Research on Factors Influencing the Formation Graphite and Effect of Graphite on Mechanical Properties of Grey Cast Iron

Gray cast iron is a common material which is widely applied in manufacture engineering. There are many effects on its microstructure such as the chemical composition, cooling rate, etc. whereas the studies of the effects of graphite morphology, graphite shape and graphite distribution on mechanical properties are limited. Grey cast iron named GX 15-30 and GX16-32 are produced in order to identify tensile strength, bending strength according to ASTM A 438 - 80 (1997), then microstructure is observed. The results show that the graphite size, graphite shape and graphite distribution varied according to the heat retention time before pouring and pouring temperature. The more the heat-remained time increases, the more the graphite content decreases and the graphite is finer, the graphite form may be different. When the heat retention time is large enough, the temperature is about 1300°C, will completely lose the nest graphite. Flexural strength, tensile strength also varies with pouring temperature and heat retention time, the pouring temperature range of 1300 to 1350°C is optimal. From the above results, it is possible to determine the optimum pour temperature and time to maintain the pouring temperature, allowing to improve the quality of the product.