Analysis of electric current supply circuits to rolls during electroplastic rolling of tungsten microstrips

Abstract

One of the important problems in the design and operation of the electroplastic deformation mill is the reliability and uniformity of the supply of powerful electric current to the deformation zone. The high density of the electric current and the uneven distribution of it leads to a different manifestation of the effect of electroplasticity along the width of the strip, an uneven temperature field, and as a result, to a decrease in the quality of the finished product. To evaluate various current supply circuits, a discrete model is proposed, in which the work rolls and the rolled strip are presented as combinations of lumped resistances. The model was used when considering four main circuits for supplying electric current to the rolls of the electroplastic deformation strip mill: straight one-sided, diagonal onesided, direct two-sided, diagonal two-sided. For all circuits, formulas were obtained for calculating the electric currents flowing in the center of the strip and along its edges. The dependences obtained using the developed model show that the greatest non-uniform distribution of electric current across the width of the rolled strip occurs with a direct one-sided current supply. At the same time, its undoubted advantage over other options is a simpler design. Diagonal single-sided and both variants of double-sided current supply (according to this model) give the same results. The main disadvantage of these options is the need to supply electric current from both sides of the rolling mill. Regardless of the selected current supply option, it is necessary to minimize the ratio of the electrical resistances of the roll materials and the deformed material. In particular, this can be achieved by increasing the diameter of the work roll, as well as by choosing a roll material with high electrical conductivity. The model for supplying electric current to the work rolls and recommendations for reducing the uneven distribution of current across the width of the strip are used in the design of electroplastic deformation mills.