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Blast furnace and iron ore - help to understand?

  1. Dec 9, 2014 #1
    OK, so back in the day, blast furnaces were used to refine the iron ore?

    Iron ore concentrate is mechanically and magnetically refined ore ? Refining usually happens at mines, or somewhere around there.

    Ore concentrate goes to blast furnace and then you get pig iron.

    Why not steel?

    I don't understand why converter steelmaking must be used (basic oxygen process) to make steel.

    Why not steel out of blast furnace? Or pure iron (let's say almost pure iron something like 99.90%)

    I'm kind of baffled by this :oops:

    What exactly is so brilliant about the basic oxygen process converter? I should ask, what is the brilliance behind the principle. I can understand that you can quickly make steel but...

    Blast furnace uses oxygen... Converter uses oxygen, why not steel out from blast furnace?
  2. jcsd
  3. Dec 9, 2014 #2


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    Pig iron is the basic material used in the production of wrought iron, cast iron, and steel. 'Steel' refers to an alloy made of iron, carbon, and other elements. There isn't just one recipe for steel: the proportions of carbon and other elements mixed with the iron are varied to make steels having different properties, for example, mild steel, high strength steel, stainless steel, etc. Pig iron typically has a high carbon content, which makes it unsuitable for making many products, which is why the various refining methods were developed: to quickly reduce the high carbon content of large quantities of pig iron, which could then be further modified to make steel and other materials.



  4. Dec 10, 2014 #3
    1. why you don't get wrought iron from blast furnace?

    2. why doesn't carbon go away in blast furnace Why not pure iron?

    3. open hearth furnace seems to be good invention that is also furnace-based decarburization technology.

    4. From my understanding part of the problem is that iron melting point rises to maximum, as the iron percentage grows to 100% (from pig iron percentage of 95% iron)

    5. So, instead of only blast furnace, now you need hotter Siemens-martin furnace? More heat , is the cure for problem?

    6. Is it necessary to use steel scrap together with pig iron to make "mixture steel" in siemens-martin.

    7. Can you make wrought iron with siemens-martin furnace, from pig iron?
  5. Dec 10, 2014 #4

    jim mcnamara

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    For your #1 & #2 questions: When you read the pig iron article, you saw that iron ore is converted to pig iron by heating the ore with limestone. The heat comes from coke (coal product). Coke is mostly what element? Carbon. Pig iron has a high carbon content. Where did the carbon in the steel come from? Coke. So, can you continue to heat in the blast furnace without adding more coke (carbon)? No. So, the steel manufacturers stop the process. And move on to another process that eats up carbon.

    Think of steel as iron with small prescribed amounts of impurities. Pig iron has too much, wrought iron too little. BTW mild steel is what almost all of the "wrought iron" work you see in fences and so on.

    The steps above are all just chemistry at hellish temperatures. The separation of dross from pig iron leaves carbon in the iron. (You should know why now.) Go back into hell and blow oxygen through the hot pig iron to remove carbon, then add back in prescribed impurities. There are huge numbers of details that have a big impact on steel. Metallurgy is the name of the studies about how these details impact the final product.
  6. Dec 11, 2014 #5
    heat is possible to be used without carbon going into heated material (it's called pyrolysis)

    in that sense you only would use heat energy on the "outside" to break chemical bonds without adding reactants

    you dont to it with iron you do pyrolysis (dry distillation) with weaker compounds like hydrogencarbon compounds (oil, tar, wood, plastics etc)
  7. Dec 11, 2014 #6


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    How are you going to reduce iron ore? Just by heating? No, you have to add carbon (as a coke) to the ore directly initially.
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