| 摘要 |
PURPOSE:To obviate weld defects in the stage of producing an electric welded steel pipe with a high frequency method by estimating the rising angle of metal flow, comparing the same with the reference value of the preset rising angle and upsetting the work adequately. CONSTITUTION:In the stage of producing an electric welded steel pipe by welding of a steel plate by high frequency induction heating, the output of an image sensor camera 3, a thickness value and a pipe forming speed value are inputted to an arithmetic circuit 7 in the state wherein the weld heat input prior to upsetting, that is, the rate of melting of welding edges is kept constant. The melting width 9 of the edges, HAZ width 10 and pipe forming speed 2 obtained are inputted to an arithmetic circuit 12. Further, the bead width or bead height after the upsetting is measured with an another image sensor camera 11, and its value is inputted to the circuit 12 which operates the rising angle of metal flow during pipe forming. The operated angle is compared with a reference rising angle 14 of metal flow having beforehand been set in a comparator 13 and the result thereof is inputted to a changing circuit 15 for the rate of upsetting, by which the rate of upsetting is controlled, and welding defects such as cold wells and penetrators are obviated. |
