Cold-work tool steels include the high-carbon, high-chromium steels or group D steels. These steels are designated as group D steels and consist of D2, D3, D4, D5, and D7 steels. These steels contain 1.5 to 2.35% of carbon and 12% of chromium. Except type D3 steel, all the other group D steels include 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 tends to be brittle during hardening. Type D2 steel is the most commonly used steel among the group D steels.
Chemical Composition : The following table shows the chemical composition of D2 tool steels.
Element
Content (%)
C
1.55-1.75
Mn
0.20-0.40
Si
0.25-0.40
P
0.030 max
Cr
11.00-12.00
Mo
0.50-0.70
V
0.10-0.50
S
0.030 max
Ni
–
w
0.40-0.60
Mechanical PropertiesThe mechanical properties of D2 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
Physical PropertiesThe 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
Forging
Forging of D2 steels can be done from 1065ºC (1950ºF) down to 954ºC (1750ºF). Do not forge below 926ºC (1700ºF).
Annealing
Annealing of D2 steels should be done at 871 to 898ºC (1600 to 1650ºF) followed by slow furnace cooling at 4.4ºC (40ºF) per hour or less.
Applications
D2 tool steels are used for long run tooling applications, where wear resistance is important, such as blanking or forming dies and thread rolling dies.
Specification
DIN 1.2601
X165CrMoV12
B.S. BD 2
ASTM A681
FED QQ-T-570
K 105
SAE J438
UNS T30402
