Making Steel

Steel is made of iron; and other elements added to make it stronger, that's been

through a blast furnace. Molten iron is blasted with oxygen, removing carbon. Carbon monoxide is formed, collected, and then used as a fuel. When converting iron to steel, the molten iron is poured into a converter. Then high-pressure pure oxygen is blasted into the converter.Steel is also made by melting down scrap steel in an electric arc furnace. (Rogers,2001)

Chemical Components

Iron is typically found as oxide ores, but can also be sulfide and carbonate in smaller quantities. The other ores will usually have to be roasted first in order to convert them into oxide. Haematite (Fe2O3) is often considered the most important of the ores. New Zealand holds a different opinion wit magnetite (Fe3O4) and titanomagnetite (Fe2TiO4) as the country's starting materials. Once the ores have been converted, the oxides get reduced from coal by the addition of carbon and the production of carbon monoxide. As the carbon first burns in air, it gives off carbon dioxide and the heat. These are necessary for the carbon dioxide to undergo an endothermic reaction with more carbon to yield carbon monoxide:
 

C + O2 → CO2 ∆H = -393 kJ mol-1
C + CO2 → 2CO ∆H = +171 kJ mol-1

The oxide ores are then mainly reduced by carbon monoxide which results from this reaction. Here, there are only small changes in enthalpy:

Fe2O3 + 3CO → 2Fe + 3CO2 ∆H = -22 kJ mol-1
Fe3O4 + 4CO → 3Fe + 4CO2 ∆H = -10 kJ mol-1

In most ironmaking the reduction will occur in a blast furnace. In New Zealand, a rotary kiln is used in direct reduction.The process of indirect reduction then takes place in an electric melter because titanium dioxide that is found in the ore results in a slag. This slag blocks common blast furnaces due to its high melting point.
The impurities will always be at high levels if iron is produced in this process making it very brittle. The primary focus of making steel is to remove these impurities, and this is done through oxidation of the elements. The oxidizing takes place as pure oxygen is blown through a lance and into the molten alloy. The Klockner Oxygen Blown Maxhutte (KOBM) that is used in New Zealand for this has oxygen blown through holes at the base of the converter. The oxides produced can either be evolved into gases or combine with limestone in order to form a slag The resultant slag can easily be seperated because it floats no the sruface of the liquid metal.

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Quality Control

The black furnace operation is highly instrumented and is monitored continuously. Times and temperatures are checked and recorded. 

           "To specify the various physical and mechanical properties of the finished product, various tests, both destructive and nondestructive, are performed. Metallurgical, hardness, hardenability, tension, ductility, compression, fatigue, impact, wear, corrosion, creep, machinability, radiography, magnetic particle, ultrasonic, and eddy current are some of the major tests that are performed by quality control personnel… Metallurgical testing is used to determine the quality of steel by analyzing the microstructure of a sample under a microscope… Next to the hardness test, the tensile test is the most frequently performed test to determine certain mechanical properties. A specifically prepared tensile sample is placed in the heads of a testing machine and an axial load is placed on the sample through a hydraulic loading system… Ductility of a material is indicated by the amount of deformation that is possible until fracture and can be determined by measuring elongation and reduction in area of a tensile sample that has been tested to failure… Compression tests are performed on small cylinders, blocks, or strips to determine the ability of a material to undergo large plastic deformations (a mechanical property also known as malleability) and its limits… The fatigue test is used to determine the behavior of materials when subjected to repeated or fluctuating loads. It is used to simulate stress conditions developed in materials under service conditions… Impact tests are used to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension, or torsion” (http://science.jrank.org/pages/6485/Steel-Quality-control.html).

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Byproducts/Waste

          There are a great many possible environmental effects from the iron industry. The first and most obvious is the process of open pit mining. Huge tracts of land are stripped to bare rock. Today, depleted mining sites are commonly used as landfills, then covered over and landscaped. Some of these landfills themselves become environmental programs, since in the recent past, some were used for the disposal of highly toxic substances which leached into soil and water.