1. Advantages of lost foam casting
① When using polystyrene foam in white mold manufacture, its density is very small, and the labor intensity of the operators is low during the operation. The foam material will not pollute the environment and damage the human body at normal temperature. It is also easy to achieve cleaner production.
② Compared with the traditional casting process, the lost foam casting process does not need the production of core, which greatly simplifies the mold making procedure, the post-treatment process of sand during casting is also simple, and the handling capacity of white mold and yellow mold between processes is also small, which greatly reduces the labor intensity. In the process of white mold processing and transportation, it is easy to realize mechanized and automatic production.
③ Due to the use of dry sand modeling, it has good fluidity, can avoid sand mixing procedures and equipment, and can greatly reduce the generation of noise and dust, which also saves the old sand recovery equipment and processes.
④ The lost foam casting method does not use the production of core. The precision of blank casting produced by this method is relatively high, and the refractory coating on the outer surface of blank is easy to fall off. In this way, the cleaning in the later stage of blank production is simple, and the labor intensity of operators can be reduced.
⑤ Carbon monoxide, carbon dioxide and other waste gases produced in the production process of lost foam casting process are relatively small. During pouring, the white mold material is thermally decomposed and gasified under the action of high temperature of molten metal, resulting in a small amount of waste gases such as carbon monoxide and dioxide, and these waste gases can be effectively treated in the process of vacuum pumping.
2. Defects caused by lost foam casting Technology in casting process
① Due to the inadequate preparation in the early stage of production, the theoretical negative pressure value of the system is designed to be relatively low, resulting in sand sticking defects in castings.
② Due to the low temperature of molten metal, the casting of workpieces is not comprehensive, cracks or fractures appear after the cast products are subjected to external forces, and there are oxidized inclusions at the fracture and they are not fused together, which is the cause of cold shut (as shown in Figure 1).
③ Metal oxides of casting materials and charge slag and slag of refractory materials. The shape of slag hole formed by these slag on the casting is irregular. From the appearance color, the slag hole caused by slag is black, while the charge slag hole is indeed white. At the same time, the ladle uses the hot melt of refractory material, which shows black slag on the casting surface, which is the cause of slag inclusion (as shown in Figure 2).
Lost foam casting technology is a major trend in the development of foundry industry in the future. It is in line with the concept of sustainable development advocated by our country. The development prospect of this technology is very broad. It has incomparable advantages over traditional casting technology. At the same time, it also meets the requirements of energy conservation and environmental protection advocated now. Its use greatly reduces the pollution of noise, dust and smoke, which also greatly improves the working environment of operators and reduces the labor intensity of operators. It is believed that the development prospect of lost foam casting is very broad.