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A Study of the Basic Phenomena During the High Power Fibre Laser Welding of Thick Section Low Alloyed Steel
A. Salminen, E. Lappalainen and T. Purtonen

The laser welding process is gaining ever growing attention. It has been found to be of particular interest in welding of automotive applications, where lasers have so far mostly been used for welding of thin sheet. A new generation of high power lasers has entered the market during the last couple of years. The easy availability of higher power brings the laser welding also to applications of thick section welding. Compared to old generation lasers, such as the CO2 laser, new lasers have better absorption, better beam quality and higher electrical efficiency. They are not as sensitive to metal vapour on top of the keyhole as CO2 laser in respect of process stability and resulting weld shape. This study investigates the performance, potential and problems of the deep penetration laser welding of S355 EN 10025 structural steel. Thicknesses up to 25 mm have been shown potential in welding with laser power between 15 and 30 kW. Visual examinations of the macrographs for all and hardness tests of part of the welded specimens were made. First versions of quality windows were drawn based on the results of the experiments.

Keywords: Fibre laser, laser welding, low alloyed steel, S355 EN 10025, weld quality

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