Research On Horizontal Electromagnetic Continuous Casting And Planetary Rolling Technology Of Copper Alloys

Copper alloys are widely used because of its excellent properties, such as high corrosion resistance, high strength and high electric conductivity and so on. Copper alloy CuNi 1 OFe 1 Mn added Ni, Fe and Mn elements in the copper matrix is widely applied to desalination of sea water, marine ship and other industries due to its property of high corrosion resistance. Cu-Cr-Zr alloy added Cr and Zr in the copper matrix is applied to high-speed railway due to its properties of high strength and electric conductivity.There is an urgent need to study a short process technology of CuNi10FelMn tubes as the traditional preparation technology is complicated, and the rate of finished products is less than 40%, so the products are less competitive. The researches indicate that the short process technology can also produce the contact wires installed on the high-speed railway with 350km/h speed, for instance, the properties of contact wires used in the Beijing-Shanghai high-speed railway are demanded that the tensile strength is above 600MPa, and the conductivity is above 80%IACS and the single plate weight is above 2500kg. Therefore, traditional vacuum casting and processing methods of Cu-Cr-Zr alloys must be changed. In a word, it is significant to study a new technology for preparing copper alloys as mentioned above.Electromagnetic stirring technology plays a significant role in improving the quality of CuNi10FelMn and Cu-Cr-Zr alloy due to grains refining and elimination of segregation. A large deformation of long billets can be achieved by planetary rolling technology and improvement of the structural properties can be realized by dynamic recrystallization. This paper studied the short process technology combining the horizontal continuous casting with planetary rolling in the preparation of CuNi10FelMn tubes, explored the effect of the rotating electromagnetic field (REF) and planetary rolling on the material properties, and then the contact wire of Cu-Cr-Zr alloy was prepared by the short process technology.This paper studied the influence of REF on the surface quality, structure and grain size of CuNi10FelMn billets and so on. The results indicate that:the average roughness Ra (μm) of tubes surface is decreased by 65.87%, and the columnar grain structure of top and bottom area is disappeared, and the grain size is refined obviously, which is 0.55mm. The distribution of elements is even. The studies of planetary rolling of CuNi10FelMn tubes indicate that there is a good property of plastic deformation as the grain size is refined obviously by dynamic recrystallization, and the tensile strength is 293MPa, and the hardness is 99HB, and the percentage of area reduction is 26%. The eccentricity of 90% tubes after planetary rolling is remained at 2.8%-6.0%, which is better than that of the extrusion process and can effectively prevent the uneven deformation during the drawing deformation. The drawing process has successfully passed the test many times, so the short process technology can be successfully used for producing the CuNilOFelMn tubes. The studies of the plastic deformation indicate that:there are three mechanisms such as solution strengthening, deformation strengthing and refined grain strengthening, and the increase of strength and the decrease of plasticity are mainly caused by the solution strengthening and deformation strengthing, however, the refined grain strengthening not only improves the strength but also improves the plasticity, only the contribution rate of raising the plasticity is not more remarkable than that of the solution strengthening and deformation strengthing. As a result, the whole properties of the tube show that the plasticity is reduced and the strength is increased by three methods.The short process technology is applied to produce the contact wires of Cu-Cr-Zr alloy in order to meet the special needs of high-speed railway over 350km/h speed. The paper studied the horizontal electromagnetic continuous casting under non-vacuum conditions, the results indicate that the low-temperature casting by decreasing 22℃can be achieved by REF, which is a key factor for non-vacuum conditions. The casting parameters of Cu-Cr-Zr alloy billet with a length of 45m, diameter ofΦ87 are:casting speed is 108mm/min, and casting temperature is 1255℃-1260℃, and the cooling water flow is 1.9 m3/h, the parameters of REF are that the current intensity is 50 A and the frequency is 30Hz. There is no crack on the billet surface and no porosity and slag on internal, and the solidification structure and the distribution of Cr, Zr, Cu of are even, and the grain refinement is significant.The Cu-Cr-Zr billet with length of 45m can be rolled by planetary rolling technology, which makes the bar achieve dynamic recrystallization. The average grain size of the billet's bar is 0.04mm, the tensile strength of which is 244.04 MPa, elongation of which is 29.31%, and conductivity of which is 75.10% IACS. The solution parameters of rolled bar are 860℃×1h. The aging parameters after cold deformation with three passes are 385℃×2h. After the processing of horizontal electromagnetic continuous casting, planetary rolling, solution treatment, cold deformation and aging treatment, the properties of finished contact wire are that the tensil strength is 610 MPa, and the conductiviey is 85%IACS. Increasing of tnesile strength is depended on the refined grain strengthening, solution strengthening, aging strengthening and deformation strengthening. The finished contact wires of 200 tons have been produced for Beijing-Shanghai high-speed railway at co-cooperation workshop, and they have been successfully passed the experiment of the highest operating speed of 486.1 km/h in the high-speed railway history on October 3,2010. A new contact wire of high strength and high conductivity achieves success.