Stainless steel not only revolutionized trains like the Burlington Zephyr. Take a look around the room you're in. Chances are you can see or at least think about many items that are made of steel. It's not easy to imagine modern life without this versatile metal, is it? Although the production of metals has been around for an awfully long time (the Iron Age began around the eighth century B.C.), it wasn't until the late 19th century that manufacturers learned how to mass produce metals inexpensively, and to forge a material as useful as stainless steel.
Already familiar with the smelting of gold, silver, and copper, metal smiths, possibly as early as 4,000 B.C., tried to use the techniques they already knew to smelt iron ore. Unsuccessful at these attempts, they sought a new technique. It wasn't until the discovery that iron ore has an affinity for (and therefore contains) oxygen that the development of iron, and later, steel, became possible.
Early processes of obtaining iron from its ore required heating the ore with a substance that had a high carbon content, such as charcoal. As temperatures within the furnace reached 1,650 degrees Fahrenheit, the ore began to release oxygen and the charcoal released carbon. These two elements then combined to form carbon monoxide, leaving behind a spongy mass of iron. If the temperature was allowed to reach 2,190 degrees Farenheit, this mass would absorb small amounts of carbon, forming wrought iron. At higher temperatures, the iron would absorb more carbon, melt, and result in a molten metal called cast or pig iron.
Though the use of iron was already widespread in Europe and North America, ironworkers continued to experiment with the metal, trying to improve the properties of soft wrought iron and hard and brittle cast iron. They tried heating, pounding, and quenching iron in cool water and learned that adding oxygen to the molten metal at high enough temperatures reduced its impurities and the carbon content. This resulted in a purer, stronger metal: steel.
One process of making steel was to heat wrought iron -- which had a low carbon content -- in clay crucibles (or vessels) with charcoal for about ten days. This would increase the carbon content enough to transform the iron into steel. The technique worked, but it was time consuming, required a lot of fuel, and produced only small quantities of steel. During the mid-19th century, the Bessemer converter -- an oval shaped furnace that blasted molten iron with oxygen -- revolutionized the production of steel. Andrew Carnegie saw the importance of the new converter and declared, "The day of iron is past. Steel is king!" His company began producing steel rails at an astounding rate, supplying the tracks the railroads were rapidly laying across North America.
The reign of steel continued with the development of alloy steels in the early 19th century. The addition of elements known for their resistance to corrosion -- elements such as gold, tungsten, and chromium -- modified the properties of steel, further strengthening the metal. The high-strength steels were able to retain sharp edges while cutting at high speeds and were utilized by new industries in the United States. Edward Budd, who manufactured the first all-steel automobiles, proved the superior strength of steel by standing an elephant atop one of his steel cars. The mass production of planes, trains, and cars, made possible by alloy steel, defined the modern world in an entirely new way.
The development of alloy steels introduced a variety of new metals, all of which had unique properties, but it was a certain combination of chromium and carbon that led to the discovery of the industry's most superior grade of steel -- stainless. Early experiments that added chromium to steel increased the strength of the metal but contained levels higher or lower than that needed to create stainless. Chromium, at levels of 10-27 percent, in conjunction with a carbon content less than 0.2 percent, created a film on the surface of steel as it reacted with oxygen in the air. This film acts as a protective layer that resists oxidation and heat, giving stainless steel its non-corrosive, rust-resistant qualities.
Pioneers in the alloying of steel each contributed to the development of stainless, but Harry Brearley, a British expert in the analysis of steel, was the first to realize its practical uses. In 1912 Brearley developed a grade of stainless that contained 12.8 percent chromium. He tested certain chemicals against the metal and found it was resistant to corrosion. Brearley quickly realized the benefits of a high-strength, rustless metal and introduced it to the cutlery industry in Sheffield, England. It became the first to mass-produce a stainless steel product.
Stainless steel, with its sleek, shiny surface and tremendous strength, is a marvel of technology. It has revolutionized most modern industries, including food, medicine, and transportation. The non-corrosive and rust-resistant properties of stainless steel have made it essential in the preparation, delivery and storage of food. Stainless steel is a standard in modern restaurant kitchens since it can be easily cleaned and dried. The surface of stainless steel resists oxidation at high temperatures, making the sterilization of medical instruments possible. Its light weight and durability allowed the development of streamlining in transportation. The streamlined design of new trains, planes, and automobiles allowed for less wind resistance, and trains such as the Zephyr helped spark a new design movement. Everything from toasters to vacuum cleaners emulated the new vehicles. Stainless steel paved the way for modern technology and continues to influence our lives every day.
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