EuroWire November 2019

Technical Article

speed with the elongation coefficient, and the copper powder content of the finished copper rod is measured. The results show that the content of copper powder in copper rod decreases from 4.3 and 4.8mg/20mm to 3.9mg/20mm. The content of copper powder can be effectively reduced by optimising the speed of roll. In view of the serious phenomenon of copper sticking on the second roll in the field, the simulation analysis of hot rolling deformation shows that the roll has large deformation and surface damage, and rolling temperature has a great influence on it. The measures for optimising and reforming the spray cooling system are put forward ( Figure 5 ). Two nozzles were added to the inlet of the number two stand, the gap of roll was adjusted to 6.6mm and 0.5 was added to the spraying platform after optimisation. The surface of rolled copper rod and roll was observed. After optimisation, the imprint on the surface of copper rod disappeared completely, and the phenomenon of non-sticking copper on the roll surface was effectively solved. (1) The coupling model of temperature field and flow field in solidification of copper liquid in continuous casting crystallising cavity was established to reveal the forming law of copper billet in the casting cavity of SCR3000 continuous casting and continuous casting. Through the corresponding finite element numerical simulation analysis, the influence of casting temperature, casting speed and heat transfer coefficient on the temperature distribution, flow characteristics and freezing point location in the crystallisation zone is explored. (2) The hot rolling model of copper rod was built, and the deformation law of copper rod in ten pass hot strip mill was discussed. By simulating the grouping rolling of hot strip mill, it is found that the surface deformation difference of copper rod in elliptical pass system is easy to cause damage. The surface temperature of copper rod decreases while the core temperature rises during rolling, and the temperature of copper rod tends to be the same after rolling under the action of heat conduction. At the same time, the rolling damage mainly concentrates on the surface of copper rod, which lays a theoretical foundation for improving the rolling production of high quality copper rod. 5 Conclusions

copper rod and its rolling interface. The core and surface temperatures of rolled copper rods are quite different. Because the contact heat transfer between copper rod and roll surface is larger and the temperature drop of copper rod surface is faster, the temperature of the copper rod core increases under the action of plastic work and friction work, and the temperature of copper rod core increases faster with the increase of rolling speed and deformation. After continuous rolling, the temperature of the whole rolling piece gradually converges under the action of heat conduction [8] . The ductile damage of copper rods under large deformation, high temperature and high strain rate rolling is an important problem in the plastic forming process of copper rods. By simulating the damage to copper rod and cross section in the continuous rolling process, the damage situation and damage distribution of copper rod in the continuous rolling process are obtained, which can accurately predict the damage location of copper rod in the hot rolling process and improve the quality of copper rod production. The damage of copper rod during hot rolling is mainly concentrated on the surface and some edges and corners, while the damage of the core is relatively small. The surface of copper rod is easily damaged during hot rolling. The small process fluctuation of the rolling mill will directly affect the surface quality of finished copper rod and reduce the mechanical properties of copper rod. 4.3 Optimising measures of hot strip rolling process Combining with the process characteristics of the SCR3000 continuous casting and rolling line and its analysis and simulation of key process parameters, and aiming at the speed and cooling process of continuous rolling mill, optimisation measures are put forward to solve the problem of high content of sticky copper and copper powder in the production line in order to improve the quality of copper rod. Because the calculation of stacking rate depends on the cross-sectional area of the rolled parts in each pass and there is no way to measure the cross-sectional area of each pass in the production site, the feasibility of matching the rotational speed of each stand motor based on stacking rate is poor. Therefore, a method of matching motor speed with elongation coefficient is proposed, and field debugging is carried out, as shown in Table 4 . According to Table 4 , the motor speed of 1 and 2 is adjusted to 1,549 rpm and 1,586 rpm, respectively, by matching the motor

National Engineering Research Centre for Equipment and Technology of Cold Strip Rolling Yanshan University Qinhuangdao 066004 China Tel : +86 0335 8387651 Email : pengyan@ysu.edu.cn Jiangsu Hengtong Precision Metal [1] Binmin Y & Weiqi Z. Improvement of Qualification Rate of Copper Rod in SCR Production Line [J]. Special Casting & Nonferrous Alloys, 2011, 4. [2] Yang Yunchuan. Study on Microstructure and Properties of SCR Continuous Casting and Rolling Copper Alloy [D]. Kunming University of Technology, 2011. [3] Sahoo S, Kumar A, Dhindaw B K, et al. Modelling and Experimental Validation of Rapid Cooling and Solidification During High-Speed Twin-Roll Strip Casting of Al-33 Wt Pct Cu[J]. Metallurgical and Materials Transactions B, 2012, 43(4): 915-924. [4] Komanduri R, Chandrasekaran N, Raff L M. Molecular Dynamics (MD) Simulation of Uniaxial Tension of Some Single-crystal Cubic Metals at Nanolevel [J], International Journal of Mechanical Sciences, 2011, 43: 2237-2260. [5] Liu Heping, Chou Shengtao, Gan Yong. Numerical Simulation on Turbulent Transport and Solidification in Mushy Zone during Continuous Casting[J]. Journal of Iron and Steel Research, 2003(02):68-73. [6] Rule W K, Jones S E. A revised form for the Johnson–Cook strength model[J]. International Journal of Impact Engineering, 1998, 21(8): 609-624. [7] Liu Jinsong. Application of MSC.MARC in Material Processing Engineering [M]. Beijing ： China Water & Power Press, 2011. [8] Liu Qingsong. Influence of continuous rolling process on quality of electrician copper rod[D]. Anhui University of Technology, 2016. (3) Through the modelling and simulation of the continuous casting and rolling process of the SCR3000 production line, the production process and equipment of copper rod continuous casting and rolling were optimised. Aiming at the phenomenon of sticking roll in hot continuous rolling and the high content of copper powder in finished copper rod, a method of matching motor speed with elongation coefficient is put forward to optimise rolling speed and change the speed of 1# and 2# to effectively reduce copper powder content in copper rod. At the same time, optimising the spray cooling system to control the rolling temperature of copper rod can effectively solve the problem of copper sticking on rolls. n 6 References

Material Co Ltd Suzhou 215232 China Tel : +86 0512 63803026 Email : jihuis@htgd.com.cn

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November 2019