Working group

Laser and Laser-Hybrid Welding

In this working group, laser and laser-hybrid welding processes are developed and advanced against the background of identifying relationships between process, structure and material behaviour and designing strategies on how to produce welds satisfying quality requirements.

In this context, a 20 kW fibre laser is used for the qualification of laser and laser-GMA-hybrid welding processes which are key to plate thicknesses up to approximately 20 mm. With our pertinent expertise we are currently occupying a unique position in BAM. Respective research studies mainly focus on applications in pipeline construction or shipbuilding.

A central point in the research work is the hot cracking behaviour of materials. In order to investigate the hot cracking susceptibility of the diverse metallic materials using different welding processes, a new hot cracking test facility (CTW-test, Controlled tensile weldability test) was designed. It can be employed for both arc and laser welding. Thermo-mechanical simulations serve to support the experimental investigations.

In close cooperation with industry and universities, numerous funded research studies are conducted in order to enhance laser and laser-hybrid welding processes and to overcome the process-related hot cracking problems.

In the past, laser-plasma-hybrid welding, for instance, was developed as a variant of the hybrid welding processes and was successfully tested for application to high-alloyed austenitic steels.

The welding behaviour auf austenitic steel constitutes a further field of expertise of the working group. Specific short-term metallurgical effects occurring during laser-GMA-hybrid welding of these materials were also examined within the scope of research projects.

Laser welding systems, workstation (5-axes portal frame) of a 6kW CO2 laser

Laser welding systems, workstation (5-axes portal frame) of a 6kW CO₂ laser

Laser welding systems, 20 kW Yb-fire laser with 500 mm focusing optics attached to the robot arm

Macrosection of a 16 mm hybrid weld; on the left – welded in flat position, on the right – welded in vertical down position

$Middle rip defect in a laser welded X70 steel; on the left – macrosection, on the right - SEM-pictures of the fracture surface of a notched bar impact test specimen$

Middle rip defect in a laser welded X70 steel; on the left – macrosection, on the right - SEM-pictures of the fracture surface of a notched bar impact test specimen (enlarged picture)

Macrosection of the laser-plasma-hybrid weld made from a 1.4565 stainless steel (on the left), hot crack in the HAZ (on the right) (enlarged picture)

Aims and research topics

Laser and hybrid welding
Welding of thick-walled components using a high-power laser
Metallurgical weldability of relatively high-alloyed and high-alloyed steels as well as nickel-base alloys
Mechanisms of hot crack formation during laser and hybrid welding
Short-term metallurgy, non-equilibrium processes
Expansion of expertise by introduction of hybrid technology and new investment in laser technology by installation of a high-power fibre laser system
Statements concerning the metallurgical and operative laser and hybrid weldability in fabrication as well as the mechano-technological properties of laser and hybrid joined components
Clarification of the influence of the structure on safety and reliability of laser and hybrid joined components

Equipment

Laser beam sources
- 6 kW CO₂-laser with 6-axes portal frame
- 4.4 kW Nd:YAG-laser with 5-axes robot
- 20 kW ytterbium-fibre laser (IPG)
Installations for hybrid processes
- Plasma torch for laser-plasma-hybrid welding using powder filler material
- Various GMA sources for laser/GMA-hybrid welding
- Cold wire feeder
Process control
- Various tools for beam diagnosis
- High-speed video camera
Hot cracking testing
- Controlled Tensile Weldability Test (CTW-Test)
- MVT-Test

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2009-09-22

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