Introduction to Foundry Sand

 

What is foundry sand?

Most metalcasting sand (FS) is high quality silica sand with uniform physical characteristics. It is a byproduct of the ferrous and nonferrous metal casting industry, where sand has been used for centuries as a molding material because of its unique engineering properties. In modern foundry practice, sand is typically recycled and reused through many production cycles. Industry estimates are that approximately 100 million tons of sand are used in production annually. Of that, four (4) to seven (7) million tons are discarded annually and are available to be recycled into other products and industries. 

Sand used at foundries is of a high quality, much of it supplied by members of the Industrial Minerals Association of North America (IMA-NA). Stringent physical and chemical properties must be met as poor quality sand can result in casting defects.  Foundries and sand producers invest significant resources in quality control of their sand systems, with extensive testing done to maintain consistency. As a result, FS from an individual facility will generally be very consistent in composition, which is an advantage for most end use applications. 

Although there are other casting methods including die casting, investment casting, and permanent mold casting, sand casting is by far the most prevalent casting technique. Sand is used in two different ways in metalcasting: as a molding material, which forms the external shape of the cast part, and as cores, which form internal void spaces in products such as engine blocks.  Since sand grains do not naturally adhere to each other, binders must be introduced to cause the sand to stick together and hold its shape during the introduction of the molten metal into the mold and the cooling of the casting.

Because casting quality is inherently linked to sand quality, many references to the properties of foundry sand  can be found in the AFS Metalcasting Library. For a basic introduction to foundry sand and its fine aggregate characteristics, please see “Basics of Foundry Sand.” 

More frequently asked questions regarding metalcasting sand can be found to the right of this webpage.