Multiple pass laser beam welding of heavy sections

State of the art of welding with carbon-dioxide laser radiation is to weld steel material up to a wall thickness of 20 mm in one pass utilizing beam powers up to 20 kW. Welding material exceeding 20 mm wall thickness requires the application of multiple pass techniques. Since the process behavior deviates from the conventional deep penetration effect measures due to beam handling and shaping have to be taken into account. Shaping of the unfocused and the focused beam and/or beam oscillation become necessary to reduce penetration depth and interlayer temperature. To avoid disadvantageous tension states inside the seam the influence edge preparation has to be optimized. Filling strategies for narrow and conventional gaps require adopted wire feed and detailed process planning. Multiple pass welds in sheet material with thickness from 25.9 mm in mild steel are performed with a modern beam source with an nominal output power of 20 kW. The effects of processing and technological parameters on the mechanical properties and the metallurgy of the seam are investigated. The results give rise to a wide range of applications of multiple pass welding with laser radiation in industries dealing with materials of high wall thickness.State of the art of welding with carbon-dioxide laser radiation is to weld steel material up to a wall thickness of 20 mm in one pass utilizing beam powers up to 20 kW. Welding material exceeding 20 mm wall thickness requires the application of multiple pass techniques. Since the process behavior deviates from the conventional deep penetration effect measures due to beam handling and shaping have to be taken into account. Shaping of the unfocused and the focused beam and/or beam oscillation become necessary to reduce penetration depth and interlayer temperature. To avoid disadvantageous tension states inside the seam the influence edge preparation has to be optimized. Filling strategies for narrow and conventional gaps require adopted wire feed and detailed process planning. Multiple pass welds in sheet material with thickness from 25.9 mm in mild steel are performed with a modern beam source with an nominal output power of 20 kW. The effects of processing and technological parameters on the mechanical pr...