Nkk Corporation

Nippon Kokan Kabushiki Kaisha

Toshihiro Takamura

Yoshiichi Ishizawa

Takemi Yamada

Motoaki Oyama

Tetsuya Sampei

Toshimichi Ohmori

Tatsuo Maeda

Yukio Nishino

Yuji Sugimoto

Mitoshi Morimoto

Fumihiro Nishimura

Takayuki Ohdake

Tetsuro Sugayoshi

Itaru Watanabe

Jinkichi Tanaka

Motoaki Suzuki

Fusao Koshiga

Yutaka Nagahama

Takayuki Odake

Koji Akiyama

Kozo Teraoka

Takero Arima

Akiyoshi Matsushita

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

This invention is of a Cr--Mo steel pipe of a wall thickness of 13 mm or less, containing C: 0.03-0.10 wt %, Si: 0.50-1.00 wt %, Mn: 0.30-0.60 wt %, P.ltoreq.0.007 wt %, S.ltoreq.0.020 wt %, Cr: 1.00-1.50 wt %, Mo: 0.45-0.65 wt %, Al: 0.002-0.010 wt % and N: 0.002-0.010 wt % and the remainder consisting of Fe and unavoidable impurities for which preheating and postheating treatments for the prevention of weld cracking and stress corrosion cracking can be effectively omitted, said steel pipe of this invention being suitable for steam piping applications such as STPA23 used in power generation plants, etc.

Method for TIG welding 1.25 Cr-0.5Mo steel pipe for which preheating and

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

A Cr-Mo steel pipe having a wall thickness of 5 to 25 mm consisting essentially of 0.03 to 0.10 wt. % C, 0.5 to 1.0 wt. % Si, 0.3 to 0.6 wt. % Mn, 0.02 wt. % or less P, 0.007 wt. % or less S, 1.0 to 1.5 wt. % Cr, 0.45 to 0.65 wt. % Mo, 0.002 to 0.1 wt. % Al, 0.002 to 0.01 wt. % N, and the balance being Fe and unavoidable impurities. In the method of welding the Cr-Mo steel pipe, the Cr-Mo steel pipe is welded by shielded metal arc welding without a preheat treatment and/or a post weld heat treatment.

Cr-Mo steel pipe and welding method thereof

It is an object to provide a vibration-damping alloy which has a high power of damping vibration and can be used to make components of a structure, machine, etc. and reduce effectively any vibration thereof and the noise thereby produced. The vibration-damping alloy of this invention contains those proportions of Al and Si which fall within the range defined by a series of points in any of FIGS. 1 to 6, and less than 0.1 wt. % Mn, the balance of its composition being Fe and unavoidable impurities. It preferably contains more than 0.5 wt. % Si, while not containing more than 0.01 wt. % of any of C, N, O, P and S.

Vibration-damping alloy

Vibration-damping alloy of 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.

In longitudinally seam-welding a pipe-blank for welded steel pipe from the inside along a groove by the metal arc welding process which comprises using direct electric current supplied to a plurality of consumable electrodes in tandem through at least one current supply cable as the welding current, an even number of consumable electrodes are used; half of said even-numbered consumable electrodes are connected in the reverse-polarity manner, i.e., to be positive in polarity, and are used as leading electrodes, and the remaining half are connected in the straight-polarity manner, i.e., to be negative in polarity, and are used as trailing electrodes; the GMA welding process is applied on the side of said reverse-polarity consumable electrodes which are the leading electrodes; and the submerged-arc welding process is applied on the side of said straight-polarity consumable electrodes which are the trailing electrodes; thereby preventing magnetization of said pipe-blank and the resulting magnetic arc blow of the welding arc by causing lines of magnetic force produced by said direct electric currents for welding flowing through said current supply cables introduced into said pipe-blank to cancel each other, and also preventing spattering of molten droplets from said straight-polarity consumable electrodes.

Method for longitudinally seam-welding pipe-bland for welded steel pipe

Growing community of inventors

Kawasaki, Japan

Toshihiro Takamura