Sand grain

Grain sizestructure of a sand, in particular a foundry sand, which is categorized into grain classes and determined by screening a sample.

With foundry sands, the sediments (VDG bulletin P 36) must be removed by a wet process and the remaining samples dried before the screen analysis is performed. The proportions of the individual minus fractions indicate the grain distribution based on which the relative grain fineness can be determined. The test procedure is described in VDG bulletin P34.

It is important that foundries periodically check the grain size and the fines in the sand, in particular. Major changes in the sand grain affect the strength of the molds and cores. In green molding sands (s. Green sand casting, Green sand molding process), an increase of the fines may lead to a dramatic reduction of the mold strength.

Additional references:
Mold sand testing, Mold sand
Green sand, Natural sandNew sand
Fused-silica sand,  Quartz sand
Special sandRecirculating system sand