Investigation of the stress-strain state and microstructure transformation of copper busbars in the deformation zone during continuous extrusion

The paper describes an extensive study of features peculiar to physical and mechanical processes occurring in metal in the deformation zone during the continuous extrusion of Cu-ETP rectangular busbars 10×60 mm in size. Finite element computer simulation was used to obtain the values of extrusion power parameters. It was noted that moment and force values increase to the point of filling the press chamber free space with metal reaching a maximum of 12.26 kN·m and 1.54 MN, respectively. The stress-strain state analysis of metal in the deformation zone made it possible to obtain distribution fields of accumulated plastic strain, strain rate intensity and average stresses, and to build the graph of metal temperature variation over time during extrusion. Maximum levels of accumulated plastic strain and compressive stresses are observed in the contact zone of the workpiece with the press container abutment. The most intense metal deformation heating also occurs there. The comparison of modeling and microstructural study results indicate that a significant portion of the cast structure grinding work occurs at the entrance to the deformation zone and at the abutment zone subjected to the highest level of compression stresses. Metal deformation during the die passage leads to an oriented crystal structure formed with a grain size of 25–30 μm. Sample hardness measurement results are consistent with the results of structure analysis in the studied areas of the deformation zone. When the workpiece passes through the compression container abutment section, deformation heating occurs, which leads to a decrease in hardness from 93 to 67 HV. After the metal passes through the die, recrystallization processes continue in it leading to a slight increase in grain size and, accordingly, a decrease in hardness from 79 to 74 HV, which continues until the busbar contacts a cooling medium.

1. Davis J.R. Copper and copper alloys. OH: ASM International, 2003.

2. Smith W.F., Hashemi J. Foundations of materials science and engineering. Boston: McGraw-Hill Professional, 2003.

3. Zinoviev A.V., Chasnikov A.Ya., Potapov P.V. Physical and mechanical properties and plastic deformation of copper and its alloys. Moscow: IRIAS, 2009 (In Russ.).

4. Shatalov R.L., Lukash A.S., Zisel’man V.L. Definition of mechanical properties of copper and brass strips on indices of hardness factors in the time of cold rolling. Tsvetnye Metally. 2014. No. 5. P. 61—65 (In Russ.).

5. Zinoviev A.V., Sokolov P.Yu., Do Van Min’, Chasnikov A.Ya. Research of resistance of deformation of simple brasses. Tsvetnaya Metallurgiya. 2015. No. 5. P. 24—25 (In Russ.).

6. Zinoviev A.V., Shmurygin E.G., Morozov G.P., Lugovov V.F., Lobkov A.I. Increasing the production efficiency of plates, sheets and strips of alloys based on copper and nickel: monograph. Moscow: Metallurgiya, 1996 (In Russ.).

7. Loginov Yu.N., Shalaeva M.S. Evolution of microroughnesses of copper pipes’ inside surface in drawing. Izvestiya Vuzov. Tsvetnaya Metallurgiya (Universities’ Proceedings. Non-Ferrous Metallurgy). 2014. No. 3. P. 39—44 (In Russ.).

8. Valiev R.Z., Langdon T.G. Principles of equal-channel angular pressing as a processing tool for grain refinement. Prog. Mater. Sci. 2006. Vol. 51. No. 7. P. 881—981. https://doi.org/10.1016/j.pmatsci.2006.02.003.

9. Wang Y.L., Lapovok R., Wang J.T., Qi Y.S., Estrin Y. Thermal behavior of copper processed by ECAP with and without back pressure. Mater. Sci. Eng. A. 2015. Vol. 628. P. 21—29. https://doi.org/10.1016/j.msea.2015.01.021.

10. Gamin Yu.V., Romantsev B.A., Pashkov A.N., Patrin P.V., Bystrov I.A., Fomin A.V., Kadach M.V. Obtaining hollow semifinished products based on copper alloys for electrical purposes by means of screw rolling. Russ. J. Non-Ferr. Met. 2020. Vol. 61. P. 162—171. https://doi.org/10.3103/S1067821220020054.

11. Valeev I.Sh., Valeeva A.Kh. On the microhardness and microstructure of copper Cu 99,99 % at radial-shear rolling. Pis’ma o materialakh. 2013. Vol. 3. No. 1. P. 38—40 (In Russ.).

12. Skripalenko M.M., Galkin S.P., Sung H.J., Romantsev B.A., Huy T.B., Skripalenko M.N., Kaputkina L.M., Sidorow A.A. Prediction of potential fracturing during radial-shear rolling of continuously cast copper billets by means of computer simulation. Metallurgist. 2019. Vol. 62. P. 849—856. https://doi.org/10.1007/s11015-019-00728-8.

13. Ivanov A.M. Press forming of prismatic and screwshaped sections of M4 copper. Izvestiya Vuzov. Tsvetnaya Metallurgiya (Universities’ Proceedings. Non-Ferrous Metallurgy). 2017. No. 3. P. 77—84 (In Russ.).

14. Vu V.Q., Prokof’eva O., Toth L.S., Usov V., Shkatulyak N., Estrin Y., Kulagin R., Varyukhin V., Beygelzimer Y. Obtaining hexagon-shaped billets of copper with gradient structure by twist extrusion. Mater. Charact. 2019. Vol. 153. P. 215—223. https://doi.org/10.1016/j.matchar.2019.04.042.

15. Adno Yu.L. The phenomenon of metallurgical mini-mills. Mirovaya ekonomika i mezhdunarodnye otnosheniya. 2014. No. 3. P. 34—45 (In Russ.).

16. Green D. Continuous extrusion-forming of wire section. J. Inst. Metals. 1972. Vol. 100. P. 295—300.

17. BWE Ltd Brochure. BWE Limited. URL: https://bwe.co.uk/wp-content/uploads/2020/04/BWELtd-Brochure-Website-After-Proof.pdf (accessed: 25.05.2020).

18. Konstantinov I.L., Sidelnikov S.B. Basics of metal forming processes. Krasnoyarsk: Siberian Federal University, 2015 (In Russ.).

19. Gorokhov Yu.V., Solopko I.V., Suslov V.P., Krylov M.A. Features of the plastic current of billet material in deformation area at conform continuous extrusion. Tsvetnye Metally. 2010. No. 12. P. 69—71 (In Russ.).

20. Shimov G.V., Fominykh R.V., Efremova A.S., Kovin D.S. Study of flow trajectories of continuously cast copper during the Conform pressing. Tsvetnye Metally. 2018. No. 4. P. 79—85 (In Russ.).

21. Fominykh R.V., Shimov G.V., Efremova A.S., Lyamina E.A. Experimental study of causes of refused of copper busbares while pressing on the line of continuous extrusion «Conform-400». In: Proceedings of the XVIII International scientific and technical Ural summer school for young scientists-metallurgists» (Russia, Ekaterinburg, 21—23 Nov. 2017). Ekaterinburg: Ural Federal University, 2017. P. 47—53 (In Russ.).

22. Song L., Yuan Y., Yin Zh. Microstructural evolution in Cu—Mg alloy processed by conform. Int. J. Nonferr. Met. 2013. Vol. 2. No. 3. P. 100—105. http://dx.doi.org/10.4236/ijnm.2013.23014.

23. Yuan Y., Li Z., Xiao Z., Zhao Z., Yang Z. Microstructure evolution and properties of Cu—Cr alloy during continuous extrusion process. J. Alloys Compd. 2017. Vol. 703. P. 454—460. https://doi.org/10.1016/j.jallcom.2017.01.355.

24. Li B., Li Ch., Yao X., Song B. Effects of continuous extrusion on microstructure evolution and property characteristics of brass alloy. Adv. Mater. Res. 2011. Vol. 189—193. P. 2921—2924. https://doi.org/10.4028/www.scientific.net/AMR.189-193.2921.

25. Li B., Wei Q., Pei J.-Y., Zhao Y. Flow characteristics of brass rod during continuous extrusion. Procedia Eng. 2014. Vol. 81. P. 647—651. https://doi.org/10.1016/j.proeng.2014.10.054.

26. Mochalin I.V., Gorokhov Yu.V., Belyaev S.V., Gubanov I.Yu. Copper busbars extrusion on «Conform» installation with prechamber. Tsvetnye Metally. 2016. No. 5. P. 75—78 (In Russ.).

27. Gorokhov Yu.V., Timofeev V.N., Belyaev S.V., Avdulov A.A., Uskov I.V., Gubanov I.Yu., Avdulova Yu.S., Ivanov A.G. Die assembly of the Conform unit for continuous non-ferrous metal forming. Izvestiya Vuzov. Tsvetnaya Metallurgiya (Universities’ Proceedings. Non-Ferrous Metallurgy). 2017. No. 4. P. 69—75 (In Russ.).

28. Gorokhov Yu.V., Timofeev V.N., Gubanov I.Yu., Plotnikova T.A., Ivanov A.G. Modernization of the Conform installation construction. In: Book of papers of the ninth International Congress «Non-Ferrous Metals & Materials» (Russia, Krasnoyarsk, 11—15 Sept. 2017). Krasnoyarsk: Nauchnoinnovatsionnyi tsentr, 2017. P. 591—596 (In Russ.).

29. Katajarinne T., Manninen T., Ramsay P. Numerical simulation of flash formation in continuous rotary extrusion of copper. J. Mater. Process. Technol. 2006. Vol. 177. No. 1—3. P. 604—607. https://doi.org/10.1016/j.jmatprotec.2006.04.054.

30. Yun X., You W., Zhao Y., Li B., Fan Z. Continuous extrusion and rolling forming velocity of copper strip. Trans. Nonferr. Met. Soc. China. 2013. Vol. 23. P. 1108—1113. https://doi.org/10.1016/S1003-6326(13)62572-8.

31. Ershov A.A., Loginov Y.N. Simulation of the Conform-type pressing process by using the QFORM VX software complex. Metallurgist. 2018. Vol. 62. P. 207—211. https://doi.org/10.1007/s11015-018-0646-6.

32. Shimov G.V., Kovin D.S., Fominykh R.V., Bogatov A.A. Modeling of the initial stage of the prechamber filling while copper busbares pressing on the continuous extrusion line «Conform-400». In: Proceedings of the XVIII International scientific and technical Ural summer school for young scientists-metallurgists» (Russia, Ekaterinburg, 21—23 Nov. 2017). Ekaterinburg: Ural Federal University, 2017. P. 599—603 (In Russ.).

33. QuantorForm2019. URL: https://qform3d.com. (accessed: 26.11.2019).

34. Polukhin P.I., Gun G.Ya., Galkin A.M. Resistance to plastic deformation of metals and alloys: Handbook. Moscow: Metallurgiya, 1983 (In Russ.).

35. Gorokhov Yu.V., Sherkunov V.G., Dovzhenko N.N., Belyaev S.V., Dovzhenko I.N. Continuous extrusion of metals: Basics of process design. Krasnoyarsk: Siberian Federal University, 2013 (In Russ.).

36. Колмогоров В.Л. Механика обработки металлов дав- лением: Учеб. для вузов. М.: Металлургия, 1986.

37. Kolmogorov V.L. Mechanics of metal forming. Moscow: Metallurgiya, 1986 (In Russ.).

38. Hallberg H., Wallin M., Ristinmaa M. Modeling of continuous dynamic recrystallization in commercial-purity aluminum. Mater. Sci. Eng. A. 2010. Vol. 527. No. 4—5. P. 1126—1134. https://doi.org/10.1016/j.msea.2009.09.043.

39. Zinoviev A.V., Koshmin A.N., Chasnikov A.Y. Effect of continuous extrusion parameters on alloy M1 round section bar microstructure and mechanical property formation. Metallurgist. 2019. Vol. 63. P. 422—428. https://doi.org/10.1007/s11015-019-00838-3.