Sumitomo Metal Industries, Inc.

Mitsubishi Jukogyo Kabushiki Kaisha

Toshio Nakamori

Kenichi Yanagi

Toshio Taguchi

Yoshio Shimozato

Atsuyoshi Shibuya

Hirohisa Seto

Junichi Uchida

Yuuji Furuzawa

Hajime Shimasaki

Masahiko Hori

Yukio Kanda

Junkichi Yoneda

Yoshiaki Nakazawa

Masashi Yamamoto

Tamotsu Toki

Keiji Miki

Mutsuo Sagara

Katsufumi Hidaka

Hirohito Masumoto

Katsufuma Hidaka

Hirotaka Nakabayashi

Yasuyuki Tanno

Hirotaka Nakabayhashi

Hiroo Maeda

Galvannealed steel sheet and manufacturing method thereof

A batchwise hot dip plating method is performed by dipping a metallic material in a molten metal plating bath, following fluxing by dipping the metallic material in a bath of a fused salt flux (e.g., a mixture of cryolite and one or more alkali metal chlorides and optionally aluminum fluoride) having a melting temperature at least 5.degree. C. higher than the temperature of the molten metal plating bath, which also serves to preheat the metallic material. In the case of hot dip plating with an Al--Zn alloy, particularly a Zn/55% Al/0.5-2% Si alloy, a bare spot-free plated coating having good appearance can be formed by a reduced duration of dipping in the plating bath without post-plating treatment to remove flux residues. The use of a plating tank having a cross section of a round shape such as a semicircular shape or an oblong semielliptic shape, rather than a rectangular box shape, brings about a significantly extended service life of the plating tank.

Hot dip plating method and apparatus

A galvannealed steel sheet suited for use in automobiles, and a manufacturing method thereof. The steel sheet has tensile strength of 340 MPa or higher and paint bake hardenability of 10 MPa or higher, and excellent resistance to powdering when press formed, and excellent resistance to chipping in cold regions. The base metal of the galvannealed steel sheet consists essentially of C: 0.004-0.008%, Si: 2.5.times.P (%)-0.20%, Mn: 0.10-0.40%, P: 0.017-0.045%, sol. Al: 0.003-0.08%, Ti: 0.002-0.015%, Nb: 0.010-0.030 %, wherein Ti (%)+Nb (%): 0.012-0.035%. A steel sheet of the chemical composition described above is hot-dip galvanized, heated up to a Fe--Zn alloying temperature at a heating velocity of 20.degree. C./sec or higher, and upon completion of the Fe--Zn alloying process, cooled down from the Fe--Zn alloying temperature at a cooling velocity of 10.degree. C./sec or higher.

A method and apparatus for molten salt electroplating a steel member are disclosed, in which the surface of the steel member is activated by anodic treatment and the molten salt electroplating is performed on the activated surface of said steel member.

Method for molten salt electroplating of steel

Method and apparatus for molten salt electroplating of steel

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Ashiya, Japan

Toshio Nakamori