Determination of Changing Factor for Laser Welding.

Abstract

Penetration depth is difficult to maintain constant in production, since it is affected by many parameters in long term operation. Present study is aiming at developing a method which can predict a welding parameter to decrease the penetration depth. An in-process monitoring system has been developed, which can separate the light emission of the keyhole plasma, PK, from that of the plasma plume, PP, by using two photo sensors set at 5 and 75 degrees with respect to the work surface. The effects of welding parameters including flow rate of Ar assist gas, laser power and focal position have been determined on the penetration depth as well as time-averaged values of PP and PK in CO2 laser welding mild steel. In the analysis in PK-PP coordinate, one cane determine which welding parameter has decreased the penetration depth from the detected change in the emission from the laser-induced plasma.