Sand casting is the oldest and most widely used metal casting process utilized to create a variety of metal components of nearly any alloy, ranging in size from a few ounces to several tonnes. Items produced by sand casting include smaller parts such as gears, propellers, and pulleys along with larger items such as machine bases. Sand casting is commonly used for automotive components and industrial machinery.
The sand castings are produced in factories known as “foundries”. Although sand casting is the oldest method of metal casting, dating back to 1000 BC, it has a low production rate as the molds are not reusable. However, complex shapes can be formed and very large parts can be produced by sand casting.
What is Sand Casting?
Sand casting is a metal casting process in which sand, combined with additives, is used as the mold material and is broken after the metal is cast to recover the metal product. More than 60 percent of all metal castings are made by the process of sand casting. Forming the required mold out of sand is time-consuming and each mold can be used only once, but as sand is found in abundance, the molds are cheap to make.
To form the mold, the sand is combined with a bonding agent such as clay and moisture is then added to the mixture to help maintain the required shape of the mold. As sand is resistant to high temperatures, a variety of metals can be cast using this process.
How Does Sand Casting Work?
The process of sand casting takes place in several steps, with the duration of the overall process depending on the size of the metal component to be cast. The first step is mold-making in which a sand mold is made based on the required pattern and sand is packed around the external area of the pattern. Next, the interior surface of the mold is lubricated to make removal of the casting easier and then the two parts of the mold are clamped together securely to prevent leakage of the metal.
After the mold is ready, molten metal is poured into the sand mold either manually or by a machine. Once the molten metal enters the mold cavity it begins to cool and solidify. The overall cooling time depends on the temperature of the metal and the thickness of the casting. The next step is the removal of the casting by breaking the sand mold, typically by a vibrating machine that shakes away the sand. The last step is trimming, where any extra material solidified to the desired component during the casting process is removed.
Sand Castings Market
The major demand drivers for the sand casting industry are automotive, industrial machinery, railways, energy and construction sectors. The top 5 sand casting producing nations are China, India, US, Germany, and Japan, with China contributing to nearly 47 percent of the global production of sand castings. While India is second after China in terms of production of ferrous castings, for non-ferrous castings the US stands at the second position.
Despite advancements in the field of metal castings, the oldest process of sand casting still maintains dominance in the field. The process of sand casting has wide applications across industries and can form metal components of nearly any size. The time-consuming nature and one-time use of sand casting molds hold back the industry.