Carbon steel; image retrieved from
http://www.steel-plastic-ball.com/
rimages/164/carbon-steel-ball-s.jpg
Carbon steel; image retrieved from http://www.steel-plastic-ball.com/ rimages/164/carbon-steel-ball-s.jpg |
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Steel is a very complex compound made from different types of minerals, both metals and nonmetals, to create many types of finished metallic products that fall under the broad term of steel, as we know it. The first signs of actual iron smelting can be traced to 4000 B.C., and the time that steel making became widespread was around 200 A.D. in India (http://en.wikipedia.org/wiki/Steel).
Variations of steel make up a lot of the things that are seen around you today. Basic examples of steel that you see around every day include your vehicle, dinnerware (knife, fork, spoon), keys, shelving units, or even the bottom of the chair you are sitting on right now. The picture of the carbon steel balls in the upper left hand corner shows just one type of steel that is not in its finished product, but is in the process of being made into something else, such as a pinball.
In the last century, a new concept of steel was created called stainless steel. Alloys of different types of minerals come together for different purposes. Steel is used in many ways because of its strength and this webpage will inform you on the minerals that come together and waste created in the process of creating this valuable commodity we know as steel.
Back to Table of Contents.Native iron is not known to exist from the Earth, but comes to the Earth through meteorites. Iron as an element in the Earth's crust, is 5% and oxygen, 47%. Combining these two elements creates minerals classified as oxides and hydroxides. Most steel is created by extracting the iron from these relatively common iron oxide minerals that are valued as iron ores minerals:
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 Manganite is a hardening component of steel; image retrieved from http://www.mii.org/ Minerals/minpics/manganite.jpg |
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The production of steel has had many changes in technology involving how it was made lots of times since steel making was first started. Producing steel does however create some other metals in the process, which are known as slag. These by-products can be used for many other things including being used in the steel making process again. This table shows the major components that make up the slag after the steel process. As you can see the main thing found is Calcium Oxide, which is one type of metal that be reused in the steel process again to purify other metals out of the iron ore. The link above is the website from where the chart is located, as well as some ways that these metals are dealt with including recycling and disposing. Slag is most often used for aggregates for all kinds of fill used in construction of roads or as a top layer to dirt used for support on roads, overpasses, highways. Slag is also used again in the steel process as something that clean the iron ore so that other impure metals can be taken out of the iron. Some slag is also added to the iron to make a compound called an alloy.
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An alloy is a mixture of metals with nonmetals or other metals that are put together to form a different substance. These alloys can be divided into three main groups. Steel is mainly made from iron and carbon. Different metals are added to steel to make different alloys. Carbon-This is the main thing added to the iron to give the steel alloy strength. The three main types of alloys associated with steel include adding metals and gases. The first type of alloy deals with adding carbon to the steel, and it was it classified by having “1% carbon, 0.6% copper, 1.65% manganese, 0.4% phosphorus, 0.6% silicon, and 0.05% sulfur”. (http://www.efunda.com/materials/alloys/alloy_home/steels.cfm) The second type of alloy deals with the iron having more carbon in it than a carbon alloy, as well as other steels that don’t have carbon in them mixed in with the metal. Low alloy steels contain between 1% and 5% of other metals mixed with the iron. The last type of alloy deals with the stainless type of steel, which is only referring to only adding chromium to the iron, therefore making it have a very bright shine with nickel mixed in with the iron too. There are a few variations that are within Stainless steels, such as the Austenitic, Ferritic, and Martensitic types. The Austenitic type of stainless steel combines 18% chromium, and 8% nickel, and is typically referred to as 18-8 stainless steel as a common term. This type of stainless steel is very strong when put in extreme environments of temperature such as extreme cold or heat. Ferritic stainless steal is made with only trace amounts of nickel and 12-17% of chromium is added to the iron here. This steel is very magnetic and usually contains some titanium or aluminum added to the iron. Martensitic steel contains no nickel, and about 12% chromium added to the iron. This type of steel is also magnetic. Detailed information is found at the Efunda website on steel alloys, see (http://www.efunda.com/materials/alloys/alloy_home/steels.cfm)
Return to ESU Mineralogy Student website pages http://www.emporia.edu/earthsci/amber/go336/webpages.htm This site was created on November 28, 2006 by B. Milner, who can be contacted for questions at bmilner@emporia.edu
Copyright 2006 Brandon Milner.
Production of Steel
Types and Uses of Slag
Slag is the term used to describe products made on the side during the process of trying to purify certain metals, in this case for steel. Slag produced is often first classified as either being either ferrous or nonferrous metals.
4 different types of slag including:
Typical steel slag chemical composition.
Constituent
Composition (%)
CaO
40 - 52
SiO2
10 - 19
FeO
10 - 40
(70 - 80% FeO, 20 - 30% Fe2O3)
MnO
5 - 8
MgO
5 - 10
Al2O3
1 - 3
P2O5
0.5 - 1
S
< 0.1
Metallic Fe
0.5 - 10
Table taken from: http://www.tfhrc.gov/hnr20/recycle/waste/ssa1.htm
Steel Alloys
Chromium-This is added to iron to make an alloy that resists rusting or to prevent oxidation.
Aluminum-This is added for the purpose of slowing the rate of growth for the grains in the iron, as well as being a good deoxidizer for the metal.Stainless Steel
References
