Fire, sweat, and innovation
Steel: Worldwide, there are more than 2,500 standardized grades of steel – a material without which our world is no longer conceivable. Steel is defined as an iron-carbon alloy with a maximum carbon mass fraction of two percent. Alloys with higher carbon content are called cast iron and unlike steel cannot be plastically shaped in rolling mills. To get to the heart of the matter: Who exactly invented steel and when cannot be pinpointed. It’s a fact that the most important ingredient of all steel grades is raw iron that emerges from the smelting of iron ores. Liquid raw iron is produced in blast furnaces by extracting oxygen from it by means of carbon.
Allegedly as early as in the 13th century BC, blacksmiths discovered that the residual coal in their furnaces caused iron to become harder and more durable. In ancient India (6th century BC) artisans would use fireproof containers (crucibles) to smelt wrought iron with charcoal to produce Wootz steel – a material that due to its sharpness and hardness is still admired today. From the 14th century onward, layers of charcoal and iron ore were stacked on top of each other in smelting furnaces with temperatures between 800 and 900 degrees centigrade (1,470 to 1,650 degrees Fahrenheit). It marked the birth of bloom, a pasty mass of metal with slag inclusions. To remove the slag, the metal was forged.
The first blast furnaces evolved from the old smelting furnaces when these became increasingly taller and were equipped with more powerful fans. For the first time, liquid iron was produced instead of bloom – marking the transition to modern steel production as we know it today. At the beginning of the 18th century, coke was massively used for smelting iron ore. It replaced wood and charcoal, which became scarcer and scarcer. While as late as in the 17th century four metric tons (4.4 short tons) of charcoal were needed to produce one metric ton (1.1 short tons) of raw iron, today, the same amount of raw iron requires less than half a metric ton of coke (0.55 short tons). The invention of the Bessemer process by the British inventor Henry Bessemer in the 1850s made mass production increasingly simple, economic, and cost-efficient. Previously, workers had to remove the unusable substances from the molten steel by stirring it and now a machine operating with compressed air performed the strenuous job of stirring. The oxygen contained in the air burned the carbon and other undesirable incidental elements. In 1850, a blast furnace worker on average would produce eight metric tons (8.8 short tons) of raw iron. Within the space of 20 years, the production quantity increased tenfold. In 1912, scientists of the German Krupp Group accidentally discovered that alloying of iron, chrome, and nickel creates corrosion-proof steel, marking the invention of stainless steel. Today, the subject of sustainability – steel is already the most frequently recycled material worldwide – plays a major role. The motion technology company Schaeffler is going to switch to climate-neutral production paths as well, the keyword being green steel. Starting in 2025, Schaeffler will purchase 100,000 metric tons (110,000 short tons) of steel produced in a nearly CO₂-free process from Swedish startup H2 Green Steel. The reason is that every year Schaeffler consumes flat steel with a weight equating to that of 92 Eiffel Towers. Compared to conventionally produced steel, the CO₂ emissions of the green steel purchased from H2 Green Steel decrease by as much as 95 percent due to the use of hydrogen instead of coke.