Refers to multiple techniques available to reduce the amount of machining and surface finishing required for the final cast part.
Casting is a manufacturing process that is used for making complex shapes that would otherwise be difficult or uneconomical to make. Casting takes many forms, including sand, continuous and die casting. A liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.
Near-net-shape casting (NSC) is a family of techniques where the initial part production provides a quality surface finish and is close to the final (net) shape. Reducing the need for machining and grinding can eliminate more than two-thirds of the production cost in some industries. NSC techniques include investment casting, spray forming (deposition), polymer blow molding, vacuum forming, compressed air forming, laser forming, rapid prototyping and nanotechnology manufacture.
With NSC, very close tolerances can be achieved with material waste reduced to a minimum. NSC techniques can be used with ferrous and non-ferrous materials such as Titanium, Aluminum, Copper, Magnesium, and Zinc and ceramics. Currently, most steel is continuously cast into slabs, billets or blooms, which later have to be reheated and rolled into final shape. Direct or NSC or thin-strip casting integrates the casting and hot-rolling of steel into one step, reducing the need to reheat the steel before rolling it (IEA, 2008). With a direct continuous steel casting approach, liquid steel can be directly cast into semi-finished products, which eliminates the need for primary rolling of ingots.
Prediction of energy savings is difficult as NSC is not a "one size fits all" approach. Generally, a consultant works with a foundry to design an approach that addresses specific requirements of the material being cast.
Status:
Baseline Description:
"Typical" Savings: 25% Low and High Energy Savings: 25% to 50%
An analysis of advanced lost foam NSC casting processes (such as Pressure Assisted Solidification and Vacuum Assisted Mold Filling) reported a 27% energy savings, a 46% improvement in labor productivity and 7% less material usage compared to other casting processes. At the same time, mechanical properties, such as fatigue resistance for Aluminum alloys, were improved. (Druschitz, 2009).
The U.S. DOE has sponsored research for the aerospace industry using net shape casting with Titanium powders (Peter, ORNL, 2013). They state that: The aerospace industry, which consumes over half of the U.S. titanium production, has very high scrap generation rates. On average, eight pounds of raw material must be machined to produce one pound of final product, with seven pounds of machinings discarded as waste. This low material efficiency results in high machining costs and significant energy consumption per pound of finished product. Their research further shows that: "Titanium components fabricated from powder metallurgy could have less than 5% to 10% scrap. When compared to conventional processes, the new titanium powders offer a 25% to 50% reduction in energy consumption".
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
ORNL, 11/22/2000. Scenarios for a Clean Energy Future, Chapter 5, The Industrial Sector Oak Ridge National Laboratory
EERE, 02/28/2007. Research Advances Application of Semi-Solid Metal Processing, Enables High Quality Die Cast Parts Energy Efficiency & Renewable Energy
EPA, 09/06/2012. Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Iron and Steel Industry Environmental Protection Agency
NADCA, 01/01/2013. About Die Casting North American Die Casting Association
William Peter, ORNL, 05/01/2013. Near Net Shape Manufacturing of New Titanium Powders for Industry U.S. DOE Advanced Manufacturing Office
A Druschitz, 01/01/2009. Advanced Lost Foam Casting Processes and Materials SAE International Journal of Material Manufacturing , 2