This video shows welding defect slag inclusion as it is happening in a CMT (Cold Metal Transfer) process. You can see in the footage how the slag inclusion (circled) floats around the meltpool. As the weld would cool down, the slag inclusion would solidify causing irregularities on the surface of the weld seam that will lower the strength and overall quality of the weld.
TWI Global describes slags as “the residue of the flux coating in MMA welding, it is principally a deoxidation product from the reaction between the flux, air and surface oxide. The slag becomes trapped in the weld when two adjacent weld beads are deposited with inadequate overlap and a void is formed. When the next layer is deposited, the entrapped slag is not melted out. Slag may also become entrapped in cavities in multi-pass welds through excessive undercut in the weld toe or the uneven surface profile of the preceding weld runs”. (www.twi-global.com)
While there could be a variety of reasons behind slag inclusions, in this case the defect was caused by too much silicone in the process, and to avoid this defect, a filler wire with less silicone should be used.
The footage was captured using a high-speed camera at 7.000 frames per second and our CAVILUX laser illumination as the light source.
Video was taken in cooperation with the Laser Application Laboratory (LAL) of Tampere University, Finland.
Read more about how to utilize laser illumination in imaging bright processes such as welding:
“Common Welding Methods and the Use of Laser Illumination in Welding Imaging”.
Read more about CAVILUX lasers.