Impurities Need to Be Removed
The steel ingredients need to be refined before they come together. That starts with the source of carbon: coal, which is ground into a powder and put in a blast furnace. There, it melts and cooks for up to 24 hours so that impurities like tar can be removed. What’s left is coke, a carbon-rich, purer version of coal.
That and the iron are then melted down together to form something called pig iron. This process, though, still has a fairly high carbon content. Iron and carbon-enriched iron are both too weak for use as steel. To reduce the carbon content from the single-digit percentages down to a few tenths of a percent requires blowing oxygen through the molten metal. Carbon latches onto the oxygen to form carbon dioxide, which is whisked away.
