Comparison of laser welds in thick section S700 high-strength steel manufactured in flat (1G) and horizontal (2G) positions

Lack of penetration, undercut and melt sagging are common welding defects for single-pass laser welds in thick plates, particularly when using a traditional 1G welding position (laser directed towards ground). This investigation shows, for the first time, that welding 13 mm thick high-strength S700 steel plates in the 2G position (laser beam perpendicular to the direction of gravity) can mitigate some of the common welding defects including undercut and sagging. A computational fluid dynamic analysis indicates that the 2G welding position can assist in achieving an appropriate balance between surface tension, hydrostatic pressure (gravity) and recoil-pressure from the metal vapour.