Tempering characteristics for P20 mold steels carburized at two different temperatures are shown in the graphs. In (a), the upper curve represents steel carburized in hardwood charcoal at 1675 to 1700°F for eight hours, air cooled in pack, reheated at 1725 to 1750°F, cooled in air, and tempered. The middle curve represents steel carburized in cast iron chips at 1725 to 1750°F, removed from pack, cooled in air, and tempered. Graph (b) shows surface hardness after heating at temperature for two hours in a carburizing compound, followed by oil quenching and tempering.
Volume 4D, Heat Treating of Irons and Steels ⇒ Tool Steels ⇒ Heat Treating of Mold Steels and Corrosion-Resistant Tool Steels ⇒ Recommended Heat Treating Practices
