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Metal Casting Technologies : September 2008
TECHNICAL FEATURE Major lost foam foundries are medium-sized and small-sized foundries.1 Many of them are private companies, while state- owned operations still dominate the whole foundry industry in China. Prior to 2003, two-thirds of lost foam foundries produced less than 2,000 tons of castings per year, and about half of lost foam foundries produced no more than 1,000 tons of castings per year. In recent years, the foundry industry in China has been under reconstruction as its macro economy has become more and more market oriented and more competitive. Some lost foam foundries, especially those small operations established by private investors with the perception of low initial investment on lost foam process, have been closed due to unexpected technology challenges and the consequential financial difficulties. At the same time, some lost foam foundries have gained significant improvement in this technology and have expanded their lost foam operations. In 2005, twelve foundries reached production of more than 8,000 ton castings per year by lost foam process respectively. In 2006, four foundries have individually achieved the annual production of more than 10,000 tons of castings by the lost foam process. In 2007, FAST Group (hereafter referenced as Group B) built a brand new lost foam operation with the capacity of 20,000 tons of castings per year and will have its capacity doubled by 2009. In contrast, the number of lost foam foundries with annual production of less than 1,000 tons of castings decreased to less than 15% of all lost foam foundries in 2006. In the past ten years, China has experienced extraordinary improvement in lost foam technology including equipment, tooling, materials, casting design, process control, and personnel training. The whole foundry community has gained more confidence with this new technology. Several state-owned large foundries are either building, or evaluating the feasibility of building, lost foam operations for mass production of castings. Although China is the largest exporter of castings to the United States, more than 90% of castings manufactured in China are consumed in domestic market.3 This statement also holds for castings produced by the lost foam process. The driving force for development of lost foam technology in China is from the challenge inside the Chinese foundry industry. The expansion of lost foam operations is also due to the increasing demand from the Chinese domestic market. In fact, castings manufactured by the top ten lost foam foundries in terms of tonnage are almost all machined and assembled into the final products sold in China. The above mentioned large state-owned foundries, which are seeking to build new lost foam operations, intend to cast parts by lost foam for domestic consumption only. Castings made by lost foam process The lost foam process is described as best suited for mass production of castings with complicated design features that cannot otherwise be made by other processes. This appears to be true in developed countries such as in the United States and several European countries where there exist lost foam operations. Lost foam process has been successfully utilized to manufacture aluminum engine blocks and heads for automobiles and marine boats in mass production in the United States. Those parts are indeed designed exclusively for the lost foam casting process. The advantages of the lost foam process have been demonstrated to the world foundry community by these successful operations. In China, lost foam technology development has shown the virtues of this process from a somewhat different perspective. In China, the lost foam Figure 2. Casting (Left) and foam pattern (Right) of a gear box produced by Group A, (Courtesy of Hongchao Sun, Heli) 66 www.metals.rala.com.au