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Question:

What is the difference between steel and iron?

I need to identify a metal. It is rusty so I suspect it is either iron or steel. Since they both have similar densities and are magnetic, how do I tell the difference betweeen steel and iron?

Answer:

Iron is a natural ore. Google: Iron ore, click on Mineral Information Institute - Iron Ore. Steel is a man-made material, consisting of iron. Google: Sir Henry Bessemer, inventor.
Iron and Steel Manufacture, technology related to the production of iron and its alloys, particularly those containing a small percentage of carbon. The differences between the various types of iron and steel are sometimes confusing because of the nomenclature used. Steel in general is an alloy of iron and carbon, often with an admixture of other elements. Some alloys that are commercially called irons contain more carbon than commercial steels. Open-hearth iron and wrought iron contain only a few hundredths of 1 percent of carbon. Steels of various types contain from 0.04 percent to 2.25 percent of carbon. Cast iron, malleable cast iron, and pig iron contain amounts of carbon varying from 2 to 4 percent. A special form of malleable iron, containing virtually no carbon, is known as white-heart malleable iron. A special group of iron alloys, known as ferroalloys, is used in the manufacture of iron and steel alloys; they contain from 20 to 80 percent of an alloying element, such as manganese, silicon, or chromium.
Steel is a refined, alloyed metal that is mostly iron. Iron, in a chemistry sense os simply Fe. In an industrial sense iron is pig iron commonly saturated with carbon, up to 4.5% and has other impurities like sulfur. Pig iron is brittle and should break rather easily, and bend very little. After a piece is broken look at the crystal structure, you should see rather small crystals. Most steel made for car body's, washing machines, file cabinets, low grade bolts and nuts etc. should flex and bend before breaking. Most steel made for things like cutting tools, axles, etc, is hardened and will chip and break rather than bend. Also you can try to heat the piece to a glowing orange temperature. It must be very hot. Cool it. If there is a lot of white flake scale on the piece it is impure and probably iron of some sort. In the end the only way exactly tell is have an analysis done and look at the chemistry.

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