A world with no steel structures in it would be unrecognizable as modern in any meaningful way. Steel is the predominant material used all over the planet for the construction of anything that needs to be strong and enduring: skyscrapers, railroad tracks, bridges, automobile frames, and countless household tools that have to tolerate a lot of stress, wear and tear.
Carbon steel is a kind of steel containing amounts of the element carbon, which you perhaps recognize from other domains of study as a very common and versatile atom.
Changing the amounts of carbon in carbon steel, which never rises above approximately 2.0 percent, can drastically change the steel's properties; high-carbon steel is a variant that, despite being brittle by industry standards, has become indispensable across countless walks of everyday human life.
What Is Steel?
Steel is not a metal but an alloy or a mixture of metals. It consists overwhelmingly of the metallic element iron (Fe), which is not only essential for construction but is required for the formation of the oxygen-carrying red blood cells in your body.
When iron is heated to very high temperatures, such as 1,300 °C, the lattice structure formed by its adjoining atoms changes shape and allows other elements, such as carbon, to in effect slop through the cracks and infiltrate the lattice. When the lattice cools, the other elements are in a sense baked into the lattice at regular intervals, becoming a part of the lattice and changing the material's properties.
- Besides the base element iron and of course some amount of carbon in many instances, other elements found in steel include manganese, cobalt, silicon and chromium.
Types of Carbon Steel
Carbon steel, as you can probably gather from the title of this article, comes in forms graded by their specific carbon content. Low-carbon steel is that which contains less than 0.25 percent of carbon; medium-carbon steel contains 0.25 percent to 0.55 percent carbon; and high-carbon steel is every other kind of carbon steel.
Low-carbon steel is not as hard as higher-carbon varieties, but is also less brittle. Although it is probably hard for you to think of any kind of steel as "soft," you can probably think of differences in how different steel objects feel even as you read this, without ever having known that this was likely because of their different carbon content.
What Is High-Carbon Steel?
Any steel with a carbon content of 0.55 percent or higher, or about one part in 180, is considered high-carbon steel. Pushing this content past 2 percent makes the result extremely brittle and of limited use, although this is how cast-iron products (e.g., wood stoves, cookware) are made. So as you can see, "high carbon" is a relative term.
High carbon steel properties include a very high strength, extreme hardness and resistance to wear, and moderate ductility, a measure of a material's ability to tolerate being deformed without actually breaking.
It is used in cutting tools, because of its ability to keep a very sharp edge under duress; it is also used for masonry nails, which can be pounded readily into rock (albeit not with your hands).
What Is Tool-Carbon Steel?
Steels with carbon content higher than 0.8 percent are known as tool-carbon steels. The name is meant as something of a clue; because of their extreme hardness, these steels are used in punch awls, shearing blades, various kinds of springs and all manner of cutting implements, knives and razors.
The iron in carbon steel, unlike that in stainless steel, is not resistant to oxidation (otherwise known in most observed instances as rust) regardless of its carbon content. However, the higher the carbon content of steel, the more resistant it is to corrosion because of its greater overall strength.
About the Author
Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs.com and the editor of "Run Strong," he has written for Runner's World, Men's Fitness, Competitor, and a variety of other publications. More about Kevin and links to his professional work can be found at www.kemibe.com.