Application Of Electromagnetic Field In Copper Continuous Casting

In this paper, we focus on the study of application of electromagnetic field in the main two copper continuous casting technologies: horizontal continuous casting and vertical semi-continuous casting, including the electromagnetic stirring in thin slab horizontal continuous casting, electromagnetic vibration in liquid metal solidification and continuous casting, and soft-contact electromagnetic continuous casting of high quality oxygen-free copper We hope these experiment investigations in laboratory and factory could brought out new techniques and promote the industry application of electromagnetic technology in copper continuous casting.Because of the disadvantages, including large width-height ratio of super thin slab, the weaken stirring effect of electromagnetic induct in EMS, the strong shielding effects of copper mould on the alternated electromagnetic field, the unsafety of brass water-cooling induct coil using in practice and the interference effects of alternated electromagnetic field on the control equipment, a kind of new stirring mode under the condition of static magnetic field coupled with orthogonal directional current was brought forward. EMS mould used in copper thin slab horizontal continuous casting for industry experiments and production was designed out and its stirring characteristics were studied deeply. Then, it was applied to Cu-Fe-P series KFC and Cu-Zn-Ni alloy horizontal continuous casting successfully. It showed that the solidification interface of copper alloy thin slab changed obviously after EMS process, the solute accumulation in solid liquid interface was repressed strongly via the electromagnetic stirring, and the segregation of Fe was reduced greatly (achieved to zero when stirring current is 800A). At the same time the solidification structure of the billet was refined, equiaxed grain zone appeared in the mid-zone and the porous shrinkage disappeared. While the column grain became thinner at the edge of the billet, its growth direction changed towards to the metal flow. The primary dendrite spacing reduced with the increasing of stirring current, and the billet's tensile strength enhanced 39% after EMS process.In lab, alloys with higher melting point such as pure aluminum and Al-4.5%Cu alloy were solidified in vibrated condition which generated by static high magnetic field with 50 Hz alternating current orthogonally. The results showed that the solidification structures were refined obviously by the electromagnetic vibration. For pure aluminum, the sample has the most grain number per area when the magnetic flux strength was 6T and the alternative current strength keeping at 10A, but on vertical section, the refine effect attenuated from top to bottom. When the magnetic flux strength was 6T and alternative current strength was 5A, the sample had the most refined solidification structure. For Al-4.5Cu alloy, the shape of dendritic crystal would not be changed by only imposing static magnetic field or alternative current singly. While it would be changed via a static magnetic field interacted with alternating current, which called electromagnetic vibration. When this multiple action was weak, the solidification structure was equiaxed crystal mixed with granular grain. Once this action was strong, the main structures were granular. When the magnetic flux strength was 10T, the liquid metal'fluctuation aggravated with the raise of alternating current strength, more and more dendritic crystal were broken up and finally changed to granular grain entirely. We found that the main cause of crystal refinement were the crystal nucleus multiplication which generated by the electromagnetic vibration and the broken up of dendritic arm by electromagnetic pressure during the dendritic crystal growth, but not the cavitations effects in general. The industry experiment using H65 brass testified the feasibility of electromagnetic vibration, which showed the refine grain and improved billet's quality.Based on the theoretical calculation and simulation experiment in laboratory, a kind of soft-contact electromagnetic mould used in copper alloy continuous casting is designed and applied successfully in the production of copper and magnesium alloy. Furthermore, a new technique acquiring oxygen-free copper called"electromagnetic (stirring) deoxidization - electromagnetic continuous casting"is proposed. By using this technique, the copper with the characters of high quality, large size and oxygen-free could be realized in the domestic enterprises under the condition of non-vacuum, low cost and continuous production. The copper content exceeds 99.97% and oxygen content lies between 5 and 10 ppm, which meet the TU1 standard, even the TU0 standard and reach the copper standard used in international vacuum electron field. The physics and mechanical property are better than that in similar products, its density reach to 8.92-8.94 g/cm3 (the copper density in theory is 8.96 g/cm3) , the mean yield strength is 51 MPa, the tensile strength is 155 MPa, the elongation percentage is 45 %, reduction of cross section area is 70 %, resistance is 0.01712 ?mm2/m(the value of annealed oxygen-free copper standard international is 0.01742Ωmm2/m), conductivity exceeds 104 % IACS which enhanced 1.75% above that in the similar production world wide,the full exhaust gas content in high temperature and vacuum is 5.6 mPa·m3/g, just about 40 % of the value in traditional Japanese production.As a sum, the research on electromagnetic stirring mould used in thin slab horizontal continuous casting, electromagnetic vibration mould and new continuous casting technique broken a new path and have practical values and establish the basis for the future development, the design and utilization of copper electromagnetic soft-contact continuous casting mould , new technique acquiring oxygen-free copper called"electromagnetic (stirring) deoxidization - electromagnetic continuous casting"were technique innovations, high quality oxygen-free copper billet with large size could produced in industry with low cost, and high physical and mechanical property.