scholarly journals Root formation and metallurgical challenges in laser beam and laser-arc hybrid welding of thick structural steel

2021 ◽  
Author(s):  
Ivan Bunaziv ◽  
Cato Dørum ◽  
Steen Erik Nielsen ◽  
Pasi Suikkanen ◽  
Xiaobo Ren ◽  
...  
Keyword(s):  
Laser Beam ◽  
Laser Beam Welding ◽  
High Hardness ◽  
Air Gap ◽  
Process Window ◽  
Deep Penetration ◽  
Hybrid Welding ◽  
Thick Plates ◽  
Single Pass ◽  
Wide Range

AbstractSingle-pass laser beam welding (LBW) of steel components with wall thickness of > 10 mm is of high interest due to enhanced productivity. Deep penetration LBW provides excessive hardness and certain quality issues such as root humping in flat position, which is associated with disability of surface tension to sustain melt dropout. High hardness is associated with fast cooling rates and shortage of filler wire transportation to the root of the fusion zone. Use of laser-arc hybrid welding (LAHW) can promote acicular ferrite by adding filler metal and additional heat input from the arc. However, LAHW may promote humping and adjustment of many parameters is required hindering its application. In this work, a 16 kW disk laser was used in butt welding of 12 mm and 15 mm thick plates with different bevelling geometries. Root humping occurred within a wide range of process parameters providing narrow process window. Twelve millimeter thick plates were successfully welded with a single-pass technique providing good quality of root by using zero air gap regardless bevelling geometry. Welding of 15 mm plates was more challenging, and the process was sensitive even with a slight parameter change. Improved results were achieved with application of small air gap. Acceptable hardness in both weld metal and heat affected zone (< 290 HV) was achieved for both plate thicknesses providing good toughness of minimum 27 J at −50°C.

scholarly journals Root formation and mechanical properties in laser keyhole welding of 15 mm thick HSLA steel

2021 ◽  
Vol 1135 (1) ◽  
pp. 012011
Author(s):  
Ivan Bunaziv ◽  
Cato Dørum ◽  
Steen Erik Nielsen ◽  
Pasi Suikkanen ◽  
Xiaobo Ren ◽  
...  
Keyword(s):  
Laser Beam ◽  
Hsla Steel ◽  
High Heat ◽  
Butt Joint ◽  
Welding Parameters ◽  
Deep Penetration ◽  
Persistent Problem ◽  
Single Pass ◽  
Wide Range ◽  
Root Quality

Abstract Deep penetration laser welding is promising in joining thick (> 10 mm) steel sections. Focused laser beam by drilling vapour cavity, the keyhole, generates deep and narrow welds. Full penetration single-pass joining has a persistent problem with root quality where humping is one of the most frequent imperfection. This strongly hampers the use of high-power laser for thick plate welding. A 16 kW disk laser was used for single-pass welding of 15 mm thick plates in a butt joint configuration. Root humping occurred within a wide range of welding parameters. This provides narrow processing window. By adding an arc source to the laser beam process, the tendency of root humping increases. To achieve humping-free welds and consistent root quality over length, a delicate balance of process parameters is required. High heat input (> 0.50 kJ/mm) was positive to achieve a combination of low hardness (< 325 HV) and good Charpy toughness at -50 °C (> 50 J).

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.

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.

LASER-MIG Hybrid Welding of Thick Plates of Mild Steel in Single Pass

2012 ◽  
Vol 45 (2) ◽  
pp. 29 ◽  
Author(s):  
G. Padmanabham ◽  
B. Shanmugarajan ◽  
K. V. Phani Prabhakar
Keyword(s):  
Mild Steel ◽  
Hybrid Welding ◽  
Thick Plates ◽  
Single Pass

Evaluation of High Penetration Hybrid Laser-GMAW Welding Process Productivity Applied in the Joining of Thick Plates and Pipelines

2022 ◽  
Author(s):  
Rafael Gomes Nunes Silva ◽  
Max Baranenko Rodrigues ◽  
Milton Pereira ◽  
Koen Faes
Keyword(s):  
Laser Beam ◽  
Arc Welding ◽  
Manufacturing Industry ◽  
Operating Time ◽  
Laser Beam Welding ◽  
Welding Process ◽  
Major Influence ◽  
Thick Plates ◽  
High Penetration ◽  
Welding Processes

Abstract Welding processes are present in all sectors of the industry, highlighting the manufacturing industry of thick plates and pipelines. In these applications, welding processes have a major influence on costs, schedules, risk analysis and project feasibility. Conventional arc welding processes, such as the gas metal arc welding (GMAW) process, have limitations when applied to high thickness joints due to their maximum achievable penetration depth. On the other hand, the laser beam welding (LBW) welding process, despite reaching high penetration depths, has several limitations mainly regarding the geometric tolerance of the joint. In this regard, the hybrid laser-arc welding (HLAW) process emerges as a promising bonding process, combining the advantages of the GMAW and LBW processes into a single melting pool. Despite the many operational and metallurgical advantages, the HLAW process presents a high complexity due to the high number of parameters involved and the interaction between the laser beam and the electric arc. The present work discusses the challenges involved in the parametrization of the HLAW process applied to the joining of thick plates and pipes, and empirically evaluated a comparison between the HLAW and GMAW processes, showing a reduction of operating time of approximately 40 times, and a reduction of consumption of shielding gas and filler material of approximately 20 times, evidencing the technical and financial contribution of the hybrid process.

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.

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