Sand

Chromite

Olivine

Olive sand, used in steel and cast iron foundries, is not considered to be a health risk since it is not hazardous with regard to silicosis. When used, stabilized sand undergoes minimum dilation and even remains unchanged between  2372 °F and 2912 °F. Such high resistance to thermal shock is a sign of its substantial refractory qualities. Moreover, this characteristic of low dilation gives extremely long product life and allows up to 97-98% sand regeneration.

Contrary to what happens with silica sands, olivine sand improves with use because it produces fewer gases during fusion. Olivine sand performs well with normal binders: bentonite, clay, sodium silicate, oil, and starch. Cores based on oil binders dry in less time without the risk of deformation before and after drying. Its resistance to the penetration of molten metal, even with high permeability, is superior to silica sands with low permeability and the quality of the binder can be considerably reduced when compared to that required by silica sands while obtaining the same level of plasticity and cohesion.

The casting procedure is the same as the traditional method employed with silica sand. Casting with olivine sand gives better surfaces than those normally obtained with silica sand, especially when casting manganese steel with fewer runners, risers, etc. A point worth mentioning is that a number of foundries using olivine sand have saved up to 50% on sand costs for each ton of cast iron produced, as well as considerable time savings in the repair and polishing operations of stainless and manganese steel castings.

back to top
 

Silica

Silica sand (industrial sand) is a high-purity quartz (SiO₂) sand deposited by natural processes. Depending on its chemical and physical characteristics, silica sand is used as glass sand, foundry sand, abrasives, fillers, and hydraulic fracturing sand (also termed "frac" sand by the petroleum industry).

The silica sand used in making glass has the most rigid industry-based specifications. Tiny amounts of impurities, such as iron, manganese, chromium, calcium, or aluminum, can alter the color and/or physical properties of the resultant glass. Foundry sand must be able to withstand the high temperatures of molten metals, hold the shape of the mold when moist (usually with the aid of a bonding agent such as clay), be permeable enough to release gases, have sufficient strength to support the weight of the metal, and be of a fine enough texture to result in a smooth casting.

Abrasive sands used in sand blasting, grinding, and polishing usually require the individual particles to be nearly the same size and somewhat angular with sharp edges. Sand used as fillers in paints, plastics, rubber, and ceramics is usually in ground form to prop open fractures created by the high pressure. This process is used to increase the permeability of the rock, thus increasing the rate of oil and gas flow. Frac sand is normally free of impurities, well sorted, and composed of very well rounded grains.

back to top
 

Zircon

This is a highly refractory sand made with 99% zirconium silicate mostly used in steel foundries for molding sand and cores. It is primarily used in steel casts whose smelting temperatures are particularly high. This sand, which is also used in refractory and ceramic production, is very important in foundries for its particular refractory qualities; it fuses at 3992 °F, which is higher than the majority of steels, including special steels. This sand is generally used as a skeleton for special mixtures, used where the steel cast is subjected to liquid metal thermal stress. It can be used as a binder—both organic and inorganic.