Implementation of Metal Casting Best Practices - EERE - U.S. ...

1. Implemented R&D and Best Practices
Aluminum Casting Facility-1 has been active in the Metal Casting R&D program to make
advances in lost foam, Semi-Solid Metals (SSM) and melting operations. The following provides
an overview of the foundry’s involvement in these efforts and the benefits it received from them.
Lost Foam with Pressure
As mentioned above, Aluminum Casting Facility-1 applies pressure during the solidification
phase of its lost foam operations to eliminate both pressure feeding of the castings and hydrogen
porosity, thereby reducing the scrap rate. A decrease in the porosity level by an order of
magnitude increases the high-cycle fatigue strength by 50%. For example, when one compares
traditional sand casting to permanent mold casting, the former has a porosity level of 1% and
high-cycle fatigue strength of approximately 8 ksi, while the typical permanent mold casting has
a porosity level of about 0.1% and high-cycle fatigue strength of 12 ksi. With copper-free
aluminum-silicon (Al-Si) alloys like A356, lost foam with pressure can lower the porosity level
to below 0.01% and obtain a high-cycle fatigue strength of 16 ksi.
This casting process allows Aluminum Casting Facility-1 to produce components that have
complex geometry with intricate features that are not easily manufactured using other fabrication
methods (e.g., die casting). Prior to the implementation of the pressurized lost foam process, the
facility used eight separate die castings to produce one part. Now, with the pressurized lost foam
process implemented, Aluminum Casting Facility-1 can produce the part with a single casting
which is lighter and less expensive and requires fewer machining operations. When compared to
traditional lost foam, the advantages of pressurized lost foam are as follows:
• Lower porosity
• Increased fatigue strength
• Casting life extension
• Casting quality improvement
The low porosity levels achievable by pressurized lost foam and the associated higher cycle
fatigue life enabled Aluminum Casting Facility-1 to develop a new product line: aluminum 275hp,
2.6-liter, 4-stroke super-charged engine blocks.
Aluminum Casting Facility-1 attributes a large part of its success with pressurized lost foam to
the work performed by the University of Alabama – Birmingham (UAB) and the Lost Foam
Consortium. Due to the work at UAB, the facility can now measure the permeability of its foam
patterns. They have also made advancements in the coatings they use, helping the facility to
reduce the level of scrap attributed to defects in the foam patterns. Lastly, the UAB work has
also provided facility management with a better understanding of the impact that metal
cleanliness can have on the final casting, which has resulted in a reduction in the number of
casting defects.
The UAB Lost Foam Consortium has played a critical role in advancing the modeling capability
of the pressurized lost foam process. Aluminum Casting Facility-1 worked with UAB and Flow-
Science to modify the code of the Flow Science 3-D Model so that they could predict the
76