41 Alloy and Unalloyed Heat Treated Steels

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 deeper than its outside case but it 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)

Derived from The Virtual Machine Shop (http://jjjtrain.com/3engineering/3eng_heat_treat/_08.html) retrieved from the Wayback Machine 17 January 2024.