Sep 13 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat Treatment Heat Treatment Annealing Tempering Hardening
Introduction
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 |
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 |
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 |
- |
Other Designations
Equivalent metals of D3 steel are:
- 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
Fabrication and Heat Treatment
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.
Annealing
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.
Tempering
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.
Hardening
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.