Evaporation characteristics in laser welding - fundamental study on theoretical modelling of laser welding (Report 2)

• Published in: Welding international 1996-01, Vol.10 (6), p.448-453
• Main Authors: Miyamoto, I, Maruo, H
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Welding
• ISSN: 0950-7116; 1754-2138
• DOI: 10.1080/09507119609549029

Evaporation characteristics in CO 2 laser welding stainless steel were experimentally analysed at power densities in a range from 5 × 10 4 to 10 7 W/cm 2 with M 2 of 1.4 and 5.6. Welding mode changes from a thermal conduction type to a deep penetration type at a critical power density around 4-5 × 10 5 W/cm 2 . Penetration depth tends to increase with decreasing M 2 with accompanying decreased evaporation loss when the power density at the work surface is the same. The latent heat of evaporation is negligibly small, at most, around 1 % of laser power. In thermal conduction welding, where the power density is less than 4-5 × 10 5 W/cm 2 , the evaporation rate per unit area was found to be equivalent to that of deep penetration welding, indicating that the recoil force of the evaporation is at least as high as that of keyhole welding, producing a shallow hemispherical depression by the recoil force in the molten pool. The evaporation rate in deep penetration welding decreases with increasing aspect ratio of the weld bead due to the condensation of the vapour at the side wall of the keyhole.