What are the five classes of steel?

There are many different types and classes of steel, but some common categories include:

1. Carbon steel: This type of steel contains carbon as the main alloying element and is the most commonly used type of steel.
2. Alloy steel: This type of steel contains one or more alloying elements in addition to carbon to improve its mechanical properties.
3. Stainless steel: This type of steel contains at least 10.5% chromium and is highly resistant to corrosion.
4. Tool steel: This type of steel is designed for use in tools and other machinery and is known for its hardness and strength.
5. Maraging steel: This type of steel is a type of alloy steel that is known for its exceptional strength and toughness.

These are some of the common classes of steel, there could be more depending on the application and specific requirements.