About Casting Aluminum
For many people, it is the need to make an obsolete part that is no longer manufactured that leads them into metal casting and casting aluminum. Perhaps they are restoring an old house to its historical glory, but discover they are unable to find the decorative hinges or other architectural hardware they need for authenticity. That's often when they will begin to look into the craft of metal and aluminum casting.
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Make the Pattern
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You must begin by making a pattern of the item you want to cast out of aluminum. Most people will carve the object out of wood. The pattern will then be used to create the mold out of the common foundry molding substance called green sand.
Making the Mold
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Green sand is different than beach sand, in that it consists of extremely fine grains that easily bond together to hold their shape. Green sand is held in a mold box and the pattern in pressed into the box. When the pattern is removed, an identically shaped cavity is left in the sand.
There are many other methods of creating the mold, such as using wax or foam to create the pattern. The pattern is then covered with the sand, plaster or ceramic slurry. Once the pattern is fully covered with the mold material, it is fired in a furnace or kiln which causes the wax or foam pattern to melt, leaving an exact replica cavity. -
Melting the Aluminum
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Aluminum has a fairly low melting temperature (740 degrees C). This makes it easy to use in metal casting. It is also easy to find aluminum to use. You can use cast aluminum cylinder heads, exhaust manifolds and other aluminum scrap.
The metal is broken into small pieces and then the aluminum is placed in a crucible for melting; a crucible is the heat-resistant container used to hold the aluminum as it is melts.
The crucible is then placed in a furnace for melting. Most metal casting hobbyists start out by building their own furnace, usually gas fired and lined with heat-resistant cement obtained from a foundry supply source. As they gain experience, they invest in a commercially sold foundry furnace.
Pouring the Aluminum Casting
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Using tongs designed especially for use with high heat and crucibles, carefully remove the crucible from the furnace. Carefully place the crucible full of molten aluminum into a pouring shank, which is a long-handled device that holds the crucible for easy pouring. Make sure you wear the proper safety gear, such as heat-resistant gloves and a protective apron, and then use the shank to hold the crucible. Pour the molten metal into the mold.
Finished
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Once the metal has cooled and solidified, then you can remove it from the mold to reveal a bright, shiny exact replica of the pattern you created.
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