Nippon Steel Corporation

Takashi Horita

Shinichi Suzuki

Kazumasa Yamazaki

Matsuo Ataka

Itaru Aoki

Yaichiro Mizuyama

Takehisa Nagao

A zinc- or zinc alloy-coated steel sheet having an excellent spot-weldability, comprising: a base steel sheet; one or more layers coated on the steel sheet, at least one of the coated layers containing zinc as a major component; and an oxidized layer formed on the outermost of the coated layers and containing zinc in an amount of from 0.03 to 3.0 g/m.sup.2, the oxidized layer containing at least one of zinc oxide and zinc hydroxide.

Process for producing a zinc or zinc alloy coated steel sheet having

In a method for roll forming a flat metal strip through a roll forming machine into a round tubular product while the metal strip is being lengthwise fed therethrough, an improved method wherein regions of a specified width extending inward from the edges of said strip are imparted with substantially zero curvature. The tube forming method prevents decrease in the wall thicknesses at the edges when used in the manufacture of a thick walled electric welded pipe, and prevents the occurrence of edge buckling and springback when used in the manufacture of thick walled pipe so that in either case a proper and satisfactory butt junction for subsequent welding can be obtained.

Method for forming electric welded pipe

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Tokai, Japan

Takashi Horita