Characteristics of Plasma Emission Signals in Fiber Laser Welding for API Steel (I) -Variation of Signals by Measuring Conditions-

API강재의 화이버레이저 용접시 유기하는 플라즈마의 방사특성 (I) -측정조건에 따른 광신호의 변화-

Fiber laser is a heat source which is introduced recently, and so has a little researched data compare with conventional laser processing. Moreover basic data for welding monitoring are also insufficient. Therefore, in this study, the change of signal with measuring position and angle of plasma emission signals were analysed as a basic experiment for real time monitoring in fiber laser welding. As a result, the signals measured from the side, front and rear had the biggest intensity at $60^{\circ}$, and frequency peak to reflect the behavior of keyhole and swing of plasma by shield gas was detected at $45{\sim}60^{\circ}$. However, both intensity of signal and the result of FFT for monitoring were satisfied at the angle of $45^{\circ}$ from the side.