D2 Tool Steel

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Mixed Tools Steel

Within the category of cold-work tool steels, a specific group known as "D steels" stands out for their high carbon and chromium content. This group encompasses D2, D3, D4, D5, and D7 steels, each containing roughly 1.5 to 2.35% carbon and a substantial 12% chromium.

While D2, D4, D5, and D7 steels all share the characteristic of air hardening and typically contain 1% molybdenum, D3 steel diverges slightly. It requires oil quenching for optimal hardening, although small sections can be gas quenched after austenitization using a vacuum environment. This unique hardening process can lead to increased brittleness in D3 tools compared to its air-hardening counterparts.

D2 steel reigns supreme as the most popular choice within the D group, prized for its exceptional performance and widespread applications.

Chemical Composition

The following table shows the chemical composition of D2 tool steels.

Element Content (%)
C 1.40 – 1.60
Mn 0.60
Si 0.60
Co 1.00
Cr 11.00 – 13.00
Mo 0.70 – 1.20
V 1.10
P 0.03
Ni 0.30
Cu 0.25
S 0.03

Physical Properties

The physical properties of D2 tool steels are outlined in the following table.

Properties Metric Imperial
Density 7.7 x 1000 kg/m3 0.278 lb/in3
Melting point 1421°C 2590°F

Mechanical Properties

The mechanical properties of D2 tool steels are tabulated below:

Mechanical Properties Metric Imperial
Hardness, Knoop (converted from Rockwell C hardness) 769 769
Hardness, Rockwell C 62 62
Hardness, Vickers 748 748
Izod impact unnotched 77.0 J 56.8 ft-lb
Poisson's ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi


D2 tool steel stands out within the D group for its exceptional wear resistance and impressive hardness achievable through a simple air hardening process. This high-carbon, high-chromium composition offers a well-balanced combination of toughness and affordability, making it a go-to choice for diverse cold work applications. Its minimal distortion during hardening ensures dimensional stability, while its moderate corrosion resistance adds a layer of protection in specific environments. D2's versatility and ease of heat treatment solidify its position as a top contender within the D steel family, offering a compelling blend of performance and practicality.