Abstract: A method for monitoring welding of an electric resistance welded steel pipe of the present invention includes: an image acquisition step in which, when an electric resistance welded steel pipe is welded, a V-convergence portion including an edge detection area and a V-convergence point, and a welding portion including a position where a molten steel starts to be discharged from an inside of a wall thickness and a bead, are imaged to obtain a captured image; a determination information acquisition step in which the captured image is image-processed, and a molten length from the V-convergence point to the position where the molten steel starts to be discharged or a molten width of the welding portion or a combination thereof is acquired as a determination information; and a determining step in which it is determined whether a cold welding has occurred by comparing the determination information with a determination threshold value set in advance for each wall thickness of the electric resistance welded steel pip

Abstract: 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.

Abstract: A method for monitoring welding of an electric resistance welded steel pipe of the present invention includes: an image acquisition step in which, when an electric resistance welded steel pipe is welded, a V-convergence portion including an edge detection area and a V-convergence point, and a welding portion including a position where a molten steel starts to be discharged from an inside of a wall thickness and a bead, are imaged to obtain a captured image; a determination information acquisition step in which the captured image is image-processed, and a molten length from the V-convergence point to the position where the molten steel starts to be discharged or a molten width of the welding portion or a combination thereof is acquired as a determination information; and a determining step in which it is determined whether a cold welding has occurred by comparing the determination information with a determination threshold value set in advance for each wall thickness of the electric resistance welded steel pip

Abstract: 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.

Abstract: 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 plate 1 into a tube and electric resistance welding the abutting end faces 4 during which blowing on at least the abutting end faces 4a in the region 6 at the welding upstream side from the weld point 9 where the temperature becomes 650° C. or more a reducing high temperature (pseudo) laminar plasma obtained by applying voltage to a reducing gas containing H2 gas: 2 to 50 vol % to which is added a balance of Ar gas alone or a mixed gas of Ar gas to which N2 gas, 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).

Abstract: The invention provides a system and method for monitoring the molten state of electric-resistance-welded pipe on-line. In the system, a mirror provided at a front end side inside a container receives light emitted by the welded parts of the tube-shaped steel strip through heat resistant glass from the side direction and reflects the image in the direction of a relay lens provided at a base end side of a relay lens unit. The relay lenses relay the image to a conversion lens, which forms the image on the imaging area of a CCD camera. Therefore, it is possible to capture the welded parts from the side direction by a resolution in accordance with the resolution of the CCD camera and possible to obtain information of the welded parts more accurately than in the past and on-line.

Abstract: A system and method for monitoring the molten state for enabling a molten state, butting state, or other state of electric-resistance-welded pipe on-line more accurately than in the past are provided. That is, a mirror 23 provided at a front end side inside a container 21 receives light emitted by the welded parts 5 of the tube-shaped steel strip 1 themselves through heat resistant glass 22 from the side direction and reflects the image of the welded parts 5 of the tube-shaped steel strip 1 in the direction of a relay lens 24 provided at a base end side of a relay lens unit 13. The relay lenses 24 relay the image of the welded parts 5 of the tube-shaped steel strip 1 to a conversion lens 12, then the conversion lens 12 forms that image on the imaging area of a CCD camera 11.

Abstract: 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 plate 1 into a tube and electric resistance welding the abutting end faces 4 during which blowing on at least the abutting end faces 4a in the region 6 at the welding upstream side from the weld point 9 where the temperature becomes 650° C. or more a reducing high temperature (pseudo) laminar plasma obtained by applying voltage to a reducing gas containing H2 gas: 2 to 50 vol % to which is added a balance of Ar gas alone or a mixed gas of Ar gas to which N2 gas, 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).