TY - CONF A1 - Schneider, André A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Laser beam welding of thick materials under the influence of local reduced ambient pressure T2 - VIII BTLA 2015 - 8th International conference "Beam technologies & laser application" N2 - The development of the vapour plume during the laser beam welding of metals with propagation directions along the laser beam axis leads to a reduction of the absorbed laser power in the keyhole. The main reasons are the scattering of the laser radiation on the condensed phase of metallic vapour as well as the defocusing of the laser beam due to the density gradient in the vapour plume. These unfavourable effects can be significantly mitigated by the application of a reduced ambient pressure thus decreasing the interaction between the laser beam and evaporation products, which leads to more stable welding process and results in increased penetration depth, as known from previous studies. A conventional technique use a vacuum chamber principle, similar to that, used for electron beam welding. Application of this technique is restricted by the chamber size and reduces thus the advantages of this approach especially for large components. We demonstrate a possibility of mobile local vacuum application, which allows to generate a reduced pressure only in small region around the keyhole. By using of specially designed mobile pressure lock which can be moved along the welding direction absolute pressure of around 200 mbar could be obtained. This is sufficient to increase the welding depth by around 50%. Coupons from S355 were welded with an incremental laser power from 5 kW to 12 kW at atmospheric pressure and compared to those welded at ambient pressure of 200 mbar. The evaluation of the longitudinal section revealed an increase of the welding depth by about 35%. Furthermore, the welding trials in butt joint configuration on 15 mm thick plates at various laser beam power performed for atmospheric and reduced ambient pressure of around 200 mbar. The increase in welding depth up to 40% was established for reduced pressure. Particularly, low welding speeds under reduced pressure were especially advantageous in terms of increasing the welding depth. T2 - VIII BTLA 2015 - 8th International conference "Beam technologies & laser application" CY - St. Petersburg, Russia DA - 21.09.2015 KW - High power laser beam welding KW - Mobile vacuum KW - Local reduced pressure KW - Vapour plume KW - Keyhole PY - 2015 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/34973 AN - OPUS4-34973 SP - 45 EP - 46 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany