Patent ID: 7236255
Filing Date: 2007-06-26
Classification: B21C,B23K,G01B

Abstract:
1. A measurement method for a bead cutting shape of an electric resistance welded pipe, for measuring the shape following cutting a bead generated on the inner face or outer face of an electric resistance welded pipe at a welding portion, said method comprising: a step for obtaining an optical cutting image, by taking an image of slit light irradiated on said bead portion with image-taking means, from an angle different to the irradiation direction of said slit light; a step for obtaining each of maximum luminance in the pipe axial direction at a given width-direction coordinate on said optical cutting image, and maximum luminance in background texture region outside of the irradiation range of said slit light; a step for performing interior division of the maximum luminance of said pipe axial direction and the maximum luminance of said background texture region by a ratio determined beforehand, and setting the obtained luminance as a threshold value; a step for taking a luminance greater than said threshold value and a weighted mean of pipe axial direction coordinates indicating said luminance as pseudo-cross-sectional direction coordinates for said width-direction coordinates and pipe axial direction coordinates; and a step for calculating the bead cutting shape of said electric resistance welded pipe based on a pseudo-cross-sectional shape obtained by stringing pseudo-cross-sectional direction coordinates in the width direction, and a predetermined conversion expression determined from a geometric positional relation of said light source of said slit light, said image-taking means, and said electric resistance welded pipe.