EDDY CURRENT FLAW DETECTING DEVICE OF ELECTROSEAMED STEEL PIPE, EDDY CURRENT FLAW DETECTING METHOD OF ELECTROSEAMED STEEL PIPE, AND ELECTROSEAMED STEEL PIPE

To provide an eddy current flaw detecting device and the like that can provide stable defect detection performance even when a pipe-making speed changes in a pipe-making step of an electroseamed steel pipe.SOLUTION: An eddy current flaw detecting device 100 includes: a differential type detection coil 1 that outputs a flaw detection signal obtained by detecting an eddy current induced in an electroseamed steel pipe P; and a flaw detector 2 to which the flaw detection signal is input. The flaw detector includes: a cut-off frequency variable type high-pass filter to which the flaw detection signal is input; and cut-off frequency setting means 26 to which a pipe-making speed of the electroseamed steel pipe is input and which sets the cut-off frequency of the high-pass filter according to the pipe-making speed. The cut-off frequency setting means sets a cut-off frequency F on the basis of the following formula (1) when the cut-off frequency of the high-pass filter is F, the pipe-making speed of the electroseamed steel pipe is V, a length of the detection coil is L, and a prescribed coefficient of 0.1≤K≤0.4 is K. F=K×V/L...(1).SELECTED DRAWING: Figure 2 【課題】電縫鋼管の造管工程において、造管速度が変化する場合であっても安定した欠陥検出能を得ることができる渦流探傷装置等を提供する。【解決手段】渦流探傷装置１００は、電縫鋼管Ｐに誘起された渦電流を検出することで得られる探傷信号を出力する差動型の検出コイル１と、探傷信号が入力される探傷器２と、を備える。探傷器は、探傷信号が入力されるカットオフ周波数可変型のハイパスフィルタと、電縫鋼管の造管速度が入力され、造管速度に応じたハイパスフィルタのカットオフ周波数を設定するカットオフ周波数設定手段２６と、を具備する。カットオフ周波数設定手段は、ハイパスフィルタのカットオフ周波数をＦ、電縫鋼管の造管速度をＶ、検出コイルの長さをＬ、０．１≦Ｋ≦０．４の所定の係数をＫとしたときに、以下の式（１）に基づいて、カットオフ周波数Ｆを設定する。Ｆ＝Ｋ・Ｖ／Ｌ ・・・（１）【選択図】 図２