Experimental approach for quantification of fluid dynamics in laser metal welding

Abstract

Laser metal welding is widely applied in industry. Nevertheless, a complete process understanding which leads to a full control of the process is not available yet. To contribute a solution for this task, we use two high-speed cameras with recording rates of up to 250 kHz and measure the velocity and direction of the fluid flow inside the keyhole with very high precision. Furthermore, we use tracer particles to measure the fluid dynamics in the keyhole. To get a deep view into the keyhole without the use of x-rays, we use a setup which allows us to look inside the keyhole during overlap welding of zinc-coated steel sheets with a spatial resolution of 25 μm per pixel and a temporal resolution of 5.3 μs per frame. Moreover, we quantify the influence of this approach on the process dynamics. Our findings show how the fluid dynamics inside the keyhole are linked to the laser power, the feed rate, and a gap between two zinc-coated steel sheets.

Advances in macro-scale laser processing

“…Due to the high sample rates of used sensing techniques and the combination of multiple measurements, a structured processing of the acquired data is crucial. One example is the use of image processing algorithms to quantify melt and gas flows in laser metal welding [254].…”

Laser Powder Bed Fusion (LPBF) of In718 and the Impact of Pre-Heating at 500 and 1000 °C: Operando Study

“…When the laser starts to irradiate the powder particle start to form the melt pool and with the movement of the laser the pool is pushed backwards due to the recoil and Marangoni force as shown in Figure 10a where the stream traces show the path of the melt pool from its initial The melt pool is propelled by five main factors. the Marangoni force, which is also known as Bernoulli's principle, impels a fluid in one direction, from the elevated temperatures zone to the reduced temperature region for such a material having a negative coefficient of surface tension (all metals and alloys, with the exception of a few special ones, will experience a negative temperature coefficient of surface tension in the range from low surface tension area to high surface tension region) [54,[85][86][87][88]. Recoil pressure is exerted toward the vaporized surface imposed as a result of an inward force perpendicular to the vaporized surface [89,90].…”

Manufacturing a prototype with laser direct metal deposition and laser welding made from martensitic steel 1.4313

“…It covers process-dependent design adjustments and deposition strategies for thin and massive geometries and overcomes the limitations of the machine and the process by part segmentation. Moreover, the process parameters such as laser type, spot size, laser power, scan speed, and layer thickness, which play a significant role in obtaining a part with optimum physical and mechanical properties [12,13], are described in this study. In the following research, laser welding will be used for joining since DMD, and laser welding can be performed centralized on the Trumpf TruLaser Cell 7020.…”