Fabrication and evaluation of electromagnetic defect detector for laser welding joint on stainless steel pipe

Inline total inspection of the laser welding joint of ultra-fine suction stainless steel pipes for medical apparatus is very important. An electromagnetic defect detector for laser welding joint on stainless steel pipe was proposed. The electromagnetic defect detector consists of a figure-eight detection coil and an exciting coil. The stainless steel pipe with laser welding joint (i.e. “acceptance”) is fixed in a coil of the figure-eight coil. And the pipes of inspection target are passed through another coil. When the “acceptance” is passed through the coil, the output voltage e₈ in the figure-eight coil equals zero. It is judged as an acceptance certainly. On the other hand, when a stainless steel pipe excluding the welding joint or the pipe with a defect (i.e. “reject”) are passed through the Coil 2, e₈ ≠ 0 is obtained. The authors fabricated and evaluated the electromagnetic defect detector. The detector was able to determine the acceptance of the reject at the laser welding joints on stainless steel pipe.