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Single-pass solid-state laser welding of plates in the thickness range of 10 to 20 mm became possible with the invention of the fibre laser. This new technique provides excellent beam quality at powers as high as 20 kW or more, and has proved applicable in several industrial applications. By replacing conventional methods with the fibre laser, it is possible to avoid multiple-pass welding that requires time-consuming bevelling. The high energy density of the fibre laser beam also reduces the heat input and consequently the distortion. However, the rapid solidification and cooling associated with laser welding can cause imbalance of the microstructure of duplex stainless steel weldments, where excessively high ferrite contents may reduce the corrosion resistance and the ductility of the material. The solution is normally to add nickel-based filler wire and to increase the heat input. By using a hybrid welding process where the laser beam and the gas metal arc (GMA) process act in a common process zone, filler metal can be added to the molten pool at higher heat input and at the same time, higher welding speed and deeper penetration can be achieved. In this work, 13.5 mm thick 2205 (EN 1.4462, UNS S31803) was fibre laser-GMA hybrid welded in a single-pass using 14 kW of laser power and ISO 22 9 3 N L as filler wire for the GMA process. The resulting welds were free from defects, with smooth surfaces and full penetration. The investigation examines the weld metal microstructure and the effect on corrosion resistance and mechanical properties. The option to add nickel foil, when hybrid welding, was also investigated, as comparison, and the effect on austenite formation was evaluated.
Single-pass solid-state laser welding of plates in the thickness range of 10 to 20 mm became
possible with the invention of the fibre laser. This new technique provides excellent beam
quality at powers as high as 20 kW or more, and has proved applicable in several industrial
applications. By replacing conventional methods with the fibre laser, it is possible to avoid
multiple-pass welding that requires time-consuming bevelling. The high energy density of the
fibre laser beam also reduces the heat input and consequently the distortion. However, the
rapid solidification and cooling associated with laser welding can cause imbalance of the
microstructure of duplex stainless steel weldments, where excessively high ferrite contents
may reduce the corrosion resistance and the ductility of the material. The solution is normally
to add nickel-based filler wire and to increase the heat input. By using a hybrid welding
process where the laser beam and the gas metal arc (GMA) process act in a common
process zone, filler metal can be added to the molten pool at higher heat input and at the
same time, higher welding speed and deeper penetration can be achieved. In this work,
13.5 mm thick 2205 (EN 1.4462, UNS S31803) was fibre laser-GMA hybrid welded in a
single-pass using 14 kW of laser power and 2209 (ISO 22 9 3 L N) as filler wire for the GMA
process. The resulting welds were free from defects, with smooth surfaces and full
penetration. The investigation examines the weld metal microstructure and the effect on
corrosion resistance and mechanical properties. The option to add nickel foil when hybrid
welding was also investigated as comparison and the effect on austenite formation was
evaluated.
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.
Within the framework of an AiF (The German Federation of Industrial Research Associations) project, investigations were conducted into the solidification behaviour of various high-alloy austenitic steels in laser and laser-GMA hybrid welding. For comparison purposes, reference was made to pure gas metalarc welding tests. It was possible to raise the welding speeds in hybrid welding compared with the individual gas metal-arc (GMA) and laser welding processes. The central subjects of the investigations were the type of solidification and the connected hot cracking behaviour during welding. In this respect, particular attention was paid not only to the kinetic effects during solidification which may be caused by the high solidification rates in laser and hybrid welding but also to their consequences.