Traditionally an alloy of iron and carbon, steel stands as one of the most commonly used metals in the world across industries from construction to blacksmithing to sewing. Early steels had variable carbon content –usually added in the forging process with charcoal — from 0.07 percent to 0.8 percent, the latter being the threshold at which the alloy can be considered proper steel. Modern steel content usually maxes out at 2 percent, a material often called cast iron. Early iterations of the alloy can be seen in Egyptian and Chinese artifacts, dating back to circa 900 B.C. and 250 B.C., respectively. Since then, new developments and the discovery of new elements have changed the nature of steel and allowed producers to create steel specialized for specific jobs.
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Humans have been making steel for thousands of years, as the alloy is stronger than its two necessary components: iron and carbon. Many human-made products from homes to piano wire use steel.
Properties of Steel
Iron has a little more hardness than copper. The addition of carbon makes the steel tougher and more durable until a certain concentration is reached, at which point it becomes brittle. That said, steel can have many different properties depending on the other elements that compose it. For example, stainless steel – which is rust resistant, relatively weak, and finds use in cutlery and knives – contains a minimum 10.5 percent chromium. Steels used in construction fall into three types: carbon-manganese steel; high-strength, low-alloy (HSLA) steel; and high-strength quenched and tempered alloy steel. Tough, versatile and resilient, steel can be found in most construction projects. Though steel can rust, and rust-resistant steels tend to be weak, it is fairly easily recycled.
Early forms of steel contained impurities that led to weakness because steel relies on a homogenous makeup for its strength. However, blacksmiths and modern metallurgists developed methods to remove them. Other techniques made steel stronger or easier to work with, such as tempering or heat-treating, and the discovery of crucible steel, which allowed the creation of new alloys by completely melting down the metals in a clay furnace.
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Uses of Steel
After its invention, steel steadily spread across the world, reaching most cultures and finding a variety of uses. Early uses of steel included weaponry, as steel held its shape and edge better than pure iron. Since then, it has found use across industries. Tools like hammers and screwdrivers contain steel, as do many of the things these tools make. The construction industry uses about a quarter of the world's steel, which can be found in almost every building made by humans. Stainless steel finds use as cutlery material; chef knives are made of different grades of knife steel; and cast iron pans remain a popular kitchen accoutrement. Steel can also be found in piano wires, sewing needles and electronics.