Last Updated 12th April, 2021
Sand casting is a vital procedure in metal casting where sand is used in the process of molding. Also referred to as sand molded casting, this process usually occurs in foundries which are specialized factories where metal casting occurs. It is not actually green in color but it is expendable mold that is made out of wet sand and is used to make the mold shape for green sand casting for metal.
In actual sense, green sand is not a kind of sand but a mixture of several ingredients. The following are the ingredients needed to make it for green sand casting:
- Silica, chromite, zircon sand or graphite
- bentonite clay, 5-11% is required.
- 2% to 4% water
- 3% to 5% inert sludge
- 0% to 1 % anthracite
For a sample home project, green sand is made by starting with 1KG of fine sand, then add 120g of bentonite clay first. The bentonite clay pellets can be broken down by putting them in a small plastic bag and hitting it with a hammer then put them in a container. Add water, mix for a while until all the lumps are gone, then add sand and mix further. Leave the mixture for a day, which will allow the clay to expand to 500% and then start mixing again. You can continue the mixture after each day for a few days before setting it out to dry. Before drying the mixture, ensure the grey clay has been covered properly by the sand.
How to cast with green sand
Making a foundry at home is not a simple thing, there is need to observe safety precautions to prevent injuries.
First, you need to create a mold that can withstand heat and the pressure of molten metal while retaining its shape.
Make a square wooden box called a flask, fill it with green sand and ram it in the drag then sprinkle it with diatomaceous earth as a parting compound.
Others may use saw dust but the quality will be lower.
Poke a wire around the green sand to eliminate pockets of air and allow for steam to escape during casting.
Make a sprue using a sprue pin, then ram it and pull the sprue out.
Part the mold cleanly and you have a complete mold made from green sand casting.
Melt scrap metal such as aluminum using a small furnace or crucible, pour the molten metal in the sprue and close up the casting.
Give it 30 minutes to 1 hour to cool, lift of the top part of the greensand mold and voila! the metal cast is made.
Green Sand video Resources: