Aluminum Production Examined.

This year's Lost Foam Div. featured nine paper presentations, with a noticeable focus on aluminum lost foam casting production. Among the topics examined were interfacial heat transfer, the effects of hydrogen and solidification time, and a countergravity lost foam process.

General Motors' MA. Tschopp, Jr. presented work conducted by the Univ. of Missouri-Rolla that examined processing variables significance in thick-section aluminum lost foam castings (132), an area of technology with little study to date. Among their findings was that a 7 sec increase in steam time changed the foam density gradient of the pattern, and that high-fusion patterns had a high surface foam density with a low center density.

Further, for each of the foam types studied, they concluded that the higher the foam density, the higher degree of fusion, and that the vertical placement of the pattern decreased velocity while the higher coating increased it. Coating had the most significant effect on the number of blisters seen.

H. Wang, R. Dinwiddie, W. Porter, Oak Ridge National Lab, and the Univ. of Alabama-Birmingham's H. Littleton and T. Moliboy shared their study on the thermal properties of foam coatings (167). Among their findings was that three endothermic physiochemical transformations occur during heating: release of moisture between room temperature and 212F (100C), burnout of organic compounds between 572-932F (300-500C), and release of chemically bound water in the range of 932-1652F (500-900C). They also concluded that the specific heat capacities of the four preheated coatings studied differed no more than 10% below 1472F (800C), and that thermal conductivity was found to decrease as the temperature increased from 212-1292F (100-700C).

On the "white side" of the process and its impact on casting quality and yield, R. Michaels and G. Walford, Photo-X Corp., described how X-ray has been applied to inspect foam beads and patterns (094). Foam density profiling and coating weight measurements have been determined via the technology. According to the authors, such technology can "link measured data to performance predictors for casting quality and defect probability and detection."