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Why South Africa Chrome Ore are Acclaimed in the Cast Steel Industry?

Published time:21 July 2020

The series of chromium ore products mainly include South African foundry grade, chemical grade, refractory grade, metallurgical grade chromium ore, Indian refractory and metallurgical grade chromium ore, Philippines chromium 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 China and has won wide acclaim from the industry.

South African chrome ore

South African chrome ore refers to chrome ore processed from chrome ore produced in South Africa. Chrome ore sand, also known as chromite sand, is a special type of foundry sand, which is a natural spinel mainly composed of chromite.
After crushing, grinding and sieving, it is divided into different specified particle sizes. Chrome ore is divided into two grades according to its chemical composition; first grade Cr2O3 ≥45%; second grade Cr2O3≥35%. In the casting production, chromium ore is mainly used as the surface sand of large steel castings to prevent the surface of the castings from sticking to sand; secondly, it is ground for refractory aggregates for casting coatings. Chrome ore is a chill material, which can replace part of chilled iron when modeling (core making).
Chrome sand

Properties of Chromite Ore Sand

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) Chromium ore has good resistance to alkaline slag and does not react with iron oxides; 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, which prevents the penetration of molten metal and prevents 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 act as an external cold iron in practical applications.
(4) The most harmful impurity in chromium ore is carbonate (CaCO3·MgCO3). When it comes into contact with high-temperature metals, it decomposes CO2, which is easy to cause porosity in the casting; usually, the chromium ore containing carbonate is passed through 900° High temperature roasting at C—950°C decomposes the carbonate.
(5) The impact 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 the casting. 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 casting is hardly affected.

Cast grade chromium ore

Casting grade chromium placer composition index, quality requirements in accordance with JB/T6984-1993

ItemCr2O3SiO2%CaO%Loss on ignition (LOI)
%
Moisture content
%
Refractoriness
°C
Index≥45%<3<1<0.5<0.5>1800

South Africa chrome ore in China

Generally, the suitable size of the sand mold for large steel castings is 40/70 mesh, and the size of the sand for medium and small parts is 50/100 mesh. There are also special circumstances such as: some small water pump industries, considering economic factors, replace zirconium sand with chromium ore. The chromium ore purchased by these factories requires very fine, 70/140 mesh, or even 100/200 mesh, and so on.

The application objects of chrome ore are mainly large-scale low-carbon steel castings. Steel castings such as Dalian Heavy Industry and Erzhong are often more than tens of tons. Such large steel castings are most suitable for the use of chrome ore as the molding material. Generally, chrome ore is required The particle size is 40/70 mesh, or even coarser. However, in the past ten years, small castings in the automotive engine industry have also used chrome ore in large quantities. This is mainly due to the high refractoriness of chrome ore, which can result in smooth and high-quality castings.


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