The Case for Steel Lost Foam Casting


Although steel is not currently widely produced with lost foam casting, the method offers many potential benefits and recent work has shown its viability. MARK DEBRUIN AND SARAH JORDAN, SKULD LLC, TIPP CITY, OHIO


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teel is a widely used mate- rial in most industrial applications despite the increasing use of nonfer-


rous alloys, composites and polymers. Although the lost foam casting method can produce steel parts, the process has not yet been adopted in the industry. However, lost foam cast- ing could provide significant benefits for the production of steel castings. Some manufacturers have adopted


lost foam technology for the casting of gray and ductile irons to take advan- tage of improved as-cast dimensional tolerances that in some cases are equal to investment casting. Tolerances of 0.005 in. (0.127 mm) for the first inch (25.4 mm) and 0.003 in. (0.0762 mm) per 1 in. (25.4 mm) thereafter are expected for castings produced from molded foams. Tolerances up to 0.002 in. (0.051 mm) per 1 in. (25.4 mm) are possible from CNC machined foams, which are used for small batches, replacement parts, or prototypes. Other benefits of lost foam casting


include part consolidation, which allows for the elimination of fasteners,


38 | MODERN CASTING October 2016


welding and other joining technolo- gies and an improved capability for casting channels and other complex shapes. Te elimination of processes allows for a leaner supply chain with reduced shipping and less inventory. With proper system design, castings produced via lost foam creates signifi- cant opportunities for cost savings. In order to cast steel via the lost


foam process, a number of techni- cal innovations were necessary. Te


primary developments over the past few years that have enabled steel to be cast using lost foam are in the coating and foam pattern material. A thorough understanding of gating, fluidized bed, fluid flow, steel metallurgy and heat transfer phenomena is also necessary in order to obtain quality castings. Te foam used in lost foam casting


requires a special bead, and the type of foam bead needed for specifically steel had additional requirements due to the


Fig. 1. Shown is SAE 1060 steel micro- structure cast via lost foam with 10% Nital etchant at 200X


Fig. 2. Shown is SAE 1060 steel micro- structure cast via lost foam with 10% Nital etchant at 400X.


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