Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Haruhiko Eguchi

Kazuhisa Kusumi

Yoshihisa Takada

Kengo Takeda

Hiroyasu Fujii

Masao Kurosaki

Hidekuni Murakami

Masayoshi Suehiro

Hisaaki Sato

Jun Hirowatari

Shintarou Fujii

Masayuki Abe

Takashi Aramaki

Jun Maki

Takashi Morohoshi

Hideaki Irikawa

Katsuhiro Fuchigami

Nobuyoshi Okada

Takayuki Ohmori

Kunio Nishimura

Yusho Oyama

Yu Ando

Masaaki Yamamoto

Masaaki Enjuji

Takahisa Honda

There is provided a hot-stamped member or a steel sheet for hot stamping having a chemical composition including, in mass %, C: 0.25% or more and 0.55% or less, Si: 0.001% or more and 2.0% or less, Mn: 0.3% or more and 3.0% or less, P: 0.02% or less, S: 0.003% or less, Al: 0.005% or more and 1.0% or less, Cr: 0% or more and 1.0% or less, Mo: 0% or more and 1.0% or less, N: 0.02% or less, Ca: 0% or more and 0.0010% or less, B: 0.0005% or more and 0.01% or less, one or two or more selected from the group consisting of Ti: 0.005% or more and 0.5% or less, Nb: 0.005% or more and 0.5% or less, V: 0.005% or more and 0.5% or less, and Zr: 0.005% or more and 0.5% or less, and Ni+Cu+Sn: 0% or more and 2% or less, and a remainder consisting of Fe and impurities.

Hot-stamped member and steel sheet for hot stamping

A high strength hot dipped galvanized steel sheet is provided. By controlling the amount of addition of Ti instead of the addition of Nb or B, it is possible to obtain an effect of retarding recrystallization and grain growth even if annealing by a continuous annealing process in a temperature range of the general annealing temperature of 720&#xb0; C. to a temperature of the lower of 800&#xb0; C. or Ac3 temperature. By controlling the rolling and heat treatment conditions, it is possible to control the ferrite phase rate, grain size of the low temperature transformed phases, ratio of average values of the nano hardnesses of the ferrite phase and low temperature transformed phases, and fluctuations of hardnesses of the low temperature transformed phases in a composite structure steel of ferrite and low temperature transformed phases and obtain a high strength hot dipped galvanized steel sheet.

High strength, hot dipped galvanized steel sheet excellent in shapeability and method of production of same

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

High-strength hop-dip galvanized steel sheet

A hot-dipped aluminum coated steel sheet including, on the surface thereof, a coating layer consisting of 2 to 15 wt % of Si, not greater than 1.2 wt % of Fe, 0.005 to 0.6 wt % of Mn, 0.002 to 0.05 wt % of Cr and the balance of Al and unavoidable impurities, and an alloy layer disposed between the coating layer and the steel sheet, having a thickness of not greater than 7 .mu.m and having a mean composition consisting of 20 to 50 wt % of Fe, 3 to 20 wt % of Si, 0.1 to 10 wt % of Mn, 0.05 to 1.0 wt % of Cr and the balance substantially consisting of Al. This steel sheet can be produced by conducting coating in a coating bath consisting of 3 to 15 wt % of Si, 0.5 to 3.5 wt % of Fe, 0.05 to 1.5 wt % of Mn, 0.01 to 0.2 wt % of Cr and the balance substantially consisting of Al, or by adjusting the sum of the concentrations of Zn and Sn in the impurities in the coating layer to not greater than 1 wt %.

Hot-dipped aluminum coated steel sheet having excellent corrosion

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Kitakyushu, Japan

Haruhiko Eguchi