Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Nippon Steel Pipe Co., Ltd

Michitoshi Tanimoto

Hideki Hamatani

Noboru Hasegawa

Michimasa Mukai

Shinji Kodama

Hitoshi Asahi

Takashi Oosawa

Nobuo Mizuhashi

Takashi Miyakawa

Sunao Takeuchi

Yoshifumi Karube

Tomohiro Nakaji

Manabu Ueda

Provided is a welding monitoring apparatus that monitors a welding state of a V-convergence region in which a strip-shaped metal sheet is converged in a V-shape, when the metal sheet is cylindrically formed while being conveyed, and both side edges of the metal sheet are heated and melted in a manner of being butted each other while being converged in the V-shape, such that an electric resistance welded steel pipe is manufactured. This welding monitoring apparatus includes an image capturing unit that captures images of a region including the V-convergence region in time series; and an image processing unit that extracts a welding point based on the images captured in time series and detects the presence or absence and a position of irregular arcing at the welding point or on an upstream side of the welding point.

Welding monitoring apparatus and welding monitoring method

A welded state monitoring system according to an aspect of the present invention is a welded state monitoring system used for plasma shielded electric resistance welding in which electric resistance welding is performed while irradiating a weld zone of a steel sheet with plasma, and is provided with a plasma irradiation device which irradiates the weld zone with plasma, a first image capturing device which captures an image of the weld zone from above and has an image sensor capable of detecting light having a wavelength of 850 nm or more, a first wavelength region limiting device which limits light incident on the first image capturing device to a wavelength region of 850 nm or more, and an image processing device which subjects the image captured by the first image capturing device to image processing and analyzes the welded state of the weld zone thereby being able to analyze the welded state without being affected by the plasma.

Welded state monitoring system and welded state monitoring method

The present invention provides a method of production of electric resistance welded steel pipe able to stably reduce weld defects due to oxides by firing plasma and furthermore able to reduce plasma jet noise and comprises shaping steel plateinto a tube and electric resistance welding the abutting end facesduring which blowing on at least the abutting end facesin the regionat the welding upstream side from the weld pointwhere the temperature becomes 650&#xb0; C. or more a reducing high temperature (pseudo) laminar plasma obtained by applying voltage to a reducing gas containing Hgas: 2 to 50 vol % to which is added a balance of Ar gas alone or a mixed gas of Ar gas to which Ngas, He gas, or both are added. At that time, it is preferable to make the applied voltage over 120V and the make the plasma blowing conditions satisfy the following formula (1). 

Method of production of electric resistance welded steel pipe and high Si or high Cr electric resistance welded steel pipe

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Tokyo, Japan

Michitoshi Tanimoto