Tuesday, October 29, 2013

Melt Cast Iron

For those of us who like to do things ourselves, there are a few ways to melt cast iron at home. You can melt a quarter kilo (half a pound) in a microwave, or perhaps you would like to try a homemade furnace for melting 50-300 grams (2 to 12 ounces). Most of the items you will need you can purchase at any hardware or art store. The temperature to melt metal is quite high, so please be sure to protect yourself. Does this Spark an idea?


1. Build the walls and floor of your refactory furnace with a heat-resistant brick. Gypsum block, cement and chamotte bricks or a high melting point ceramic of silica or alumina are the best choices.The furnace should have a cylindrical shape about 1.5 times the diameter of your crucible. The opening should be at the top with a hole in the center the same size as the torch hole.Leave a hole at the bottom of the wall at a tangential entry for the torch. Make sure it fits exactly.

2. Weigh the metal and fill the crucible. The crucibles that work best with cast iron DO NOT include graphite. A crucible made with Hessian clay works the best. Put the crucible in the furnace.

3. Light the fire using newspaper as kindling between the wall and the crucible. Turn on the gas (torch) slowly and once the paper catches you can turn the torch to full power. If the torch roars loudly, it's fine.

4. Inhale a whiff as the fire burns. If there is a bad smell, then the combustion isn't complete because the walls are too cold. Take the lid off the furnace for a few minutes and put it back on to fix this problem.

5. Use a thermocouple to watch the heat. You want to heat the cast iron to 1300ªC / 2500ªF for fifteen minutes. You will know you have reached this temperature when the crucible's bottom is light yellow, nearly blinding in color.

6. Remove the crucible from the furnace and heat. Add a teaspoon of borax to dissolve all oxides.

7. Pour the molten cast iron metal into the molds you have purchase. Let cool.

Tags: cast iron