Alloys Steel – D3

Alloys Steel – D3 | ASTM A681 | FED QQ-T-570 | SAE J437 | UNS T30403 | DIN 1.2080

D3 (UNS T30403) Tool Steel – High-Carbon, High-Chromium, Cold-Work Steel

Cold-work tool steels which include D2, D3, D4, D5, and D7 steels are high-carbon, high-chromium steels. Apart from D3 steel all group D steels have 1% Mo and are air hardened. Type D3 steel is oil-quenched; though small sections can be gas quenched after austenitization using vacuum. As a result, tools made with type D3 steel tend to be brittle during hardening. Type D2 steel is the most commonly used steel among the group D steels. The D3 steels contain 1.5 to 2.35% of carbon and 12% of chromium.

Chemical Composition

The following table shows the chemical composition of D3 tool steels.

Element Content (%)
C 2.00-2.35
Mn 0.60
Si 0.60
Cr 11.00–13.50
Ni 0.30
W 1.00
V 1.00
P 0.03
S 0.03
Cu 0.25

Physical Properties

Physical properties of D3 tool steels are given below:

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

Stress Relieving

Heat to 650-700ºC. Soak for 2-4 hours then furnace cool.

Heat Treatment

D3 tool steel requires hardening and tempering to achieve maximum properties. For maximum accuracy, the parts of D3 tool steel should be stress relieved after roughing operations. Stress should be relieved at 648°C (1200°F) for one hour and cooled slowly.

Mechanical Properties

The mechanical properties of D3 steels are tabulated below:

Properties Metric Imperial
Izod impact unnotched 28.0 J 20.7 ft-lb
Poisson’s ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi


Annealing of D3 tool steel needs to be done in a controlled atmosphere furnace. D3 tool steels should be heated thoroughly to 871°C (1600°F) and cooled slowly at a rate of not more than -6°C (20°F) per hour, until the furnace is black. Then the material should be removed and air cooled.


The D3 tool steel should be cooled to room temperature and should be tempered immediately. The parts should be placed in the tempering furnace and increased slowly to the desired tempering temperature. Tempering for 1 hour per inch of thickness is required.

Thermal Properties

The following table shows the thermal properties of D3 steels.

Properties Conditions
T (°C) Treatment
Thermal expansion 12 x 10-6/ºC 20-100


D3 tool steel should be heated properly since it is very sensitive to overheating and if not heated maximum hardness cannot be achieved. The work should be directly placed in a furnace preheated to 954°C (1750°F) and soaked for 20-25 minutes, plus 5 minutes per inch of thickness, and then oil-quenched to harden it.


  • AFNOR Z 200 C 12
  • DIN 1.2080
  • UNI X 21O Cr 13 KU
  • JIS SKD1
  • B.S. BD 3
  • ASTM A681
  • FED QQ-T-570
  • SAE J437
  • SAE J438
  • UNS T30403


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