Deep penetration welding with high-power CO2lasers

Experiments performed over the past year have involved the use of near-diffraction-limited lasers at power levels up to 20 kW for welding applications. This is a substantially higher power level than used in all previously reported experiments. As a result of the higher powers, significantly deeper penetration has been achieved. The optical cavity for the lasers used in these tests was an unstable oscillator, producing a near-diffraction-limited output with an obscuration of approximately 50 percent. The measured penetration for these tests is in reasonably good agreement with established correlations for vacuum electron beam welding data, indicating a strong similarity between the two types of welding. It is shown that a power of 2-4 kW is needed to produce thermally efficient welds in low-thermal-diffusivity plate materials such as 1/2-in stainless steel, and that higher powers are needed for the more highly conducting metals.