How are carbon steels classified as either low, medium, or high carbon steels?
Carbon steels are alloys, where carbon occurs as the interstitial alloy.
The percentage by mass of carbon occurs between 0.1 and 2.0%. Why the different percentages? Well, you get alloys with different properties. If you have ever used a stainless knife versus a carbon steel knife, you find that the carbon steel knife is much easier to sharpen.