Kawasaki Steel Corporation

Other

Hisatada Nakakouji

Toshio Ichida

Hajime Ogata

Kazuo Mochizuki

Toshio Irie

Kyoko Hamahara

Kyoko Yamaji

Yasuhiro Akeda

Sachiko Otsuka

A surface-treated steel strip adapted for electric resistance welding is prepared by forming a first layer of iron-nickel alloy on a steel strip, said first layer having a weight ratio of Ni/(Fe+Ni) in the range between 0.02 and 0.50 and a thickness of 10 to 5,000 angstroms, forming a second layer of tin or iron-tin-nickel alloy on said first layer by tin plating to a coating weight of 0.1 to 1 g/m.sup.2 of tin and optionally, causing the tin to reflow, and forming a third layer on said second layer by effecting an electrolytic chromate treatment, said third layer consisting essentially of metallic chromium and hydrated chromium oxide, wherein the electrolytic chromate treatment is carried out in a bath which contains an amount of a chromate compound to give 10 to 100 g/l of CrO.sub.3 and has a weight ratio of H.sub.2 SO.sub.4 /CrO.sub.3 in the range between 3/1000 and 1/100.

Process for preparing surface-treated steel strips adapted for electric

A tin-free steel strip comprising a steel strip, 40 to 150 mg/m.sup.2 of a metallic chromium layer on the steel surface, and 5 to 25 mg/m.sup.2 of a chromium compound containing layer thereon wherein the metallic chromium layer contains a plurality of protrusions, exhibits improved corrosion resistance and weldability and is thus useful in the manufacture of welded cans. Preferably, 1.times.10.sup.11 to 1.times.10.sup.14 protrusions having a diameter of 5 to 1000 nm at the base thereof are present per square meter of the metallic chromium layer surface. The tin-free steel strip is produced by chromium plating a steel strip in an aqueous solution containing CR.sup.6+ preferably to a weight of 40 to 140 mg/m.sup.2, subjecting the chromium plated strip to anodic electrolysis, preferably at an eectricity quantity of 0.1 to 10 C/dm.sup.2, and subjecting the strip to a cathodic treatment in an aqueous solution containing Cr.sup.6+ and a chromium plating aid so as to deposit additional metallic chromium, preferably in a weight of 10 to 60 mg/m.sup.2.

Tin-free steel strips useful in the manufacture of welded cans and

A surface-treated steel strip comprising a steel substrate, islands of metallic tin distributed on one major surface of the steel substrate, and a chromate coating deposited on the substrate major surface to cover the tin islands can be coated with lacquer, baked and then seam welded into food cans.

Surface-treated steel strips seam weldable into cans

Growing community of inventors

Chiba, Japan

Hisatada Nakakouji