Comparing 300, 400 and 500 Series Steel

Steel power line structure

Steel is an invaluable material that’s used in the production of countless products. Defined as an alloy of iron and carbon, it’s stronger and more durable than most other materials. These physical characteristics make it ideal for automotive engines, machines, handheld tools, bridges, buildings and more.

With that said, steel is often graded according to its specification composition. Different types of steel have a different composition, which is reflected upon their respective series. You’ll often find screws and bolts made of either 300, 400 or 500 series steel. Below is a comparison of 300, 400 and 500 series steels.

What Is 300 Series Steel?

300 series consists of steels that can only be hardened using cold-working methods. They are known as austenitic steels because they are comprised of large amounts of chromium and nickel. 300 series steels contain iron as well, but they have higher levels of chromium and nickel than that of non-austenitic steels.

With high levels of chromium and nickel, 300 series steels offer excellent resistance to corrosion and rust. Chromium and nickel inhibit oxidation, thereby protecting the iron compounds from corrosion and rust.

What Is 400 Series Steel?

400 series consists of steels with a higher composition of chromium and manganese than that of 300 series steels. Unlike the 300 series, 400 series steels can be hardened using hot-working methods. Exposure to heat makes 400 series steels more workable without damaging them. 400 series steels actually become harder when exposed to heat.

Even though they have a high chromium content, 400 series steels are more susceptible to rust and corrosion than their 300 series counterparts. Moisture, for instance, can cause oxidation of the iron compounds within 400 series steels. Nonetheless, 400 series steels offer excellent strength and protection against physical wear and tear.

What Is 500 Series Steel?

Finally, 500 series steels are known as heat-resistant chromium alloys. They contain exceptionally high levels of chromium that prevent deformation when exposed to heat. 500 series steels are used in applications where heat is a concern. Chromium itself can withstand temperatures in excess of 1,000 degrees Fahrenheit, making 500 series steels an excellent choice for such applications. With a high chromium content, however, 500 series steels aren’t as strong or durable as other steels.

300, 400 and 500 aren’t the only series in which steels are classified. There are also 100, 200 and 600 series. Nonetheless, most steel fasteners are made of either 300, 400 or 500 series.

All steels are compromised primarily of iron and carbon, but they often contain small amounts of other metals to change their physical properties. The series of a particular type of steel simply denotes is composition.

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