The engineering application of the electroplastic effect in the cold-drawing of stainless steel wire
Introduction
The electroplastic effect (EPE) is the phenomenon in which the flow stress in a straining test is affected significantly by the application of a high density current pulses (103–104 A/mm2). Conrad et al. [1], [2], [3], [4] found such EPE phenomenon in various materials. Furthermore, it has been claimed that such current pulses can lead to improvement in metal-working operations [5].
The authors have investigated the effect of current pulses on the plastic properties of materials in the wire-drawing process. A substantial decrease of drawing force and a good improvement of the elongating ratio has been found [6]. In this paper, a more detailed investigation was made of such EPE phenomenon on the mechanical and magnetic properties and the microstructure on the surface of the cold-drawn wire.
Section snippets
Experimental work
A schematic illustration of the drawing system is presented in Fig. 1. The material used in this experiment was austenitic stainless steel 1Cr18Ni9, with a original diameter of 1.6 mm and in the pristine softened state. The current pulses were applied at the front and the back of the wire-drawing die, the latter having a half-angle of the cone of α=11.5°. The wire was first drawn without current and then with the application of current pulses so as to compare the effect of the current pulses on
The drawing force and the mechanical properties
With the application of the current pulses to the wire during drawing process, the drawing force decreased compared to conventional wire drawing, Fig. 2 shows that the drawing stress has decreased by about 50%. Simultaneously, the mechanical properties of the wire have changed greatly (Table 1).
Magnetic properties of the wire
From the data on magnetic properties of the wire with and without the application of current pulses, It is found that with the introduction of the current pulses, the saturated magnetization Bs has been
Discussion
From the macro-morphologic images of the wire, it is found that the wire drawn without current pulses has a lot of the above-mentioned “knots”, which can be seen with the naked eye, at the surface of the wire. This means that the surface quality will not be acceptable in factory production, and an annealing treatment will be needed, but as mentioned the wire drawn with current pulses has no such kind of “knots” (Fig. 4). The reason of the formation of such “knots” is that during the
Conclusions
- 1.
With the application of electric current pulses to the cold-drawing process of 1Cr18Ni9, the drawing stress will be decreased to about 50% compared with the conventional wire-drawing process. Also, the plasticity of the wire is improved.
- 2.
The wire drawn with electric current pulses has a better surface quality than that drawn by the conventional process.
- 3.
Numerous ferromagnetic phases are formed in the conventional wire-drawing process. With the introduction of the current pulses, however, the
Acknowledgements
This project is supported by the National Nature Science Foundation of China.
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