D2 Tool Steel

D2 Tool Steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium-rich alloy carbides in the microstructure. These carbides provide good resistance to wear from sliding contact with other metals and abrasive materials. Although other steels with improved toughness or improved wear resistance are available, D2 provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms.

APPLICATIONS: Rolls, punches, dies for blanking, forming, trimming, and thread rolling, shear knives, food-processing knives, and gauges.

Composition

Relative Properties

Physical Properties

• Density: 0.278 lb/in³ (7695 kg/m³)
• Specific Gravity: 7.70
• Modulus of Elasticity: 30 x 10⁶ psi (207GPa)
• Machinability: 50-60% of a 1% carbon steel

Heat Treating Instructions

Hardening

Preheating: To minimize distortion and stresses in large or complex tools use a double preheat. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1150-1250°F (621-677°C) equalize, then heat to 1400-1450°F (760-788°C). For normal tools, use only the second temperature range as a single preheating treatment.

Austenitizing (High Heat): Heat slowly from the preheat. Furnace or Salt: 1850-1875°F (1010-1024°C).

Quenching: Air or pressurized gas to 150-125ºF (66-51ºC). Sizes up to 4 inches (101.6 mm) in thickness will through harden when air cooled from 1575ºF (857ºC). Sizes up to 6 inches (152.4 mm) in thickness will through harden when air cooled from 1625ºF (885ºC).

Tempering: Temper immediately after quenching. Hold at temperature for 1 hour per inch (25.4 mm) of thickness, 2 hours minimum, then air cool to ambient temperature. The typical tempering range is 350 to 400ºF (177 to 204ºC).

For maximum wear resistance, temper between 300-350°F (149-177°C) for a hardness of 62-64 HRC. For the optimal balance between wear resistance and toughness, temper between 500-550°F (260-288°C). This will produce 58-60 HRC.

For maximum toughness, double temper, 2 hours plus 2 hours, at temperatures above 950°F (510°C). This will produce hardness of less than 58 HRC.

To minimize internal stresses in cross sections greater than 6 inches (152.4 mm) and to improve stability in tools that will be EDM'd after heat treatment, soaking times of 4 to 6 hours at the tempering temperature below 950°F (510°C) are strongly recommended.

Annealing: Annealing must be performed after hot working and before re-hardening. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1600-1650°F (871-899°C), and hold at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 255 HBW.