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Demands for improved productivity, efficiency, and quality pose challenges to the welding industry, significantly the laser beam welding process. As the materials become increasingly sophisticated in their chemical composition to provide ever-better functionally specific properties, a more complete and precise understanding of how such materials can join for optimal effectiveness and efficiency will become essential. The objective of the present study is to review the current literature and discuss future trends. This thorough review study provides a comprehensive systematization and corresponding advances of constituent technologies on laser beam welding process modeling (LBWPM), including types of modeling including characteristics of weld joint (geometrical, metallurgical, and mechanical), monitoring (pre-process, in-process, and post-process), length scale (macroscale, mesoscale, and microscale), and approach of modeling (empirical-based and theoretical-based). The relevant case studies will be evaluated, discussed, and compared. In the end, the general trends, and strong indications of LBWPM, seen in the future, will be discussed. The current study also provides a good foundation for future research and creates awareness of the developmental direction of laser beam welding process modeling in manufacturing industries.

Abstract For a practical pulse laser beam welding (PLBW) process of metal sheets assembled in butt joint configuration, the precise control of the assembling clearance has been a challenge. The existence of machining burrs and assembly errors will lead to forming severe defects, such as misalignment, welding leakage, and penetrating. In this paper, a pair of Ti6Al4V plates with a 0.2-mm air gap was tested by an improved PLBW process. A three-dimensional multi-phase and multi-physical field coupling model of the Ti6Al4V plate with a reserved air gap was established according to the weld profile, and the dynamic behavior of the keyhole and molten pool was simulated. The transient temperature field, velocity field, keyhole size, and liquid bridge connection were calculated by using different welding heat input parameters. The results showed that the weld profile simulated by the CFD model is in good agreement with the experimental results, and the deviation is between 0.68 and 7.95%. After the laser power reaches the peak value, the metal steam eruption weakens and the obvious Marangoni vortex appears in the molten pool. The simulated keyhole is always in three stages, that is, the keyhole appears and then gradually forms the through-hole. The through-hole keeps oscillating, and finally, the keyhole shrinks and disappears when the laser power drops to zero. With the increase of laser peak power, the keyhole shape becomes more curved, indicating that the keyhole oscillation is enhanced. With the increase in welding speed, the stability of the molten pool is improved, and the area of the liquid bridge rises more regularly.

Vacuum laser beam welding, also known as subatmospheric laser welding, is a promising welding process that simultaneously offers deep penetration and sound welding quality. It has both the welding quality of electron beam welding and the flexibility of laser welding. In this study, vacuum laser beam welding was applied to Ti–6Al–4 V alloy, which has strong affinity with oxygen and which is usually welded via arc welding under a strictly controlled atmosphere or by electron beam welding in a vacuum chamber. In low vacuum laser welding, the ambient pressure was maintained at about 1 kPa by a vacuum pump while supplying shielding gas. The effects of the type of shielding gas, the shielding gas flow rate, and the nozzle stand-off distance on the laser-induced plume generation, degree of weld bead oxidation, and bead cross sections were investigated. Helium shielding was found to lead to excellent suppression of plume generation and bead oxidation regardless of the stand-off distance. For argon shielding, a low stand-off distance of 10 mm is necessary to prevent plume generation and oxidation. The shielding gas flow rate was not a critical parameter, unlike the type of shielding gas used and nozzle stand-off distance in this study.

Compared to single-beam laser welding, dual-beam laser welding can increase the area of the connection between the face plate and the core plate, improve structural mechanics performance, and suppress porosity. Therefore, dual-beam laser welding is taken to join the sandwich structure. However, the interaction of dual beam during laser welding is not clear and how to suppress porosity needs to be investigated. A numerical model considering dual-beam ray tracing was proposed to investigate the influence of spot spacing on pore formation during parallel dual-beam laser welding of sandwich structures. Most pores were observed near the interface between the face plate and the core plate, where the necking and bulge of molten pool created a region for bubble entrapment. Increasing the spot spacing was found to reduce the frequency of keyhole collapse and possibility of bubble formation due to decreased aspect ratio of keyhole. On the one hand, the lower rear wall of the keyhole protruded less towards the molten pool at larger spot spacing, so the bubble size was smaller when the keyhole collapsed. On the other hand, with increased spot spacing, temperature and velocity of the fluid flow from the bottom of the keyhole decreased, resulting in smaller area enclosed by the bulge and necking, which was beneficial for preventing the coalescence of formed bubbles and facilitating their escape. With the spot spacing increased from 0.6 to1.0 mm, the porosity obtained from the experiment decreased from 1.46 to 0.18%, and so was the maximum pore size from 0.93 to 0.25 mm.

The welding industry is facing increasing demands for improved productivity, efficiency, and quality, particularly in the laser beam welding process. As advanced materials with complex compositions are used to achieve specific functional properties, there is a growing need for a comprehensive and precise understanding of how these materials can be effectively and efficiently joined. In this paper, we present an innovative and comprehensive model that can accurately predict the geometrical, metallurgical, and mechanical characteristics of the laser beam welding process. The model consists of two main subsystems: the thermal dynamic model and the characteristic model. The thermal dynamic model captures essential parameters such as melt pool dimension, maximum temperature, and cooling rates throughout the welding process. This enables the prediction of geometrical characteristics of the weld, particularly in terms of melt pool dimension. The characteristic model encompasses sections dedicated to geometrical, metallurgical, and mechanical characteristics. By analyzing the cooling rate, the model can diagnose important metallurgical characteristics, including primary dendrite arm spacing (PDAS) and secondary dendrite arm spacing (SDAS). Based on the PDAS and SDAS, the model predicts the mechanical strength during the welding process. The results of our study demonstrate the exceptional accuracy of model 2, which incorporates both primary and secondary dendritic arm distances. The model achieved impressively low error rates of only 0.8298% and 0.8300% for PDAS and SDAS, respectively. These findings highlight the model’s reliability and effectiveness in predicting the mechanical strength of welded joints during the laser beam welding process. This comprehensive model offers valuable insights and predictive capabilities that are crucial for optimizing the welding process and achieving superior productivity, efficiency, and quality. By accurately predicting the geometrical, metallurgical, and mechanical characteristics, it enables engineers and researchers to make informed decisions, enhance process control, and ensure the successful integration of advanced materials in laser beam welding applications.

Continuous wave laser beam welding (CWLBW) of titanium alloy has been widely investigated experimentally and numerically in terms of scientific understanding and technology application. The existing CWLBW related to numerical modeling mostly ignored the essence of continuous laser input, and the simulation was usually performed using a constant laser power. In this study, the deep penetration CWLBW process of Ti6Al4V plates was modeled mathematically by taking the high-frequency pulsed laser into account. The dynamics of the keyhole and weld pool at different welding speeds were numerically solved and contrastively analyzed. The results show that the improved heat source model yields sufficient accuracy on seam profile prediction. As the welding proceeds, temperature field and the keyhole morphology fluctuate significantly due to the variation of the heat input within a pulse period, which is hardly a common observation under a constant laser irradiating condition. With the increase of welding speed, the depth of weld pool decreases, and the keyhole dimensions becomes less symmetrical along the welding direction and less oscillating in quasi-steady stage, indicating a higher in-process dynamic stability. The current work provides a more precise description and a further understanding of heat and mass transfer behaviors during a CWLBW process.

Laser beam welding of metals has progressed dramatically over the last years mainly arising from joining applications in the field of electromobility. Allowing the flexible, automated manufacturing of mechanically, electrically, and thermally stressed components, the process is more frequently applied for joining highly reflective materials, for example for battery tab and busbar connections. The local, non-contact energy input favors this welding technology; however, joining of copper and aluminum sheets still poses a challenge due to the physical properties of the joining partners and intermetallic phases from dissimilar metal interaction, which reduce seam performance. The use of green laser radiation compared to infrared laser radiation offers the advantage of a significantly increased absorptivity for copper materials. A changed incoupling behavior is observed, and a lower deep penetration threshold has been already proven for 515 nm wavelength. When copper and aluminum are welded with the former as top sheet, this welding mode is essential to overcome limited aspect ratios from heat conduction welding. However, the opportunities of applying these beam sources in combination with spatial power modulation to influence the interconnection area of copper-aluminum joints have not yet been studied. The aim of this work is therefore to investigate the seam properties and process stability of different overlap welding strategies using green laser radiation for dissimilar metal welding. A microstructural analysis of the different fusion zones and mechanical strength of the joints are presented. In addition, the experimental parameter sets were analyzed regarding their application in battery module busbars by examining the electrical resistance and temperature distribution after welding. A parameter window was identified for all investigated welding strategies, with the stitched seam achieving the most stable results.

This paper aims at investigating the effect of laser welding parameters on the hardness profile, using hardness mapping analyses, and welding geometry of galvanized steel plates. Hardness distribution and geometry deflection of galvanized welded thin plates are commonly applied in fields where weld quality is of utmost importance. Due to the welding process and material condition, welding galvanized steel is one of the problematic matters in welding technology. Here, the design of experiment (DOE) approach is used to study the effect of process parameters. Using a pattern matrix of micro-indentation hardness experiment, the welding defects are visualized on the hardness profile of the weld cross-section. The effect of process parameters on welding defect formation is then qualitatively analyzed. The geometrical defects of welding such as weld width and voids are then quantitatively studied based on analysis of variance (ANOVA), and predictive models of welding voids and weld seam width are developed based on the regression method. Response surface method (RSM) is then applied to define the trend of process factor interaction on the welding defects. The experimental results confirm the reliability of developed predictive models of welding defect geometry, weld width, and void area of laser-welded galvanized blanks. Graphic abstract

The laser weldability of aluminum alloy is unstable due to low laser beam absorption rate, low viscosity, and high thermal diffusivity. As a result, defects such as porosity and sagging are easily formed in the fusion zone. Vacuum laser beam welding (VLBW) has been introduced to ensure better weldability by using a relatively low ambient pressure. This allows for deep penetration depth and stable keyhole behavior compared to welding under atmospheric conditions. To evaluate the effects of ambient pressure on laser welding characteristics, VLBW was performed with similar and dissimilar aluminum alloys. Varying the pressure inside the vacuum chamber affected the welding characteristics. It is inferred that variation in ambient pressure changes the interactions between the laser source and substrate, such as the laser energy transfer, plasma plume generation, and the behavior of keyhole and molten pool. The penetration depth increased with decreasing ambient pressure for the same heat input conditions. Also, decreasing the ambient pressure reduced the formation of defects such as sagging, underfill, and porosity. Plasma plume generation was also varied depending on the ambient pressure, and plasma plume height and intensity were compared using a CCD camera. In this experiment, an ambient pressure of 10 mbar was sufficient to ensure good welding properties and stability. Below 10 mbar, the VLBW system is considered an effective alternative to processes that require high vacuum environments.

Underwater laser beam welding (ULBW) with filler wire was applied to Ti-6Al-4V alloy. Process parameters including the back shielding gas flow rate (BSGFR) (the amount of protective gas flowing over the back of the workpiece per unit time), focal position, and laser power were investigated to obtain a high-quality butt joint. The results showed that the increase of BSGFR could obtain the slighter oxidation level and refiner crystal grain in the welded metals. Whereas the back shielding gas at a flow rate of 35 L/min resulting in pores in the welded metals. With the increasing of the heat input, the welded metals went through three stages, i.e., not full penetration, crystal grain refinement, and coarseness. Crystal grain refinement could improve the mechanical properties, however, not full penetration and pores led to the decline in mechanical properties. Under optimal process parameters, the microstructure in the fusion zones of the underwater and in-air weld metals was acicular martensite. The near the fusion zone of the underwater and in-air weld metals consisted of the α + α′ phase, but almost without the α′ phase in the near base metal zone. The tensile strength and impact toughness of the underwater welded joints were 852.81 MPa and 39.07 J/cm2, respectively, which approached to those of the in-air welded joints (861.32 MPa and 38.99 J/cm2).