Siberian Federal University, Krasnoyarsk, Russia:

N. N. Dovzhenko, Professor of a Chair “Metal Forming”
I. L. Konstantinov, Assistant Professor of a Chair “Metal Forming”, е-mail: ilcon@mail.ru
S. B. Sidelnikov, Professor, Head of a Chair “Metal Forming”

LLC “RUSAL ETC”, Krasnoyarsk, Russia:
Yu. O. Avdeev, Manager of a Project “Energy-efficient designs of electrolysers”

A method for producing trimetal blanks, which are to be used as an electrolytic aluminum cathode rod, was developed. The results of the study on parameters of a technology for connecting copper and steel plates through the nickel layer are presented. In order to obtain a steel-nickel-copper composite material, the mating faces of blanks from steel St3 (Ст3), nickel NP2 (НП2) and copper M1 were polished, degreased with acetone, and collected into a bag, which was compressed in a hydraulic press to enable a 225 to 260 MPa pressure in the metals’ contact area. The bag was fixed with clamps in a compressed state and subjected to diffusion bonding in an oven at (980±20) ^оC, where it was held for 60 min. As a result, the received bags may be subject to nondestructive cutting, carried out with the help of a cutting disc that is perpendicular to the plane of the layers in the samples for mechanical testing and microstructure research. The study of the sample’s microstructure on a scanning electron microscope showed that, as a result of diffusion, transitional layers were formed between iron and nickel, as well as between nickel and copper. The depth of interdiffusion between iron and nickel was 25–30 microns, and the thickness of the transitional layer between copper and nickel was about 40 micrometers. The resistance to shear trimetal welds, obtained after diffusion bonding between steel and nickel, was about 70 MPa, whereas the resistance was 50 MPa in the case of bonding between copper and nickel. Tensile strength testing of the layers showed that a failure occurred between layers of nickel and copper, and the tensile strength of the gap between layers of the metal was about 100 MPa. To assess the relevancy of the results, experiments were conducted in a laboratory to test the possibility of obtaining trimetal. The experiments were carried out on bulk samples with natural sizes of cross-sections of the cell’s cathode bars. The dimensions for the bag blanks were: 115230 mm steel section with 170 mm length; 12150 mm copper section with 160 mm length, and 150160 mm nickel size with 0.5 mm thickness. The metallurgical studies and tests on mechanical samples, cut out from the resulting perform, showed that the structure and properties of the bulk composite’s weld correspond to the results obtained with respect to model samples.
These researches were carried out by employees of LLC “RUSAL Engineering and Technology Centre” in cooperation with scientists of the Siberian Federal University in the framework of the Federal Target Program “Priority research and development of scientific-technological complex of Russia for 2014–2020” on the theme “Development of aluminum obtaining technology with a reduction of energy consumption in operating electrolyzer at 300–1000 kW/t of aluminum by agreement No. 14.579.21.0032 for subsidies. Unique identifier of the project: RFMEFI57914X003.

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