Detection And Process Experiment Research On Gas Evolution Of Molding Sand

The rate and volume of gas evolution of forming material, such as molding sand and core sand, in the process of molten metal pouring and solidification, which is very important for the quality of casting. In foundry industry, the quality, the rejection rate and other technical indicators of casting are closely related to gas evolution of various molding sand. Therefore, how to accurately measure the gas evolution of various molding sand is essential. But testing machine for measuring gas evolution of various molding sand which commonly used internationally work under conditions set artificially, and the artificial setting conditions is very different from the casting condition. Therefore, the measurement result does not really reflect gas evolution of various molding sand during pouring and solidification of molten metal.Gas evolution of furan resin sand, phenolic resin sand and sodium silicate sand were measured using the apparatus designed and made by myself during pouring and solidification of molten metal. The volumes and rates of gas evolution curves as function of time were obtained. Further, effect of the amount of binder, pouring temperature and the contact area between molding sand and molten metal on the gas evolution of molding sand were researched. Moreover, A mould was designed for measuring the gas back pressure at the molding sand-metal interface. The gas back pressure of furan resin sand, phenolic resin sand and sodium silicate sand were measured. Besides, the temperature field of the molding sand was simulated during pouring and solidification of aluminum alloy. The relation between the temperature field and gas evolution was researched. In the end, testing machine was improved according to the dates of gas evolution of molding sand. A testing machine which controlled by single chip microcomputer for collecting and measuring the gas evolution was preliminary designed. It is more simple to operate, and it is more convenient to deal with the experimental results.Experimental results show that, under the same conditions, the volume and rates of gas evolution of the furan resin sand is highest, then phenolic resin sand, and the lowest one is sodium silicate sand. There are two times the volume and rate of gas evolution of molding sand are bigger during solidification of aluminum alloy. Accordingly, double peaks appear on the curve of gas evolution rate, the first one appears between 5s and 7s, the second one appears between 108 s and 125 s. The higher the amount of binder, the pouring temperature and the contact area between molding sand and molten metal, the higher the volume and rates of gas evolution of molding sand, The effects of amount of binder and the contact area are significant, Pouring temperature has slight effect. Besides, the amount of binder has significant effect on the volume of gas evolution of the furan resin sand, It has slight effect on phenolic resin sand and sodium silicate sand. In the three different molding sand-molten metal interfaces, the gas back pressure at furan resin sand-molten metal interface is the highest, then the phenolic resin sand-molten metal interface and sodium silicate sand-molten metal interface. The closer the distance between molding sand and furan resin sand-molten metal interface, the higher the temperature of molding sand, and the lower the residual volume of gas evolution of molding sand, Vice versa. The residual volume of gas evolution of furan resin sand at the next of molding sand-molten metal interface is 10 ml/g, the residual volume of gas evolution of molding sand at the next of centre of sample is 24 ml/g.