Nippon Steel Corporation

Usinor

Yoshihisa Takada

Masayoshi Suehiro

Hidekuni Murakami

Haruhiko Eguchi

Hiroyasu Fujii

Masao Kurosaki

Koki Tanaka

Kazuhiko Honda

Akira Takahashi

Yoichi Ikematsu

Hideaki Sawada

Hisaaki Sato

Shunichi Hayashi

Masayuki Abe

Takehide Senuma

Kunio Nishimura

An exemplary embodiment of an aluminum type plated steel sheet which excels in discoloration resistance, and weldability, which does not decorate after re-heating and which can prevent increasing of strength, and a heat shrink band using the same are provided. For example, the heat shrink band can be made of an aluminum type plated steel sheet consisting of a steel sheet being composed of, e.g., not more than about 0.005 mass % of C; not more than about 0.005 mass % of N; not less than about 0.1 mass % and not more than about 0.5 mass % of Si; not more than about 0.1 mass % of P; not more than about 0.02 mass % of S; not less than about 1.05 mass % and not more than 2.0 mass % of Mn; not more than 1.0 mass % of sol Al; a residual amount of Fe and inevitable impurities, and an aluminum type plated layer mainly consisting of Al being deposited thereon. Such exemplary sheet can be prevented from a discoloration upon, e.g., being re-heated at a temperature of not less than about 500&#xb0; C. to not more than about 700&#xb0; C.

Aluminum type plated steel sheet and heat shrink band using the same

The present invention stably provides a high-strength hot-dip galvanized steel sheet having a high tensile strength and no non-plated portions and being excellent in workability and surface properties even when the employed equipment has only a reduction annealing furnace and a steel sheet containing relatively large amounts of Si, Mn and Al that are regarded as likely to cause non-plated portions is used as the substrate. The present invention: secures good plating performance even when the steel sheet contains Si, Mn and Al by adding Ni to a steel sheet, thus forming oxides at some portions in the steel sheet surface layer, and resultantly suppressing the surface incrassation of Si, Mn and Al at the portions where oxides are not formed; enhances the effect of Ni and accelerates the formation of oxides by further adding Mo, Cu and Sn; and moreover, in the case of a TRIP steel sheet, secures austenite by determining the ranges of Si and Al strictly, avoiding the deterioration of plating performance caused by the addition of Ni, and further adding Mo in a balanced manner. In addition, the present invention, in a TRIP steel sheet, improves press formability by regulating a retained austenite ratio and accelerates the formation of oxides by regulating a hydrogen concentration and a dew point in annealing before plating.

High-strength hot-dip galvanized steel sheet and method for producing the same

The present invention provides an alloyed molten zinc plated steel sheet having an area of the Fe and Zn alloy phase in the unformed parts in the plating layer of less than 10% of the area of the steel sheet as a whole and superior in strength and shapeability and a method of producing this alloyed molten zinc plating steel sheet by a continuous zinc plating production system which enables production at a low cost without modification of the system or addition of steps, said alloyed molten zinc plated steel sheet characterized by comprising a steel sheet including C: 0.05 to 0.40%, Si: 0.2 to 3.0%, and Mn: 0.1 to 2.5%, the balance comprised of Fe and unavoidable impurities, having on its surface a Zn alloy plating layer comprised of Fe in a concentration of 7 to 15 wt %, Al in a concentration of 0.01 to 1 wt %, and the balance of Zn and unavoidable impurities, said plating layer containing oxide particles of at least one type of oxide selected from an Al oxide, Si oxide, Mn oxide, and complex oxides of the same alone or in combination.

Alloyed molten zinc plated steel sheet and process of production of same

A molten zinc plated steel sheet superior in plating bondability and provided with both strength and shapeability is provided and a method of producing this molten zinc plating steel sheet by a continuous zinc plating production system which enables production at a low cost without modification of the system or addition of steps is provided, said molten zinc plated steel sheet characterized by comprising, by wt %, a steel sheet including C: 0.05 to 0.40%, Si: 0.2 to 3.0%, and Mn: 0.1 to 2.5%, the balance comprised of Fe and unavoidable impurities, having on its surface a Zn plating layer containing Al: 0.01 to 1% and the balance of Zn and unavoidable impurities and containing inside the steel sheet within 2 &#x3bc;m from the interface of said plating layer and steel sheet oxide particles of at least one type of oxide selected from an Al oxide, Si oxide, Mn oxide, or complex oxide comprised of at least two of Al, Si, and Mn.

High strength molten zinc plated steel sheet and process of production of same

High-strength hop-dip galvanized steel sheet

Disclosed are a high strength hot-dip galvanized or galvannealed steel sheet, which has improved press formability and plating adhesion and is useful as a member for automobile, building, electric or other members, and a process for producing the same. This high strength hot-dip galvanized or galvannealed steel sheet comprises: (a) a steel sheet substrate comprising, by weight, carbon (C): 0.05 to 0.2%, silicon (Si): 0.2 to 2.0%, manganese (Mn): 0.2 to 2.5%, and aluminum (Al): 0.01 to 1.5%, the silicon and the aluminum having a mutual relationship represented by formula 0.4(%)&#x2266;Si+0.8 Al (%)&#x2266;2.0(%), the steel sheet substrate further comprising at least one member selected from the group consisting of (i) 0.003 to 1.0% of tin (Sn), (ii) 0.005 to 1.0% in total of at least one member selected from antimony (Sb), bismuth (Bi), and selenium (Se), (iii) 0.005 to 1.0% in total of at least one member selected from beryllium (Be), magnesium (Mg), calcium (Ca), and zirconium (Zr), and (iv) 0.005 to 1.0% in total of at least one member selected from scandium (Sc), yttrium (Y), lanthanum (La), and cerium (Ce), with the balance consisting of iron (Fe) and unavoidable impurities, the volume fraction of retained austenite in the steel structure being 2 to 20%; and (b) a zinc (Zn) coating layer provided on said steel sheet substrate.

High strength hot-dip galvanized or galvannealed steel sheet having improved plating adhesion and press formability and process for producing the same

A TRIP-type high strength steel plate having good workability is provided which, while reducing the amount of alloying elements added which increase the production cost, ensures a contemplated retained austenite structure, has good adhesion to zinc plating, and can also be applied to highly corrosion resistant surface treated steel plates. The high strength steel plate having improved workability and plating adhesion is such that a high concentration, i.e., 0.03 to 2.0% by weight, of nitrogen is incorporated, the contents of silicon and aluminum, which form nitride, are preferably regulated respectively to not more than 0.5% by weight and not more than 0.3% by weight, and, in addition, calcium, sodium, magnesium, etc. are optionally added to control the formation of iron nitride, whereby the volume fraction of the retained austenite phase in the metal structure is regulated to 3 to 20% by weight.

High strength steel plate having improved workability and plating adhesion and process for producing the same

The invention relates to a high strength hot-dip galvanized and galvannealed steel sheets with excellent drawability for press forming and excellent plating adhesion that is useful as a member for automobiles, construction, electric devices and the like, and to a process for its manufacture. According to an embodiment of the invention, the steel sheet contains in terms of weight percent, C: 0.05-0.2%, Si: 0.2-2.0%, Mn: 0.2-2.5%, Al: 0.01-1.5%, Ni: 0.2-5.0%, P: <0.03% and S: <0.02%, the relationship between Si and Al being such that 0.4(%)&lE;Si&plus;0.8 Al(%)&lE;2.0% and the remainder consisting of Fe and unavoidable impurities, the volume percentage of the retained austenite is 2-20% and the steel sheet surface wherein the relationship between the Ni and Si, Al in 0.5 &mgr;m of the steel sheet surface layer is such that Ni(%)&lE;&frac14; Si&plus;&frac13;Al(%), has a Zn plating layer comprising Al: &lE;1% with the remainder Zn and unavoidable impurities.

High strength galvanized steel plate excellent in adhesion of plated metal and formability in press working and high strength alloy galvanized steel plate and method for production thereof

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Kitakyushu, Japan

Yoshihisa Takada