 This iron that is first obtained from the blast furnace is known as cast iron or pig iron. Cast iron contains about 4% carbon, which comes from coke used in the extraction process from hematite in the blast furnace. This cast iron is brittle, which means that it breaks instead of forming many different shapes when a force is applied. Cast iron is used to make manholes in roads, certain types of cookware, and some piping materials. The carbon content of cast iron can be removed if we blow oxygen into molten cast iron, fresh from the blast furnace. The oxygen reacts with carbon to create carbon monoxide, which can be reused in the extraction process. If we removed almost all the carbon in cast iron, we get wrought iron. Wrought iron is as close to pure iron as we can get. Wrought iron is very soft and malleable, and was once molded into fences. Since it is soft and malleable, it does not have as many real life applications as steel, which is an alloy of iron. An alloy is a mixture of two or more elements, with at least one of the elements a metal. Steel is an alloy of iron and carbon. We can get varying strengths of steel, all depending on the percentage of carbon, and therefore many different applications for that type of steel. Low carbon steel, or mild steel, contains less than 0.25% carbon. The presence of carbon atoms within the metallic structure of iron makes it stronger. Think about it, when a force is applied to a metal, the metal ions slide over one another. If we insert carbon atoms into this metallic structure, it will be harder for the metal ions to slide over one another, thereby strengthening the overall structure. High carbon steel is used to make the outer bodies of cars and ships, nails, many building materials, and even bridges. High carbon steel can contain anywhere from 0.5 to 1.5% carbon. High carbon steel is expected to be stronger than low carbon steel, because of the higher percentage of carbon. Since high carbon steel is stronger, it is used to make many cutting and manufacturing tools such as drill bits. Now we have to be a bit careful with high carbon steel, as the higher carbon content also makes it rather brittle, just like cast iron. As useful as these alloys might be, low carbon and high carbon steel can rust when exposed to oxygen and moisture. So there needs to be a layer of grease or paint to prevent corrosion. Stainless steel, as implied in its name, does not rust. Stainless steel is an alloy of iron, chromium, nickel, and a small percentage of carbon. Stainless steel is very strong and hard. Therefore, it is used to make many cutlery, some types of cookware, and industrial equipment. An even stronger alloy is manganese steel, with a 15% composition of manganese. Because of its incredible strength, manganese steel is used to make railway tracks, equipment used to crush rocks, and cement mixture. An alloy of iron and titanium, and a small percentage of nickel, chromium, and carbon, is titanium steel. An interesting property is that it is very resistant to high temperatures. Titanium steel is also lighter than other alloys of iron, and because of these properties, it has extensive applications in the aerospace industry. Titanium steel is used to make the outer bodies of airplanes and spacecrafts. Another very interesting application is its use in the medical field. It is used to make many artificial joints and in hip replacement surgeries.