OBRABOTKAMETALLOV TECHNOLOGY Vol. 24 No. 3 2022 When the action of vapor pressure forces is taken into account, numerical calculations show a much greater depth of penetration of the base metal, the width of the deposited beads in this case increases by about 20 %. Under the action of vapor pressure forces in the liquid metal, a crater is formed and the metal is displaced to the periphery of the liquid weld pool. The crater has an elongated shape in the direction coinciding with the projection of the plane of action of electron beams. Changes in the ratio of forces acting on the weld pool and the formed fi ller material droplets lead to a transition to the coarse-droplet metal transfer. Taking into account the vapor pressure forces, when the deposition velocity vector is located in the plane of the electron beam action, there is an asymmetry in the geometry of the deposited beads. This is due to the fact that the vapor pressure force vectors from the effects of thermal sources, being in the location plane of the deposition vector, limit the movement of the liquid metal in the longitudinal direction and displace it to the periphery of the deposited bead; with the direction of surges have a stochastic nature. At the location of the deposition velocity vector perpendicular to the plane of action of electron beams, a more uniform geometry of the beads is observed, because the distribution of forces acting on the weld pool does not prevent the movement of the liquid metal into its tail part. In this case, there are no local surges outside of the deposited bead. Investigation of the effect of the azimuthal tilt angle of the electron beams. Figs. 4 and 5 show the results of numerical analysis of the deposition process of vertically fed wire material, fused by two symmetrically acting electron beams, at different azimuthal tilt angles of the electron beams. The computational results show that as the azimuthal angle decreases, the projection area of electron beams on the substrate plane decreases, while the width of the active zone also decreases. This leads to an increase in the height of the deposited beads while the volume of the fi ller material is maintained. The energy density in the heating spot and the penetration ability of the electron beams also increases. When the velocity vector is located in the plane of action of electron beams with a decrease in the azimuthal angle of each source, the depth of penetration increases and the height of the deposited bead increases. The width of the deposited beads remains practically unchanged. Reducing the azimuthal angle has a positive effect on the uniformity of the deposited beads, eliminating the possibility of local surges to the periphery, while the entire incoming fi ller metal is involved in the formation of the bead and there is a fi ne-drop transfer of the fi ller material. As the azimuthal angle of each source increases, the probability of surges to the periphery increases, due to the fact that the vapor pressure force vectors from the effects of thermal sources, located in the plane of the depositing vector limit the movement of the melt in the longitudinal direction and the more it is pushed to the periphery of the deposited bead, the closer the azimuthal angle of each source to the horizontal. When the velocity vector is perpendicular to the plane of action of electron beams with a decrease in the azimuthal angle of action of each source, the width of the deposited beads decreases and the depth of substrate penetration and height of deposited beads increases. Results and discussion Numerical experiments to determine the dependences of the geometric characteristics of the deposited beads on the infl uence of the vapor pressure forces, the direction of action of the heat sources and the azimuthal angle of the heat sources showed that consideration of the vapor pressure force has a signifi cant impact on the results of numerical simulation of the formation of the weld pool and the hydrodynamic processes occurring in it, as well as on the transfer modes of the fi ller metal. It was found that at the location of the deposition velocity vector perpendicular to the plane of action of electron beams, a more uniform geometry of the rolls is observed, because the distribution of forces acting on the weld pool does not prevent the movement of the liquid metal to its tail part. At the same time, increasing the azimuthal angle of action of heat sources increases the probability of surges to the periphery of the deposited bead, which is associated with the limitation of the melt movement in the longitudinal direction by the vapor pressure forces.
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