Electron Beam Welding Process Research Articles

Research on electronic optical monitoring technology and system design for vacuum electron beam welding process

Electron beam welding technology is increasingly used in industrial manufacturing due to its high power density and the purity of welded joints. In vacuum environments, traditional optical and machine vision monitoring methods are susceptible to contamination by metal vapors, which hinders the monitoring effect. Due to the limitations of optical monitoring methods, electronic optical imaging technology is a new alternative monitoring method that has been introduced into the electron beam processing in recent years, but the complexity of the industrial electron beam welding environment makes it relatively less studied in the field of electron beam welding. In this study, a YAG scintillator detector is proposed to collect the backscattered electron information generated by the interaction of electrons with the sample, and an FPGA real-time processing system is used to realize the weld quality monitoring in the industrial electron beam welding processes. The distribution law of backscattered electrons in space is simulated by Monte Carlo method, and the results show that the number of distribution in the 40°∼60° angle region is more, the backscattering coefficient increases with the increase of the incident angle of the electron beam, and the backscattering coefficient of the samples with large atomic numbers is relatively high. The field monitoring experiments show that the designed system exhibits good sensitivity to the characteristic morphology, and the imaging resolution reaches more than 200 μm, and the weld hole defects are clearly visible. A good linear correlation between the current change curve during scanning and the actual shape profile is shown, while the image resolution is better when the spot current is 1 mA.

Comparison of fatigue crack growth design curves on GMAW and EBW joints of high strength steels

There is a growing demand in the industrial sector for the use of high-strength structural steels (HSSSs), which can achieve a significant weight reduction in structures. These structural steels are usually produced by quenching and tempering (Q + T) or thermomechanical treatment (TM), and their applications in welded structures pose several challenges for the users. In industrial practice, gas metal arc welding (GMAW) is basically the most commonly used fusion welding process, which has a relatively high heat input. However, at HSSSs, there is a need for low heat input but, at the same time, productive welding processes. High-energy density welding processes, e.g., electron beam welding (EBW), offer a unique opportunity to weld these steels. The widespread use of HSSSs is also hampered by the fact that the benefits of high strength can be exploited primarily under static loading. At the same time, different welded structures made of HSSSs are often subjected to cyclic loading, and possible weld defects and material discontinuities are major risks in this case. During our experiments, GMAW and autogenous EBW processes were applied to make welded joints from S960 Q + T and TM structural steels. The fatigue resistance of the welded joints was characterized by fatigue crack growth (FCG) tests, considering the increased crack sensitivity of HSSSs. A statistical approach was followed both in the design of the experiments and in the evaluation of their results. Based on the test results fatigue crack propagation design curves were determined for the investigated GMAW and EBW welded joints. The design curves were compared with each other, with design curves of lower strength material (S690QL) and with the recommended fatigue crack growth laws of BS 7910.

Investigation of the effects of beam oscillations in electron beam–welded S1100M TMCP steel

The development of thermomechanically controlled processed (TMCP) high-strength steel (HSS) has significantly contributed to designing and developing the intricate structural components. It has broader applications in the cranes and lifting process industry (base frame, crane jibs, and crane columns), trailers, agricultural and forestry machinery, earth-moving equipment, etc. However, the development of new-grade steels with higher tensile strength led to higher requirements for welded joints, and the associated weldability issues have inspired detailed studies on electron beam welding (EBW) with different beam oscillations. Beam oscillation application with EBW processes improves the welding efficiency, weld quality, weld geometry, keyhole, etc., affecting the welded joints mechanical and microstructural properties. Thus, the present study investigates the impact and comparison of various beam oscillations on the microstructural and mechanical properties of EB-welded S1100M steel. The influence of welding parameters on the microstructure of welded joints was analyzed using a scanning electron microscope (SEM) and electron backscattered diffraction (EBSD). The analysis focused on evaluation of grain sizes, morphologies, distributions, and crystallographic orientations of different phase constituents in fusion zone (FZ) and heat-affected zone (HAZ). The mechanical properties were analyzed using hardness, tensile, and Charpy V-notch impact tests. The texture in the FZ is typically random, while the HAZ typically exhibits a strong rolling texture. In general, the cooling rate in EBW is very fast, possibly resulting in a fine-grained structure and reduced formation of coarse second-phase particles in the weld zone. The elliptical beam oscillation showed the highest hardness in HAZ 450 HV10. Elliptical beam oscillation slightly improves the welded joint’s tensile strength, and the impact test showed mixed fracture behavior.

Improved Joint Formation and Ductility during Electron-Beam Welding of Ti6Al4V and Al6082-T6 Dissimilar Alloys

The current work is based on investigating the influence of different technological conditions of electron-beam welding on the microstructure and mechanical properties of joints between Ti6Al4V and Al6082-T6 dissimilar alloys. The plates were in all cases preheated to 300 °C. Different strategies of welding were investigated such as varying the electron-beam current/welding speed ratio (Ib/vw) and applying a beam offset towards the aluminum side. The heat input during the experiments was varied in order to guarantee full penetration of the electron beam. The macrostructure of the samples was studied, and the results indicated that using a high beam power and a high welding speed leads to an increased formation of defects within the structure of the weld seam. Utilizing a lower beam current along with a lower welding speed leads to the stabilization of the electron-beam welding process and thus to the formation of an even weld seam with next to no defects and high ductility. Using this approach gave the highest ultimate tensile strength (UTS) of 165 MPa along with a yield strength (YS) of 80 MPa and an elongation (ε) figure of 18.4%. During the investigation, improved technological conditions of electron-beam welding of Ti6Al4V and Al6082-T6 dissimilar alloys were obtained, and the results were discussed regarding possible practical applications of the suggested approach along with its scientific contribution to developing further strategies for electron-beam welding of other dissimilar alloys. The downsides and the economic effect of the presented method for welding Ti6Al4V and Al6082-T6 were also discussed.

Solidification Behavior and Microstructure Evolution in Dissimilar Electron Beam Welds Between Commercially Pure Iron and Nickel

Electron beam welding processes have highly accurate control of both spatial and temporal heating profiles which provide unique capabilities in dissimilar metals joining. In this work, electron beam welds were made between commercially pure nickel and iron to determine the effect of fusion zone composition on solidification behavior and microstructure evolution. The weld was made with a beam deflected in a circular pattern to enable joining and promote mixing. The beam traveled at a shallow angle of approximately 1 deg to the joint interface starting in the nickel and finishing in the iron. The shallow angle created a weld with a composition gradient along its 110 mm length. The solidification behavior and final weld microstructure were characterized using both light optical microscopy and scanning electron microscopy. Electron backscatter diffraction was used to determine the phase fractions in the fusion zone. A change in solidification mode from face-centered cubic austenite to body-centered cubic ferrite was observed as a function of fusion zone composition. Weld cross-sections containing 65.5 wt pct Fe and 76.9 wt pct Fe had a two-phase fcc + bcc microstructure. Using the compositions and phase fractions, the two-phase region was estimated to be between 56.4 and 79.7 wt pct Fe. Martensite was observed in cross-sections containing between 76.9 wt pct Fe and 98.1 wt pct Fe, which was confirmed using hardness measurements.

Study of Microstructure and Performance Evaluation of Zr-Sn-Nb Joints by Electron Beam Welding.

In this work, Zr-Sn-Nb alloy was joined by electron beam welding (EBW). A defect-free Zr-Sn-Nb joint with sound appearance was obtained. The grains in the weld zone (WZ) and heat-affected zone (HAZ) are significantly coarsened. The columnar grains with a maximum grain size of 0.5 mm are distributed in the upper region of the WZ, while the equiaxed grains are almost located in the bottom region of the WZ. The WZ is mainly composed of the dominant α-Zr, α'-Zr and a few β phases. The grain orientation of WZ and HAZ is uniform, indicating that no obvious preferred orientation existed. Coarse grains and fine acicular α' phases increase the strength of the joint, but reduce the plasticity and toughness of the joint. The tensile strengths of the joints at room temperature (RT) and 375 °C were 438 MPa and 313 MPa, respectively. The RT impact energy of the joint is 18.5 J, which is only 58.3% of the BM. The high purity of the EBW process and unsignificant grain orientation minimizes damage to the corrosion resistance of Zr-Sn-Nb alloy joints. The corrosion weight gain of the joint specimen and the BM specimen were 12.91 mg/dm2 and 12.64 mg/dm2, respectively, and the thicknesses of the cross-section corrosion layer were 12-15 μm and 9-12 μm, respectively.

Data mining techniques for quality improvement of electron beam welding process

Besides the fulfilment of the technological requirements for the geometry of the obtained welded joints by electron beam welding, there is a necessity to avoid the conditions, which more probably will lead to defect appearance. It is assumed that the appearance of defects is more probable under some regime conditions. For the modelling of the dependence of bivariate quality characteristics (such as the defect appearance) on the process parameters two different modelling approaches are applied and compared – logistic regression and neural networks. The implemented model-based approaches are compared and applied for the prediction of the defect appearance, depending on the variation of the electron beam process parameters.

Microstructural and mechanical properties of electron beam welded super duplex stainless steel

The electron beam welding of super duplex stainless steels is associated with challenges due to the concentrated heat input and the nitrogen loss that result in a predominantly ferritic structure after the solidification. This study presents an approach to overcome this issue by feeding nickel-based filler wire into the melt pool in welding of 2507 super duplex stainless steel. Results showed that the high-frequency beam oscillation combined with a multi-beam technique led a good mixing between the base metal and the filler wire, even at a large depth-to-width ratio. Additionally, the weld geometry was characterized by near-parallel fusion lines and a narrow heat-affected zone. The nickel addition resulted in a balanced microstructure in the weld metal with ferrite fractions of 35–55 %, despite a significant nitrogen loss, consequently leading to impact energy values of 215 ± 15 J and hardness values of 285 ± 15 HV. The findings of this investigation allow fabricators to effectively design electron beam welding processes for producing thick-walled super duplex stainless steel components.

Investigation of the influence of pulse parameters on the resulting weld seam quality in pulsed electron beam welding of AW 6061

Utilizing pulsed lasers in favor of a continuous wave in laser beam welding is a well-established method to achieve higher process efficiency and reduce heat input into the workpiece, which is especially useful for thin-walled workpieces (Steen, 2005). In addition, pulsed processes have shown to lead to smaller grain sizes due to higher cooling rates, which can lead to a reduction in hot cracks in some aluminum alloys (Beiranvand et al., 2019). Since an electron beam can also be pulsed, a technique industrially utilized in electron beam drilling, the same principles apply (Schultz, 2000). However, pulsed electron beam welding is rarely used in industrial welding applications due to the risk of pores, spiking and sputtering resulting from the pulsed process dynamic, especially in the deep welding regime (Kautz, 1991). This study aims to develop a pulsed electron beam welding process for AW 6061 sheet metal, which is susceptible to hot cracking. The influence of the welding and pulse parameters, as well as the combination of a pulsed beam with high frequency beam oscillation is discussed. Furthermore, suitable welding parameters for pulsed electron beam welding of AW 6061 are developed, and the increased efficiency of pulsed welding is shown by comparison to continuous welds.

Nanomechanical, mechanical and microstructural characterization of electron beam welded Al2219-T6 tempered aerospace grade alloy: A comprehensive study

As compared to traditional fusion welding processes, electron beam welding (EBW) is known to produce structurally robust microstructures and narrow heat-affected zone (HAZ) in metals. The process becomes more significant for the tempered alloys vulnerable to heat exposure. In the present investigation, Al 2219-T6 alloy was joined using the EBW process. The microstructural, mechanical, and nanomechanical characteristics of the resulting joint were investigated. EBW resulted in a narrow HAZ (22 μm) with a 430 mm fusion zone (FZ). A dendritic structure was observed in the FZ zone, while second-phase particles were absent indicating their dissolution during welding and interesting formation of Al2Cu mixture around the dendrites. The limited content of Cu in the base metal (BM) resulted in the formation of a solid solution in the FZ, along with the presence of fine equiaxed grains in the HAZ and equiaxed dendritic grains in the FZ zone. The X-ray diffraction analysis confirmed the absence of peaks corresponding to incoherent phases in the FZ. Compared to the BM, micro-hardness measurements revealed a 12.7 % increase in the hardness in the HAZ, while a significant decrease of approximately 19 % was observed in the FZ. The joint exhibited reduced tensile strength, ultimate strength by 42.2 %, and yield strength by 47.3 % when compared to the BM. The fracture analysis indicated a ductile failure mode with the presence of microvoids. Nano-indentation tests at various loads demonstrated a decrease in the nanohardness from the BM to the HAZ and FZ regions. Atomic force microscopy (AFM) analysis revealed significant pile-ups in the FZ, indicating the occurrence of plastic deformation during the welding process. The presented findings are valuable for the joint and structure design of Al −2219T6 alloy in particular and other Al alloys in general.

Effect of welding processes on ferrite content, microstructure and mechanical properties of super duplex stainless steel 2507 welds

Abstract Super duplex stainless steel (SDSS) plates of 6 mm thickness have been welded using tungsten inert gas, activated tungsten inert gas, electron beam welding and friction stir welding processes. Among these, in the first two, melting and solidification of material occurs slowly whereas, it is faster in electron beam welding process and no melting occurs in friction stir welding. Macro and microstructural studies, hardness surveys, tensile tests and percentage of ferrite content were compared for all the welds. The ferrite–austenite phase balance is 50 % each, with electron beam weld metal at about 65 % ferrite. This showed the hardness of the weld metal and heat affected zones to be higher than base metal. The weldment joint efficiencies are more than 90 %. The fracture location is found to be in the weld metal for tungsten inert gas and activated tungsten inert gas weld, in the nugget for friction stir welds and in the base metal for electron beam welds. The ductility of electron beam weld joints is 32 % while it is around 20 % for the others. The preferred order while choosing the welding process should be activated tungsten inert gas welding, tungsten inert gas welding, electron beam welding, and friction stir welding.

Numerical Fatigue Strength curve for the C1 Wedge Connection

AbstractThis paper presents an investigation on the fatigue life prediction of the C1 Wedge Connection based on advanced finite element analysis. Recently developed, this connection links tubular sections of wind turbine towers using small horizontally placed bolts to slide two wedges, which pull the fork‐shaped upper flange and shaft‐shaped lower flange of the tower together. The fork‐shaped upper flange is manufactured using electron beam welding. A 3D finite element model is developed in ABAQUS software to simulate the behavior of the connection. A sequential thermal‐mechanical analysis is performed to simulate the electron beam welding process and estimate the residual stresses and distortions. The crack initiation at the lower flange, where the largest stress range is observed, governs the fatigue resistance of the connection. Fatigue crack initiation is assessed using the strain‐based local approach and code‐based methods such as the EN1993:1‐9 and DNV‐RP C2003. A comparison of the predictions from these methods is presented.

Electron Beam Welding Process for Ti6Al-4V Titanium Alloy.

The electron beam welding process of titanium alloys induces a series of physicochemical changes in the material that remain a relevant and necessary area of investigation. A necessary step performed after the electron beam welding process of titanium alloys in the Ti6Al-4V grade to mitigate the resulting thermal stresses is the post-weld heat-treatment process conducted through stress relieving. This study presents the comparative analysis results of the mechanical properties and structure of the Ti6Al-4V titanium alloy after electron beam welding and subsequent stress-relieving heat treatment at a temperature of 590 °C for 2 h. The analysis focused on the levels of mechanical properties such as microhardness in the heat-affected zone and weld, tensile strength, and microstructure analysis in the heat-affected zone and weld. The aim of the research was to answer the questions regarding whether the post-weld heat treatment through stress relieving after electron beam welding of the Ti6Al-4V titanium alloy would significantly affect the changes in mechanical properties and microstructure of the alloy and whether the applied welding speed in the study would cause a significant depletion of alloying elements in the material. During the course of the study, it was found that conducting the electron beam welding process at a speed of 8 mm/s resulted in a depletion of one of the alloying elements (aluminum) in the face area. However, the decrease in aluminum content was not significant and did not exceed the critical value of 6% specified in the material standards, which determined the material's application based on its strength properties.

Research of Friction Stir Welding (FSW) and Electron Beam Welding (EBW) Process for 6082-T6 Aluminum Alloy.

The paper presents the results of the joining tests of the EN AW-6082 T6 alloy. The materials were joined using the EBW high-energy (electron beam welding) and friction stir welding (FSW) methods. In the case of FSW welding, the following parameters were used: the linear speed was 355 mm/min, and the rotational speed of the welding tool was 710. In the case of EBW welding, the following parameters were used: accelerating voltage U = 120 kV, beam intensity I = 18.7 mA, welding speed v = 1600 mm/min and, in the case of a smoothing weld, U = 80 kV, beam intensity I = 17 mA, and welding speed v = 700 mm/min. Comprehensive microstructural tests of all welded joints (MO, SEM and TEM) and mechanical property tests (tensile and hardness tests) were carried out. The topographies of the fractures after the tensile test were also examined. Based on the results, it was found that the strength properties of the EBW joint were reduced by 23% and the FSW joint by 38% compared to the base material. A decrease in elongation was also noted, with an FSW elongation of 7.2% and an elongation of 2.7% for EBW. In the case of the EBW joint, magnesium evaporation was found in the weld during welding, while in the FSW joint, the dissolution of the Mg2Si particles responsible for strengthening the material during heat treatment to the T6 state was observed.

A fundamental investigation into the role of beam focal point, and beam divergence, on thermo-capillary stability and evolution in electron beam welding applications

In this work a novel mathematical framework, that fully describes fusion and vapourisation state transitions in multi-component substrates, has been applied to assist in understanding the fundamental mechanisms of thermo-capillary (keyhole) formation and stability during the electron beam welding process. Specifically the role of electron beam divergence, and the location of the beam focal-point within the substrate, is numerically investigated. It is shown that the location of the beam focal point directly influences the keyhole formation dynamics and leads to drastically different keyhole structures. It is further shown that a less divergent electron beam has a greater penetration rate and produces a more stable thermo-capillary. Finally the chemical heterogeneity induced due to preferential element evaporation during the process is explored and significant Manganese loss is predicted from the simulated SA508 steel substrate.

Numerical simulation of the temperature field of T2 copper/304 steel dissimilar metal electron beam welding

ANSYS workbench finite element analysis software was adopted to simulate and study the thermal process of electron beam welding of T2 copper and 304 steel heterogeneous materials in this paper. A solid model was established according to the size of the specimens, and a double ellipsoidal moving heat source model of the temperature field of the specimens of the three-dimensional dynamic simulation was imposed. Copper and steel welding transient temperature field distribution pattern and molten pool morphology were studied, and the temperature field welding thermal cycle curve was analyzed. The results show that the peak temperature of the steel side is higher than the copper side, the morphology of the welding pool is basically biased toward the steel side, and the highest temperature during the welding process appears in the center of the weld on the steel side about 0.5 mm.

Microstructural characterization and hardness of an electron beam welded low carbon Ni-Cr-Mo low alloy steel

In this paper the microstructure and hardness of electron beam weld joints of 16NCD13, low alloy steel in the as-welded and post weld heat treated (PWHT) conditions have been explored. The as-received base metal (BM) was in annealed condition. The BM microstructure depicted ferrite and carbides (Fe3C). In the as-welded condition the fusion zone(FZ) contained martensite in coarse grains and small amount of ferrite. The as-welded joints exhibited high hardness in the FZ and heat affected zone (HAZ) due to the occurrence of martensite during the weld thermal cycle. The PWHT employed is low temperature tempering commercially designed to preserve hardness and strength of as quenched martensite while relieving the internal stresses and providing small increase in toughness.The PWHT did not cause any significant reduction in hardness in the FZ and HAZ as tempering is carried out at 150 °C for 2 h and air cooled.The BM and FZ were characterised using optical microscopy, field emission scanning electron microscopy (FE-SEM), electron back scattered diffraction (EBSD) and Xray diffraction techniques. The current study is pursued with the aim of obtaining a comprehensive understanding of the fusion zone (FZ) and heat affected zone (HAZ) developed during electron beam welding process in as-welded and post weld heat treated conditions.

Effects of Welding Speeds on Microstructures and Properties of a CoCrNiSi0.2 Medium Entropy Alloy in Electron Beam Weld Joints

As an excellent welding technique, the electron beam welding technology may easily melt certain refractory metals by the high energy generated during the electron beam welding process, thus obtaining well-formed joints with a large depth of fusion and small deformation. The technology has been applied to weld high- or medium-entropy alloys, and obviously improved performances of joints. In this study, the electron beam welding technology was used to weld a medium-entropy CoCrNiSi0.2 alloy. Microstructures of the weld joints and its quasi-static mechanical properties affected by changing the welding speeds were also studied. The research showed no obvious HAZ in the CoCrNiSi0.2 medium entropy alloy, and the weld zone and base metal present a single FCC phase. Furthermore, grain refinement occurs in the weld zone, and the hardness test shows that the hardness of weld zones are generally higher than that of the base metals correspondingly. In contrast to specimens at other welding speeds, the weld joints possess a higher hardness and a maximum tensile strength at 360 mm·min−1, a higher yield strength of the weld joints occured at 720 mm·min−1, and the fracture presents a form of ductile fracture.

Hybrid optimization strategy for evaluating sustainable performance of the electron beam welding process

With the escalation of climate change, the practice of sustainable welding has become imperative in today's manufacturing industries. Sustainable welding practice via advanced modeling and optimization techniques is a recent idea that has highly been emphasized in various studies for the sustainable production of components. This work, therefore, assess the sustainable performance of the electron beam welding (EBW) process using a novel hybrid optimization search strategy (FL-AHP-TLBO) that optimizes two sustainable characteristics i.e. net energy (Enet) as ‘environmental consideration’ and depth of penetration (P), weldment area (WA), ultimate tensile strength (UTS) being three quality factors as ‘economic consideration’. The optimization approach combines soft computing fuzzy logic (FL) modelling with the teaching-learning-based optimization (TLBO) algorithm to simultaneously optimize these factors while an analytical hierarchy process (AHP) is used to determine the optimal weightage for each factor. The approach yields a minimum fitness value of − 0.39945 at optimum parameter setting V= 60 kV, I= 38 mA, S= 1200 mm/min, and O= 600 Hz. On validation, the methodology improves the sustainable measures by 1.115% for P, 2.5150% for WA, 7.0423% for Enet, and 2.5836% for UTS. The proposed methodology also was found simple and adequate with a faster convergence rate, higher consistency, and results in an overall improvement of 7.377% over the traditional optimization approaches.

Special Features of Control of the Process of Electron Beam Welding

Special Features of Control of the Process of Electron Beam Welding