Hoshino

Hiroki Nakamaru

Masayasu Nagoshi

Seiji Nakajima

Naoto Yoshimi

Hiroshi Kajiyama

Yoichi Makimizu

Kyoko Fujimoto

Wataru Tanimoto

Masahiko Tada

Sakae Fujita

Junichiro Hirasawa

Takayoshi Yano

Takashi Kawano

Masaaki Yamashita

Shin Ishikawa

Chikara Kami

Masaki Tada

Satoru Ando

Yoshiharu Sugimoto

Shoichiro Taira

Hideki Nagano

Etsuo Hamada

Toshihiko Ooi

Tooru Tsuru

Stainless steel sheets including a Ni and O-containing coating on the surface that has excellent weld penetration characteristics and excellent crevice corrosion resistance, and a method for producing such stainless steel sheets. A stainless steel sheet includes a Ni and O-containing coating on a surface of the stainless steel sheet. The Ni and O-containing coating has a coating weight of greater than or equal to 0.1 g/mand less than or equal to 20 g/m. The Ni and O-containing coating has a composition including, in at. %, Ni: greater than or equal to 25% and less than or equal to 60%, and O: greater than or equal to 40% and less than or equal to 70%.

Stainless steel sheet including Ni and O-containing coating on surface and method for producing stainless steel sheet

A method is provided for producing a hot-pressed member including heating a Ni-based coated steel sheet, which includes, on a surface thereof, a Zn&#x2014;Ni alloy coating layer containing 13% by mass or more of Ni, in a temperature region of an Ac3 transformation point to 1200&#xb0; C.; and then hot-pressing the steel sheet.

Method for producing hot-pressed member

A hot-pressed member includes a steel sheet, a Ni-diffusion region present in a surface layer of the steel sheet, and an intermetallic compound layer and a ZnO layer which are provided in order on the Ni-diffusion region, the intermetallic compound layer corresponding to a &#x3b3; phase present in a phase equilibrium diagram of a Zn&#x2014;Ni alloy, wherein a spontaneous immersion potential indicated in a 0.5 M NaCl aqueous air-saturated solution at 25&#xb0; C.&#xb1;5&#xb0; C. is &#x2212;600 to &#x2212;360 mV based on a standard hydrogen electrode.

Hot-pressed member

A method for producing a hot-pressed member includes heating a coated steel sheet, which includes, on a surface thereof, a Zn&#x2014;Ni alloy coating layer containing 10% by mass or more and less than 13% by mass of Ni at a coating weight of over 50 g/mper side of the steel sheet, in a temperature region of an Actransformation point to 1200&#xb0; C. at an average heating rate of 12&#xb0; C./second or more, and then hot-pressing the steel sheet.

In order to obtain a cold rolled steel sheet having excellent press formability, a cold rolled steel sheet has, on a surface thereof, an organic-inorganic composite film containing: an organic resin; and a crystalline layered material. The organic-inorganic composite film has an average film thickness of 0.10 to 2.0 &#x3bc;m and contains 0.5 part or more by weight of the crystalline layered material as a solid with respect to 100 parts by weight of a solid of the organic resin. The crystalline layered material preferably is, for example, a layered double hydroxide represented by [MM(OH)][A].zHO, where: Mis one or more of Mg, Ca, Fe, Ni, and Zn; Mis one or more of Al, Fe, and Cr; and Ais one or more of OH, CO, Cl, and (SO).

Cold rolled steel sheet

A zinc-based metal plated steel sheet is excellent in tribological properties during press forming. An oxide layer containing crystalline 3Zn(OH)&#xb7;ZnSO&#xb7;xHO is formed on a plated surface. The oxide layer has a thickness of 10 nm or more. The crystalline oxide layer is composed of 3Zn(OH)&#xb7;ZnSO&#xb7;3-5HO.

Zinc-based metal plated steel sheet

In order to obtain a cold rolled steel sheet having excellent press formability, a cold rolled steel sheet has an inorganic film containing a crystalline layered material having an average film thickness of 10 nm to 2000 nm on a surface thereof. The crystalline layered material preferably is, for example, a layered double hydroxide represented by [MM(OH)][A].zHO, where: Mis one or more of Mg, Ca, Fe, Ni, and Zn; Mis one or more of Al, Fe, and Cr; and Ais one or more of OH, CO, Cl, and (SO).

A method for manufacturing high-Si cold rolled steel sheets includes heating a cold rolled steel sheet with a direct flame burner (A) having an air ratio of not more than 0.89 when the temperature of the cold rolled steel sheet that is being increased is in the temperature range of not less than 300&#xb0; C. and less than Ta&#xb0; C., subsequently heating the cold rolled steel sheet with a direct flame burner (B) having an air ratio of not less than 0.95 when the temperature of the cold rolled steel sheet is in the temperature range of not less than Ta&#xb0; C. and less than Tb&#xb0; C., and subsequently soak-annealing the cold rolled steel sheet in a furnace having an atmospheric gas composition which has a dew point of not more than &#x2212;25&#xb0; C. and contains 1 to 10 volume % of Hand the balance of N.

Method for manufacturing high-Si cold rolled steel sheet having excellent chemical conversion properties

A zinc-based metal plated steel sheet is excellent in tribological properties during press forming. An oxide layer containing crystalline 3Zn(OH).ZnSO.xHO is formed on a plated surface. The oxide layer has a thickness of 10 nm or more. The crystalline oxide layer is composed of 3Zn(OH).ZnSO.3-5HO.

A hot-dip galvanized steel sheet includes a plating layer substantially composed of the &#x3b7; phase and an oxide layer disposed on a surface of the plating layer. The oxide layer has an average thickness of 10 nm or more and includes a Zn-based oxide layer and an Al-based oxide layer. A method for producing the hot-dip galvanized steel sheet includes a hot-dip galvanization step, a temper rolling step, and an oxidation step.

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Tokyo, Japan

Shinji Ootsuka