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Alexander Kaplan - One of the best experts on this subject based on the ideXlab platform.
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The penetration efficiency of thick plate Laser-Arc Hybrid Welding
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Double-sided fiber Laser-Arc Hybrid Welding was used to join 45 mm thick high strength steel over a wide range of parameters in order to investigate the efficiency of the process. Air gap size, I- and Y-groove type preparation, pulsed and cold metal transfer pulsed arc modes, arc-laser setup, and travel speeds were compared, and in all cases, sufficient filler material was provided to fully fill the gap. The welds were investigated using high speed imaging and cross-sectional analysis to identify penetration depths, morphology, and imperfections. Larger joint air gaps were found to contribute most to weld penetration depth. Surprisingly, increased line energy decreased penetration efficiency in most cases. The Laser-Arc interdistance was also investigated, revealing an arc size and melt flow dependency for achieving higher penetration depth for a leading arc. It was found that, although penetration can be optimized, solidification cracking can be a limiting factor in the application of deep penetration Hybrid Welding for thick steel section joining.
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process stability during fiber laser arc Hybrid Welding of thick steel plates
Optics and Lasers in Engineering, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Abstract Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc Welding. Deep penetration Laser-Arc Hybrid Welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern Welding consumables such as metal-cored wire and advanced Welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG Hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of Welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.
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Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:A standard Laser-Arc Hybrid Welding (S-LAHW) and LAHW with preplaced cut wire inside the groove before Welding were studied and compared. The S-LAHW setup revealed problems with filler wire deliver ...
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Deep penetration fiber Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:The present investigation addresses Laser-Arc Hybrid Welding of 45 mm thick steel with variation in a wide range of process parameters. High volume fraction of acicular ferrite formed in the upper ...
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Geometrical aspects of hot cracks in Laser-Arc Hybrid Welding
Journal of Laser Applications, 2014Co-Authors: Greger Wiklund, Odd M Akselsen, Arve J. Sørgjerd, Alexander KaplanAbstract:Hot cracks were frequently found in double sided Laser-Arc Hybrid Welding thick section (20 mm) low carbon steel. Other research has usually investigated the metallurgical resolidification mechanisms of the welded metal alloy, but here possible relationships between the hot cracks and geometrical aspects of their surrounding weld and heat-affected zone cross sections were studied. The motivation behind this research was to identify guidelines for Laser-Arc Hybrid Welding to avoid hot cracks. Weld cross sections were used to analyze hot cracking because they are rather easy to prepare and straightforward to alter through the process parameters. In this study, hot cracks were found in a preferred geometrical window, namely, in the middle of the narrow deep region of the weld which was generated by the laser beam. From the cross section analysis, a first indicator was that a more inclined, converging shape of the lower part of the weld cross section can avoid hot cracks, associated with different energy input and resolidification front geometry. Significant reduction of the Welding speed has avoided hot cracks, being a second indicator.Hot cracks were frequently found in double sided Laser-Arc Hybrid Welding thick section (20 mm) low carbon steel. Other research has usually investigated the metallurgical resolidification mechanisms of the welded metal alloy, but here possible relationships between the hot cracks and geometrical aspects of their surrounding weld and heat-affected zone cross sections were studied. The motivation behind this research was to identify guidelines for Laser-Arc Hybrid Welding to avoid hot cracks. Weld cross sections were used to analyze hot cracking because they are rather easy to prepare and straightforward to alter through the process parameters. In this study, hot cracks were found in a preferred geometrical window, namely, in the middle of the narrow deep region of the weld which was generated by the laser beam. From the cross section analysis, a first indicator was that a more inclined, converging shape of the lower part of the weld cross section can avoid hot cracks, associated with different energy inpu...
Jan Frostevarg - One of the best experts on this subject based on the ideXlab platform.
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Application of Laser-Arc Hybrid Welding of steel for low-temperature service
The International Journal of Advanced Manufacturing Technology, 2019Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander F. H. KaplanAbstract:Laser-Arc Hybrid Welding (LAHW) is more often used in shipbuilding and oil and gas industries in recent years. Its popularity arises due to many advantages compared to conventional arc Welding processes. The laser beam source is used to achieve much higher penetration depths. By adding filler wire to the process area, by means of an arc source, the mechanical properties can be improved, e.g. higher toughness at low temperatures. Therefore, LAHW is a perspective process for low-temperature service. Applicability of LAHW is under concern due to process stability and mechanical properties related to heterogeneous filler wire distribution through the whole weld metal in deep and narrow joints. This can cause reduced mechanical properties in the weld root as well as problems with solidification cracking. The fast cooling rate in the root provides hard and brittle microconstituents lowering toughness at low temperatures. Numerical simulations and experimental observations showed that an increase in heat input from the laser beam is an effective way to reduce the cooling rate, which is also possible by applying preheating.
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The penetration efficiency of thick plate Laser-Arc Hybrid Welding
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Double-sided fiber Laser-Arc Hybrid Welding was used to join 45 mm thick high strength steel over a wide range of parameters in order to investigate the efficiency of the process. Air gap size, I- and Y-groove type preparation, pulsed and cold metal transfer pulsed arc modes, arc-laser setup, and travel speeds were compared, and in all cases, sufficient filler material was provided to fully fill the gap. The welds were investigated using high speed imaging and cross-sectional analysis to identify penetration depths, morphology, and imperfections. Larger joint air gaps were found to contribute most to weld penetration depth. Surprisingly, increased line energy decreased penetration efficiency in most cases. The Laser-Arc interdistance was also investigated, revealing an arc size and melt flow dependency for achieving higher penetration depth for a leading arc. It was found that, although penetration can be optimized, solidification cracking can be a limiting factor in the application of deep penetration Hybrid Welding for thick steel section joining.
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process stability during fiber laser arc Hybrid Welding of thick steel plates
Optics and Lasers in Engineering, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Abstract Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc Welding. Deep penetration Laser-Arc Hybrid Welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern Welding consumables such as metal-cored wire and advanced Welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG Hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of Welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.
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Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:A standard Laser-Arc Hybrid Welding (S-LAHW) and LAHW with preplaced cut wire inside the groove before Welding were studied and compared. The S-LAHW setup revealed problems with filler wire deliver ...
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Deep penetration fiber Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:The present investigation addresses Laser-Arc Hybrid Welding of 45 mm thick steel with variation in a wide range of process parameters. High volume fraction of acicular ferrite formed in the upper ...
Ivan Bunaziv - One of the best experts on this subject based on the ideXlab platform.
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Application of Laser-Arc Hybrid Welding of steel for low-temperature service
The International Journal of Advanced Manufacturing Technology, 2019Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander F. H. KaplanAbstract:Laser-Arc Hybrid Welding (LAHW) is more often used in shipbuilding and oil and gas industries in recent years. Its popularity arises due to many advantages compared to conventional arc Welding processes. The laser beam source is used to achieve much higher penetration depths. By adding filler wire to the process area, by means of an arc source, the mechanical properties can be improved, e.g. higher toughness at low temperatures. Therefore, LAHW is a perspective process for low-temperature service. Applicability of LAHW is under concern due to process stability and mechanical properties related to heterogeneous filler wire distribution through the whole weld metal in deep and narrow joints. This can cause reduced mechanical properties in the weld root as well as problems with solidification cracking. The fast cooling rate in the root provides hard and brittle microconstituents lowering toughness at low temperatures. Numerical simulations and experimental observations showed that an increase in heat input from the laser beam is an effective way to reduce the cooling rate, which is also possible by applying preheating.
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The penetration efficiency of thick plate Laser-Arc Hybrid Welding
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Double-sided fiber Laser-Arc Hybrid Welding was used to join 45 mm thick high strength steel over a wide range of parameters in order to investigate the efficiency of the process. Air gap size, I- and Y-groove type preparation, pulsed and cold metal transfer pulsed arc modes, arc-laser setup, and travel speeds were compared, and in all cases, sufficient filler material was provided to fully fill the gap. The welds were investigated using high speed imaging and cross-sectional analysis to identify penetration depths, morphology, and imperfections. Larger joint air gaps were found to contribute most to weld penetration depth. Surprisingly, increased line energy decreased penetration efficiency in most cases. The Laser-Arc interdistance was also investigated, revealing an arc size and melt flow dependency for achieving higher penetration depth for a leading arc. It was found that, although penetration can be optimized, solidification cracking can be a limiting factor in the application of deep penetration Hybrid Welding for thick steel section joining.
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process stability during fiber laser arc Hybrid Welding of thick steel plates
Optics and Lasers in Engineering, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Abstract Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc Welding. Deep penetration Laser-Arc Hybrid Welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern Welding consumables such as metal-cored wire and advanced Welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG Hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of Welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.
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Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:A standard Laser-Arc Hybrid Welding (S-LAHW) and LAHW with preplaced cut wire inside the groove before Welding were studied and compared. The S-LAHW setup revealed problems with filler wire deliver ...
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Deep penetration fiber Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:The present investigation addresses Laser-Arc Hybrid Welding of 45 mm thick steel with variation in a wide range of process parameters. High volume fraction of acicular ferrite formed in the upper ...
Odd M Akselsen - One of the best experts on this subject based on the ideXlab platform.
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Application of Laser-Arc Hybrid Welding of steel for low-temperature service
The International Journal of Advanced Manufacturing Technology, 2019Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander F. H. KaplanAbstract:Laser-Arc Hybrid Welding (LAHW) is more often used in shipbuilding and oil and gas industries in recent years. Its popularity arises due to many advantages compared to conventional arc Welding processes. The laser beam source is used to achieve much higher penetration depths. By adding filler wire to the process area, by means of an arc source, the mechanical properties can be improved, e.g. higher toughness at low temperatures. Therefore, LAHW is a perspective process for low-temperature service. Applicability of LAHW is under concern due to process stability and mechanical properties related to heterogeneous filler wire distribution through the whole weld metal in deep and narrow joints. This can cause reduced mechanical properties in the weld root as well as problems with solidification cracking. The fast cooling rate in the root provides hard and brittle microconstituents lowering toughness at low temperatures. Numerical simulations and experimental observations showed that an increase in heat input from the laser beam is an effective way to reduce the cooling rate, which is also possible by applying preheating.
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The penetration efficiency of thick plate Laser-Arc Hybrid Welding
The International Journal of Advanced Manufacturing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Double-sided fiber Laser-Arc Hybrid Welding was used to join 45 mm thick high strength steel over a wide range of parameters in order to investigate the efficiency of the process. Air gap size, I- and Y-groove type preparation, pulsed and cold metal transfer pulsed arc modes, arc-laser setup, and travel speeds were compared, and in all cases, sufficient filler material was provided to fully fill the gap. The welds were investigated using high speed imaging and cross-sectional analysis to identify penetration depths, morphology, and imperfections. Larger joint air gaps were found to contribute most to weld penetration depth. Surprisingly, increased line energy decreased penetration efficiency in most cases. The Laser-Arc interdistance was also investigated, revealing an arc size and melt flow dependency for achieving higher penetration depth for a leading arc. It was found that, although penetration can be optimized, solidification cracking can be a limiting factor in the application of deep penetration Hybrid Welding for thick steel section joining.
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process stability during fiber laser arc Hybrid Welding of thick steel plates
Optics and Lasers in Engineering, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:Abstract Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc Welding. Deep penetration Laser-Arc Hybrid Welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern Welding consumables such as metal-cored wire and advanced Welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG Hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of Welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.
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Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:A standard Laser-Arc Hybrid Welding (S-LAHW) and LAHW with preplaced cut wire inside the groove before Welding were studied and compared. The S-LAHW setup revealed problems with filler wire deliver ...
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Deep penetration fiber Laser-Arc Hybrid Welding of thick HSLA steel
Journal of Materials Processing Technology, 2018Co-Authors: Ivan Bunaziv, Jan Frostevarg, Odd M Akselsen, Alexander KaplanAbstract:The present investigation addresses Laser-Arc Hybrid Welding of 45 mm thick steel with variation in a wide range of process parameters. High volume fraction of acicular ferrite formed in the upper ...
Xiaoyan Zeng - One of the best experts on this subject based on the ideXlab platform.
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Influence of Welding angle on the weld morphology and porosity in Laser-Arc Hybrid Welding of AA2219 aluminum alloy
Welding in the World, 2019Co-Authors: Cong Chen, Ming Gao, Yiping Shen, Xiaoyan ZengAbstract:The influence of Welding angle on weld morphologies and porosity characteristics was studied in Laser-Arc Hybrid Welding of AA2219 aluminum (Al) alloy. The upward sloping and vertical weld (USVW) was performed better than the downward sloping and vertical weld (DSVW). The high-speed camera was used to observe the Welding process. It is found that the Welding process becomes stable when the transitional position of the droplet was 2 mm away from the keyhole. By analyzing the force act on keyhole and characteristics of the pool, it is found that the weld morphologies and porosity characteristics were associated with gravity-laser angle (β), which affects the keyhole stability and characteristics of the pool. The results showed that the flow velocity was accelerated when the β increased, which was a benefit for decreasing porosity. This is because the gravity in the direction of the Welding accelerates the pool flow. Due to the increasing of the β, the static pressure and the vapor pressure in the keyhole were increased, which improved the stability of the keyhole and decreased the porosity.
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Microstructure and mechanical properties in three-dimensional Laser-Arc Hybrid Welding of AA2219 aluminum alloy
Journal of Laser Applications, 2019Co-Authors: Cong Chen, Ming Gao, Xiaoyan ZengAbstract:The weld microstructure and property of the three-dimensional Laser-Arc Hybrid Welding of AA2219 aluminum alloy were studied in this paper. It is indicated that they were mainly influenced by the gravity-laser angle (β). The results showed that the width of the columnar grains zone gradually reduced with increased β, and it disappeared when β increased to 60°. When β was constant, an optimized arc current value existed with which the best tensile property was obtained. The tensile property increased first then decreased with increased β. When β reached 60°, the maximum tensile strength and elongation 320 Mpa and 5%, respectively, were acquired. It was concluded that the enhancement of weld property depended on porosity decreasing and microstructure refinement.The weld microstructure and property of the three-dimensional Laser-Arc Hybrid Welding of AA2219 aluminum alloy were studied in this paper. It is indicated that they were mainly influenced by the gravity-laser angle (β). The results showed that the width of the columnar grains zone gradually reduced with increased β, and it disappeared when β increased to 60°. When β was constant, an optimized arc current value existed with which the best tensile property was obtained. The tensile property increased first then decreased with increased β. When β reached 60°, the maximum tensile strength and elongation 320 Mpa and 5%, respectively, were acquired. It was concluded that the enhancement of weld property depended on porosity decreasing and microstructure refinement.
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Influences of synergy effect between laser and arc on Laser-Arc Hybrid Welding of aluminum alloys
Optics & Laser Technology, 2019Co-Authors: Chen Zhang, Ming Gao, Xiaoyan ZengAbstract:Abstract Researchers generally believe that synergy effect between laser and arc enables Laser-Arc Hybrid Welding to acquire obvious advantages of efficiency and quality in Welding aluminum alloys. However, influences of physical essence of the synergy effect on Welding process were not clear. In this study, basic principle of the synergy effect and its influences on Welding process were obtained by spectral analysis of Hybrid plasma plume and high-speed photographic analysis of Welding process. First, the principle of the synergy effect is that laser interacts with arc to render electron energy level to transition. This process emits more photons, which enhance the heat input to the weld materials. The synergy effect is quantified by spectral intensity. It increases with the laser power, and decreases with the arc current and Laser-Arc distance. It is proportional to the cross section of weld, especially the upper, and beneficial to improve the Welding energy utilization. Secondly, the amount of spatter in Laser-Arc Hybrid Welding is significantly less than that of arc Welding. The bigger weld pool, the downward melt flow, and the reduced droplet transfer force generated by the synergy effect make the transferring droplets more easily absorbed by the weld pool, which stabilizes the transfer process and reduces the generation of spatter. The research results are beneficial for understanding Hybrid Welding mechanism and optimizing the Welding process.
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effects of groove parameters on space constraint of narrow gap laser arc Hybrid Welding
Journal of Manufacturing Processes, 2018Co-Authors: Yunfei Meng, Geng Li, Xiaoyan ZengAbstract:Abstract Obvious space constraint effect (SCE) related to energy transfer was found in narrow gap Laser-Arc Hybrid Welding (NGHW). It was significantly affected by changing the width of rectangle groove (WG) and the angle of Y-shape groove (αG), and the central crack and sidewall notch occurred on weld cross-section when WG ≤ 4 mm or αG ≤ 60°. The SCE was quantitatively characterized by the dimensionless parameter of melting energy increment (ψ), which is the increment of melting efficiency of NGHW to the Hybrid Welding without narrow gap. The larger the ψ, the stronger the SCE. The ψ of rectangle groove was up to 30% when the WG was at 6 mm, while the maximum of the ψ of Y-shape groove was only 7% when the αG was at 60°. According to the calculated ψ and the defect occurring tendency, the optimized groove of NGHW was confirmed as the rectangle groove with 6 mm-width, and was verified by a 25 mm-thick joint. Besides, the effects of SCE on the energy transfer in narrow gap were discussed according to the behaviors of arc column and laser-induced plasma.
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effect of heat input on weld microstructure and toughness of laser arc Hybrid Welding of martensitic stainless steel
Journal of Materials Processing Technology, 2017Co-Authors: Chen Zhang, Xiaoyan ZengAbstract:Abstract Laser-Arc Hybrid Welding of AISI 420 martensitic stainless steel (MSS) was carried out, and the microstructure-toughness relationship was discussed and established. The coarse-grained heat affected zone (CGHAZ) is the weakest area of the weld. The CGHAZ microstructure and the toughness assessed by Erichsen cupping test had a good agreement with the increase of heat input, indicating that the toughness was not only dependent on the grain size but also the contents of inter- and intra- granular carbides within the CGHAZ. By introducing the effects of the carbides, an equivalent grain diameter (D e ) was proposed to establish a new Hall-petch relationship between the CGHAZ microstructure and the toughness, whose fitting degree was increased from 0.677 to 0.974. The weld toughness was acceptable to meet the rolling requirement when the D e was smaller than 11 μm, under which the weld fractured along the base metal rather than the CGHAZ.
