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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.

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.

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.

Investigations were carried out into the conditions of free formation of welded joints in electron beam welding in the flat position with continuous penetration, and also into the dynamic model of the discharge of liquid metal of the weld pool from the root in which the metal moves downwards at a higher speed in the initial stage; but during movement of the heat source the magnitude of acceleration decreases as a result of the reduction in the width of the welded joint due to solidification and increase in surface tension forces. A procedure for determining the minimum permissible welding speed at which the welded joints can form without undercutting in the tip is described.

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.

Requirements for equipment for electron-beam welding of small-size pieces are presented. Features of physical processes of the formation of low-power electron beams in process installations are shown. Mathematical simulation methods were used for the analysis of the operation of a three-electrode electron gun and for the choice of operation modes of power sources. The design and characteristics of the developed inverter power source for the electron-beam gun are described. The design of an electron-beam welding unit for small-size pieces is given.

Investigations were carried out into the special features of the process of electron beam welding (EBW) with the supply of nitrogen into the weld pool. The effect of the gas medium on the focusing of the electron beam and the depth of penetration is described. The dependence of the chemical composition of weld metal and of the mechanical properties of the welded joint on the amount of supplied nitrogen is determined. It is assumed that it is sufficient to alloy the welded joints in austenitic creep-resisting steels with nitrogen during EBW in order to increase the hot cracking resistance of the weld metal.

Investigations were carried out on the special features of the structure and properties of electron beam welding joints in 150 mm thick plates of pearlitic steel 16GNMA and 160 mm plates of 12Kh2MFA steel. It is shown that using vacuum as the shielding medium results in the efficient removal of gases from the weld pool and reduces the content of alloying elements with high vapour tension.

(2005). Formation of diffusion interlayers in electron beam welded joints in diaphragms of steam turbines. Welding International: Vol. 19, No. 9, pp. 717-723.