Chrome – the unique element


Chrome is a kind of element that has the most abundant content in via race which is composed by chrome, molybdenum and tungsten. Nearly four hundred over one million of the Earth’s crust total amount are composed by various metals, among which chrome is the 13th largest element.

The storage of chrome and its mineral exploitation

In terms of current consumption level, the exploded chrome reserves can be used for centuries, meanwhile, its resources that are available for using will also be redoubled by developing the existing reserves with higher cost. The active mining exploitation is widely distributed in the global: in 2003, the chrome yield of South Africa accounted for 48 percents of the total chrome yield, at the same time, Kazakhstan and India respectively accounted for 19 percents and 15 percents. Brazil, Finland, Turkey and Zimbabwe altogether accounted for 12 percents of the total chrome yield. Other 11 small producers accounted for 6 percents of the chrome yield. In 2003, about fifteen million tons of chromite ore that are available for sale have been exploited.

The usage of chrome

Chrome is rarely used alone. It is a kind of additive with very high quality and can give new properties for the alloys and materials such as: intensity, hardness, durability, cleanliness, color and the resistance to temperature, abrasion and corrosion. As chrome has various properties, it is indispensable in countless daily applications. Chrome, mainly regarded as the initial forms of chromite and ferrochrome, is applied in iron and nonferrous metal industry and chemical industry, besides, chromate is directly used as the molding sand casted by thermal conductivity in the refractory industry. Chrome powder is widely used in the industry, for example, it can be used in the powder metallurgy and used as the additives of diamond tool, special alloys for electrical element, wielding material and aluminum alloy, etc.

The application of chrome on stainless steel

About 93 percents of five million and three hundred thousand tons of ferrochrome produced in 2003 were used in the production of stainless steel. Chrome is an important and unique factor in producing stainless steel as it can prevent stainless steel from “stainless” and give excellent oxidation resistance and corrosion resistance ability for stainless steel.

The commonly used production method is melting the carbon steel and stainless steel pieces in electric arc furnaces and adding a certain amount of other ingredients including ferrochrome, which will be further refined in another container filled with high-temperature gas and using vacuum technology. Liquid stainless steel is casted into steel ingots, steel embryos and steel plates by heating or cooling process in metal processing and manufacturing in the converter. Stainless steel often has 10 percents to 30 percents of chrome content as well as other elements such as molybdenum and nickel so as to further improve some of its special property. However, chrome is indispensable. Heat resistant steel is also a category of stainless steel, in which the performance of chrome is as well irreplaceable. The consumption rate of stainless steel is progressively increased in 5 percents per year and is more and more applied in food and beverage industry, construction industry, mining industry and automobile industry. Chrome is easy to use while stainless steel is easy to recycle which will not threaten to the environment.

The application of chrome on other metallurgical aspects

The addition of chrome will improve a series of properties of low alloy steel, especially improving its hardness, which is a kind of performance that can balance the hardness and viscosity in every cross section of steel used in the engineering industry. Bearings, tools, high-strength low alloy steels and the steel used in anlaufen are all the specific subclass steel type that use chrome. In addition, the alloy cast iron is an important part in the cast iron products that use chrome, which is widely applied in pumps, valves, catheters, rolling mills, abrasive disks and chrome-bearing cast iron and makes them have hardness, viscosity, the stability of the shape and the resistance to corrosion, wear, shock and loss. Metal chrome is almost a kind of constant additive of nickel alloy, cobalt alloy, non-conductive alloy and superalloy to ensure their use under high-temperature and highly corrosive conditions. Furthermore, some aluminum, copper and titanium alloys will also add a small amount of metal chrome.

The application of chrome on chemical aspects

The application of chrome on chemical aspects reflects in a large number of chemicals, which is usually generating sodium dichromate products by adding chromium iron ore into sodium carbonate powder and roasting them in the furnace, meanwhile, the derivative chemicals will also be produced. There are two special properties of chromium: chemicals-durability and color stability, which will be connected with some of its main usage.

By adding the chromium salt, the natural raw materials such as leather, wood and timber will keep stable in the durable use. In addition, chromium salt can keep other mixtures (the mordant feature) such as the colorful dyes, bactericide and insecticide permanently fixed on the raw materials. Besides, the biggest chemical application of chromate is used in the leatherworking.

The second largest chemical usage of chrome is being used as chromium pigment which applied in oil paint, printing ink and plastic dyeing. Its distinctive colors are chrome green, chrome oxide green, chrome yellow and molybdenum yellow. Zinc and strontium chromate are used as the corrosion resistant primer paint. Chrome also can be used in the chromium-plating, coatings for other surface, catalysts, mud flush drilling, water treatment, the dyeing of textiles and refractory materials.

The applications of chrome on refractory materials

Due to the high melting point of chrome, it has been used as the synthesis of refractory materials for about more than 100 years. It is used in various refractory brick, casting products, stamping ingredients and the mixtures having majority compositions of magnesium oxide and chromite. It is used as the bush of aod container in the steel industry, the bush of coal combustion reflex furnace and converter in the copper industry and the bush of rotary kiln in the combustion area in the cement industry. Due to more stringent requirements on refractory materials performances and the technological application of water-cooled upper wall and side wall, pyrometallurgy production is gradually replaced although it is changing the technology at the same time. However, as the regenerative magnesium oxide-chromite grains are used in the refractory material, the decline rate of pyrometallurgy production has been slow down. The high property chromic oxide refractory materials derived from the chemical products are used in making glass furnace. Furthermore, by using the thermal conductivity casting molding sand that contains chromate, the thermal conductivity of casting will be increased, its full or partial cooling will be improved and the integrity of casting will be enhanced.