Sep 11 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesOther DesignationsFabrication and Heat Treatment Heat Treatment Forging Annealing TemperingApplications
Introduction
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. This makes tools made with type D3 steel brittle during hardening. Type D2 steel is the most commonly used steel among the group D steels.
The following sections will discuss more about D5 steels.
Chemical Composition
The chemical composition of D5 tool steels is given below:
| Element |
Content (%) |
| C |
1.40 – 1.60 |
| Mn |
0.60 |
| Si |
0.60 |
| Co |
2.50-3.50 |
| Cr |
11.00 – 13.00 |
| Mo |
0.70 – 1.20 |
| V |
1.00 |
| P |
0.03 |
| Ni |
0.30 |
| Cu |
0.25 |
| S |
0.60 |
Physical Properties
The physical properties of D5 tool steels are outlined in the following table:
| Properties |
Metric |
Imperial |
| Density |
7.7 – 8.03 x 1000 kg/m3 |
0.278 – 0.290 lb/in3 |
| Melting point |
1426°C |
2600°F |
Mechanical Properties
The mechanical properties of D5 tool steels are tabulated below.
| Properties |
Metric |
Imperial |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
| Elastic modulus |
190-210 GPa |
27557-30457 ksi |
Other Designations
The other designations of D5 tool steels are:
- ASTM A681
- SAE J437
- SAE J438
- UNS T30405
- FED QQ-T-570
Fabrication and Heat Treatment
Heat Treatment
D5 steels should be preheated very slowly up to 815°C (1500°F), then temperature should be increased to 1009°C (1850°F) and held for 20 to 45 minutes. Then they are air quenched.
Forging
Forging of D5 steels can be done at 1065°C (1950°F) down to 1750°F. Do not forge below 926°C (1700°F).
Annealing
Annealing of D5 steels should be done at 886°C (1627°F) followed by slow furnace cooling at 4°C (40°F) per hour or less.
Tempering
D5 steels can be tempered at 204°C (400°F) for achieving Rockwell C hardness of 61 and at 537°C (1000°F) for a Rockwell C hardness of 54.
Applications
Applications of D5 steels include thread rolling, blanking or forming dies operating at temperatures below 482°C (900°F).