DIY: Electric Heater Wire FurnaceAluminum melting can be done on both small and large scales. Hobbyists melt aluminum for casting. Industrial applications range from recycling plants to processing aluminum for production of semi-fabricated products. Aluminum products include for sheet, plate and extrusion. Electric heater wire can be used to make an aluminum-melting furnace to meet many production needs. |
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Types of Melting Furnaces
There are many choices available for purchasing a melting furnace. Silicon carbide, electric or gas fired crucibles, rotary and tower furnaces are some of the types used in different melting applications. A reverberatory furnace is the most common type use for melting aluminum. These furnaces often use natural gas but are not very energy efficient; efficiency is usually between 20 to 30%.
In the U.S., 95% of aluminum melting is done in gas reverberatory furnaces. In industrial applications, 60% of furnaces are operated with natural gas. Only 27% of melting furnaces are powered with electricity. In addition to a lower rate of efficiency, gas powered furnaces may have a material loss rate of 3 to 5%. As molten aluminum is exposed to hot gases, it will form dross or slag.
Electrical Furnaces
Electric furnaces are often used in foundries and steel mills. In large-scale operations, the use of power tracking, flexible, medium-frequency induction power supplies provides an increase in electrical efficiency as high as 97%.
To determine the energy efficiency of a melting furnace:
Efficiency = theoretical energy required divided by the actual energy used times 100
While emissions are produced to create electricity, facilities that use electric furnaces do not produce onsite emissions from melting aluminum. Electrical furnaces are a good choice when it comes to reducing emissions in metalworking.
Using electric heater wire to make a melting furnace
Materials and Supplies
• K23 fire brick, 8 pieces
• Resistance wire: 70 feet of Nichrome 18 gauge electric heater wire. Kanthal A-1 or D wire may be used to create a higher temperature.
• Scrap steel for a frame
• File
• Drill with regular and cutter bit
• Round metal stock for winding wire
• Lathe, can be used instead of winding by hand
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Instructions
1. Wind the electric heater wire tightly around the round stock.
2. Lay out the firebrick in the pattern shown.
3. Holes are marked one inch apart along the left edge; offset the holes on the right by one inch down the length.
4. Use a straight edge to draw lines from the top hole on the left to the top hole on the right. Repeat for each set of lines.
5. A file is used create groves in the lines drawn on each brick. Ensure that all of the groves line up from brick to brick. Groves should be about 1 ¾ inch deep.
A video presentation is available to assist you in creating the groves and assembling the oven structure.
6. Loosen the coiled wire until it resembles a spring.
7. Two holes will need to be drilled through the brick for the electric heater wire entrance and exit.
8. The coiled wire will fit into the grooves in the brick.
9. Connections need to be added to both ends of the wire to attach the electrical supply.
Remember to follow strict safety precautions when building and working with your aluminum-melting furnace. The electrical coils are not insulated; care must be taken to avoid electrical shock. The furnace coils and molten metal will be extremely hot. Gloves, goggles and protective clothing should be worn to prevent burns. Work must be performed in a well-ventilated area to avoid inhaling fumes. Use the video presentation for complete instructions.
This can be used as an internal support structure during high temperature operations for ceramic castings. You will need to know the melting point of your wire and the maximum temperature that can be created.
Melting Temperatures
To create an aluminum-melting furnace, te melting temperature of the metal you are working with is a key factor in the type and size of wire needed. A chart is provided to assist you in your basic calculations.
Aluminum and silver have higher melting temperatures than pewter, lead and tin. Exact melting temperatures for metals do depend on the alloy. This chart provides a reference to the furnace temperatures needed to melt aluminum materials. A furnace that can achieve the melting point for aluminum can be used to melt metals with lower temperature requirements.
| Metal | Melting Temperature | |
| °C | °F | |
| Aluminum | 660 | 1220 |
| Aluminum Alloy | 463-671 | 865-1240 |
| Aluminum Bronze | 660-655 | 1190-1215 |
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Silver, Coin |
879 | 1615 |
| Silver, Pure | 961 | 1761 |
| Silver, Sterling | 893 | 1640 |
| Tin | 232 | 449.4 |
| Pewter | 170-240 | 338-464 |
| Lead | 327.5 | 621 |