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
Nuggets
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).
Pig
Iron
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.
Pellets
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.
Concentrates
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.
Fines
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.
Uses
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 |