|There are three basic types of unalloyed carbon steels which have different hardenability characteristics. They are:
- Low carbon Steel: Composed of mainly iron and from .1 to .3% carbon, this steel cannot be heat-treated but is easily welded.
- Medium carbon Steel: Composed of mainly iron and from .3 to .6% carbon, this steel can be heat-treated and gain toughness and hardness.
- High carbon Steel: Composed of mainly iron and from .6 to 1.7% carbon. The steel that contains from .6 to 1% carbon is the unalloyed steel that is often heat-treated.
Alloy steels that can be heat treated are:
- Tool Steels, which contain up to 1.3% of carbon
- Alloy Steels, which contain a few percent of alloying elements that enhance their heat-treat ability.
The table shows annealed, maximum, and minimum values of tensile strength (in pounds per square inch) that a selected few materials can be heat treated to
Some common AISI four digit monikers
Low Carbon (1020)
Medium Carbon (1040)
High Carbon (1095)
Alloy Steel (4130)