D2 Tool Steel can be heat treated to increase hardness and durability. Markforged recommends heat treating D2 Tool Steel to optimize material properties, though it can be used as-sintered. Heat D2 Tool Steel part in a standard (non-vacuum) furnace to 1000°C (1830°F) . Hold part at temperature for 30-45 minutes. Air quench part to below 65°C (150 °F). Temper D2 Tool Steel Tool Steel part in a standard furnace. For each temper, heat part to 200°C (392°F) and temper for 30 minutes. If double tempering, let part cool to room temperature between tempers.