Failure Analysis of Cast Lead–Antimony Battery Grids
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This paper presents the failure investigation of lead-acid battery grids received from a local battery manufacturer. Distortion, cracking, and brittleness were observed in as-cast grids. These battery grids were gravity cast by re-melting of locally made Pb–Sb ingots. However, similar distortion and brittleness were not observed in grids of similar design cast by re-melting of imported Pb–Sb ingots. Spectroscopy, optical and scanning electron microscopy, SEM–EDS analysis, and microhardness measurements were carried out on both types of grids to find out the root cause of failure. It was concluded that the distortion and cracking were mainly caused because of coarse dendritic microstructure with interdendritic and intercellular segregation produced by either high pouring temperature or low cooling rates employed during casting. This conclusion suggests that the casting parameters may have differed for the two types of ingots used. However, another contributing factor was thermal stresses induced during solidification and the brittleness of the locally produced ingots which contained a high arsenic content.
KeywordsPb–Sb alloy Battery grid Distortion Embrittlement Segregation Dendrites Cellular structure
The authors thank Prof. Dr. Ashraf Ali (Chairman of Materials Engineering Department, NED University, Karachi) for his guidance and valuable suggestions. They also thank Mr. Badar-ul-Hasan (Technical Officer, SUPARCO) for his technical assistance and discussion throughout this work and Mr. Yousuf (Centralize Science Laboratory, Karachi University) for providing SEM–EDS facility.
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