Nkk Corporation

Yoshiichi Ishizawa

Toshihiro Takamura

Mitoshi Morimoto

Fumihiro Nishimura

Tetsuro Sugayoshi

Tatsuo Maeda

Yuji Sugimoto

Yusuke Minami

Shuji Hashizume

Yutaka Nagahama

Takayuki Odake

A method for manufacturing a laser-welded steel pipe, comprising: (a) providing a hot-rolled steel sheet consisting essentially of 0.005 to 0.2 wt. % C, 0.1 to 0.35 wt. % Si, 0.5 to 2 wt. % Mn, 0.01 wt. % or less P, 0.003 wt. % or less S, 0.001 to 0.1 wt. % Nb, 0.001 to 0.006 wt. % Ca and the balance being Fe; (b) continuously forming an open pipe by passing the hot-rolled steel sheet through multi-stage forming rolls, the open pipe having opposed edge faces which confront each other; (c) heating the opposed edge faces of the open pipe by electric resistance heating; and (d) pressure-welding the heated opposed edge faces together by projecting a laser beam in a substantially vertical direction onto an edge joining point of the opposed edge faces and squeezing the opposed edge faces together by passing the open pipe through opposing rolls, to control an upset, the upset being a difference between a coil width (mm) of the open pipe and a circumferential length of the pipe formed after welding (mm).

Method of making a steel pipe by electric resistance heating of opposing

A high strength martensitic stainless steel contains:

High-strength martensitic stainless steel and method for making the same

An electric-resistance-welded steel pipe with high strength consists essentially of 0.05 to 0.30 wt. % C, 0.6 to 2.0 wt. % Mn, 0.03 to 0.70 wt. % Si, and 0.01 to 0.05 wt. % Nb. The balance is Fe and inevitable impurities, the steel pipe having a martensitic phase ratio of 60 to 100% and having a tensile strength of 120 to 170 kgf/mm.sup.2.

Electric-resistance-welded steel pipe with high strength

An electric-resistance-welded steel pipe with high strength. The pipe consists essentially of (a) 0.05 to 0.30 wt. % C, (b) 0.6 to 2.0 wt. % Mn, (c) 0.03 to 0.70 wt. % Si, (d) (i) 0.5 wt. % or less Mo by itself or (ii) 0.5 wt. % or less Mo with 1.2 wt. % or less Cr or (iii) 0.5 wt. % or less Mo with 0.1 wt. % or less V or (iv) 0.1 wt. % or less V and (e) the balance being Fe and inevitable impurities. The steel pipe has a martensitic phase in an amount of 60 to 100% and has a tensile strength of 120 to 170 kgf/mm.sup.2. The steel pipe is useful as an impact bar for the inside of an automobile door.

Growing community of inventors

Kawasaki, Japan

Yoshiichi Ishizawa