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Role of thermal fluid dynamics in alloying element distribution and weld porosity in powder feeding-based laser welding of Al alloy
摘要： This work develops a model incorporating the powder transport, laser heating, and molten pool dynamics to describe the mixing process of alloying element and reveal the mechanisms of bubble dynamics in powder feeding-based laser welding. Simulation results show that the different roles of recoil pressure: driving the molten metal flow at the rear part of keyhole in partial penetration and maintaining the stable keyhole profile in full penetration, are responsible for the difference between their melt flow behaviors. Driven by the melt flow, the alloying element transport path can be generalized as the shallow areas, the rear areas, the central and bottom areas in partial penetration. It permits a relatively uniform silicon distribution. However, two vortices rotating in the opposite direction in full penetration results in a higher concentration of Si in the upper part. Meanwhile, we conclude three steps for the bubble dynamics: bulge formation, bubble formation, bubble being captured by re-formed keyhole or being captured by the solid-liquid interface or escaping from the free surface. Such phenomena manifest that the contributions to the processing quality and metallurgy quality of welded joints come from the complex melt flow behaviors, which are confirmed by a series of experiments.
关键词： Thermal fluid dynamics,Alloying element distribution,Melt flow,Powder feeding-based laser welding,Weld porosity
更新于2025-09-23 15:19:57
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[Laser Institute of America ICALEO?? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18a??22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Preliminary laser welding tests of 22MnB5 steel with a butt joint and lap joint configurations
摘要： In recent years, the automotive industry has expanded the use of hot stamping and press hardening processes. Using ultra-high-strength steels, such as 22MnB5, allows car manufacturers to build lighter, stronger and safer vehicles at a reduced cost and generate lower CO2 emissions. In the research the laser weldability of 22MnB5 steel was tested. The test plates were produced using a constant heating temperature of 900°C and a variable furnace time of between 250 and 600 seconds. The samples were quenched in a water-cooled flat die to ensure a fully martensitic structure and good flatness. The welding tests were made using a 10 kW disk laser equipped with the optics of Precitec. Various welding energies were used to determine the effects of heating and cooling on the mechanical properties of the welds. The weld inspections conformed to ISO standard 13919-1 and automotive testing code SEP 1220-3 (Testing and documentation guideline for the joinability of thin sheet of steel - Part 3: Laser beam welding) where applicable. The radiographic inspection showed some porosity and a lack of penetration on both the face and root side of almost every weld. Despite these serious imperfections, the destructive tests were performed and showed relatively good results. The maximum achieved yield strength was over 1200 MPa, reaching almost the strength of the base material 22MnB5. The maximum value of hardness in the laser welds of 22MnB5 steel was 500 HV; the same as the hardness of the base material. However, a relatively narrow softened zone exists in the HAZ area, which has a hardness value of 200 HV.
关键词： press hardening,ultra-high-strength steels,22MnB5 steel,automotive industry,laser welding
更新于2025-09-23 15:19:57
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Hot cracking in autogenous welding of 6061-T6 aluminum alloy by rectangular pulsed Nd:YAG laser beam
摘要： Due to high hot crack susceptibility of Al-Mg-Si alloys, autogenous welding by rectangular pulsed laser beam has not been generally successful in the removal of cracks. In this research, the effect of pulsed Nd:YAG laser parameters and preheating on the creation of hot cracks in the 6061-T6 aluminum alloy was investigated. The sample that was fabricated by the laser parameters including 1 Hz, 0.12 mm/s, 10 ms, and without preheating exhibited the highest cooling rate and the smallest dendrite arm spacing but no hot crack was observed. The tensile test specimens of this sample fractured at a point far from the weld metal and a decrease in the precipitation of silicon and magnesium in the inter-dendritic space and the reduction of thermal stresses resulted in the elimination of hot cracks. However, according to macro-scale models for the creation of hot cracks, preheating decreased the tensile stresses in the BTR (brittle temperature range), but increasing the preheating temperature led to increasing rather than decreasing the hot crack length. In this case, the formation of hydrogen porosity, the segregation of silicon and magnesium, and the creation of low melting point compounds were the important parameters affecting the hot crack initiation and growth.
关键词： Laser welding,6061 aluminum alloy,Stress simulation,Solidification microstructure,Hot crack modeling,Rectangular pulse
更新于2025-09-23 15:19:57
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Spatter feature analysis in laser welding based on motion tracking method
摘要： In this work, the spatter motion features in laser welding process have been investigated using image motion tracking method. According to the acquired results, both the distribution and motion features of extracted spatters exhibit two characteristic ejection directions, forward and backward along the welding direction. Along with the welding speed increase, the spatter motion trend of being ejected backward along the welding direction enhances. The spatter motion features are discussed according to the pressure induced by the vapor plume. The joint force synthesised from the impact force (induced by hydrodynamic pressure) and the shear force (induced by the viscosity between vapor plume and molten metal) have been found driving the molten metal to move upward. The maximum joint force is performed when the vapor plume is ejected in two certain inclinations, respectively -40 ° forward and 50 ° backward to the vertical axis. In addition, the molten metal behind the keyhole is easiest to be pushed away from the weldpool and form the spatters compared to rest of the directions.
关键词： laser welding,spatter formation,motion track method
更新于2025-09-23 15:19:57
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Real-time penetration state monitoring using convolutional neural network for laser welding of tailor rolled blanks
摘要： In this paper, an innovative monitoring system capable of diagnosing the penetration state during the laser welding process is introduced, which consists of two main blocks: a coaxial visual monitoring platform and a penetration state diagnosis unit. The platform can capture coaxial images of the interaction zone during the laser welding through a partially transmitting mirror and a high-speed camera. An image dataset representing four welding states was created for training and validation. The unit mainly consists of an embedded power-efficient computing TX2 and image processing algorithms based on a convolution neural network (CNN). Experiment results show that the platform can stably capture state-of-the-art welding images. The CNN used for a diagnosis of the penetration state is optimized using an optimal network structure and hyperparameters, applying a super-Gaussian function to initialize the weights of the convolutional layer. Its latency on TX2 is less than 2 ms, satisfying the real-time requirement. During the real laser welding of tailor-rolled blanks, a penetration state diagnosis with an accuracy of 94.6 % can be achieved even if the illumination changes significantly. The similar accuracy between the validating set and a real laser welding demonstrates that the proposed monitoring system has strong robustness. The precision and recall ratios of the CNN are higher than those of other methods such as a histogram of oriented gradients and local binary pattern.
关键词： Laser welding,Coaxial visual monitoring,Penetration state diagnosis,Convolutional neural network (CNN),Tailor-rolled blank
更新于2025-09-23 15:19:57
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Microstructure and mechanical properties of welding–brazing of Ti/Al butt joints with laser melting deposition layer additive
摘要： Laser welding–brazing of Ti/Al butt joints was performed with coaxial Al–10Si–Mg powders feeding. The experimental results indicated that a sound Ti/Al butt joint could be obtained by an additive layer approach. The influence of the laser melting deposition layers on the weld appearance, interfacial microstructure and tensile properties were investigated. High-quality joints were produced when five and seven layers were deposited. The morphology and thickness distributions of the interfacial intermetallic compounds (IMC) at the brazing interface along the thickness direction of the joint varied with the number of deposition layers. Continuous serrated IMC was obtained in joints produced by seven deposition layers, and the IMC layer was distributed homogenously along the thickness direction. The maximum thickness difference of the IMC was only approximately 0.12 μm. The microstructure of the IMC layer was composed of a nanosized granular Ti7Al5Si12 phase and serrated Ti(Al, Si)3 phase. The maximum tensile joint strength reached 240 MPa, 80% of that of the aluminum base metal, and the lower tensile strength of the other joints was caused by insufficient IMC layer or a porosity defect.
关键词： Tensile strength,Laser melting deposition,Interfacial IMC,Laser welding–brazing,Ti/Al butt joint
更新于2025-09-19 17:15:36
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Influence of Magnesium on Spatter Behavior in Laser Deep Penetration Welding of Aluminum Alloys
摘要： The quality of welds, as well as the necessity of post-processing, is challenged by spatter generation during the laser keyhole welding process. In this study, the influence of the magnesium content on spatter behavior is studied for three aluminum alloys (Al99.5, AlMg3, and AlMg5). A synchronized dual high-speed camera system is used to observe the spatter behavior and to reconstruct 3D spatter trajectories as well as determine the characteristics of spatter velocity, flight path angle, and approximate spatter size. The mean spatter velocities and flight path angles of the welding experiments with the three alloys were in welding direction between 4.1 m/s and 4.6 m/s and 44.8°, respectively. Furthermore, the AlMg alloys show excessive spatter behavior with spray events of more than 50 spatters at a time, and less frequently spatter explosions. Spatter spray events show a character similar to spatter explosions. Volumetric evaporation is proposed as effecting these events. In contrast, and resulting from a different mechanism, pure aluminum (Al99.5) shows group ejection events with at least 10 spatters at a time. In this study, there are no correlations between spatter velocities and flight path angles, nor between velocities and approximate spatter sizes.
关键词： high-speed imaging,keyhole welding,aluminum alloy,welding,laser welding,spatter
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Experimental and numerical study on laser welding of glass using a CO2 laser and glass fiber as filler material
摘要： Automated laser welding with filler wires for bridging gaps and for connecting complex devices has been established for different metal materials. In spite of that, it is still a challenge to transfer this welding process to the brittle material glass. Therefore, glass welding is often realized through a manual process by heating the glass with a gas flame. In addition, welding of non-rotational components requires filler material for gap bridging between the joining partners, which is applied manually today. This work presents an experimental and numerical study on laser welding of fused silica using glass fiber as a filler material to bridge gaps. The goal was to achieve a defined weld penetration depth and heat affected zone which is important for the production of optical elements. Therefore, a CO2 laser heats up the glass components as well as the glass fiber within a temperature controlled welding process. The numerical investigations were used to identify the general process window for welding fused silica. Within the experimental study, the process parameters, such as the defined welding temperature, laser focal spot size, and feed rate were varied to investigate their impact on the welding outcome. In addition, the impact of the filler wire coating on the material composition of the welded component in the joint zone was investigated. Compared to the manual process, laser welding with glass fiber as a filling material leads to a highly reproducible process enabling a high automation level.
关键词： fused silica,temperature controlled welding,heat affected zone,laser welding,glass fiber,filler material,glass,CO2 laser,weld penetration depth
更新于2025-09-19 17:13:59
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High Power Fiber Laser Welding with Filler Material
摘要： Industry today is continually challenged to improve quality, reliability, reduced cycle times, and improve the overall manufacturing efficiency. This is driving manufacturers across various market sectors to consider fiber laser welding and the possibility to automate their welding processes to improve consistency and part quality. Another driver is the changing workforce dynamics. It is hard to find or train skilled workers who can consistently and reliably weld aluminum, titanium, and high-strength nickel alloys. This is particularly true when welding with filler material where the base materials are subject to porosity and cracking during the welding process.
关键词： Fiber Laser Welding,Titanium,Filler Material,Nickel Alloys,Aluminium,Laser Welding
更新于2025-09-19 17:13:59
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Effects of Cr2O3 active agent on the weld process dynamic behavior and joint comprehensive properties of fiber laser welded stainless steel thick plate
摘要： In this study, the dynamic behaviors of metal vapor, plasma, keyhole, and weld pool during activating laser welding of stainless steel thick plates are monitored in real time by employing a novel "sandwich" method in combination with a high-speed camera system. Meanwhile, the welding quality of specimens is inspected and analyzed from the aspects like joint weld formation, mechanical properties, microstructure, and element distribution. The effects of Cr2O3 active agent on the welding stability and quality of specimens are explored. According to the results, adequate coating of active agent on the specimen surface can weaken and suppress the generation and drastic changes of metal vapor and plasma inside and outside the keyhole, increase the keyhole depth, improve the keyhole shape, weaken the oscillation amplitude of weld pool, and prolong the change cycles of keyhole and weld pool. Consequently, the stability of welding process is enhanced, the generation of porosity and splash defects is inhibited preferably, the quality of weld formation is improved, the weld penetration is increased, the grain structure in weld zone is refined, the width of heat affected zone is narrowed, and the joint strength and toughness are enhanced, without showing apparent change of the relative element contents in the welded joint. In conclusion, coating of Cr2O3 active agent on the specimen surface is effective in improving the welding properties of laser welded stainless steel plates.
关键词： Welding quality,Fiber laser welding,Plasma morphology,Cr2O3 active agent,Weld pool behavior
更新于2025-09-19 17:13:59