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- Hybrid welding (3)
- Orbital welding (3)
- Fibre-optic lasers (2)
- High-pressure pipelines (2)
- Hybrid laser-arc welding (2)
- Laser (2)
- Laser beam welding (2)
- Plasma (2)
- Austenitic steel (1)
- Austenitischer Stahl (1)
An oscillating (AC) magnet field was used to suppress porosity formation and to stabilize the surface of the weld pool in bead-on-plate partial penetration 4.4 kW Nd:YAG laser beam welding of AW-5754 plates in PA position. The magnet was mounted on the laser welding head. The magnet field (up to 0.4 T and 10 kHz) was oriented perpendicular the welding direction.
The analysis of the weld cross-sections and x-ray images shows a drastic reduction (up to 90%) of porosity contents in the welds. The observed effects can be explained in terms of electromagnetically (EM)
induced 'Archimedes' forces as well as the EM stirring flow in the weld pool. Moreover, usage of AC magnetic fields results in a significant reduction (up to 50%) of the surface roughness of the welds. This effect can be explained in terms of electromagnetic (EM)
contribution to the surface tension (the Garnier-Moreau effect)
Peculiarities of the process of orbital laser-arc welding of thick-walled large-diameter pipes
(2010)
Laser Plasma Hybrid Welding of Austenitic Stainless Steels - Phenomena of Process Instability
(2007)
Laser plasma hybrid welding has been proved to be a very stable hybrid welding process and
welds of high quality can be produced, especially if high surface quality and low spattering is
demanded such as in welding fabrication of high alloyed austenitic stainless steels.
In particular cases, even though welds display high outer quality, X-ray examinations
revealed weld defects which may range from low porosity to blowhole-like cavities. The
phenomena and the main influencing parameters such as arc current, welding speed and
focal point position are discussed. Parameter fields will be suggested for welding plates of
different austenitic stainless steel grades with thicknesses ranging from 3 to 8 mm. The
results are based on welding experiments carried out using a 4.4 kW diode pumped Nd:YAGlaser.
Thus, also the influence of the feeding fibre diameter has been investigated and it was found
that the resulting beam shape has a major effect on the welding performance.
With an availability of the modern high power fibre lasers the application range of laser and laser hybrid welding can be significantly increased. For the implementation of this new technology in the economically extremely interesting application of pipeline construction it is necessary to fulfil a series of systematic research studies. As it has been shown in the past the fibre laser hybrid wielding of pipeline Steel X65 up to 32 mm thickness is possible with appropriate quality. For the use of laser-hybrid welding in pipe laying insensibility towards tolerances and the possibility of girth welding are very important factors in addition to the weld seam quality. The aim of a Research project carried out in the Federal Institute for Materials Research and Testing (BAM) was the development of a welding procedure using high power fibre laser in combination with GMAWProcess which could be applied for welding of pipelines. For tests segments of linepipes with an outer diameter of 914 mm and a wall thickness of 16 mm have been welded using specially designed equipment for girth welding of pipes. First promising results for the use of laser-hybrid welding of thick materials could be demonstrated. The gap-bridgeability and misalignement was studied.