When choosing the right steel for your project, you may come across D2 tool steels and D3 tool steels. Both are high-carbon, high-chromium tool steels commonly used in many industries. This article will discuss the differences between these materials to help you decide which is best for your needs.
D2 and D3 tool steels are high-carbon, high-chromium tool steels designated as group D steels in the AISI classification system. D-type tool steels, developed as potential substitutes for high-speed steels in cutting tools, were found to lack sufficient hot hardness and were too brittle for machining. Despite this, the high carbon and alloy content results in a large volume fraction of hard alloy carbides, providing excellent wear resistance in cold-work applications.
Chemical composition comparison
| AISI Type | UNS No. | C (%) | Mn (%) | Si (%) | Cr (%) | Ni (%) | Mo (%) | V (%) |
| D2 | T30402 | 1.40-1.60 | 0.60 max | 0.60 max | 11.00-13.00 | 0.30 max | 0.70-1.20 | 1.10 max |
| D3 | T30403 | 2.00-2.35 | 0.60 max | 0.60 max | 11.00-13.50 | 0.30 max | … | … |
Major factors comparison
The table compares the properties of D2 and D3 tool steels in three categories: wear resistance, toughness, and hot hardness.
- Wear Resistance: D2 and D3 tool steels exhibit excellent wear resistance, scoring 8 out of 10.
- Toughness: D2 tool steel has a toughness score of 2, while D3 tool steel has a score of 1.
- Hot Hardness: Both D2 and D3 tool steels have a hardness score of 6.
Manufacturing factors comparison
Compare D2 and D3 based on their availability, cost, and machinability. The vertical axis shows their scores on this item, out of 10.
Comparison of other parameters
| Factor | D2 | D3 |
| Usual Working Hardness, HRC | 58-64 | 58-64 |
| Depth of Hardening | D | D |
| Finest Grain Size at Full Hardness, Shepherd Standard | 7 1/2 | 7 1/2 |
| Surface Hardness as-Quenched, HRC | 61-64 | 64-66 |
| Core Hardness (25 mm or 1 in. diam round), HRC | 61-64 | 64-66 |
| Quenching Medium | A | O |
| Hardening Temperature, °C (°F) | 980-1025 (1800-1875) | 925-980 (1700-1800) |
| Dimensional Change on Hardening | L | L |
| Safety on Hardening | H | M |
| Susceptibility to Decarburization | H | H |
| Approximate Hardness as-Rolled or Forged, HB | 550 | 400 |
| Annealed Hardness, HB | 217-255 | 217-255 |
| Annealing Temperature, °C (°F) | 870-900 (1600-1650) | 870-900 (1600-1650) |
| Tempering Range, °C (°F) | 205-540 (400-1000) | 205-540 (400-1000) |
| Forging Temperature, °C (°F) | 1010-1095 (1850-2000) | 1010-1095 (1850-2000) |
Compressive Strengths of D2 and D3 tool steels after hardening to maximum hardness and tempering at temperatures noted
| Steel | Tempering Temperature (°C) | Tempering Temperature (°F) | Hardness (HRC) | Ultimate Compressive Strength (MPa) | Ultimate Compressive Strength (ksi) |
|---|---|---|---|---|---|
| D2 | 175 | 350 | 61.5 | 3841 | 557 |
| D2 | 230 | 450 | 59.5 | 3641 | 528 |
| D3 | 175 | 350 | 63.5 | 3634 | 527 |
| D3 | 230 | 450 | 61.5 | 3290 | 477 |
Torsional impact energy absorbed by D2 and D3 tool steel specimens as a function of tempering temperature
Data source: Bethlehem Steel Co.;
The graph illustrates the relationship between tempering temperature and torsion impact energy for two different materials, labeled D2 and D3. Tempering temperature is shown in Fahrenheit and Celsius, while torsion impact energy is displayed in joules (J) and foot-pounds (ft-lbf).
Comparison of ductility in static torsion tests of D3 and D2 tool steels, quenched to maximum hardness and tempered at different temperatures.
Data from Teledyne VASCO
The image showcases the torque-deformation curves for two different types of steel, Type D3 and Type D2, subjected to various heat treatments.
Effect of tempering temperature on energy absorption of unnotched Izod D2 and D3 tool steel
Data from Jessop Steel Co., Allegheny Ludlum Industries, and Teledyne Firth-Sterling Steel Co.
The image presents a graph illustrating the impact of tempering temperature on the Unnotched Izod impact strength of two steel types: Type D2 and Type D3.
Application range comparison
The high-carbon, high-chromium D-type steels are divided into two groups according to carbon content. D3 belongs to high-carbon steel (including D4 and D7), possessing the highest wear resistance but with low toughness. D2 belongs to low-carbon steel (including D5), which has relatively high wear resistance and slightly higher toughness than D-type steels with a carbon content of 2% or more. High-carbon steel can be chosen instead of D2 if a longer production cycle is expected. However, high-carbon steel is more difficult to process. D2 steel is sometimes used for hot trimming of forgings, but high carbon, high chromium steels are primarily used for cold working applications.
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