Institute of Materials Science and Metallurgy, Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg:

Yu. N. Loginov, Professor, e-mail: j.n.loginov@urfu.ru

S. L. Demakov, Assistant Professor

A. G. Illarionov, Assistant Professor

S. I. Stepanov, Researcher

Ural Mining-Metallurgical Company, JSC “Joint Enterprise “Katur-Invest”, Verkhnyaya Pyshma, Russia:

T. P. Kopylova, Technologist

The purpose of this work is definition of differences in impact of strand-type and conveyor annealing for thermal copper wire treatment. Batch of industrial and laboratory experiments with copper wire, obtained by rod drawing, was carried out for comparison of strand-type and conveyor annealing effect. Wire with 2 mm diameter was manufactured at two enterprises, using drawing mills, operating in sliding mode. Deformation degree was 2.8, and relative cross-sectional area reduction was 94%. The strand-type annealing was carried out with resistive annealing adapter, mounted into working line of drawing machine with drawing speed of 18 m/s. Thermal effect time was 0.015 s. In the second method, annealing was carried out in conveyor electrical resistance furnace in water vapor atmosphere during 59 minutes. Both methods were characterized by similar values of tensile strength and contraction ratio. Tensile strength was increased with respect to hot-rolled condition from 240 MPa to 260 MPa, which can be explained by grain structure grinding and texture state change. At the same time, the yield strength was decreased from 142 MPa to 108 MPa (by 24%). Next batch of experiments was set with energy changing, where short strand-type annealing was carried out with changing of current in machine annealing adapter with drawing of wire with diameter of 1.78 mm at a speed of 25 m/s. Annealing current density was stepwise changed from 691 to 731 A/mm². After drawing, testing samples were selected and mechanical properties were determined by sample tension. Dependence of tensile strength function on current density was poorly defined with a minimum difference of maximum and minimum values at the level of ~4%. More signified minimum at the current density of 715 A/mm² was observed for conditional yield strength. Maximum value (149 MPa) differed from minimum value (133 MPa) by 11%. Maximum elongation of 38% was reached at the same current density. Thus, it is shown that increase of plastic properties can be reached by either conveyor annealing, or optimization of current density in strand-type annealing operation. With respect to the strand-type annealing, conveyor annealing makes a slightly lower tensile strength of copper possible, and significantly reduces yield strength. Minimum strength properties and maximum plastic properties were reached at a current density of 715 A/mm².

Authors express their gratitude for financial support of the development programs of Ural Federal University, and support of leading Russian Universities for increasing of their competitiveness No. 211 of the Government of Russian Federation No.02.A03.21.0006, and Ministry of Education and Science of Russian Federation, within the realization of the state task of Ural Federal University No. 2014/236.

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