Experimental study of weld position detection based on keyhole infrared image during high power fiber laser welding

Keyhole is one of the important phenomena in high-power laser welding process.By studying the keyhole characteristic and detecting the seam offset during high-power fiber laser welding,an infrared sensitive high-speed camera arranged off-axis orientation of laser beam was applied to capture the dynamic thermal images of a molten pool.The 304 austenitic stainless steel plate butt joint welding experiment with laser power 10 kW was carried out.Through analyzing the keyhole infrared image,the weld position was calculated.Least squares method was used to determine the actual weld position.Image filtering technique was used to process the keyhole image,and the keyhole centroid coordinate were calculated.Also,least squares method was used to fit the keyhole centroid curve equation and establish a nonlinear continuous model which described the deviation between keyhole centroid and weld seam.The heat accumulation effect affected by the infrared radiation was analyzed to determine whether the laser beam focus spot deviated from the desired welding seam.Experimental results showed that the keyhole centroid has related to the seam offset,and can reflect the welding quality.