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Specific features of fabricating welded structures of the international thermonuclear experimental reactor (ITER) blanket components are considered. The results from elaborating the technology for electron-beam welding of cooling system’s channel caps in the first wall bearing structure (FWBS) of the ITER blanket shielding module are presented. The design of welded joint samples made of Grade 316L(N) steel and the welding equipment are described. The welding techniques and butt joint design features whose use makes it possible to obtain the required strengthening of weld bead and to avoid metal droplets from appearing in the FWBS inner cavities are considered. A simplified thermal–mechanical model of the cap-welding technological process is described, and the results from experimentally evaluating the structural and mechanical state of the obtained welded structures are presented. A comparison between the modeling and experimental results is given. It is pointed out that the stressed and strain state varies in an active manner at the initial loading stage. Initially, the metal in the heat-affected zone (HAZ) experiences plastic deformation followed by elastic relief at the subsequent stages. It is pointed out that the postweld deformations are on the whole characterized by a low level and remain within the permissible limits. The distribution of mechanical properties in weld joint local zones determined using the indentation method is given. The results from tensile tests and an indenter impressing test show that the weld metal has even better mechanical characteristics than the parent metal. Data are presented from metallographic investigations, which testify that there is no growth of grains in the HAZ, which is due to high rates of cooling in the used welding method. Based on the results of elaborating the electron-beam welding technology and using the developed techniques, an FWBS mockup has been fabricated that complies with the class VQC 1A tightness requirements.

Electron beam deposition is a process that involves the use of an electron beam as a source of energy and wire as a raw material for the fabrication of metal products with complex shape in a vacuum...

The results of studying the interrelation that links the electron beam welding (EBW) thermal efficiency, thermophysical properties of the material, and welding speed are presented. Thermal efficiency was determined by a combined experimental and computational method based on measuring the penetration areas and evaluating the energy expenditure for melting with the known welding mode parameters. The study was carried out on a series of microsections prepared from welded joints of 5V titanium alloy, grade 40Kh13 steel, D16 duralumin, BrKh1Tsr bronze, and TsM2A molybdenum. It is shown that in EBW with deep penetration, its thermal efficiency increases with increasing the welding speed and decreasing the welded material thermal diffusivity. The experimental dependence of the thermal efficiency on the welding speed is approximated with sufficient accuracy by a logarithmic curve. Thus, in increasing the EBW speed from 20 to 120 m/h, the thermal efficiency increases from 54% to 67% for 5V titanium alloy, from 46% to 63% for 40Kh13 steel, and from 18% to 40% for D16 duralumin. The thermal efficiency in welding bronze (at an EBW speed of 30 m/h) and in welding TsMA molybdenum (at a speed of 20 m/h) was 15% on the average. An analysis of the thermal efficiency curve versus the dimensionless parameter vd/2a has shown that the thermal efficiency for all materials can be approximated by a single logarithmic dependence. An empirical relationship is proposed, using which the welding thermal efficiency can be determined as a function of welding speed and material thermal diffusivity.

Possibilities of increasing the electron beam energy concentration in the electron-optical system of a welding gun characterized by a traditional scheme in which a focusing lens and a deflecting system are installed sequentially along the beam and a new scheme based on a focusing–deflecting system with combined fields are considered. A technique based on solving the paraxial equations of trajectories and calculating aberration integrals is described, which allows one to determine the total diameter of the electron beam. Based on the described methodology, a model of a new focusing–deflecting system with combined fields has been developed. It is shown that the new scheme of the electron-optical system allows one to increase the energy concentration in the region of the interaction of the beam with the material in comparison with the traditional one.

A computer model has been developed to investigate the processes of heat and mass transfer under the influence of concentrated energy sources on materials with specified thermophysical characteristics, including temperature-dependent ones. The model is based on the application of the volume of fluid (VOF) method and finite-difference approximation of the Navier–Stokes differential equations formulated for a viscous incompressible medium. The “predictor-corrector” method has been used for the coordinated determination of the pressure field which corresponds to the continuity condition and the velocity field. The modeling technique of the free liquid surface and boundary conditions has been described. The method of calculating surface tension forces and vapor recoil pressure has been presented. The algorithm structure is given, the individual modules of which are currently implemented in the Microsoft Visual Studio environment. The model can be applied for studying the metal transfer during the deposition processes, including the processes with electron beam spatial oscillation. The model was validated by comparing the results of computational experiments and images obtained by a high-speed camera.

The article discusses the features of producing articles by the method of electron beam additive forming of alloys based on aluminium. The technology of obtaining a thin wall from a deformable alum...

The mathematical formulation of electron beam melting and liquid metal transfer model in wire-based additive manufacturing with temperature dependencies of thermophysical properties is described. A description of the model algorithmic implementation based on the use of numerical methods for solving the Navier-Stokes equations system and the Volume of Fluid (VOF) method for tracking the free surface of a liquid on the cubic mesh cells is given. An iterative method for calculating the pressure field that ensures the fulfillment of the incompressibility condition for a viscous fluid is described. The paper also paid attention to the description of methodology for calculating the forces acting on the free surface of the melt, including surface tension forces and metal vapor pressure forces. One of the key elements of the proposed model is method for volumetric distribution of electron losses calculating, considering their scattering during the interaction of an electron beam with a curved melt surface. Electron beam focusing influence on the distribution of energy losses and the dynamics of penetration channel formation has been studied. An algorithm for visualizing the free surface of the melt based on the use of the Gaussian function, is described.

The energy spectra of the ion saturation current of the Langmuir probe in the plasma formed over the keyhole directly during the process of electron-beam welding of steel 09G2S with the varied parameters (e.g., the welding speed and focus coil current) has been investigated. The presence of typical zones with the energy spectrum peaks in the low-frequency and high- frequency bands has been shown. It has been established that the peak location in the high- frequency range of the energy spectrum does not depend on the welding modes and the position of the probes relative to the keyhole. The low-frequency range of the energy spectrum depends on the vapor flow density of the keyhole and is rather sensitive to the welding modes. The use of electron beam oscillation makes it possible to control plasma flows and hydrodynamic processes in the penetration channel.

The process of producing compounds of VM-80 tungsten–copper alloy with BrX1Tsr chrome–zircon bronze using the methods of electron-beam brazing, surfacing, and welding is considered as applied to creating billets for producing bimetallic electrical contacts. The structures of the bimetallic contact and the main processes of electron-beam brazing, surfacing and welding of the specified materials are studied; the microstructure and mechanical properties of joints produced by the methods of electron-beam brazing and surfacing are investigated; and practical recommendations are given for the performance of further thermal treatment so as to improve the mechanical properties of obtained compounds. The results of this work may be of interest for specialists in the area of electrical-equipment design.

Investigations were carried out into the production of combined welded joints in 316L(N) austenitic steel and BrKh1Tsr (CuCrZr) and CuAl10Ni5Fe4 bronzes 30 mm thick by electron beam welding (EBW). ...

Molten pool free surface shape calculation and its evaluation in time for analysis of electron beam melting and welding processes is a very important problem. Unfortunately, experimental methods can provide only a part of the necessary information. Electron beam heating creates the conditions for intense metal transfer, and pool surface shape affects the energy absorption efficiency. This paper reports the method which combines the Monte-Carlo simulation for spatial and energy parameters of heating source calculating with the Volume of Fluid algorithm for liquid free-surface numerical evaluation. The velocity and pressure field technique calculation in a molten pool with the action of surface tension forces and vapor recoil pressure is described. It is shown that the proposed simulation method allows to study heat and mass transfer transient processes, including deep penetration channel formation. Model validation was carried out. Simulation results are shown to be consistent with experimental data obtained using a high-speed camera.

An improved method for calculating the minimum permissible electron beam welding (EBW) speed with continuous penetration is described. Calculations are carried out to construct nomograms for determ...

A complex method for analyzing the processes in the systems of indirect cathode heating for electron- beam welding guns is proposed. The necessity of considering the electron-beam formation process in a cathode assembly with predetermined geometric characteristics is justified for calculating the distribution of the heat-flux density over the main-cathode surface. The typical distribution of the heat-flux density over the surface of the main cathode, which is heated via electron bombardment using a spiral wire heater, is analyzed. A method for calculating the temperature distribution over the structural elements of a typical cathode assembly is described, and the calculation results are analyzed. The influence of the nonuniformity of the electronbeam- current density distribution over the heated surface of the main cathode and the heat dissipation on the temperature and emission-current-density distributions on the working surface of the main cathode is considered. The advantages of the proposed method in comparison with existing idealized mathematical models and its suitability for solving problems of designing various electron guns are demonstrated.

Experiments were carried out to investigate the effect of electron beam welding speed in the range 20–120 m/h on the properties of welded joints in 20-mm-thick plates of D16 alloy. The distribution of magnesium in the cross section of welded joints in dependence on the welding speed was determined. The structure of the welded joints was investigated by optical and electron microscopy. The hardness in different zones of the welded joints after welding and different types of heat treatment was measured. The relationship between the chemical composition, structure and mechanical properties of the welded joints produced at different welding speeds was determined.

An express method of direct measurements of the current density distribution of axially symmetric electron beams is proposed. It is shown that use of the technique is urgently needed to improve the reproducibility of the results of electron-beam processing. Comparative analysis of existing methods to measure the parameters of electron beams used for technological purposes is carried out. A technique to restore a radial distribution of electron beam current density as well as a device to implement the technique is developed. The results of radial distribution recovery are analyzed in the case in which the initial distribution is given in the form of a model function of normal distribution. An algorithm to determine estimated sizes of the area within which spatial distribution discretization is carried out is developed. Based on analysis of the experimental dependences, it is shown that the suggested numerical method can be applied to all types of axial-symmetric distributions. The nature of errors occurring after distribution function recovery is analyzed. A technological projection of express diagnostic systems for the processing electron beams is made taking into account parameters of the existing element base.

An experimental technique for the acquisition of current-density distributions of continuously operating electron beams with an electron energy of 60 keV is proposed. The measurement results for different cross-sectional areas of the beam with a power of 2.1 kW and a current density around 1 × 105 A/m2 are given.

It is shown that the processing parameters of electron beams with power up to 6 kW and energy of 60 keV used in electron beam installations can be determined by means of light radiation from drift space. A digital photo camera-assisted technique to obtain an image is described. It is shown that the registered image processing allows one to obtain information on the internal structure of an electron beam. The dependence of focal length on the focusing magnet lens current is obtained. The peculiarities of current density distribution over beam cross section are revealed. It is found that the behavior of the beam current density distribution depends strongly on the conditions of major cathode heating. The proposed method to determine electron beam parameters can be applied to control operation conditions of processing equipment, for example, to find the accuracy of gun adjustment, as well as cathode state, from the behavior of the power density distribution. The obtained dependences of beam parameters on the operating conditions of an electron gun can be used when choosing processing parameters to reduce the quantity of work on experimental optimization of welding conditions.

Existing analytical methods for calculating electron-beam welding modes, which provide welds with required penetration depth, are described, and main disadvantages of these methods are shown. A new calculation method based on a model of moving cylindrical heat source, which involves moving of a cylinder with constant surface temperature in an infinite plate, is proposed. The proposed calculation method takes into account energy losses during metal melting and its partial evaporation. A comparison of experimental and calculated data obtained using the developed method and existing methods, is presented. Plates with a thickness of 32 mm from 5V titanium alloy, 27 mm from 40 Kh13 steel and 20 mm from D16 duralumin were used for experiments. It was shown that the developed method application made it possible to calculate with appropriate accuracy a required beam power during EBW of various materials.

The paper is devoted to the study of the thermo-EMF of various metals and alloys, which are widely used in welded structures. For the selected steels, the relationship between the absolute thermo-EMF and their structural class was established, and the dependences of the thermo-EMF on temperature were obtained. For some groups of steels, a method of predicting the thermo-EMF by chemical composition was developed.

The work describes a method for measuring the magnetic field induced by thermoelectric currents in control points above welded specimens and presents the measurement results. The dissimilar 60-mm thick steel samples are welded by electron-beam welding (EBW). The grades of the pairs of steels are 09Mn2Si + 12Cr18Ni10Ti, 09Mn2Si + 20Cr13 and 20Cr13 + 12Cr18Ni10Ti. The study shows that the electron beam in the weld root deflects towards the material with larger positive potential of integral thermal EMF. The deflection is uneven along the specimens, which necessitates taking into account the geometry of welding joints when elaborating the mathematical models of the process. Maximum deflection for the studied pairs of materials correspondingly amounts to 0.6, 2,8 and 3.8 mm, which is critical for producing a high-quality seam. In addition, the alteration of magnetic induction in control points during EBW was obtained.

Annotation The paper derives a relation describing the shape of an electron beam axis affected by thermoelectric currents during welding of dissimilar materials. The treatise suggests a new method for determining the adjustment actions for preventing lack of penetration in the weld root and derives an expression for determining the critical degree of weld penetration during welding of dissimilar austenitic and pearlitic steels. The received results can be used to make high-quality welding connections of thick dissimilar materials by eliminating incomplete penetration and ensuring necessary penetration degree of welded edges along the whole part thickness.

The paper is devoted to the definition of the minimum electron beam power that is required to obtain stable layer formations during the additive electron beam wire deposition. Correlation between the minimum energy that is needed for stable deposition and the deposition speed has been established. Additionally, the influence of the electron beam oscillation type on geometrical parameters of single layers have been investigated.

The paper is devoted to the study of welded joints formation process both from homogeneous and dissimilar materials. The investigated welded joints were made by an electron beam using intermediate inserts of small thickness in a narrow gap. The influence of insert size as well as gap size on the stability of weld formation is shown. Electron beam oscillation configurations which eliminate incomplete penetration in weld root are determined. Values of thermal efficiency are experimentally found for different welding speeds. The results of structure study for dissimilar welded joints of plates from carbon steel 20 and austenitic corrosion-resistant AISI 316L steel are presented. The values of penetration rate for base and filler metal are calculated and experimentally confirmed.