Introduction to Metallurgy

Welcome to Metallurgy Monday, where today we're going to talk about IRON.

Iron is an amazing element that has an incredible impact on the growth of our civilization and the things that allow us to live how we do, as well as the development of life as we know it! Iron is a transition metal, which means it has valence electrons - or free electrons - ready to react with other elements in TWO shells or orbits, rather than just one like a lot of other metals. This is what gives iron the AMAZING ability to form oxides, sulphites and all sorts of crazy iron-(insert element) compounds and minerals.

The reactivity of iron is part of why even though it's so common, making up to 5% of the earth's crust, it cannot actually exist as a terrestrial metal on earth. Oxygen is the number one killer of iron, because iron has such an affinity for good 'ol O2. In fact, the reason you are alive is because of iron! Hemoglobin, an iron-rich protein in your blood, is what captures oxygen in your lungs and then transports it all around your body! How wild is that!? All of this matters because when early humans started working iron, it would have just been dirt and rocks, so the current hypothesis is that originally we started forging iron that we found from meteorites.

Meteoric iron has been found in places like the tomb of Tutankhamen and even in Indonesia, where people recognized it and learned how to work it. These gifts from above were considered magical and spiritual, and had a LOT of importance associated with them. When the iron age kicked off, we started recognizing and processing iron ore. Unlike copper, gold, lead, tin, and silver, iron couldn't be smelted over a small fire. It required a lot of infrastructure and knowledge to smelt it. That's because when a metal is trapped in an oxide or a sulphide - or pretty much any type of -ide - it needs a reduction reaction to separate the iron from the oxide. This was accomplished with a special furnace that burned charcoal. As the charcoal is consumed normally, the reaction is C + O2 = CO2; carbon dioxide is the byproduct of carbon (charcoal) burning in the presence of O2 (oxygen). The crazy thing is that in a furnace, the temperatures are well over 2800F and so the carbon dioxide starts to react with the extra oxygen being pumped in to make the fire hotter - the term is actually "superheated"- this forms carbon monoxide (CO2 + C = 2CO). This carbon monoxide-rich environment is what is needed to pull the oxygen from the oxide, or ore, and leaves us with the metallic iron! Because the carbon monoxide-rich environment has more of an affinity for oxygen than the iron does, the iron in the oxide just lets the oxygen go and converts back to iron! It's the neatest thing.

Even though I'm a metallurgist, I still think it's magic.

Metallic Iron from Smelting Workshop

The balanced chemical equation for the reduction process is: Fe2O3 +3CO --> 2Fe + 3CO2. The people who discovered this method of extracting iron from the rocks and dirt around them had NO idea how their discovery would change history, eventually giving us the internal combustion engine, modern medicine and lifesaving vaccines, refrigeration to keep our food safer longer, airplanes and eventually LANDING ON THE MOON! Iron is a real-life magic metal, and next week we'll get into what happens what we get ever crazier with our dirt-metal. Stay tuned!