Single-turn Coils for Magnetic Pulse Welding of High-strength Steel Parts

Magnetic pulse welding provides high quality joining of fuel pin cladding for fast nuclear reactors. The tool coil there operates under the most stressful conditions: 40 T magnetic fields with tens of microseconds duration. This requires minimal coil inductance and affects the capabilities and lifetime of the coils. Two approaches are being practiced to enhance the coil durability: material research and construction optimization. The first approach considers the use of high strength steels or composite materials for the coil working area. The present work is aimed to realize the second approach – the use of multi position coils in order to maximize the number of parts welded in one coil. Experiments and finite element modeling were carried out for two designs of two- and four-position single-turn coils, which were made to process several workpieces in one current pulse. The main parameters measured and calculated were the magnetic field between the coil and the workpiece, and the ratio of its amplitude to the discharge current, Bm/Im. The currents flowing through the coils were about 700 kA, which correspond to the magnetic fields of 40–45 T. The FEM modeling revealed a 17–19% drop of the magnetic induction near the insulated slit, which, however, did not prevent the helium-tight joining of the tubes to the end plugs

Effect of the method for producing Cu-Cr3C2 bulk composites on the structure and properties

Copper-chromium carbide composites containing a carbide phase of 20-30 vol% were obtained with the use of solid- and liquid-phase mechanosyntheses, followed by magnetic pulse compaction (MPC) and spark plasma sintering. The morphology, structural-phase composition, density, hardness and electrical conductivity of the composites were investigated. The structure of composites obtained by MPC represents regions of copper matrix hardened by superfine carbide precipitates surrounded by a layer of chromium carbide. In the composites obtained by spark plasma sintering, the copper matrix hardened by superfine carbide precipitates was divided into areas surrounded by a copper-chromium layer. A composite obtained by the MPC of the powders synthesized using solid-phase mechanosynthesis (MS) (copper, chromium and graphite) had the highest values ofVickers microhardness (4.6GPa) and Rockwell hardness (HRA 69). The best value of electrical conductivity (36% IACS) was achieved using liquid-phase MS (copper, chromium and xylene) and spark plasma sintering. Liquid-phase MS is the only way to synthesize the powder with a small amount of the carbide phase and without contamination. © 2017 Indian Academy of Sciences.Government Council on Grants, Russian FederationFederal Agency for Scientific Organizations: 0428-2014-0002, 0389-2014-0002This work was supported by the Government of the Russian Federation (Federal Agency for Scientific Organizations) under the themes of the state task, no. 0389-2014-0002 and no. 0428-2014-0002 and by the Program of UD RAS, Project reg. no. AAAA-A17-117040610324-3

Magnetic Pulse Welding of the “Tube – Plug” Pair of STS410 Steel

The research was focused on the magnetic pulse welding (MPW) of 12.5% Cr steel STS410. The experiments were performed in the tube-plug geometry (both details were made of the same steel). Magnetic pulse unit consisted of pulsed current generator (PCG) loaded to a single-turn coil. Magnetic field amplitude of 40 T was generated in the coil during experiments. The amplitude of pulsed current reached 750 kA. The effects of energy storage capacity, charging voltage, and end plug shape were studied. The welded samples were investigated by optical microscopy. The optimal velocities of impact and contact front motion were evaluated as 300 m/s and 3-3.5 km/s, respectively. The paper includes the leakage test results as well. To date, the joints with a helium leak rate of 10-9 mbar·l·s-1 have been produced

Surface modification of steel inductor as an approach to enchance its durability in high pulsed magnetic fields

The work concerns both a theoretical analysis of magnetic and thermal effects in conductor with inhomogeneous initial conductivity and realization of this approach on steel, oriented on inductors production, by steel surface modification. Monotonically changing spe-cific resistance of steel was suggested to be realized via steel pack chromizing.This work was performed as part of state task No. 0389-2015-0025 and supported in part by RAS Program Project No.18-2-2-8

STUDY ON MECHANICAL PROPERTIES OF COMPACTED AND FIBROUS MATERIALS BASED ON NANOSTRUCTURED COPPER-NIOBIUM COMPOSITE

Mechanical properties of fibrous and powder materials based on nanostructured Cu-Nb alloy were studied as influenced by anneal temperature. At 800°C anneal, the UTS of powder materials (805–930 MPa depending on powder grade) is 1.5–1.7 times higher than of commercial wire, but with lower plasticity.Работа выполнена при частичной финансовой поддержке РФФИ и Госкорпорации «Росатом» в рамках научного проекта № 20-21-00050

Study of a Material Based on a Nanostructured Copper-Niobium Alloy for the Development of Magnetic Pulse Tools

The results of study of samples made of finely dispersed Cu-Nb by powder method are given. Comparative tests of materials stability under the generation of magnetic fields up to 40 Tl of microsecond duration are carried out.Работа выполнена при частичном финансировании грантов РФФИ (20-58-00029 Бел_а, 20-21-00050 Росатом)

Cu−Fe3C(Cr3C2)Cu-Fe_3C(Cr_3C_2) Bulk Nanocomposites Prepared by Mechanosynthesis Followed by Magnetic Pulse Compaction

The $Cu-Fe_3$ and $Cu-Cr_3C_2$ bulk nanocomposites are prepared by consolidation of the mechanically alloyed powders. The structure and properties (density, Vickers microhardness and electrical conductivity) of them have been studied. It is shown that microhardness is equal to 236 HV and 470 HV for a Cu-5 vol.% carbide phase and for a Cu-30 vol.% carbide phase, respectively. The microhardness which can be influenced by the heat treatment temperature depends on the grain size of the Cu matrix. The electrical conductivity values of 38-44% IACS (International Annealing Copper Standard) at room temperature have been found

Astigmatic transformation of Bessel beams in a uniaxial crystal

We investigate theoretically and experimentally the astigmatic transformations of Bessel beams at propagation perpendicularly to the c-axis of a uniaxial crystal. The analogy between this transformation and the astigmatic distortion of the plane wave by an inclined axicon is analytically shown. The influence of the polarization direction of radiation relative to the c-axis of a crystal on electric field components of the ordinary and the extraordinary beams is investigated