IRON ORE PRODUCTS
Iron ores are rocks and minerals from which metalliciron can be economically extracted. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite, limonite or siderite.
For industrial use and processing the mined ore is usually prepared and sold to steel makers as concentrate, fines, pellets, pig iron ore iron nuggets.
Iron ore fines are a screened small fraction of high grade direct ship ore. The grade ranges from 56% to 66% iron (Fe) with the deleterious elements managed through ore blending. Fines are primarily sold to sinter plants and are typically cheapest product available to the steel industry blast furnaces.
Iron ore concentrate is an output product from processed ores that have been milled (crush, grind, magnetic separation, +/- flotation) to separate deleterious elements and produce a higher quality product of 63% to 69% iron (Fe) compared to fines. It is sold to sinter and pellet plants and, due to its quality, usually commands a slight premium but is overall priced competitively with iron ore fines.
Pig iron is the intermediate product of smelting iron ore with coke, usually with limestone as a flux. It has a very high carbon content, which makes it very brittle and not useful directly as a material except for limited applications. Grades range from 90% Fe (HBI) to 96% Fe.
The traditional shape of the molds used for these ingots was a branching structure formed in sand, with many individual ingots at right angles to a central channel or runner. Such a configuration is similar in appearance to a litter of piglets suckling on a sow. When the metal had cooled and hardened, the smaller ingots (the pigs) were simply broken from the much thinner runner (the sow), hence the name pig iron. As pig iron is intended for remelting, the uneven size of the ingots and inclusion of small amounts of sand was insignificant compared to the ease of casting and of handling. Pig iron contains varying amounts of contaminants such as sulfur, silicon and phosphorus. Its only significance is that of an intermediate step on the way from iron ore to cast iron and steel.
Iron nuggets are high in purity and iron content (>95% Fe). In the process of producing iron nuggets, all the iron oxide is reduced and no FeO remains in the nugget. The contents of silicon, manganese, and phosphorus in the product depend on raw material selection. The product sulfur level also depends on the sulfur contained in the feed reductant; however, it is often possible to reduce the sulfur level remaining in the nugget to an acceptable range (typically <0.03%). The final nugget product does not re-oxidize and does not generate fines. Therefore, it is easier than DRI and HBI products to handle and transport. The nuggets can be continuously fed to an electronic arc furnace (EAF).
The pelletizing of iron ore produces spheres of typically 8-18 mm (0.31-0.71 inch) diameter. The process combines agglomeration and thermal treatment to convert the raw ore into pellets with characteristics appropriate for use in a blast furnace and grades of 67%-72% Fe. Additional materials are added to the iron ore (pellet feed) to meet the requirements of the final pellets. This is done by placing the mixture in the pelletizer, which can hold different types of ores and additives, and mixing to adjust the chemical composition and the metallurgic properties of the pellets. In general, the following stages are included in this period of processing: concentration / separation, homogenization of the substance ratios, milling, classification, increasing thickness, homogenization of the pulp and filtering.
In the United States, almost all of the iron ore that is mined is used for making steel. The same is true throughout the world. Raw iron by itself is not as strong and hard as needed for construction and other purposes. So, the raw iron is alloyed with a variety of elements (such as tungsten, manganese, nickel, vanadium, chromium) to strengthen and harden it, making useful steel for construction, automobiles, and other forms of transportation such as trucks, trains and train tracks.
While the other uses for iron ore and iron are only a very small amount of the consumption, they provide excellent examples of the ingenuity and the multitude of uses that man can create from our natural resources.
Powdered iron: used in metallurgy products, magnets, high-frequency cores, auto parts, catalyst. Radioactive iron (iron 59): in medicine, tracer element in biochemical and metallurgical research. Iron blue: in paints, printing inks, plastics, cosmetics (eye shadow), artist colors, laundry blue, paper dyeing, fertilizer ingredient, baked enamel finishes for autos and appliances, industrial finishes. Black iron oxide: as pigment, in polishing compounds, metallurgy, medicine, magnetic inks, in ferrites for electronics industry.
Source: Mineral Information Institute