and determine how best to heat treat the materials. But that’s no small step, Shankar said. “In wrought alloys, you


have a cast billet that is then rolled out. That is when the properties are elevated [beyond that of traditional casting al- loys],” he said. “Similarly, with cast versions of the alloys, once you have the near-net- shape casting, you still must heat treat to gain the elevated properties that are comparable to the wrought alloy.” Dave Weiss, Eck Industries, Manitowoc, Wis., also is work- ing with a research team to develop a cost effective method of casting wrought alloys. Weiss would like to develop a method that can easily slide into current metalcasting process fl ows. “[Wrought aluminum] alloys typi-


The centrifugal casting process (used here by Johnson Brass to produce the above motor housing) works well with low-fl uidity wrought alloys.


cally contain very low levels of sili- con, so they have fairly wide freez- ing ranges,” Weiss said. “If you just allow them to freeze on their own, it is diffi cult to feed them. That’s


why the hot tearing occurs. You can avoid those [defects] by appropriate risering and cooling rates.” Casting wrought alloys should


be no different than pouring other diffi cult-to-cast materials, Weiss said. For example, many of the principals


used in the casting of 200 series aluminum can be applied to the wrought compositions. “In [200-series] aluminum casting,


typically we use aluminum chills or iron chills. [With wrought] alloys, we use copper chills, and in some


SEPTEMBER/OCTOBER 2010


METAL CASTING DESIGN AND PURCHASING


37


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