## 6 Conclusions  
1. A cylindrical electrode (work roll or guide roll) with copper-embedded steel was designed, and the electric field distribution characteristics of wide Mg strip EPR were simulated by the multi-point device. The influence of the electrode connection mode and electrode material on the electric field uniformity of an Mg strip was analyzed. The results showed that the variation coefficient of the temperature rise is 0.05 to 0.105 for the copper-embedded steel being used as a work roll, which is smaller than the variation coefficient of the temperature rise for the steel roller being used as a work roll. The copper-embedded steel being used as the work roll helps to improve the electric field uniformity of the wide Mg alloy strip. Moreover, as the \(J_{e}/J_{ave}\) distribution is fitted, the \(P_{2}\) coefficient can be used to describe the uniformity of the electric field. This model is convenient for the online evaluation of transient electric field distribution characteristics of the Mg alloy strip.
2. In order to accurately analyze the electric field distribution characteristics of the Mg strip EPR process and reduce the errors in the electric field due to experimental bias in the electric field measurements, finite element simulations were performed to model the electric thermal field under the same operating conditions. The electric field is returned by combining the experimental and simulation results. On the one hand, the characteristics of the electric field distribution can be obtained accurately, which facilitates the analysis of the transient evolution law for localized electric fields. On the other hand, the electric field characteristics of the electrode (work roll and guide roll) can be analyzed, so that the influence of electrode material and structure on the electric field characteristics can be described quantitatively. The results demonstrate that the uniformity of an electric field can be improved by the copper-embedded steel electrode and the symmetrical connection mode of the electrode, which facilitate carrying out the obtain stable constant electric field and temperature field. Obviously, it is highly beneficial to improve the electroplastic effect of the wide Mg EPR.  
Figure 9: The optical microstructure in the entrance of rolling mill: (**a**) edge of the loop drive side; (**b**) center; (**c**) edge of the operating side.  
3. A multi-pass EPR was performed on a wide Mg strip, and it was demonstrated that a uniform electric field distribution can improve the quality of the wide Mg strip. The thickness of the Mg strip was reduced from 1.0 mm to 0.5 mm by four passes without annealing by a reasonable electrostatic rolling process. It is shown that regulating electric field parameters can better complete the EPR process of the wide Mg strip, and reduce the occurrence of edge cracks.  
Conceptualization, G.L., L.Y. and H.Z.; methodology, G.L., L.Y. and H.Z.; software, G.L.; validation, G.L., L.Y. and H.Z.; formal analysis, G.L., L.Y. and H.Z.; investigation, G.L., L.Y. and H.Z.; resources, L.Y.; data curation, G.L.; writing--original draft preparation, G.L., L.Y. and H.Z.; writing--review and editing, G.L., L.Y. and H.Z.; and visualization, G.L. and L.Y. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Returned Overseas Scholar Foundation of Hebei Province (Grant No. C20210321) and the Natural Science Foundation of Hebei Province (Grant No. E2021203106).  
Not applicable.  
The authors declare no conflict of interest.