Green Sand Casting

Green sand casting is a low cost means of producing many of the engineered components of today's modern equipment and machinery. The practice of melting metal and pouring it into a desired shape dates back centuries. While the basic concept of sand casting hasn't changed over time, the methods have.

Green sand is a prepared mixture of silica sand (both new and reclaimed), various bonding clays, carbonaceous materials and water. The ingredients are mixed to form the prepared green sand. A critical component in the casting process, green sand preparation has become the focus of process automation in recent years.

The Green sand is conveyed to the shop floor where it is ready to be used for molding. A pattern is placed between two halves of a flask. The top half of the flask forms the “cope” and the bottom half the “drag”. Green sand is then placed into the cope and drag flask halves. After squeezing the sand against the pattern, each half of the mold is stripped off the pattern. The resulting impressions in the sand form the mold cavity that the molten metal will fill to form a casting. The pattern is then removed and the mold halves put back together. The result is a finished mold that is ready for pouring.

A furnace melts the raw charge materials consisting of scrap steel, pig iron and scrap/return to a temperature of approximately 2600-2800 degrees Fahrenheit. Various alloys and inoculants are added at this point in order to obtain the casting's desired mechanical properties.

The molten iron is then poured into the mold. The liquid metal is delivered to the mold cavity via a gating system designed to maximize casting quality and yield. Within a matter of minutes, the molten metal is solidified. The casting is then allowed to cool in the mold for a predetermined length of time before shakeout.

When cool, the gating system is removed from the casting and recycled as scrap/return. Secondary cleaning operations will remove any excess sand adhered to the casting surface. Lastly, parting line flash and gating marks are removed in a grinding operation. The raw casting is now ready for further processing. (i.e. Machining, painting, plating...) In some instances, no further processing is necessary as the part has been designed to function as a raw casting.

Variations of Green Sand Molding

  • High Density Molding
  • Flaskless Molding
  • Tight-Flask Molding
  • Skin-Dried
  • Dry Sand Molding


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