Evaluation of Different Cast Iron Grades for Stub-Anode Connection in Aluminum Electrolytic Cells
The electrolytic process in the aluminum reduction cells is affected by the overall voltage drop in the anode section, and this in turn is significantly influenced by the voltage drop at the connection between the anode and the steel stubs holding the anode. Cast Iron Collars are used to fix the stub to the anode and the optimum cast iron grade, which results in the minimum voltage drop, is still debated. This work was carried out to investigate the cast iron parameters leading to the lowest electrical resistance at the stub/collar/anode connection. Firstly, the performance of the currently used high phosphorus cast iron connection collars in the course of service cycle of an operational cell was studied by measuring the voltage drop between the stub and the anode. The variation in voltage drop between the stub and the anode was correlated to the changes in cast iron microstructure over a complete life cycle of the anode, i. e. up to 30 days and at increasing temperatures up to 850℃. Fixation collars were cast from different grades of cast iron,i. e. grey iron with carbon equivalent ranging from 3.9 to 4. 5,SG iron with compositions typical of ferritic and pearlitic grades as well as the currently used(due to castability considerations) high-phosphorus iron. A bench-scale experimental set-up was used to simulate the operating conditions in the stub/cast iron collar/graphite anode block connection and to measure the electrical resistance. The thermal expansion properties of the different grades of cast iron were measured using a high precision automatic dilatomer. The electrical resistance at the connection was related to the electrical resistivity of the cast iron, changes in the microstructure with temperature, and the thermal expansion. It seems that the contact pressure at the steel stub-cast iron collar-anode connection rather that the resistivity of cast iron plays the major role in determining the electrical resistance and hence the voltage drop. The contact pressure may be enhanced by the formation of higher volume fraction of graphite during solidification and/or by the decomposition of carbides in the as-cast structure with prolonged heating during the cell operation.
A. A. Noral M. A. Waly M. M. Mourad A. A. Ahmed M. A. Agour
Central Metallurgical R&D Institute ( CMRDI) , Cairo, Egypt Aluminum Co. of Egypt(Egyptalum) .Nagaa Hammadi,Egypt
国际会议
69th World Foundry Congress(第69届世界铸造会议 WFC 2010)
杭州
英文
378-386
2010-10-16（万方平台首次上网日期，不代表论文的发表时间）