Laser straightening of steel panels using a power controlled laser beam as the innovative thermal source is a newly developed straightening process. Lasers allow concentrating the thermal energy and will, in connection with dedicated measuring devices, make thermal straightening more efficient while reducing the impact on residual stresses in the material. In this paper, 4-mm, 6-mm and 8-mm thick steel sheets with various surface coatings were used for the definition of process parameters. Experiments showed that laser straightening is in principle suitable for ship production. Especially compact and mobile high power diode lasers with several kilowatts of output power have the potential for a semi-automatic straightening process on the dockyard. The microstructural developments in the heat affected zone were also observed and discussed. The investigated low-zinc silicate shop primers have high absorption coefficients for the diode laser radiation. A single spot pyrometer can be used as a sensor for real-time temperature monitoring and on-line laser power control to avoid overheating. The developed system controls the laser power to keep the surface temperature constant with an exactness of 15 deg C. Because the laser optic works without a focussing lens the results of the laser straightening process are independent of the working distance from the laser to the workpiece. The measurement of the two-dimensional temperature field is useful for process optimisation. The performance of the developed semi-automated thermal straightening process using a power controlled laser beam system for spot heating to avoid overheating of the steel has been experimentally confirmed.
Straightening of ship structures using a laser beam
Richten von Schiffstrukturen unter Einsatz eines Laserstrahls
2007
6 Seiten, 10 Bilder, 7 Quellen
Conference paper
English
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