Electron Beam Welding Technique Research Articles

Microstructure and mechanical properties of electron beam welded dissimilar steel to Fe–Al alloy joints

Electron beam welding (EBW) technique was used to perform dissimilar joining of plain carbon steel to Fe–7%Al alloy under three different weld conditions such as with beam oscillation, without beam oscillation and at higher welding speed. The effect of weld parameters on the microstructure and mechanical properties of dissimilar joints was studied using optical microscopy, SEM, EBSD, hardness, tensile and erichsen cup tests. Microstructure results show that the application of beam oscillation resulted in uniform and homogeneous microstructure compared to without beam oscillations and higher welding speed. Further, it was observed that weld microstructure changes from equiaxed to columnar grains depending on the weld speed. High weld speed results in columnar grain structure in the weld joint. Erichsen cup test results show that the application of beam oscillation results in excellent formability as compared to high weld speed. Tensile test results show no significant difference in strength properties in all three weld conditions, but the ductility was found to be highest for joints obtained with the application of weld beam oscillation as compared to without beam oscillation and high weld speed. This study shows that the application of beam oscillations plays an important role in improving the weld quality and performance of EBW dissimilar steel to Fe–Al joints.

Design considerations for the semi-digital hadronic calorimeter (SDHCAL) for future leptonic colliders

The first technological SDHCAL prototype having been successfully tested, a new phase of R&D, to validate completely the SDHCAL option for the International Linear Detector (ILD) project of the International Linear Collider (ILC), has started with the conception and the realisation of a new prototype. The new one is intended to host few but large active layers of the future SDHCAL. The new active layers, made of Glass Resistive Plate Chambers (GRPC) with sizes larger than 2 m2 will be equipped with a new version of the electronic readout, fulfilling the requirements of the future ILD detector. The new GRPC are conceived to improve the homogeneity with a new gas distribution scheme. Finally the mechanical structure will be achieved using the electron beam welding technique. The progress realised will be presented and future steps will be discussed.

Narrow gap laser welding for potential nuclear pressure vessel manufacture

High power density electron beam and laser beam welding show their unique advantages in the welding of thick-section steels for potential nuclear pressure vessel manufacture. Compared with traditional submerged arc welding or newly developed narrow-gap submerged arc welding, electron beam welding and laser beam welding techniques offer high welding speeds, low heat inputs, lower levels of residual stresses and distortion, while consuming less filler material and power. As a part of the new nuclear manufacturing EPSRC Program, this study aimed to develop narrow gap laser welding procedures and parameters for joining 30–130 mm thick ferritic steels for potential application to pressure vessel manufacture in civil nuclear power plants. The results showed that high quality welded joints in 30 mm thick steels had been achieved with a combination of an autogenous root pass and multipass narrow gap (4–5 mm parallel grooves) welding with a defocused laser beam welding and filler wire addition, at laser powers of 7.5–8 kW, a welding velocity of 0.4 m/min, a diameter of the laser spot of 6 mm, and wire feed rates of 4–6 m/min. The results also showed that cracking, lack of sidewall fusion, and porosity were the main defects in multiple pass narrow gap laser welds in thick-section ferritic steels if the welding parameters were not optimized. The microhardness of the multipass weld was lower than that of the autogenous weld as tempered martensite was achieved in multipass welding.

Welding of Mo-Based Alloy Using Electron Beam and Laser-GTAW Hybrid Welding Techniques

In the current study, welding of TZM (molybdenum-based alloy) plates in square-butt configuration was carried out using electron beam and laser-GTAW hybrid power sources. Microstructures of weld joint containing three zones—parent metal, heat-affected zone, and fusion zone—were clearly identified when examined through optical and scanning electron microscopy. The weld joints were found to be sound with very wide fusion and heat-affected zones. The microstructure of the fusion zone was coarse-grained. as-solidified microstructure, while the microstructure of heat-affected zone was the recrystallized microstructure with reduction in grain size as distance from the fusion line increased. Microhardness profile using Vickers hardness tester was obtained across the weld region, and the tensile properties of the weld joints were evaluated by performing room temperature tensile test and fracture was examined using scanning electron microscope. Joint coefficient of the weld joints were ~40 to 45 pct of that of the parent metals with nonmeasurable tensile ductility with predominantly transgranular mode of fracture indicating weakness along the grain boundary. Detailed orientation imaging and transmission electron microscopy were carried out to understand the most dominating factor in introducing weld joint brittleness.

Microstructure and corrosion behavior of Zr-702 joined by electron beam welding

Zirconium alloy (Zr-702) joints welded by electron beam welding technique were characterized by studying the microstructures and corrosion tests. X-ray diffraction and transmission electron microscope analysis showed that the joints were consisted of α-Zr and β-Zr phases. Small β-Zr blocks were distributed along the edges of lamellar α-Zr in the fusion zone. Analysis of corrosion behavior of the joints showed that the Zr3Fe intermetallic was presented in the base metal strongly affected the corrosion resistance. The heat-affected zone and fusion zone showed better corrosion resistance than that of the base metal.

Correlation of the Barkhausen Noise with Metallurgical and Mechanical Characteristics of Welded Low Carbon Steel

The influence of Electron Beam welding technique on the microstructure, mechanical and magnetic properties of low carbon steels was presented and evaluated. Samples with dimensions of 12 cm x 6 cm x 1.5 mm were prepared from stock plate, installed on the welding table and welded at welding speeds and pulsed currents following a predesigned protocol. In order to examine the influence of welding on the magnetizing behavior of low carbon steel, magnetic Barkhausen noise were conducted on the surface of the welded samples. The results were further evaluated by examining the microstructure and mechanical properties of the welded samples by using scanning electron microscopy and micro-hardness measurements, respectively.

Correlation of Magnetic Properties and Residual Stress Distribution Monitored by X-Ray and Neutron Diffraction in Welded AISI 1008 Steel Sheets

In this paper, two identical American Iron and Steel Institute 1008 steels sheets were welded together in a butt joint configuration, with the welding line direction parallel to the rolling direction. The sheets were welded using the electron-beam welding technique. Stress distribution was monitored in the surface and the bulk of the welded samples using X-ray Bragg–Brentano and neutron diffraction methods, respectively. Accordingly, surface and bulk magnetic properties, namely magnetic Barkhausen noise and quasi-dc permeability, were monitored in the same area. Both surface and bulk magnetic measurements exhibit good agreement with the surface and bulk stress measurements obtained by the diffraction methods, after a proper calibration procedure. Complementary measurements with scanning electron microscopy and Vicker’s microhardness tester provide similar good agreement between the microstructural characterization and the residual stress distribution.

Microstructure and mechanical behaviors of electron beam welded NiTi shape memory alloys

The vacuum electron beam welding (EBW) technique was employed to weld Ni50.8Ti49.2 shape memory alloy sheets, and the microstructure, transformation behaviors and mechanical behaviors of the welding joints were investigated systematically. The microstructure observation showed that the weld seam was composed of coarse columnar crystals at the center and relatively fine columnar crystals near the fusion line. The abnormal high intensity of B2200 peak in XRD patterns and preferred orientation in EBSD indicated that the grains in the weld seam have grown preferentially along the 〈100〉 crystal orientation. Differential scanning calorimetry (DSC) curves exhibited an increase of the martensite start temperature (Ms) of the weld seam, which led to the mixed microstructure of martensite and austenite at room temperature. As a result, the ultimate tensile strength of the welding joint was 85% as high as that of the base metal at room temperature, while it could reach 93% at 223K when both the weld seam and the base metal were in pure martensitic state.

Tensile Ductility of Electron Beam Welded Titanium Alloys

Butt welded joins were produced between commercially pure (CP) titanium and various titanium alloys using an electron beam welding technique. The materials used were CP Ti, Ti-6Al-4V (Ti64) and Ti-5Al-5V-5Mo-3Cr (Ti5553). Grain boundary structures, mechanical properties, compositional profiles across the welds and fracture modes are presented. CP Ti has always been known for its excellent weldability, Ti64 has good weldability and, preliminary results indicated that Ti5553 alloy is also weldable.

Progress in the development of reduced activation ferritic-martensitic steels and fabrication technologies in India

The Indian reduced activation ferritic-martensitic (RAFM) steel, meeting the stringent chemical composition requirements with respect to radiologically undesirable elements as well as trace and tramp elements, has been produced by vacuum induction melting followed by vacuum are refining. Also, the optimum combination of normalising and tempering heat treatments was determined. Detailed investigations on the microstructure, including thermodynamic and kinetic features of phase transformations, and tensile, creep and ductile–brittle transition behaviour of this steel indicate that the Indian RAFM steel has the required microstructure, phase stability, creep rupture strength, elevated temperature tensile strength as well as low ductile-to-brittle transition temperature. Systematic investigations have been conducted to optimise the welding parameters to produce crack-free welds using laser and electron beam welding techniques. Salient features associated with materials development, fabrication technologies and characterization of Indian RAFM steels are highlighted.

Effects of beam offset on mechanical properties and corrosion resistance of Alloy 690–SUS 304L EBW joints for nuclear power plant

The current study investigates the effect of the beam offset (BOF) on the microstructure, mechanical properties, and the corrosion resistance of the fusion zone (FZ) of Alloy 690–SUS 304L stainless steel (SS) dissimilar metal butt joints formed by electron beam welding (EBW). The experimental results showed that as the value of the BOF increased from 0 to 0.30 mm, i.e. the electron beam shifted progressively toward the Alloy 690 base metal (BM), the tensile strength of the FZ fell from 582.1 to 541.2 MPa. However, the modified Huey test results indicated that the interdendritic corrosion resistance of the FZ was significantly enhanced. Pit nucleation potential value ( E np) was raised from 385 to 1050 mV. An offset of 0.30 mm appears to be the optimal BOF setting when fabricating Alloy 690–SUS 304L SS dissimilar metal butt joints using the EBW technique.

Increase in the Alpha to Gamma Transformation Temperature of Pure Iron upon Very Rapid Heating

In recent years, laser and electron beam welding techniques have been developed with heating rates reaching 1 million K/s, and nonequilibrium microstructures sometimes result. In the present study, the alpha (bcc) to gamma (fcc) transformation in pure iron is studied using a bank of storage batteries for heating and a high speed data acquisition system to monitor the temperature determined from a thermocouple spot welded to the specimen. Heating rates up to 300,000 K/s were obtained with the transformation temperature increasing from the equilibrium value of 1185 K (912 °C) to over 2200 K (1927 °C). The results are presented in terms of continuous heating and isothermal transformation curves.

Microstructure and properties of electron beam welded joint of Ti–22Al–25Nb/TC11

Dissimilar joining of Ti–22Al–25Nb alloy and an α + β titanium alloy TC11 were carried out using electron beam welding technique. The microstructure, microhardness, and mechanical properties of the joint have been investigated. The results show that EBW can be used the joining of dissimilar TC11 alloy and Ti–22Al–25Nb alloy. The microstructure of the heat affected zone (HAZ) of TC11 alloy is martensite α ′ phase, a large quantity of O / α 2 particles precipitate in the weld and the microstructure of the HAZ of Ti–22Al–25Nb alloy is B2 phase. The room-temperature tensile strength of the joint is higher than that of the TC11 alloy base, and the impact toughness value of the joint is found to be about 42% of that of the TC11 alloy base.

고속 추진체용 Alloy 718 노즐 단조품의 전자빔 용접성 평가

In this study, mechanical properties of Alloy 718 welded after forgings for jet propulsion component was investigated. Hot-forged and machined work-pieces(<TEX>$230mm\times70mm\times15mm$</TEX>) which have different grain sizes are welded by electron beam welding technique. After welding, the components were solution heat-treated and aged. Samples were sectioned to analyze the microstructural evolution and formation of micro-crack. It was found that HAZ grain boundary liquation crack generally initiates in the coarse grains rather than the fine grains. Needle-like phases with high Nb contents were found at the outer part near the base metal. Vickers hardness and tensile tests were carried out at room temperature and at <TEX>$649^{\circ}C$</TEX>. The tensile properties of electron beam welding specimens exhibited around 100MPa and 10% decrease in strength and elongation, respectively.

Evaluation of electron beam welding technique for the integration of robust sensor elements into high-pressure automotive systems

For “on board” diagnosis purposes of the injected fuel quantity flow sensitive elements based on the thermo-resistive measurement principle were integrated into finished Common Rail injection nozzles of valve-covered orifice (VCO) or mini-sac hole (MSH) class. Electron-discharge machining as well as electron beam welding technique are key technologies for a reliable integration procedure. To demonstrate negligible influence on the hydraulic performance of the nozzle after modification an optical measurement set-up is used to record temporally resolved the propagation of the spray patterns ejected from the six injection holes simultaneously. From these investigations the impact on the structural distortion of the valve caused by the welding seam is proved as its position can be directly linked to any chances in spray performance of each individual injection hole. Reducing the energy input during the electron beam welding lowers substantially the asymmetry in spray patterns from hole to hole as the needle uncovers the six injection holes more symmetrically. Besides this important finding, the numerical calculations indicate that the implementation of the sensor chip slightly amplifies the asymmetry induced by the welding process due to an additional weakening of the nozzle body which is confirmed experimentally. Despite these challenges, however, it is demonstrated that appropriate parameters for the integration procedure can be found affecting the hydraulic performance negligible compared to the original state.

Structural investigation of Ni–Nb–Ti–Zr–Co–Cu glassy samples prepared by different welding techniques

Although, bulk metallic glasses exhibit remarkable mechanical, physical and chemical properties, their critical size (the largest size of fully glassy sample produced by casting) is limited. The utilization of a welding technique enables producing larger glassy samples. Ni 53Nb 20Ti 10Zr 8Co 6Cu 3 glassy alloy ribbon samples prepared by melt spinning of the pre-alloyed arc-melted ingots were welded by the electron-beam and fiber laser-beam welding techniques. The detailed structural investigations of the welded bead and thermally affected zone were performed by micro-area X-ray diffractometry, scanning and transmission electron microscopy. At certain optimized welding conditions the amorphous structure can be retained after melting. The obtained data are promising for future applications of the laser and electron-beam welding techniques to glassy alloys.

CuCrZr alloy hot cracking during electron beam welding

The precipitation hardened copper chromium zirconium material used in thermonuclear fusion machines has been selected for its good thermomechanical properties at high temperature, associated with the possibility of industrial assembling by electron beam welding. However, repeated occurrence of micro cracks which may propagate and then reduce lifetime, was observed. Consequently, the qualification of a crack-free electron beam welding technique for these copper alloys is a key issue and requires further investigation of the assembling process.

Microstructure and mechanical properties of electron beam weld joints of a Zr41Ti14Cu12Ni10Be23 bulk metallic glass with Zr

The electron beam welding technique was used to join Zr41Ti14Cu12Ni10Be23 bulk metallic glass (BMG) to crystalline pure Zr. Compositional, microstructural, and mechanical property variations across the welded interface were evaluated. It is shown that a crystalline layer develops close to the welding interface. Transmission electron microscopy of this layer indicates the crystalline phase to be tetragonal with lattice parameters close to that reported for Zr2Ni. However, the composition of this phase is different as it contains other alloying additions. The interface layer close to the bulk metallic glass side contains nanocrystalline Zr2Cu phase embedded in the glassy matrix. Nanoindentation experiments indicate that the hardness of the crystalline layer, although less than the bulk metallic glass, is more than the Zr itself. Commensurately, tensile tests indicate that the failure of the welded samples occurs at the Zr side rather than at the weld joint.

High-temperature DTA studies of A xM F 3 compounds ( [formula omitted], Rb, Cs; [formula omitted], Cr; and [formula omitted

A x VF 3 ( A = K , Rb, Cs; x = 0 – 1.0 ) and A x CrF 3 compounds were sealed inside high-temperature DTA molybdenum sample cups using electron beam welding techniques. Melting temperatures of the A x VF 3 compounds ranged from 1050 to 1400 °C; those of A x CrF 3 from 850 to 1200 °C. Reconstructive transitions were observed for A x VF 3 compounds between 650 and 950 °C, and for A x CrF 3 compounds between 550 and 825 °C. A displacive transition was observed to occur in VF 3 at 490 °C. Order–disorder transitions were determined by X-ray diffraction techniques. In the A x VF 3 compounds, electronic ordering and ordering of partially filled A + sites were observed to occur between 100 and 300 °C. Ordering phenomena in the A x CrF 3 compounds (in addition to electronic ordering and ordering of partially filled A + sites) included Jahn–Teller cooperative ordering. These compounded transitions occurred between 300 and 500 °C.

Investigation of electron-beam welding in wrought Inconel 706—experimental and numerical analysis

Electron-beam welding (EBW) is commonly employed in the aeroengine industry for the welding of high integrity components, fabricated from high-strength superalloys. For such applications, it is important to predict distortions and residual stresses induced by the process. Melt run trials have been carried out on nickel-base superalloy Inconel 706 plates using the EBW technique in order to analyse the effects of welding parameters on geometrical characteristics and microstructure of the bead. Butt-welded plates have been then investigated by means of tensile tests, microstructural analysis, and X-ray diffraction measurements. A finite element model of the process has been set up using an uncoupled thermal–mechanical analysis. The heat source was modelled using a superimposition of a spherical and a conical shape heat source with Gaussian power density distribution in order to reproduce the nail shape of the fusion zone (FZ). The parameters of the source were chosen so that the model would match with experimentally determined weld pool shape and temperatures, measured with thermocouples. Subsequently, the thermal analysis was used to drive the non-linear mechanical analysis. The predicted residual stresses were then compared with X-ray diffraction measurements. It was found that the correct thermal and residual stresses prediction is influenced by the shape of the fusion zone, the highest thermal tensile stress arising under the nailhead of the fusion zone where microfissuring can be observed.