FEATURES OF FORMING THE VT1-0+AMG5 JOINT DURING EXPLOSION WELDING WITH THE INFLUENCE OF ACOUSTIC VIBRATIONS

The work is devoted to the study of the influence of the introduction of acoustic vibrations during explosion welding of the VT1-0 + AMg5 pair. A comparative study of joints obtained by the conventional method of explosion welding and explosion welding with the effect of acoustic vibrations in various welding modes has been carried out. The results of the study of the microstructure and mechanical properties allow us to speak about the positive effect of the introduction of acoustic vibrations during welding VT1-0 + AMg5, which consists in expanding the weldability area and reducing the volume of the melted metal in the joint zone. It is also shown in the work that the nature of surface preparation before welding can have a significant effect on the strength of the joint.

STRUCTURE AND PROPERTIES OF MELTED AREAS FORMED AT THE BORDER OF SECTION IN EXPLOSION WELDED JOINTS ALUMINUM-IRON-BASED ALLOY

The influence of the composition of iron-based alloys on the microhardness of the areas of the melted metal in explosion-welded joints with aluminum is investigated. It is shown that, other things being equal, the presence of chromium in the composition of an iron-based alloy leads to an increase in the hardness of the alloys by 1-2 GPa, and joint alloying with chromium and nickel, by 3 GPa.

Experimental Study on Melt Decontamination of Stainless Steel and Carbon Steel Using Induction Melting

Many nuclear power plants (NPP) facilities have aged and are being dismantled around the world. As a result, large amounts of radioactive metal waste are generated during decommissioning. Carbon steel, stainless steel, and Inconel are the most common metals used in NPP, and radioactive contaminants are mostly accumulated in the corrosion layer. There are various radionuclides, but the main ones are 60Co, 137Cs, 54Mn and 51Cr. 60Co is the major activated corrosion product and responsible for high gamma radiation and longer half-life (5.27 years.) also makes it the most difficult to remove. Therefore, we investigated the melt decontamination characteristics of 60Co by introducing various slags using induction melting for stainless steel and carbon steel. Cobalt plating and cobalt oxide film coatings were used as specimens instead for safety purposes. The amount of cobalt removed from the slag was analyzed by using XRF. About 11% of the cobalt was removed from the contaminated metal due to slag oxide formation. The distribution of cobalt in the melted metal was also almost homogeneous according to the XRD analysis.

Effect of Temperature on δ-Ferrite Morphology of Carbon Steel and Austenitic Stainless Steel Welds

δ-ferrite was formed in the weld metal when the melted metal solidified to the room temperature. The δ-ferrite morphology depended on the composition, temperature gradient and growth rate. Research on the influence of heat treatment temperature (400°C, 600°C, 900°C) on the morphology changes and the δ-ferrite content is presented in this paper using optical microscopy, SEM, TEM. The δ-ferrite concentration reduced continuously in increasing temperature (from 23.5% after welding to 11% at 900°C for 10 hours). Besides, the formation of sigma phase and carbides at 600°C were the main cause of increasing hardness values in the fusion zone. However, the heat treatment at a temperature of 900°C eliminated both the sigma phase and brittleness.

INFLUENCE OF HIGH-VELOCITY IMPACT PARAMETERS ON THE STRUCTURE AND PROPERTIES OF THE VT1-0 + AMG5 JOINT

The paper presents the results of studying the joints of VT1-0 titanium with the aluminum-magnesium alloy AMg5, obtained by explosion welding in different modes of impact. The analysis of microstructures showed that, depending on the conditions of collision, the boundary of the joint zone can have both a wave and a waveless profile. Areas of melted metal are formed even with minimal energy input, but until a certain point they do not significantly affect the strength of the joint. At relatively low values of the energy W, titanium weakly dissolves in aluminum and is present in the melted areas in the form of crushed particles. A further increase in the modes of explosion welding leads to an increase in the degree of dissolution of titanium in melts, which is accompanied by the appearance of cracks. The results of the performed mechanical tests showed that the values of the peel strength of the layers are noticeably higher and reach an equal-strength joint in comparison with the method of welding through an intermediate layer of pure aluminum. In the investigated range of welding modes, the strength of the joint increases in the energy range W = 0,85...1,1 MJ/m, and at W = 1,1 MJ/m it reaches a maximum. With a further increase in the modes of explosion welding, the strength of the joint decreases, which is associated with a change in the structure of the melted regions with the formation of brittle intermetallics in them.

Kinetics of Diffusion Interaction in Cr15Ni60-AD1 Layered Composite

The structure, phase and chemical composition of the diffusion interaction zone, formed at the interlayer boundary of a layered composite of the alloy Cr15Ni60-aluminum AD1, are studied. The temperature-time conditions for its nucleation and growth are determined. The diffusion zone has a fine predominantly heterogeneous structure and consists of solid solutions based on aluminides Al3Ni, Al3Ni2 and Al7Cr, as well as the ternary compound Al5FeNi. It is shown that the intensity of diffusion zone growth at the interlayer boundary of the bimetal Cr15Ni60-AD1 is determined mainly by the heating temperature, and the dependence of its thickness on the exposure time obeys a parabolic law. The presence of chemical micro-inhomogeneity in the form of a melted metal at the interlayer boundary does not have a qualitative effect on the kinetics of the process: at the first stage, the diffusion zone repeats the contour of the fusion, and then, as the service time increases, «absorbs» it.

Modeling of conditions for formation of melted metal bath and weld during facing with consumable electrode and additional fi ller wire

The capabilities of computer simulation of complex multifactorial surfacing processes are discussed. Physical and mathematical model for the formation of melted metal bath and weld during consumable electrode surfacing with additional fi ller wire of parts and components of pipeline valves is presented. The basis of the model is equations system of heat transfer and pressure equilibrium on the surface of the melt. In the boundary conditions of the equations, change in the geometry of the surface due to transverse vibrations of the surfacing torch is taken into consideration. Numerical solution of the equations system showed that the main source of heat is heat from the droplets of the electrode and fi ller materials, its distribution is mainly determined by the amplitude and period of transverse vibrations. The results of process numerical simulation are presented. The results of the study are used in the development of innovative technological processes for surfacing of parts and components of pipeline valves.

Perspective technology of recycling of radioactive contaminated metal based on its melting

Melting of the radioactively contaminated metal converts it as a source of ionizing radiation from a surface distribution of radionuclides into the source with their volume distribution. From the surface of the melted metal gamma radiation of a part of radionuclides is emitted, which are in its scope. Alpha and beta radiation are absorbed completely in the metal. To obtain a radiation-safe metal it is necessary that the amount of gamma-emitting radionuclides, which are loaded into the furnace together with the charge, did not exceed the established allowable level. The radiation safety criterion of the melted metal is the maximum value of the gamma radiation power from its surface, the established limit of the individual annual effective radiation dose is not exceeded. There is a need for experimental verification of theoretical results was obtained. The use of this technology will allow the return to industrial production of large amounts of accumulated radioactively contaminated metal and creates conditions for the prevention of environmental violations.