Operational windows for C.W. Nd:YAG laser welding of thin sheets of copper and alloys without filler material

Abstract

In the past, the low infrared absorptivity of copper and high rate at which it dissipates heat has made it a difficult material to be laser welded. Under these circumstances, elevated optical power and welding speed are required. The latest generation of multi-kilowatt Nd:YAG lasers have opened a new perspective to this problem. The main objective of this investigation was to establish the laser beam power and speed values required to properly butt-weld copper, bronze (6 wt.% tin) and brass (35 wt.% zinc), in three thicknesses, using a continuous wave Nd:YAG laser of 4 kW maximum power. The resulting welds were visually inspected and those with continuous weld seams, full penetration and small heat affected zones were considered acceptable and their power and speed parameters used to plot the operational windows. Parameter ranges of operational windows are summed up as follows: copper (3 - 4kW, 1000 – 7000 mm/min); bronze (1.5 – 4 kW, 1500 – 10000 mm/min); brass (0.5 – 4 kW, 1000 – 9000 mm/min). The selected welds were all tensile tested to fracture point, the highest ultimate strength observed for copper was 226 MPa, for bronze 427 MPa and for brass 363 MPa. With the help of these findings, industry will have a reference point that indicates the power and speeds required in order to laser weld these materials.In the past, the low infrared absorptivity of copper and high rate at which it dissipates heat has made it a difficult material to be laser welded. Under these circumstances, elevated optical power and welding speed are required. The latest generation of multi-kilowatt Nd:YAG lasers have opened a new perspective to this problem. The main objective of this investigation was to establish the laser beam power and speed values required to properly butt-weld copper, bronze (6 wt.% tin) and brass (35 wt.% zinc), in three thicknesses, using a continuous wave Nd:YAG laser of 4 kW maximum power. The resulting welds were visually inspected and those with continuous weld seams, full penetration and small heat affected zones were considered acceptable and their power and speed parameters used to plot the operational windows. Parameter ranges of operational windows are summed up as follows: copper (3 - 4kW, 1000 – 7000 mm/min); bronze (1.5 – 4 kW, 1500 – 10000 mm/min); brass (0.5 – 4 kW, 1000 – 9000 mm/min). The selec...