A must-see for foundry: why South African chrome ore must be used for foundry

Mineral products mainly include South African foundry grade, chemical grade, refractory grade, metallurgical grade chrome ore, Indian refractory and metallurgical grade chrome ore, Philippines chrome ore and other ore products from many countries. Among them, South African foundry-grade chrome ore sells well in more than 20 provinces and cities across the country and has won wide acclaim from the industry. Now let the editor of Dalian Jintuo Company give you a detailed introduction to why chromite sand is popular.

Application of chromite sand in foundry

Chromite sand belongs to the chromium spinel group. The main mineral composition is FeO·Cr2O3. The actual mineral is composed of a mixture of various spinels.

The density of chromite sand is 4-4.8g/cm3, the Mohs hardness is 5.5-6, and the refractoriness is >1900°C.

The main properties of chrome ore

(1) Chrome ore has good resistance to alkaline slag and does not react with iron oxide, etc.; therefore, in practical applications, chromium ore can avoid thermal and chemical sticking of sand;

(2) During the molten metal casting process, the chromium ore itself undergoes solid phase sintering to prevent the penetration of molten metal, thereby preventing mechanical sand sticking;

(3) The thermal conductivity of chromium ore sand is several times larger than that of silica sand, which can increase the cooling rate of castings. Therefore, chromium ore sand can play the role of external cold iron in practical applications;

(4) The most harmful impurity in chromium ore is carbonate (CaCO3·MgCO3), which decomposes CO2 when it comes in contact with high-temperature metals, which is easy to cause porosity in the casting; usually, chromium ore containing carbonate is passed through It is roasted at 900°C—950°C to decompose the carbonate.

(5) The influence of the particle size of chrome ore on its refractoriness The particle size of chrome ore can significantly affect its refractoriness. In the past, it was believed that too coarse particle size would reduce the surface finish of castings. However, the surface of sand molds and cores made of chrome ore are usually sprayed with a certain thickness of paint, so that the surface finish of the castings is hardly affected.

Generally, the suitable size of the sand mold used for large-scale steel casting is 40/70 mesh, and the size of the sand used for medium and small parts is 50/100 mesh. There are also special circumstances such as: some small water pump industries, considering economic factors, use chromium ore instead of zirconium sand. The chromium ore purchased by these factories is required to be very fine, requiring 70/140 mesh, or even 100/200 mesh, and so on.