Plume temperature diagnosis with the continuous spectrum and Wien’s displacement law during high power fiber laser welding

Abstract

The laser-induced plume is an essential physical phenomenon during high power fiber laser welding. Its physical nature can be investigated by diagnosing its temperature. In order to overcome the lack of sufficient line spectra in the temperature diagnosis, the continuous spectrum method (based on the continuous spectrum and Wien's displacement law) is thus developed in this research. The optical spectra emitted by the plume or plasma were detected by using a SP-2500i spectrometer during bead-on-plate welding with an IPG YLS-6000 fiber laser or fiber laser-arc hybrid. The rationality of the continuous spectrum method was evaluated by comparing the plasma temperatures diagnosed by applying the continuous spectrum and line spectra. The results reveal that the continuous spectrum method used in temperature diagnosis is rational. When the line spectra cannot be detected due to an increase in detected height, the plume temperature can be still obtained by using the continuous spectrum method.

Control of the plume induced during high-power fiber laser welding with a transverse arc

“…The calculation principle of the Boltzmann plot method was elaborately detailed in [9,10], and is not repeated in the present work. The selected line spectra in [8,10] could also provide references for this study. Based on the spectral information of the plume/plasma at different heights, as measured by spectrometer, the variation tendencies of their temperatures in the fiber laser beam center at varying heights were plotted and presented in figure 2(c).…”

“…The bead-on-plate welding was carried out with 5 kW of power, 2 m min −1 in welding speed and 0 mm in defocus distance on commercial pure iron with a size of 100 mm × 50 mm × 10 mm. The arrangement and parameter setting of the laser, the spectrometer, the high-speed camera, and the basic technological parameters in the welding process as described in [8] were adopted. The tungsten electrode of the tungsten inert gas (TIG) arc was mounted 6 mm above and parallel to the workpiece surface.…”

Effects of a paraxial TIG arc on high-power fiber laser welding

“…8, the temperature of the hybrid welding plasma was much higher than that of the plume both vertically and horizontally, indicating that the hybrid welding plasma contained much more heat energy than the plume. Meanwhile, the line spectra intensity of iron atom I mn is proportional to the density of the iron atom [25]. The line spectra emitted by the hybrid welding plasma in shorter times possessed a much stronger light intensity than the plume (Fig.…”

Observation and characterization of quasi-continuous wave kW-class laser interaction with metal and metal oxide targets using a high-speed camera and microscopes

“…From the spectra of the zirconia targets shown in figure 13, the spectra of zirconium atom in the range between 408 nm and 422 nm, the neutral lines are identified [23] and some of the intense lines show self-absorption because a relatively cold plasma region becomes much larger due to much longer interaction period compared with that of the nano-second laser interaction. In the present experimental conditions, the temperature of each plume is expected to be several thousand degrees Celsius [13,18,20,24].…”