Steel is a ferrous metal, meaning it comes from, or contains iron. To make steel we must first have iron ore, which is mined from the ground. The iron ore is then smelted in a blast furnace, adding carbon and removing impurities.
The blast furnace is an enormous steel shell, cylindrical in shape, and lined with heat-resistant brick. Iron ore and other iron materials, coke (a fuel made from coal), and limestone are put into the furnace from the top. As they work their way down into the body of the furnace, also called the “stack,” they heat up. The burning coke releases gas, removing a significant amount of oxygen from the iron ore. The limestone, halfway down the furnace, reacts with the impurities in the other materials, forming a slag (stony waste matter).
The slag then absorbs the ash created from the burning coke, and silica in the ore is reduced to silicon, which then dissolves in the iron with some of the carbon. Molten slag forms at the very bottom of the furnace where temperatures reach over 3,000 degrees Fahrenheit. It floats upon a deep pool of molten iron. Finally, the iron is drained from the hearth of the furnace through a tap hole.
Blast furnaces operate continuously until the refractory lining wears down. The duration of one furnace operation from start to finish is called a “campaign.” One campaign can continue over several years.
The world produces a tremendous amount of steel every year. However, it is never wasted. Steel is actually one of the most recycled materials on earth. Statistics show that 88% of steel in the world is recycled, and two out of every three tons of newly made steel comes from old recycled stock. North America alone recycles 69% of its steel each year.
Today, steel is used in so many different ways for so many different things: strapping tools, household appliances, residential and commercial construction, eating utensils, and more.
This incredible material isn’t new by any means. The production of steel tools and weapons dates back to ancient times. The earliest known pieces of steel were excavated by archaeologists in Asia Minor, and could be dated back to 1800 B.C.
