Steel Production: History, Composition, and Manufacturing Processes

Understanding Steel Composition

Iron is the most widely used metallic element in the world. However, it is rarely used in its chemically pure form; instead, it is alloyed with carbon to create steel. Iron ore is typically found as:

What is Steel?

Steel is not a pure metal in the chemical sense, but an alloy of a metal (iron) and a nonmetal (carbon). It retains the core characteristics of iron while achieving significantly improved properties through the addition of carbon and other metallic or nonmetallic elements. For context, a hydrogen atom consists of a single electron orbiting a nucleus containing one proton.

Steel Fabrication Processes

Pig iron is the product obtained by the reduction and melting of iron ore in a blast furnace using coke. Its carbon content typically varies between 3% and 4%, which makes the material hard but brittle.

Until the mid-nineteenth century, the carbon content of pig iron was reduced using primitive methods like the puddling furnace or crucible furnace to produce steel. With the Industrial Revolution, methods for reducing carbon in cast iron became faster and more efficient.

The Bessemer Revolution

In 1850, England revolutionized steel production by making it more practical, economical, and productive. Henry Bessemer, an English engineer, achieved steel production by blowing cold air through a mass of liquid iron. The device used for this process was called a converter.

In 1860, the first commercial Bessemer converter was introduced in the United States. The industry expanded rapidly, with production rising from 42,000 tons in 1871 to over 10 million tons by 1910.

Modern Steelmaking Techniques

Initially, steel converters were inflated with air (using Bessemer, Thomas, and Siemens-Martin furnaces). In 1948, the LD furnace was introduced in Linz, Austria, utilizing oxygen injection—a method that remains the industry standard today.

Additionally, starting in 1878, efforts were made to develop electric furnaces. Engineers worked to overcome challenges regarding power supply and electrode durability. In 1890, the first electric furnace, the Heroult, was put into operation.

Blast Furnace and Steelmaking Methods

The following section outlines the primary steelmaking processes and early electric furnaces that defined production throughout the twentieth century.

Flow Diagram of Steelmaking