Melt Aluminum

Aluminum is one of the most heavily used metals in modern manufacturing. Its durability and plasticity make it an ideal material for multiple functions. Because of this, aluminum is a great metal for DIY forging. With the right information and materials, forging aluminum can be a fun hobby or a source of extra income.

Steps

Melting Aluminum in a DIY Foundry

1. Position your foundry. Set your foundry in a metal stand or on an insulated surface. Make sure that the surface can withstand the more than 1220 degrees Fahrenheit (660 degrees Celsius) needed to melt the aluminum. Avoid any wooden or plastic surfaces because they will melt or burn. For the best results, set your foundry in a sturdy metal stand that will not easily tip over.
2. Place the charcoal and the crucible in the foundry. Place a layer of charcoal in the bottom of the foundry and then set your crucible on top of it. Fill in the space between the insulation and the crucible with more charcoal. Make sure that the crucible is in the center of the foundry.
   • A steel crucible works the best for melting aluminum.
   • Placing a layer of charcoal under the crucible will help it heat up quicker and more evenly.
3. Insert the blower tube into the air supply port. Once you have filled the foundry with charcoal and the crucible, set up your bellows. Place the steel end of the blower tube into the foundry. You can blow into the plastic end to maintain air flow or attach an electric hair dryer, which will provide a more constant flow of air.
   • Because it is at an angle, place something under the blower tube to prop it up. This will keep it from breaking or damaging the foundry.
4. Light the foundry. With the bellows and crucible in place, ignite the charcoal in the foundry. The easiest way to do this is with a propane torch, which will quickly heat up the coals. As the coals heat, blow through the blow tube or turn the hair dryer onto low. This will stoke the fire and help increase the heat. Place the lid on the foundry and let it warm up.
   • Let the foundry heat for about 10 minutes before placing aluminum inside of it.
   • The temperature in the foundry will need to be above 1220 degrees Fahrenheit (660 degrees Celsius).
   • Once the crucible is glowing orange, the foundry is hot enough to melt aluminum.
5. Place aluminum in the crucible. Once the foundry is hot enough, you can begin melting aluminum. You can choose to either: remove the lid and place uncrushed cans in the crucible, or leave the lid on and place crushed cans in the crucible through the vent hole. Both methods work well, but if you leave the lid on less of the metal will be oxidized. The cans will melt in a matter of seconds, so you need to quickly add more cans to the crucible.
   • It is important to quickly add new cans in order to create a pool of molten aluminum. This is necessary to prevent the cans from being overheated and turning into a gas, a process known as oxidization.
6. Remove the crucible from the foundry. With a pair or metal tongs, slowly remove the crucible from the foundry. To prevent oxidization, be sure to remove the molten aluminum from the foundry at least three minutes after the last piece of aluminum melted.
7. Separate the pure aluminum from the slag. Once you have melted enough aluminum to fill your crucible, you will want to remove any impurities. Things like aluminum cans will have lots of other materials in them (plastics and other metals) that will create slag or dross. The slag will form a thick clumpy layer on top of your pure molten aluminum. The easiest way to remove the slag is to slowly pour out the molten aluminum into a steel mold, and then tap the slag out of the crucible.
   • Use a metal rod or tongs to skim slag off of the top before pouring.
   • Keeping the crucible clean allows you to melt more aluminum quickly.
8. Cool the ingots in water. After pouring the molten aluminum into a mold, you will want to cool it off. The easiest way to do that is take your tongs and place the ingot into water for about 10 seconds. After soaking in the water, the ingot should be cool enough to touch. However, you should use your tongs to avoid being burned.
   • The pure aluminum ingots can now be reused for later castings and will not produce as much slag as before.

Making a DIY Aluminum Foundry

1. Make the outer body. Purchase a 12” x 12” 10 quart steel bucket with an open top. This common steel bucket can be purchased at most home and garden stores.
   • Because of the heat you will generate, it is important that you use a steel bucket. Other materials may melt or become brittle under the intense heat generated by your foundry.
2. Mix the materials for the lining. In a five quart bucket, or larger, mix 21 cups of plaster of Paris, 21 cups of play sand, and 15 cups of water. Quickly stir the ingredients together by hand. It is important to moisten all of the dry powder and work out any lumps. After a few minutes of stirring, the mixture should be runny and a uniform color.
   • Because the mixture will set in roughly 15 minutes, it is important that you do the step with some urgency.
3. Pour the insulation into the bucket. Once you have worked out any lumps, slowly pour the insulation mixture into the steel bucket. The fluid should fill the bucket, leaving about three inches of space at the top.
   • To avoid creating a mess, pour slowly to limit splattering.
4. Form the center of the foundry. Fill a 2.5 quart bucket with water or sand and place it in the center of the insulation mix. Slowly push the bucket into the mix. Move the bucket up and down a few times to help level the mixture before it sets. Finally, hold the bucket still for two to three minutes and let the mixture set around it.
   • Once the plaster has hardened, the small bucket should stay in place once you remove your hands.
   • Let the plaster mix sit for one hour to harden.
   • Clean off any splattered plaster from around the top edges of the steel bucket.
5. Remove the inner bucket. After the plaster has hardened, use a pair of pliers or channel locks to remove the plastic bucket you used to create the opening. Grip the bucket with your pliers and twist it in on itself. With enough torque, the bucket should cleanly pop free from the plaster mix.
6. Drill a hole for the air supply port. In order to promote air flow, you will need to drill a hole in your foundry for a blower tube. Use a 1-3/8” hole saw, attached to an electric drill, to cut a hole in the top line of the bucket (about three inches from the lid). Once you have cut through the bucket, position the blade at a roughly 30-degree angle and drill. This hole should be the perfect size to accommodate a one-inch steel tubing, which will act as your blower tube.
   • The hole saw can found at your local hardware store.
   • Make sure that your hole saw is capable of cutting through metal.
   • Creating an angled air supply port will prevent molten aluminum from flowing out of the foundry if your crucible fails.
7. Make a blower tube. Take a 1” x 12” steel pipe and screw on a 1” PVC coupling at one end. Once you have attached the coupling to the steel pipe, slide a 1” x 24” PVC pipe into the smooth end of the coupling. The coupling should have a threaded end for the steel pipe and a smooth end for the PVC pipe.
   • The blower pipe should fit smoothly into the air supply port, but not so snugly that it is difficult to slide it in and out of the hole.
8. Create a lid. Fill a 5 quart bucket with 10 cups of plaster of Paris, 10 cups of sand, and 7 cups of water. Stand up two 4” U-bolts in the plaster mixture, placing the ends with the nuts down in the mix. Let the plaster set for an hour. Once it has set, you can simply pop the lid out of the bucket. Finally, drill a hole in the top of the lid using an electric drill and a 3” hole cutting saw.
   • The vent hole will relieve pressure inside the foundry and allow you to add metal without taking off the lid.
   • Try to make the lid hole the same diameter as your crucible. This will help prevent heat loss when you melt your aluminum.

Preparing to Melt Your Aluminum

1. Find proper pieces of aluminum. The best sources for scrap aluminum are old machine parts. Car cylinder heads, transmission cases, water pump housings and pistons are all great examples. More common sources are things like beer and pop cans, furniture frames, home siding, window frames, and turkey and pie pans. However, these sources tend to be weaker alloys that have lots of impurities, which means that they create more slag and oxidize quickly.
   • An easy way to melt aluminum cans and prevent oxidizing is to add them to a pool of already molten aluminum.
2. Wear proper safety equipment. When you are working around extremely high temperatures, it is important to wear proper safety gear. When handling molten metal you should wear a thick shirt, pants, an apron, a face shield or glasses, and leather gloves. These things will prevent molten metal from burning your skin. Because molten aluminum can give off noxious gasses, you should also wear a mask.
3. Find an open or well-ventilated space. When working with molten aluminum, some alloys will give off noxious fumes. Because of this you will want to work in a well-ventilated space or outdoors. This will also help keep you cool while working around extreme heat and avoid dehydration or heat stroke.
   • If you begin feeling sick, have a headache, or are dizzy, turn down the foundry and take a break. Go to a cool place and drink some water.
4. Use proper tools. Before you begin melting aluminum, make sure that you have the necessary tools for handing molten metal. You will need a pair of metal tongs, a metal strainer or stirring rod, a crucible, and a foundry. Things like the foundry and crucible can be made at home or bought at a store or online.
5. Be safe. Because of the relatively low temperature necessary to melt aluminum, it can be melted in a variety of unsafe methods outside of a foundry. Avoid melting aluminum in large bonfires or on BBQ grills. These methods are less controlled and can lead to a fire or injury.
   • If you are new to working with molten metals, be sure to work with a more experienced person before attempting to melt aluminum.

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Sources and Citations

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