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 Hybrid laser-arc welding of laser- and plasma-cut 20-mm-thick structural steels

2022 ◽  
Author(s):  
Ömer Üstündağ ◽  
Nasim Bakir ◽  
Sergej Gook ◽  
Andrey Gumenyuk ◽  
Michael Rethmeier
Keyword(s):  
Laser Beam ◽  
Arc Welding ◽  
Laser Beam Welding ◽  
Digital Camera ◽  
Welding Process ◽  
Beam Power ◽  
Beam Diameter ◽  
Hybrid Laser Arc Welding ◽  
Single Pass ◽  
New Findings

AbstractIt is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges.

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.

scholarly journals Spectroscopic closed loop control of penetration depth in laser beam welding process

2012 ◽  
Author(s):  
Teresa Sibillano ◽  
Antonio Ancona ◽  
Domenico Rizzi ◽  
Francesco Mezzapesa ◽  
Ali Riza Konuk ◽  
...  
Keyword(s):  
Laser Beam ◽  
Penetration Depth ◽  
Closed Loop ◽  
Laser Beam Welding ◽  
Welding Process ◽  
Closed Loop Control ◽  
Loop Control

scholarly journals Numerical Model for Predicting Bead Geometry and Microstructure in Laser Beam Welding of Inconel 718 Sheets

2018 ◽  
Author(s):  
Iñigo Hernando ◽  
Jon Iñaki Arrizubieta ◽  
Aitzol Lamikiz ◽  
Eneko Ukar
Keyword(s):  
Numerical Model ◽  
Laser Beam ◽  
Inconel 718 ◽  
Laser Beam Welding ◽  
Welding Process ◽  
Bead Geometry ◽  
Predictive Tool ◽  
Melt Pool ◽  
Dendritic Arm Spacing ◽  
Weld Seams

A numerical model was developed for predicting the bead geometry and microstructure in Laser Beam Welding of 2 mm thickness Inconel 718 sheets. The experiments were carried out with a 1 kW maximum power fiber laser coupled with a galvanometric scanner. Wobble strategy was employed for sweeping 1 mm wide circular areas for creating the weld seams and a specific tooling was manufactured for supplying protective Argon gas during the welding process. The numerical model takes into account both the laser beam absorption and the melt-pool fluid movement along the bead section, resulting in a weld geometry that depends on the process input parameters, such as feed rate and laser power. The microstructure of the beads was also estimated based on the cooling rate of the material. Features as bead upper and bottom final shapes, weld penetration and dendritic arm spacing were numerically and experimentally analyzed and discussed. The results given by the numerical analysis agree with the tests, making the model a robust predictive tool.

scholarly journals Assessment of the Effect of Laser Welding on the Properties and Structure of TMCP Steel Butt Joints

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1312 ◽  
Author(s):  
Jacek Górka
Keyword(s):  
Laser Beam ◽  
Welded Joints ◽  
Research Work ◽  
Laser Beam Welding ◽  
Welding Process ◽  
Tensile Tests ◽  
Carbon Equivalent ◽  
Quality Level ◽  
Butt Joints ◽  
Plastic Properties

The research work and related tests aimed to identify the effect of filler metal-free laser beam welding on the structure and properties of butt joints made of steel 700MC subjected to the TMCP (thermo-mechanically controlled processed) process. The tests involved 10-mm thick welded joints and a welding linear energy of 4 kJ/mm and 5 kJ/mm. The inert gas shielded welding process was performed in the flat position (PA) and horizontal position (PC). Non-destructive testing enabled classification of the tested welded joints as representing the quality level B in accordance with the requirements set out in standard 13919-1. Destructive tests revealed that the tensile strength of the joints was 5% lower than S700MC steel. The results of tensile tests and changes in structure were referred to joints made using the MAG (Metal Active Gas) method. The tests of thin films performed using a high-resolution scanning transmission electron microscope revealed that, during laser beam welding, an increase in dilution was accompanied by an increase in the content of alloying microadditions titanium and niobium, particularly in the fusion area. A significant content of hardening phases in the welded joint during cooling led to significant precipitation hardening by fine-dispersive (Ti,Nb)(C,N) type precipitates being of several nanometres in size, which, in turn, resulted in the reduction of plastic properties. An increase in the concentration of elements responsible for steel hardening, i.e., Ti and Nb, also contributed to reducing the weld toughness below the acceptable value, which amounts to 25 J/cm2. In cases of S700MC, the analysis of the phase transformation of austenite exposed to welding thermal cycles and the value of carbon equivalent cannot be the only factors taken into consideration when assessing weldability.

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