Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Please note that all times are shown in the time zone of the conference. The current conference time is: 7th Dec 2021, 10:42:19am CET

 
 
Program for LiM 2021
Session
Macro: Joining 1
Time:
Wednesday, 23/June/2021:
11:15am - 12:30pm

Session Chair: Dr. Andrey Gumenyuk, Bundesanstalt für Material Forschung und -prüfung (BAM), Germany
Location: Room 1
ICM Ground Floor 125

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Presentations
11:15am - 11:30am

Investigations on the weld seam geometry of ultrasonic assisted laser beam welded round bars in and beside antinode position

Jan Grajczak1, Christian Nowroth2, Sarah Nothdurft1, Jörg Hermsdorf1, Jens Twiefel2, Jörg Wallaschek2, Stefan Kaierle1

1Laser Zentrum Hannover e.V., Germany; 2Gottfried Wilhelm Leibniz Universität Hannover

Laser beam welds are usually symmetric. They can be forced to form asymmetric weld seams by introducing ultrasound.

Ultrasound can be used for grain refinement and reducing segregation. The investigations describe ultrasonic assisted laser beam welding around antinode position of a stationary ultrasonic wave.

The experiments are carried out with 2.4856 round bars, a laser beam power of 6 kW, a welding speed of 0.95 m/min and ultrasonic amplitudes of 0 µm and 4 µm. The welding positions are placed 0/7.5/15.0 mm on the right and left side of antinode position. Afterwards sample macrographs and micrographs of metallgraphic cross sections are made. It turns out that the asymmetry is direction dependent. In result, the understanding of interactions between welding area and passing ultrasound is improved.



11:30am - 11:45am

Observation of the weld pool shape in partial penetration welding and its influence on solidification crack formation for high-power laser beam welding

Nasim Bakir1, Ömer Üstündag1, Andrey Gumenyuk1,2, Michael Rethmeier3,1,2

1Bundesanstalt für Materialforschung und -prüfung (BAM), Germany; 2Fraunhofer Institute for Production Systems and Design Technology; 3Institute of Machine Tools and Factory Management, Technische Universität Berlin

Solidification cracking is still a particular problem in laser beam welding, especially in the welding of thick-walled plates. In this study, the influence of weld pool geometry on solidification cracking in partial penetration welding of thick plates is a subject of discussion. For this purpose, a special experimental setup of steel and quartz glass in butt configuration and lateral with high speed camera was used to capture the weld pool shape. Additionally, laser beam welding experiments were carried out to compare the crack positions and the cross section with the high-speed camera observations. The results showed a bulge in the weld pool root separated from the upper region by a nick area. This leads to the fact that three different longitudinal lengths with different solidification areas are taking place. This temporal sequence of solidification strongly promotes the solidification cracks in the weld root.



11:45am - 12:00pm

Occurrence of coating-related accumulations within the seam in laser beam deep penetration welding of aluminum-silicon coated press-hardened steels

Benjamin Karwoth, Thorsten Mattulat, Peer Woizeschke

Bremer Institut für angewandte Strahltechnik GmbH, Germany

In case of laser beam deep penetration welding of press-hardened and Al-Si-coated Mn-B-steels being coated to protect the base metal from scaling during press hardening, a reduced joint strength is observed in relation to the basemetal. One influencing factor is the insertion of coating constituents into the weld seam during the welding process. The objective of this study was to investigate the influence of partially decoated sheets on the amount of accumulation occurring in the seam of the overlap weld of two sheets. For this purpose, the samples were partially decoated in different ways before the joining process. The welds were analyzed by means of cross-sections. The results indicate that especially the coating on the contact surfaces of the sheets in the lap joint affects the accumulation of coating constituents. Partial decoating of one or both contact surfaces was able to significantly reduce the amount and size of the accumulations.



12:00pm - 12:15pm

Thermal cycles and cahrpy impact toughness of single-pass hybrid laser-arc welded thick-walled steels

Ömer Üstündag1, Nasim Bakir1, Andrey Gumenyuk1,2, Michael Rethmeier3,1,2

1Bundesanstalt für Materialforschung und -prüfung, Germany; 2Fraunhofer Institute for Production Systems and Design Technology; 3Institute of Machine Tools and Factory Management, TU Berlin

The study deals with the influence of the heat input on the grain sizes, thermal cycles and Charpy impact toughness for hybrid laser-arc welding of 25 mm thick structural steel S355J2 using a 20-kW high-power laser in combination with an electromagnetic weld pool support. The main focus is on the change of the mechanical properties over the entire seam thickness. The cooling times were measured using a pyrometer in combination with an optical fibre in three different locations near to fusion lines corresponding to different heights of the seam. Also, Charpy impact specimens were taken from different parts of the weld joint corresponding to the different heights. The heat input was variated between 1.8 kJ/mm and 3.2 kJ/mm. Despite the observed decreased values of both t8/5 cooling time and the Charpy impact toughness in the root part of the seam, the required values could be reached in dependance on applied heat input.



12:15pm - 12:30pm

Non-contact focus spot and focus shift measurement of high power lasers in the manufacturing of differential gears

Nicolas Meunier

MKS Instruments - Ophir Brand, Germany

The higher the power and energy density in the focus of the laser beam, the more efficient is the process in terms of traverse speed, hardness increase, deformation and other effects. Even a minimal focus shift or an imprecisely adjusted tool center point (TCP) shows extremely negative impact on the quality of the weld. Traditional measurement methods are too complex to capture the focus shift or to quickly check the focus position. The non-contact beam profiling technology developed by MKS Ophir eliminates limits in terms of power, and the measurement takes only seconds. Especially for 24/7 industrial use, MKS Ophir developed a fully automated, robust device with an easy to use operating interface.

Nicolas Meunier, Business Development Manager High Power und Automotive Products Ophir, explains the measurement principle and presents real world use cases.



 
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