Classification of Sand Casting
Green Sand Molds
A typical green sand mixture contains 89 percent sand, 4 percent water, and 7 percent clay. Green sand is an industry favorite because of its low cost and solid overall performance. The “green” in green sand refers to the moisture content present in the mixture during pouring.
Green sand molds have sufficient strength for most sand casting applications. They also provide good collapsibility, permeability, and reusability. The main difficulties arise to the moisture content. Too much moisture can cause defects in the casting, with the moisture tolerance dependent on the metal being cast.
Cold Setting Processes
Sometimes non-traditional binders are used in industrial sand casting. Conventional casting binders require heat to cure, while these alternative binders bond chemically at room temperature when mixed with sand – hence the term cold setting processes. Technically advanced, these relatively recent sand casting processes are growing in popularity. Cold setting processes are more expensive than green sand molds, but they produce castings with exceptional dimensional accuracy.
Shell Molding
Shell mold casting is a relatively recent invention in molding techniques for mass production and smooth finish; it was first used by Germany during the Second World War. The molding material is a mixture of dry, fine silica sand with minimal clay content and 3-8 percent thermosetting resin (phenol formaldehyde or silicon grease). When the molding mixture drops on to the heated pattern plate, a hard shell of around 6 mm thickness is formed. In order to cure the shell completely, it must be heated to 440 to 650°F (230 to 350t) for several minutes.
How to form castings with sand molds
Sand casting process steps:
1. Pattern making: according to the drawings to make the mold, the mold is divided into wood mold, metal mold, foam mold and so on according to the material.
2. Core making: core box is used to make mold core, which can form the internal shape of casting.
3. Sand molding: molding sand is used to form the mold cavity of the casting. Molding is the key to casting.
4. Melting and pouring: according to the required metal chemical composition, the alloy material is melted in a suitable melting furnace to form qualified liquid metal. Then the molten is injected into the molds to fill the whole cavity.
5. Cleaning: shake off the sand on the surface of the casting, and shot blasting the casting to make the surface smooth.
Is sand casting fit for you?
Sand casting is widely used in industry. In all casting production, sand casting accounts for nearly 70%, and most of them are green sand casting. It will be your best choice if your parts meet the following requirements:
1. Low production cost and simple production process.
2. Short production cycle.
3. There is no restriction on the shape of parts, and complicated design can be cast.
4. It can produce large workpieces with casting weight of more than ten tons.
Almost all metals can be cast, such as gray iron, ductile iron, steel alloy, copper alloy, aluminum alloy, etc.
5. Flexible production quantity, suitable for small batch production.
In addition to the above advantages, we must also understand its disadvantages. Compared with investment casting, the surface of sand casting is rough and the tolerance is around CT11.
From ferrous metals to nonferrous metals, sand casting can cast almost all metal grade. TIAMMAY can cast parts in the following materials.
• Grey Iron、Ductile Cast Iron、White Cast Iron、High Cr Cast Iron
• Carbon Steel、Alloy Steel、Stainless Steel
• Copper
• Aluminum
