Nippon Steel Corporation

Takayuki Ohmori

Jun Maki

Nobuyoshi Okada

Masahiro Fuda

Teruaki Izaki

Seijun Higuchi

Kenichi Asakawa

Tetsurou Takeshita

Haruhiko Eguchi

Minoru Fujinaga

Fumio Yamamoto

Yusho Oyama

Katsuhiko Yabe

Masaaki Yamamoto

Masaaki Enjuji

Nobyoshi Okada

Koji Umeno

Yu Ando

The present invention provides a hot-dip Al-plated steel sheet for fuel tanks excellent in air-tightness after welding and corrosion resistance subsequent to forming. The present invention provides, as concrete means, a hot-dip Al-plated steel sheet comprising a steel sheet comprising up to 0.003% of C, up to 0.03% of Si, up to 0.3% of Mn, up to 0.02% of P, up to 0.006% of N, up to 0.1% of Ti, Ti and Nb in a total amount of at least the atomic equivalent of (C&plus;N) and up to 0.2%, 1 to 30 ppm of B, and the balance Fe and unavoidable impurities, and a plating layer comprising 2 to 13% of Si, and the balance Al and unavoidable impurities on the surface of the steel sheet, the steel sheet showing a total elongation of at least 45% after plating. Alternately, the hot-dip Al-plated steel sheet may have a chromate coating in an amount of 5 to 100 mg/m on the surface, and it may also have a resin coating on the top surface. As a result, the Al-plated steel sheet is excellent in elongation after Al plating. The Al-plated steel sheet is, therefore, significantly excellent in corrosion resistance subsequent to forming in the internal environment of fuel tanks compared with conventional steel sheets. Accordingly, the Al-plated steel sheet also having excellent air-tightness after welding is most appropriate as a material for fuel tanks of automobiles.

Rust preventive carbon steel sheet for fuel tank having good welding gastightness and anticorrosion after forming

A coating aluminized steel sheet suitable for fuel tanks, which comprises (a) a steel sheet, (b) an aluminized-plating layer formed on one or both sides of the steel sheet and based on aluminum or an aluminum alloy containing 2-15 wt% silicon, and (c) a coating layer formed on at least one of the aluminizing layers and selected from the group consisting of i) a resin chromate film having a film thickness of 0.1-2 &mgr;m and containing a resin and a chromic acid compound, with the resin/metal chromium weight ratio in the range of 0.5-18, ii) an inorganic-based chromate film with the coating layer formed to 10-200 mg/m in terms of metallic chromium, which comprises 100 parts by weight of a chromic acid compound in terms of metallic chromium and 100-1000 parts by weight of colloidal silica, and further comprises any one or more of 100-600 parts by weight of a phosphoric acid compound, 10-200 parts by weight of a phosphonic acid or phosphonic acid salt compound and less than 50 parts by weight of a resin, and iii) an inorganic-based chromate film with a coating amount of at least 10 mg/m and less than 35 mg/m in terms of metallic chromium. There are provided automobile fuel tanks with excellent durability, forming formability and weldability, and a seam welding process for fuel tanks.

Preservative steel plate having high resistance weldability, corrosion resistance and press formability for automobile fuel tanks

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

A hot-dip aluminium coated steel sheet having excellent corrosion resistance and heat resistance, comprising a steel substrate containing 3 to 18% chromium, not more than 0.02% carbon, 0.1 to 1.5% manganese, 0.005 to 0.08% aluminium, not more than 0.1% silicon, with the balance being iron and unavoidable impurities, and aluminium coating on said sheet substrate. The coated sheet may further comprises a coating layer of nickel or nickel-iron alloy (Ni: 1 to 99%) beneath the aluminium coating, or an Al-Fe-Si-Ni-Cr alloy coating layer of 1 to 10.mu. in thickness and containing 0.05 to 5% nickel, 0.2 to 10% chromium, beneath the aluminium coating.

Hot-dip aluminum coated steel sheet having excellent corrosion

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Kitakyushu, Japan

Takayuki Ohmori