Beam Welding Research Articles

Autogenous welding of copper pipe using orbital TIG welding technique for application as high vacuum boundary parts of nuclear fusion devices

This research work describes the development of autogenous orbital gas tungsten arc welding for oxygen-free copper pipe. Neutral beam system for fusion devices consists of the different water-cooled component, which is designed and fabricated from pure copper to have the excellent thermal and electrical conductivity from the functionality point of view. Due to their application in a high vacuum along with the nuclear environment, a weld joint of full penetration configuration with a 100% volumetric examination is a mandatory requirement. Welding of pure copper has always been a challenging task because of its high conductivity and reflectivity, even with the use of high energy beam welding techniques (e.g., Electron beam welding and laser beam welding). Further, to compensate the heat dissipation, if the higher arc energy is provided to the base material, it results in the loss of strength, and therefore the selection of welding process and determining the parameters plays a crucial role for pressure withstanding welded connections. Though electron beam welding is a conventionally practiced process for welding of pure copper, the need for massive infrastructure limits its applicability to the large components. The present aim to have an understanding of the applicability of pulsed TIG process, in an autogenous mode for welding of pure copper material is presented. During this research work range of process parameters were used to assess the quality and strength of the joint. The range of process parameters was used to retain the mechanical properties of base material to the extent possible level. While doing, so weldability assessment was made for the shielding gas, welding program (pulse current, background current, and their duty cycles), joint geometry, arc length, and heat inputs. The mechanical and microstructural properties have been evaluated for the range of these parameters. The results have also been compared with the properties achieved by the electron beam welding process to understand what best researchers can achieve with the conventional welding process compared to high energy beam welding.

The behavior of TIG welding arc in a high-frequency axial magnetic field

The effect of high-frequency axial magnetic field (HFAMF) on the shape of the welding arc and welding formation of tungsten inert gas (TIG) welding is analyzed theoretically and experimentally. The 316L stainless steel plate was welded with HFAMF produced by the excitation coil installed on the welding torch. The influence of the HFAMF on the welding process is studied by changing the magnetic frequency from 0 to 2000 Hz. The experimental results show that when the magnetic field frequency reaches 1500 Hz, the arc rotation radius is decreased to the minimum; the arc shape changes from cone to compressed cylinder; and the arc temperature, the arc pressure, and the depth-width ratio of the weld beam reached the maximum. Otherwise, the effect of applied HFAMF on the stress of arc and weld pool is discussed, and the mechanism of arc contraction is analyzed.

Influence of welding process on the properties of dissimilar titanium alloy weldments: a review

The extensive use of titanium alloys in a variety of complex industrial applications may be attributed to their properties of high strength-to-weight ratio, corrosion resistance and high temperature strength. Recently, the use of dissimilar titanium alloys has become popular to achieve contrasting characteristics in a single unit. In the fabrication of the structures, joining methods such as welding hold the key in the attainment of the desired characteristics. The present study is aimed at reviewing various state-of-the-art processes used for welding of dissimilar titanium alloys. In particular, the influence of different welding methods such as gas tungsten arc welding (GTAW), laser and electron beam welding on the microstructure, mechanical properties and other characteristics of dissimilar weldments of α, α + β and β titanium alloys has been emphasized. The underlying phenomena that govern the effect of weld processing parameters on the mechanical strength, microstructure and weld joint quality of the alloys were exploited. Moreover, detailed investigations on the fusion zone porosities and evolution of intermetallic concept at the interfacial regions have been examined. Furthermore, different remedial approaches to enhance the joint quality such as beam offsetting, process hybridization, aging and post-weld heat treatments are investigated thoroughly. The latest trends in dissimilar welding of titanium alloys to upheave further research in this area have been reported in the context of their application in industrial applications.

Simulation and Experimental Validation of EBW Studies in Austenitic Stainless Steel AISI-321

Electron beam welding of austenitic stainless steel AISI-321 has been studied with butt weld configuration. The numerical simulation is done in both thermal and structural analysis modes using ANSYS™ software for welding as well as tensile testing. Optimization of the process parameters such as the welding speed, power, beam offset and number of passes was carried out to obtain a sound weld joint using bead on trials and also through welding simulation to get a full penetration weld. Voltage of 60 kV with current of 90–95 mA was found to be optimum parameters for electron beam welding for the welding of a 4-mm-thick plate. The microstructure examination of various weld zones has been carried out. The tensile tests were carried out on the welded samples at room temperature and elevated temperatures (1173 K, 1223 K and 1273 K). It is observed that, with increasing strain rate, there is an increase in strength of the weldment at elevated temperatures indicating positive strain rate sensitivity. Further, a comparative study between the simulated and experimental results of room temperature tensile tests has been carried out. A good match in ambient temperature engineering stress–strain curves obtained through simulation and experimentation has been observed. The fractography analysis of the ambient temperature tensile tested specimens was carried out. It has been observed that the material exhibits necking and a cup cone fracture with fine dimples indicating a ductile fracture.

A comparative study on microstructure and mechanical properties of HG785D steel joint produced by hybrid laser-MAG welding and laser welding

Hybrid Laser-arc welding (HLAW) and laser beam welding (LBW) of HG785D steel were investigated by comparing microstructure, mechanical properties and heat source melting efficiency. Same microstructure of lath martensite (LM) was observed in fusion zone (FZ) of the two welded joints. However, coarser grain size and more random crystallographic orientations of FZ in HLAW joint were investigated via electron back-scatter diffraction (EBSD) analysis. M-A constituent and equiaxed ferrite (EF) were observed in finer-grain HAZ of HLAW joint, whereas fine martensite was obtained in LBW joint. More M-A constituent and granular bainite (GB) appeared in coarse-grain HAZ of HLAW joint. Higher heat input and lower cooling rate of HLAW compared to LBW resulted in presence of different microstructure. All the tensile specimen in both cases fractured at the base metal, while distinct difference in microhardness and low-temperature impact property was observed. Lower microhardness and higher impact energy of fusion zone were obtained in HLAW joint. Moreover, heat source melting efficiency of HLAW for 6-mm-thick HG785D steel plate could be improved by 26% compared to LBW.

Comparative Study on Microstructure and Aluminum Distribution Between Laser Beam Welding and Electron Beam Welding of Ti–6Al–4V Alloy Plates

Ti–6Al–4V alloy plates with a thickness of 4 mm were joined by electron beam welding (EBW) and laser beam welding (LBW). The comparison of LBW and EBW was performed according to grain morphology, microstructure, aluminum distribution, and microhardness of the joints. Results indicate that compared with LBW joint, more equiaxed grains are observed around the central zone of the EBW joint. The microstructure in fusion zone (FZ) of EBW joint presents more uneven with obviously coarser acicular martensite α′. Moreover, the aluminum element content of EBW joint is substantially lower, which demonstrates a more significant burning loss behavior in EBW process. The lower aluminum content in the upper center areas of the joints is attributed to the more significant element burning loss caused by higher temperature, whereas more uniform aluminum distribution in the upper part of the joints is ascribed to stronger convection form within the upper part of the joint. In addition, the characteristics of convection and thermal field within the molten pool are recognized as vital factors influencing the aluminum distribution. The lower microhardness profile in FZ of the EBW joint is principally attributed to coarser acicular martensite α′ and lower aluminum element in EBW joint.

Laser-Driven Programmable Metal Transfer in GMAW

Conventional pulsed laser-enhanced gas metal arc weld-ing (GMAW) employs a single fiber laser focused and aimed on the droplet neck position to produce a laser recoil force and thus ensure the droplet detachment despite the am-perage of the welding current. One drop per laser pulse metal transfer is obtained, and the droplet deflects away from the wire axis along the laser incident direction. This implies that the droplet trajectory may also be controlled if the direction of the laser recoil force can be adjusted. Such a controllability is expected to bring an entirely new capa-bility to the GMAW process: active control on the weld beam geometry. To this end, double-sided, laser-enhanced GMAW was proposed and experimentally verified in this pa-per. The two lasers were symmetrically positioned, and both aimed at the droplet neck. The laser pulse peak power, du-ration, and pulse phase of the two lasers can all be programmed to regulate the laser recoil forces. The metal transfer under twin laser irradiations (same laser pulses and phases) was first verified. Then the effectiveness on controlling the droplet trajectory of three proposed control strategies — peak power matching, peak width matching, and phase matching of the two lasers — were evaluated. The results showed laser peak power matching is optimal for obtaining desired droplet trajectory. Since the laser can be easily controlled in real time, the transfer frequency, droplet size, and trajectory can all be adjusted in real time, and the metal transfer evolves into programmable transfer.

MHD Double‐diffusive thermosolutal Marangoni convection non‐Newtonian Casson fluid flow over a permeable stretchable sheet

AbstractIn the present paper, we have discussed the thermosolutal Marangoni force acting on the electrically conducting Casson fluid flow over a permeable horizontal stretching surface. It is presumed that the condition at the interfaces is influenced by the surface tension, which is proportional to the temperature and concentration profiles. At the interface, both concentration and temperature are heated in such a way that they are quadratic functions in Furthermore, we have introduced the magnetic field in the transverse direction of the fluid flow along with heat generation/absorption, thermal radiation, viscous dissipation, and first‐order chemical effect with heat and mass flux into the present system. Similarity transformations have been used to convert the system of the nonlinear partial differential equations into a system of nonlinear ordinary differential equations (ODEs). The reduced ODEs are then solved using the MATLAB program bvp4c, which is based on the fourth‐order Runge‐Kutta and shooting method. The impact of various pertinent flow parameters on the flow field, temperature, and species concentration has been studied through graphs. To know the characteristics of shear stress, heat and mass rate near the boundary, numerical values of them are also calculated and given in the tabular form. The results show that the momentum boundary layer's thickness is getting thicker with an increase in solutal surface tension ratio, while its opposite trends have been observed in the thermal boundary layer region, this is due to the Marangoni effect. This Marangoni effect is very much important in the field of melting metals, crystal growth, welding, and electron beam.

Analysis of temperature and stress-strain fields during laser beam welding of a TRIP steel

Transformation Induced Plasticity (TRIP) steels belong to the group of Advanced High Strength Steels (AHSS) that are characterized by good strength-strain combination and formability required for special applications in the automotive industry. The excellent combination of strength, ductility and formability of TRIP steels is achieved by a careful control of microstructure development in the process of their production. The microstructure of multiphase TRIP steels typically consists of ferrite, carbide-free bainite and metastable retained austenite, which can be transformed into martensite by plastic deformation. Upon crash, this feature allows the TRIP steels to absorb more energy, ensuring greater passenger safety. In the automotive industry, TRIP steels are mainly joined by resistance spot welding, laser or electron beam welding. Generally, the thermal cycle of a fusion welding process destroys the sophistically designed microstructure of these steels in fusion and heat-affected zones resulting in deterioration of mechanical properties of the weld joint. Negative consequences of the welding process can be eliminated using proper welding parameters. The paper deals with numerical simulation and analysis of the temperature and stress-strain fields developed during the laser beam welding of a CMnSiNb TRIP steel sheets with the thickness of 2 mm. Simulation model takes into account non-linear temperature and phase dependent material properties. The heat input during the laser beam welding is modelled using the conical volumetric heat source. The optimal welding parameters for production of butt joints of CMnSiNb TRIP steel sheets using the TruDisk 4002 disc laser with the maximum power of 2 kW are designed.

Mechanical Properties Characterization of Welded Automotive Steels

Among the various welding technologies, resistance spot welding (RSW) and laser beam welding (LBW) play a significant role as joining methods for the automobile industry. The application of RSW and LBW for the automotive body alters the microstructure in the welded areas. It is necessary to identify the mechanical properties of the welded material to be able to make a reliable statement about the material behavior and the strength of welded components. This study develops a method by which to determine the mechanical properties for the weldment of RSW and LBW for two dual phase (DP) steels, DP600 and DP1000, which are commonly used for the automotive bodies. The mechanical properties of the resistance spot weldment were obtained by performing tensile tests on the notched tensile specimen to cause an elongation of the notched and welded area in order to investigate its properties. In order to determine the mechanical properties of the laser beam weldment, indentation tests were performed on the welded material to calculate its force-penetration depth-curve. Inverse numerical simulation was used to simulate the indentation tests to determine and verify the parameters of a nonlinear isotropic material model for the weldment of LBW. Furthermore, using this method, the parameters for the material model of RSW were verified. The material parameters and microstructure of the weldment of RSW and LBW are compared and discussed. The results show that the novel method introduced in this work is a valid approach to determine the mechanical properties of welded high-strength steel structures. In addition, it can be seen that LBW and RSW lead to a reduction in ductility and an increase in the amount of yield and tensile strength of both DP600 and DP1000.

Study of Inconel 718 Welded by Bead-On-Plate Laser Welding under High-Frequency Micro-Vibration Condition

Inconel 718 alloy laser-welded joints have poor mechanical properties due to the presence of Laves phases and liquation cracks. This paper intends to solve the above problems by high-frequency micro-vibration-coupled bead-on-plate laser welding. According to the shape of the weld beam, the upper part of the weld is defined as the nail head, and the lower part is the nail body. The results showed that high-frequency micro-vibration can achieve grain refinement. The micro-vibration could break the primary dendrite arm to form secondary dendrite and reduce epitaxial growth of the cellular crystal region. Micro-vibration exacerbated the flow of Niobium (Nb) elements surrounded by dendrites and reduced dendritic segregation, which decreased the formation of Laves phases. The combination of interdendritic Nickel (Ni), Titanium (Ti), and Nb and the precipitation of strengthening phases γ′ and γ″ were promoted. When the vibration acceleration was 50.10 m/s2, it could inhibit the formation of Laves phases among dendrites and the size of the bulk Laves phase was effectively reduced. The cracks generated in the Inconel 718 alloy were distributed at three locations including the nail-head, the nail-body, and the junction of nail-head and nail-body. When the vibration frequency was 919 Hz, the length of the liquation crack reduced from 180 to 110 μm. While under 1331 Hz, the expansion of the liquation crack was extended, with the length of 200 μm.

Conceptual Development of a Novel Ultra-Thin and Transparent 2 T Superconducting Detector Solenoid for the Future Circular Collider

In the frame of the ongoing Future Circular Collider (FCC) Study, a novel ultra-thin and maximum radiation transparent solenoid for next generation particle detectors is under development. Actually, two versions providing 2 T and 3 T for the FCC-ee and FCC-hh detectors, respectively, are engineered, but here we report on the 2 T version only. Essential aspects of the design are presented. The mechanical and thermal stability of the cold mass is investigated. New, very high-yield stress Al-stabilized NbTi/Cu conductors are required to allow a 0.4 * X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> radiation thickness. For conductor production, welding of dissimilar aluminum alloys will be necessary. Electron beam and friction stir welding techniques were tested to connect the Ni-doped pure Aluminum stabilizer to the very high-yield strength Al-7068 alloy. The welding results and their applicability are presented and discussed. The proposed conduction-based cold mass cooling scheme using heat drains, and quench protection were analyzed and results are presented.

Investigations on the fatigue strength of beam-welded butt joints taking the weld quality into account

For the fatigue design of welded structures under constant amplitude loading, often the nominal stress approach based on design S-N curves is used. The design S-N curves, which can be found in commonly used guidelines, cover arc welds as well as beam welds. However, the experimental data basis for the guideline consists mainly of arc-welded joints. Beam-welded components on the other hand show different weld geometries (e.g., weld width, weld enforcement, weld radii) compared with arc-welded components. The local geometry of weldments as well as imperfections can affect the fatigue strength, theoretically in dependence of the ultimate strength. Therefore, the fatigue strength of beam-welded samples in the high cycle fatigue range made from S355J2+N and S960Q was tested in this study. Additionally, the weld geometry of all samples was measured and classified according to the weld quality groups in ISO 13919-1. Furthermore, numerical notch stress calculations were conducted to cover imperfections and weld geometries that were not covered by the experimental investigations. Finally, recommendations for the fatigue resistance of beam-welded butt joints are given. Correlations between the fatigue strength and certain quality groups of selected geometrical features and imperfections are shown.

Plastic damage and deformation defect of friction stir welding for aluminum alloy

2219 aluminum alloy plates were welded by friction stir welding, which was a solid bonding technology to solve the traditional problems for aluminium alloy welding. The morphology, microstructure and mechanical properties of the joint were investigated. Through analyzing the flowing pattern of the plastically deformed metal in the nugget zone, the strength weakening of the joint were analyzed and summarized. The reason of weakening strength was due to the plastic deformation and damage of the metal, which resulted in the defect formation and the mutational interface. The results show that the well-formed weld beam is similar to the base metal, which has the plastic fracture morphology. However, if there are pores, holes and other welding defects in the weld beam, the fracture morphology is brittle fracture, then the tensile strength is about 70% of base metal and the elongation is about 7%, which means that the advantages of high strength aluminium alloy are not fully utilized.

Dissimilar Welding of Maraging Steel (250) and 13-8 Mo Stainless Steel by GTCAW, LBW and EBW Processes

The frequently used aerospace materials, i.e., ultra-high-strength maraging steel (250) and corrosion-resistant 13-8 Mo stainless steel in the solution-annealed and cold-worked condition, have been joined by three fusion welding processes, namely interpulse TIG welding, and high energy density fusion processes like electron beam welding (EBW) and laser beam welding (LBW). The interpulse TIG welding process was carried out by using W2 grade maraging steel filler wire. The dissimilar joints were welded by EBW and LBW processes without any filler wire. All the dissimilar welded joints were characterized by microstructural observations and validated by mechanical properties in the as-welded as well as precipitation-hardened conditions after welding. The weld microstructures and microhardness profiles were correlated to the tensile strength of weld. Electron beam welded joint with precipitation hardening after welding, i.e., soaking at 510 °C and subsequent air cooling, demonstrated the superior mechanical properties among all the welds.

Comparison among the environmental impact of solid state and fusion welding processes in joining an aluminium alloy

The life-cycle assessment methodology was used to evaluate the environmental impact of friction stir welding of AA5754-H114 aluminium alloy sheets. Other works in literature considered the environmental impact of friction stir welding, but in this study the influence of different process parameters on midpoint category impacts were analysed. Friction stir welding was performed under different values of rotational and welding speeds. Moreover, pin tool wear and mechanical properties of joints were also evaluated. The pre- and post-processing stages were also considered. Raw materials, energy and all inputs associated with each stage of product life cycle were collected and evaluated to analyse the environmental impact index. The results showed that, irrespective of the rotational speed, the lowest welding speed investigated leads to the highest energy consumption and, consequently, to the highest values of the midpoint category impact. On the contrary, at the highest welding speed, the environmental impact assumes the lowest values. By concerning the rotational speed, its effect on the midpoint category impact is strongly reduced compared with the one given by the welding speed. A performance index, obtained by considering both the midpoint category impact and ultimate tensile strength of the joints, was also defined. Finally, the environmental sustainability of friction stir welding was compared with two different fusion welding technologies, namely gas tungsten arc welding and laser beam welding. The results showed that friction stir welding was characterized by midpoint category impacts much lower than those of the gas tungsten arc welding, while such discrepancies decreased with the laser beam welding.

Laser Welding of Dissimilar Metal Joint of 6061 Al Alloy and Al Matrix Composite

In this paper, dissimilar metal joints of 6061 aluminum alloy and aluminum matrix composite material are investigated by laser welding. TiB2 particles were added into the lap joint. The welding process, microstructure, and the corrosion properties of welding joints are examined. The results demonstrate that the selected optimization process parameters are laser power 6 kW, welding speed 0.6 mm/s, pulse width 11.5 ms, and laser frequency 4.5 Hz. There are a few obvious pores in the molten pool. Al2Ti, Fe2Si, and Al0.5Fe3Si0.5 are present in the microstructure. During the welding process, some TiB2 particles are decomposed and reacted with molten Al. Other TiB2 particles are nucleated and solidified, and the excess TiB2 particles are pushed to the grain boundaries by molten Al. TiB2 particles are wetted well by molten matrix metal. The corrosion resistance of alloys in different conditions decreased in the following order: the weld beam &gt;6061 Al &gt; AMC.

Experimental and numerical study on fatigue performance for TIG welding and EB welding of RAFM steel plate

The Reduced Activation Martensitic/Ferritic steel (RAFM steel) is known as one of the most important materials for future fusion reactor blanket. Welding process is unavoidable during the blanket manufacturing, so it is necessary to research the welding performance of the RAFM steel. Simulations and experiments regarding fatigue behavior of the RAFM steel welding specimens have been done in this paper. The simulation of fatigue behavior of tungsten inert gas (TIG) welding and electron beam (EB) welding of the RAFM steel were carried out by using ANSYS mechanical engineering code. The fatigue behavior for two types RAFM steel specimens of TIG welding and EB welding were also tested by SDS200 electro-hydraulic servo fatigue testing machine. The fatigue performance of the weld joint both for TIG welding and EB welding was tested by applying the same gradient load. The experimental results were studied to analyze the impact of fatigue resistance for the analyzed welding technologies of RAFM steel, and the results indicate that the EB welding is stable under increasing stress. Outcomes of this study can provide some beneficial indications for the blanket design of China Fusion Engineering Testing Reactor (CFETR) in the future.

Stability evaluation of laser-MAG hybrid welding process

This paper describes the laser-MAG hybrid welding of high-strength steel (HSS) formulated with 1.2 mm diameter austenitic stainless steel (ASS) filler wire. A high-speed camera and Hannover analyzers were used to obtain real-time images of droplets and electrical signals during the hybrid welding process. Image processing and mathematical statistics were performed to study how the ratio of laser power to arc power affected the weld morphology, droplet transfer characteristics, instantaneous current probability density. The welding stability was evaluated by using the variation rate of weld width as the main reference. This study provides the fundamentals necessary to select reasonable parameters to obtain better weld stability during the laser-MAG hybrid welding process. The results of this study show that both the laser power and arc power strongly influence both the penetration depth and the width of the weld during the laser-MAG hybrid welding process, respectively. The droplet transfer mode and the ratio of laser energy to arc energy are strongly affected by the distance between the laser and the arc in the laser-MAG hybrid welding process. The droplets have a negligible effect on the keyholes when the distance between the laser and arc is in the range of 2.5–3.5 mm. The welding current is 160 A, which is the critical current of short-circuiting transfer to globular transfer. The critical transition current of globular transfer and projected transfer was shown to occur at a welding current of 180 A. When the welding current is 206 A, the critical transition current of projected transfer and spray transfer is observed. When the welding current is 206–240 A, the fluctuation of the width of weld beam is not significant. When the droplet transfer mode is projected transfer, the welding stability is the best.

A comparative study on laser beam and electron beam welding of 5A06 aluminum alloy

With the increasing of laser power and energy density, laser welding has the potential to replace electron beam welding for aluminum alloy in many conditions. This paper present an comparison investigation between laser beam welding and electron beam welding for 5A06 aluminum alloy. The characteristics of laser beam and electron beam welded joints are compared, including the micro-structure, mechanical property, area of melting zone and depth-to-width ratio. Moreover, the component distribution in different zones of the welded joints is analyzed. It is found that the micro-structure and mechanical property of electron beam welded joint is better than that of laser beam welded joint.