Study On Microstructure And Properties Of Pb - Ag Alloy By Refining Process

With the development of the society, people’s requirement for the environment is higher and higher, pyrometallurgy is gradually replaced by hydrometallurgy which has became the mainstream of extraction methods of metal. The performances of the electrode which serves as the core of the Hydrometallurgy directly affects the benefits. Although the materials of anode innovate constantly, but at present, the Pb-Ag alloy electrode is always the most widely used in this fields, which have the advantage of low cost, good electrochemical performance and ease of processing and recycling. However, there are also some disadvantages that are difficult to completely solve by traditional preparation method, such as low intensity, big resistance, high energy consumption and so on. So the important subject in the fields of hydrometallurgy and electrochemistry is to find a new preparation method which can increase the Pb-Ag alloy electrode comprehensive performance.Throughout the research status at home and abroad, researchers concentrate too much energy on the ratio of alloy in the past, and ignore the connection of inner structure and performance of the alloy. Even small dense structure can accelerate the electrons transmission in the anode, thereby resistance can be reduced, which makes the comprehensive performance of the anode improved in different extent, and then achieves the goal of saving energy and reducing consumption. The study has found that by using physical field and strong plastic force field technology, low cost and high performance lead alloy anode material can be obtained, in addition, the preparation method and technology are good for environment and adapt to the current national conditions.Through the study of the of Pb-0.5%Ag alloy with ultrasonic method, equal channel angle pressing, hot rolling, cold rolling and ultrasonic+rolling of five kinds of grain refining processes. The data of the resistivity of electrode, cell voltage, polarization curves, Tafel curves, η-lg figure and microhardness are analyzed to study the influence of different process parameters on the structure and mechanical properties, optimize the technological parameters of the different processes. Comprehensive comparison of different kinds of technology, the best process parameters of lead alloy can be obtained. In addition, this study explores the size and structure of grain on its performance, which can reach the goal of technology adjustment to regulating grain size and structure to getting the best comprehensive performances.The results show that ultrasonic+rolling method is the best preparation technology, the optimum process parameters are:the melt temperature is 370 ℃, rolling time is lmin, annealing temperature is 140 ℃, reduction is 20%. Under the condition of the process, compared with the casting of lead alloy anode, electric conductivity, electrochemical properties and mechanical properties can be greatly improved. The resistivity can be reduced by 44.86%, polarization potential can be reduced by 18.13%, cell voltage can be reduced by 4.82%, and hardness can be increased 2.23 times. Through the analysis of Tafel and η-lg, which found that this process is helpful to obtain low corrosion current and overpotential, the corrosion resistance of anodic and the electron transfer rate are improved, and getting excellent electrochemical performance. At the same time, the organizational structure of grain can change the local corrosion to the homogeneous corrosion, and the service life of anode is enhanced. Through the study of the grain size, organization structure and performances can be found that with the increase of grain size, the comprehensive performances of anode would increases first and then decreases. Excessive refinement of grain will have big dislocation density, too many grain boundaries. The matrix of coarse grain is loose, it will lead the electronic transmission down. Only the moderate grain size which is about 10 μm, the structure can be uniform, and anode can get good comprehensive performances. In addition,recrystallization organization is the best structure, the materials have low internal stress and certain thermal stability.After the treatments of multi-functional fields, many defects of lead alloy anode can be greatly solved. It is benificial to promote the development of the lead alloy electrode as well as reduce the energy consuption of electrolysis area, it has important practical significance.