The modern steel industry is one of the largest manufacturing industries in the world, but is one of the most energy and greenhouse gas emission intense industries, contributing 8% of global emissions. However, steel is also very reusable: it is one of the world's most-recycled materials, with a recycling rate of over 60% globally.

Iron and steel manufacturing processes include cokemaking, sintering, briquetting, ironmaking (including direct-reduced ironmaking), steelmaking, vacuum degassing, ladle metallurgy, casting, hot forming, forging, and finishing (e.g., acid pickling, descaling, cold forming, surface cleaning, hot coating and annealing).

The modern steel industry began in the late 1850s. Since then, steel has become a staple of the world's industrial economy.

In 1875, Britain accounted for 47% of world production of pig iron, a third of which came from the Middlesbrough area and almost 40% of steel. 40% of British output was exported to the United States, which was rapidly building its rail and industrial infrastructure.

Two decades later in 1896, however, the British share of world production had plunged to 29% for pig iron and 22.5% for steel, and little was sent to the U.S. The U.S. was now the world leader and Germany was catching up to Britain. Britain had lost its American market, and was losing its role elsewhere; indeed American products were now underselling British steel in Britain.

From 1875 to 1920 American steel production grew from 380,000 tons to 60 million tons annually, making the U.S. the world leader. The annual growth rates in steel 1870–1913 were 7.0% for the US; 1.0% for Britain; 6.0% for Germany; and 4.3% for France, Belgium, and Russia, the other major producers.

This explosive American growth rested on solid technological foundations and the continuous rapid expansion of urban infrastructures, office buildings, factories, railroads, bridges and other sectors that increasingly demanded steel. The use of steel in automobiles and household appliances came in the 20th century.

After an early career in railroads, Andrew Carnegie foresaw the potential for steel to amass vast profits. He asked his cousin, George Lauder to join him in America from Scotland. Lauder was a leading mechanical engineer who had studied under Lord Kelvin. Lauder devised several new systems for the Carnegie Steel Company including the process for washing and coking dross from coal mines, which resulted in a significant increase in scale, profits, and enterprise value.

Lauder would go on to lead the development of the use of steel in armor and armaments for the Carnegie Steel Company, spending significant time at the Krupp factory in Germany in 1886 before returning to build the massive armor plate mill at the Homestead Steel Works that would revolutionize naval warfare.

By 1889, the U.S. output of steel exceeded that of Britain, and Andrew Carnegie owned a large part of it. By 1900, the profits of Carnegie Bros. & Company alone stood at $480,000,000 with $225,000,000 being Carnegie's share.

When World War II ended, no industry was stronger or more important than American steel.

American steel mills were producing steel at a furious pace, making more than half the world's steel in the late 1940s, and about 40% of the world's steel throughout the 1950s. From 1948 to 1958, American steel mills averaged nearly 700,000 workers.

But over the years, the steel industry has suffered a steady decline, becoming less competitive and far less central to the American economy. Today only 83,000 people still work in the nation's steel mills.

Today China's steel industry produces roughly half the steel in the world, according to World Steel, a global industry trade group. American mills produce less than one tenth the volume of China. China's steel production went from a third of the output of American mills in 1981 to match US production only 12 years later. It's posted an 800% increase in production since then.