ITP Metal Casting: Advanced Melting Technologies: Energy Saving ...

Executive Summary
The metal casting industry is one of the most energy-intensive manufacturing sectors with the
melting process accounting for over half (55%) of its energy consumption. Although its high
energy expenses have been a significant concern for metal casters, the industry continues to use
melting technologies with poor energy efficiency. The purpose of this study is to explore “Grand
Challenge” or breakthrough opportunities that might dramatically reduce melting energy and to
identify potentially energy-saving R&D areas based on the findings. The study was conducted to
guide the Metal Casting subprogram of the Industrial Technologies Program (an initiative of the
U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy) in pursuing its
energy reduction goal. The scope of the study includes current and emerging melting
technologies in the industry worldwide, along with experimental technologies, retrofits for
existing systems, and best practices.
The seemingly simple melting operation – heating metals to turn them into liquids for pouring –
is actually complex, involving a series of steps that incur material and energy losses. These
losses are attributable to several factors: undesired conduction, radiation and convection, stack
loss (flue gases), and metal loss. The extent of the losses depends on the furnace design, the fuel
used, and the method of imparting heat to the metals. Exhibit 1 compares the efficiency and
metal loss for different types of furnaces. The low thermal efficiency of current furnaces calls for
high-priority R&D to improve melting technologies.
Melting Furnace
Typical
Capacities*
Crucible (Gas) 15 lbs - 1.5 tons
Common Use Melt Loss
Thermal
Efficiency
Aluminum 4-6% 7-19%
Magnesium 4-6% 7-19%
Copper-base 2-3% 7-15%
Cupola 100 lb/hr - 20 tons/hr Iron 3-12% 40-50%
Direct Arc †
1.5 tons -100 tons Steel 5-8% 35-45%
Immersion (low temperature
melting)
1,600lb/hr Zinc N/A 63-67%
Induction †
Reverberatory
Electric †
2 lbs - 50 tons
0.5 tons - 125 tons
Gas 0.5 tons - 125 tons
Aluminum 0.75-1.25% 59-76%
Copper-base 2-3% 50-70%
Magnesium 2-3% 59-76%
Iron 1-2% 50-70%
Steel 2-3% 50-70%
Aluminum 1-2% 59-76%
Zinc 2-3% 59-76%
Aluminum 3-5% 30-45%
Zinc 4-7% 32-40%
Rotary N/A Aluminum N/A 35%
Stack Melter (Gas) 1 ton/hr - 10 tons/hr Aluminum 1-2% 40-45%
*Information received from communication with AFS
Source: DOE/CMC http://cmc.aticorp.org/datafactors.html
† The primary energy efficiencies of these furnaces are much lower (about one-third) than the listed efficiencies due to the use of
electricity, which involves sizeable energy losses during generation and transmission.
Exhibit 1: Efficiency and metal loss for different furnaces
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