Blue diode lasers have high energy efficiency due to their high absorption rate of 60% in pure copper. Since pure copper has a high thermal conductivity, a high laser intensity which is the large amount of heat input to a unit area and per unit time is required. A 200 W blue diode laser was condensed to a spot diameter of 50 μm, and a laser intensity of 1.0 × 10~7 W/cm~2 was obtained. Bead-on-plate welding was performed on pure copper having a thickness of 0.2 mm with this high-intensity blue diode laser. When the laser density was 2.5 × 10~6 W/cm~2, full penetration welding was not obtained at a welding speed of 10 mm/s. On the other hand, at a laser intensity of 1.0 × 10~7 W/cm~2, full penetration welding was obtained until the welding speed was 35 mm/s. The energy required for full penetration welding and the occurrence of spatter were investigated when the laser intensity was controlled by changing the laser power while keeping the spot diameter constant at 50 μ m.
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