Keyhole shapes during laser welding of thin metal sheets

摘要: Camera observations of the full penetration keyhole laser welding process show that shape is elongated under certain conditions. Under these unfavourable circumstances, susceptible to holes in weld bead. Existing models pressure balance at wall cannot explain this elongation. In paper a new model presented, accounting for doubly curved wall. model, surface tension has one term tends close and another tries open it. Model calculations when diameter same order as sheet thickness, latter part can become dominant, causing elongate. Experiments on thin aluminium (AA5182) mild steel (DC04) sheets verify calculations. As radius depends focused spot, it was found both materials ratio spot thickness must be above critical value prevent These radii are 0.25 AA5182 0.4 DC04, respectively. Furthermore, differences appearance bead between circular welds could explained by model.