Welding Seam Turbulent Tracking Technique for Spiral Welded Pipe Ultrasonic Flaw Detection

Abstract

In the process of spiral submerged-arc welding automatic flaw detection, the weld edge reflection echo is very close to the back edge of the detection gate (generally around 3Ls, is equal to steel transversal wave approximately 4.5mm); therefore once the detector approaches the welding seam, the edge refection echo will enter in the gate, which causes the false alarming. In the past, the mechanical cam tracking, approaching switches tracking and photograph tracking methods were applied, but the mechanical cam tracking and the approaching switches tracking method have low precision, the result is not good. Although photograph tracking method has high measure precision, because of the light scattering of the water flow on the surface of the steel pipe, which will affect the precision. Both photograph tracking and stepping motor-driven methods is commonly used national wide, the effect is not good. Base on the above situation, the electromagnetic welding seam tracking and servo control electromechanical system with functions of electromagnetic tracking and servo control is developed.