Abstract: The objective of the present invention is to enable accurate detection of a mismatch during electric resistance welding.

Abstract: 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.

Abstract: 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.

Abstract: An electric resistance welding operation management device manages a welding operation during manufacture of electric resistance welded steel pipe, in which heat is input to a steel plate, that is being conveyed along a specific conveyance direction and formed into a circular tube shape while pressing side faces of the metal plate with a pair of squeeze rolls, to weld together two circumferential direction edge portions of the metal plate converging in a V-shape. The electric resistance welding operation management device includes an image input section that inputs plural images and each including a Vee convergence region of the steel plate. The electric resistance welding operation management device includes a welding point position derivation section that derives the position of a welding point.

Abstract: An electric resistance welding operation management device 100 manages a welding operation during manufacture of electric resistance welded steel pipe, in which heat is input to a steel plate 1, that is being conveyed along a specific conveyance direction and formed into a circular tube shape while pressing side faces of the metal plate 1 with a pair of squeeze rolls 2a, 2b, to weld together two circumferential direction edge portions 11a, 11b of the metal plate 1 converging in a V-shape. The electric resistance welding operation management device 100 includes an image input means that inputs plural images, successively captured over 3 sec and each including a Vee convergence region of the steel plate 1.