scholarly journals On the relationship between the bulge effect and the hot cracking formation during deep penetration laser beam welding

Procedia CIRP ◽  
2020 ◽  
Vol 94 ◽  
pp. 5-10
Author(s):  
Antoni Artinov ◽  
Marcel Bachmann ◽  
Xiangmeng Meng ◽  
Victor Karkhin ◽  
Michael Rethmeier
Keyword(s):  
Laser Beam ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Deep Penetration ◽  
The Relationship

scholarly journals Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing

Metals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 985 ◽  
Author(s):  
Pedro Alvarez ◽  
Lexuri Vázquez ◽  
Noelia Ruiz ◽  
Pedro Rodríguez ◽  
Ana Magaña ◽  
...  
Keyword(s):  
Grain Size ◽  
Laser Beam ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Welding Parameters ◽  
Minor Effect ◽  
Alloy 718 ◽  
Material Source ◽  
Cross Sectional ◽  
Varestraint Test

Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 is usually welded in a solution annealed state. However, even with this thermal treatment, cracks can be induced during standard industrial manufacturing conditions, leading to costly and time-consuming reworking. In this work, the cracking susceptibility of wrought and investment casting alloy 718 is studied by the Varestraint test. The test is performed while applying different welding conditions, i.e., continuous tungsten inert gas (TIG), low frequency pulsed TIG, continuous laser beam welding (LBW) and pulsed LBW. Welding parameters are selected for each welding technology in order to meet the welding quality criteria requested for targeted aeronautical applications, that is, full penetration, minimum cross-sectional welding width and reduced overhang and underfill. Results show that the hot cracking susceptibility of LBW samples determined by the Varestraint test is enhanced due to extended center line hot cracking, resulting in a fish-bone like cracking pattern. On the contrary, the minor effect of material source (wrought or casting), grain size and pulsation is observed. In fact, casting samples with a 30 times coarser grain size have shown better performance than wrought material.

scholarly journals Characterization of Temperature Fields in Laser Beam Welded Hollow-Cylindrical Cold Crack Samples from High Strength Steel 100Cr6

2021 ◽  
Author(s):  
Eric Wasilewski ◽  
Nikolay Doynov ◽  
Ralf Ossenbrink ◽  
Vesselin Michailov
Keyword(s):  
Laser Beam ◽  
High Strength Steel ◽  
Unit Length ◽  
Laser Beam Welding ◽  
High Strength ◽  
Temperature Fields ◽  
Deep Penetration ◽  
Heating Rates ◽  
Hydrogen Distribution ◽  
Cooling Rates

Abstract This work presents a comparative study of thermal conditions that occur during laser beam welding of high strength steel 100Cr6 that often leads to a loss of technological strength and may conditionally produce cold cracks. The results from both experiments and thermal-metallurgical FE-simulations indicate that the type of heat coupling changes significantly when welding with different process parameters, e.g., in the transition between conduction and deep penetration welding. Further, the simulations show that as a result of the high welding speeds and reduced energy per unit length, extremely high heating rates of up to 2x104 K s-1 (set A) resp. 4x105 K s-1 (set B) occur in the material. Both welds thus concern a range of values for which conventional Time-Temperature-Austenitization (TTA) diagrams are not currently defined, so that the material models can only be calibrated using general assumptions. This noted change in energy per unit length and welding speeds causes significantly steep temperature gradients with a slope of approximately 5x103 K mm-1 and strong drops in the heating and cooling rates, particularly in the heat affected zone near the weld metal. This means that even short distances along the length present a staggering difference in relation to the temperature peaks. The temperature cycles also show very different cooling rates for the respective parameter sets, although in both cases they are well below a cooling time t8/5 of one second, so that the phase transformation always leads to the formation of martensite. The results from this study are intended to be used for further detailed experimental and numerical investigation of microstructure, hydrogen distribution, and stress-strain development at different restrain conditions.

Development of a novel optical measurement technique to investigate the hot cracking susceptibility during laser beam welding

2018 ◽  
Vol 63 (2) ◽  
pp. 435-441 ◽  
Author(s):  
N. Bakir ◽  
V. Pavlov ◽  
S. Zavjalov ◽  
S. Volvenko ◽  
A. Gumenyuk ◽  
...  
Keyword(s):  
Laser Beam ◽  
Measurement Technique ◽  
Optical Measurement ◽  
Laser Beam Welding ◽  
Hot Cracking

scholarly journals Influence of oscillating magnetic field on the keyhole stability in deep penetration laser beam welding

2021 ◽  
Vol 135 ◽  
pp. 106715
Author(s):  
Ömer Üstündağ ◽  
Nasim Bakir ◽  
Andrey Gumenyuk ◽  
Michael Rethmeier
Keyword(s):  
Magnetic Field ◽  
Laser Beam ◽  
Laser Beam Welding ◽  
Deep Penetration ◽  
Oscillating Magnetic Field

Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding

2020 ◽  
Vol 234 (5) ◽  
pp. 722-731
Author(s):  
Sören Hollatz ◽  
Marc Hummel ◽  
Lea Jaklen ◽  
Wiktor Lipnicki ◽  
Alexander Olowinsky ◽  
...  
Keyword(s):  
Laser Beam ◽  
Data Processing ◽  
Laser Beam Welding ◽  
Measurement Data ◽  
Welding Process ◽  
Deep Penetration ◽  
Limited Information ◽  
Depth Measurement ◽  
Interferometric Measurement ◽  
Weld Depth

Analysing the quality of weld seams is still a challenging task. An optical inspection of the surface is giving limited information about the shape and depth of the weld seam. An application for laser beam welding with high demands regarding the weld depth consistency is the electrical contacting of battery cells. The batteries themselves have a limited terminal or case thickness that must not be penetrated during the welding process to avoid leakage or damage to the cell. That leads to a minimum weld depth to ensure the electrical functionality, and a maximum weld depth indicated by the case thickness. In such applications, a destructive analysis is not suitable which leads to the demand for a non-destructive measurement during the process. Using a coaxial, interferometric measurement setup, the keyhole depth during the deep penetration welding is measureable. For a keyhole with a depth of a couple of millimetres, such a system is commercially available. In micro scale, however, these systems are facing several challenges such as scanning systems, small spot diameters of a few tens of micrometres and narrow keyholes. This study contains an investigation of an interferometric measurement of the keyhole depth and the suitability for laser micro welding. Therefore, the data processing of the achieved measurements is investigated, and the results are compared with the depth measurement of metallographic analysed samples. Stainless steel is used to investigate the behaviour and the stability of developed data processing strategy and the resulting depth values.

Developments and Trends in Laser Welding of Sheet Metal

2005 ◽  
Vol 6-8 ◽  
pp. 59-70 ◽  
Author(s):  
Frank Vollertsen
Keyword(s):  
Laser Beam ◽  
Sheet Metal ◽  
Spot Welding ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Thick Sheet ◽  
Laser Systems ◽  
Thick Sheet Metal ◽  
Metal Welding ◽  
Remarkable Progress

There is some remarkable progress in laser beam welding of sheet metal which is driven by the advent of improved laser systems and process technologies. Here, potentials for reducing distortion and avoiding hot cracking are highlighted, and examples of current developments are given in the field of thin and thick sheet metal welding including spot welding of difficult-to-weld materials and material combinations.

scholarly journals The bulging effect and its relevance in high power laser beam welding

2021 ◽  
Vol 1135 (1) ◽  
pp. 012003
Author(s):  
Antoni Artinov ◽  
Xiangmeng Meng ◽  
Nasim Bakir ◽  
Ömer Üstündağ ◽  
Marcel Bachmann ◽  
...  
Keyword(s):  
Laser Beam ◽  
Penetration Depth ◽  
Weld Pool ◽  
High Power ◽  
High Speed ◽  
Laser Beam Welding ◽  
Hot Cracking ◽  
Alloying Elements ◽  
High Power Laser ◽  
Power Laser

Abstract The present work deals with the recently confirmed widening of the weld pool interface, known as a bulging effect, and its relevance in high power laser beam welding. A combined experimental and numerical approach is utilized to study the influence of the bulge on the hot cracking formation and the transport of alloying elements in the molten pool. A technique using a quartz glass, a direct-diode laser illumination, a high-speed camera, and an infrared camera is applied to visualize the weld pool geometry in the longitudinal section. The study examines the relevance of the bulging effect on both, partial and complete penetration, as well as for different sheet thicknesses ranging from 8 mm to 25 mm. The numerical analysis shows that the formation of a bulge region is highly dependent on the penetration depth and occurs more frequently during partial penetration above 6 mm and complete penetration above 8 mm penetration depth, respectively. The location of the bulge correlates strongly with the cracking location. The obtained experimental and numerical results reveal that the bulging effect increases the hot cracking susceptibility and limits the transfer of alloying elements from the top of the weld pool to the weld root.

scholarly journals Numerical Study on the Influence of the Plasma Properties on the Keyhole Geometry in Laser Beam Welding

2022 ◽  
Vol 9 ◽  
Author(s):  
Donato Coviello ◽  
Antonio D’Angola ◽  
Donato Sorgente
Keyword(s):  
Laser Beam ◽  
Numerical Study ◽  
Laser Beam Welding ◽  
Welding Process ◽  
Beam Power ◽  
Deep Penetration ◽  
Multiple Reflections ◽  
Absorption Mechanism ◽  
Plasma Properties ◽  
Workpiece Surface

Keyhole laser welding is the benchmark for deep-penetration joining processes. It needs high incident laser beam power densities at the workpiece surface to take place. The gaseous phase plays a fundamental role to keep the deep and narrow keyhole cavity open during the process. The plasma created in this process is a mixture of ionized metal vapors and the environmental gas and it develops inside the keyhole (keyhole plasma) and above the workpiece surface (plasma plume). The presence of plasma implicates absorption, scattering, and refraction of laser beam rays. These phenomena alter the power density of the laser beam irradiating the workpiece surface and thus affect the resulting welding process. In this work, a mathematical and numerical model has been developed to calculate the keyhole shape taking into account the plasma absorption effects. The model considers the keyhole walls as the liquid-vapor interface and computes the keyhole geometry applying a local energy balance at this interface. In addition, the model takes into account the multiple reflections effects inside the cavity through an iterative ray-tracing technique, and calculates the absorption mechanism due to inverse Bremsstrahlung for each ray along its segmented path inside the keyhole. Results show the effect of plasma properties on the keyhole shape and depth.

scholarly journals Laser beam welding setup for the coaxial combination of two laser beams to vary the intensity distribution

2022 ◽  
Author(s):  
M. Möbus ◽  
P. Woizeschke
Keyword(s):  
Laser Beam ◽  
Penetration Depth ◽  
Intensity Distribution ◽  
Laser Beam Welding ◽  
Sample Surface ◽  
Laser Beams ◽  
Deep Penetration ◽  
Focal Position ◽  
Laser Systems ◽  
Laser Sources

AbstractDeep-penetration laser beam welding is highly dynamic and affected by many parameters. Several investigations using differently sized laser spots, spot-in-spot laser systems, and multi-focus optics show that the intensity distribution is one of the most influential parameters; however, the targeted lateral and axial intensity design remains a major challenge. Therefore, a laser processing optic has been developed that coaxially combines two separate laser sources/beams with different beam characteristics and a measuring beam for optical coherence tomography (OCT). In comparison to current commercial spot-in-spot laser systems, this setup not only makes it possible to independently vary the powers of the two laser beams but also their focal planes, thus facilitating the investigation into the influence of specific energy densities along the beam axis. First investigations show that the weld penetration depth increases with increasing intensities in deeper focal positions until the reduced intensity at the sample surface, due to the deep focal position, is no longer sufficient to form a stable keyhole, causing the penetration depth to drop sharply.

Sign in / Sign up

Export Citation Format

Share Document