Tool Steel D2
D2 tool steel, designated UNS T30402 and DIN 1.2379, is a high-carbon, high-chromium cold work tool steel that belongs to group D of the AISI classification. It is characterized by its high wear resistance, high hardness after quenching and tempering, excellent dimensional stability, and outstanding toughness for cold applications, making it the most widely used of the group D steels.
Equivalent Designations
Section titled “Equivalent Designations”Equivalent materials to D2 tool steel according to the main international standards are:
| Standard / Country | Designation |
|---|---|
| DIN (Germany) | 1.2379 |
| BS (United Kingdom) | BD 2 |
| ASTM (USA) | A681 D2 |
| UNS (USA) | T30402 |
| FED (USA) | QQ-T-570 D2 |
| SAE (USA) | J437 / J438 D2 |
Chemical Composition
Section titled “Chemical Composition”The nominal chemical composition of D2 steel, expressed in mass percentage, is as follows:
| Element | Content (%) |
|---|---|
| Carbon (C) | 1,40 – 1,60 |
| Manganese (Mn) | 0,60 max. |
| Silicon (Si) | 0,60 max. |
| Chromium (Cr) | 11,00 – 13,00 |
| Molybdenum (Mo) | 0,70 – 1,20 |
| Vanadium (V) | 1,10 max. |
| Cobalt (Co) | 1,00 max. |
| Nickel (Ni) | 0,30 max. |
| Copper (Cu) | 0,25 max. |
| Phosphorus (P) | 0,03 max. |
| Sulfur (S) | 0,03 max. |
Mechanical Properties by Heat Treatment Condition
Section titled “Mechanical Properties by Heat Treatment Condition”The mechanical properties of D2 steel depend on the heat treatment cycle. The following table shows typical values after air quenching from 1010 °C (1850 °F) and tempering at 204 °C (400 °F), a condition that provides a Rockwell C hardness of 62.
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| Rockwell C Hardness | 62 HRC | 62 HRC |
| Vickers Hardness | 748 HV | 748 HV |
| Knoop Hardness (converted) | 769 HK | 769 HK |
| Izod impact strength, unnotched | 77,0 J | 56,8 ft·lb |
| Modulus of Elasticity | 190 – 210 GPa | 27 557 – 30 457 ksi |
| Poisson’s Ratio | 0,27 – 0,30 | 0,27 – 0,30 |
Physical Properties
Section titled “Physical Properties”D2 tool steel has a density of 7,7 × 10³ kg/m³ (0,278 lb/in³) and a melting point of 1421 °C (2590 °F). These properties, together with its low machinability in the annealed condition, define its behavior in service and during manufacturing.
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| Density | 7,7 × 10³ kg/m³ | 0,278 lb/in³ |
| Melting Point | 1421 °C | 2590 °F |
Thermal Properties
Section titled “Thermal Properties”The mean linear coefficient of thermal expansion of D2 steel is 10,4 × 10⁻⁶ /°C in the range 20 to 100 °C (5,78 × 10⁻⁶ /°F).
| Property | Conditions | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Coefficient of Thermal Expansion | 20 – 100 °C | 10,4 × 10⁻⁶ /°C | 5,78 × 10⁻⁶ /°F |
Heat Treatment and Fabrication
Section titled “Heat Treatment and Fabrication”The hardening of D2 steel is achieved by air quenching. To obtain maximum hardness and minimize distortion, the following parameters must be observed:
Forging Forging is performed in the range of 1065 °C to 954 °C (1950 °F to 1750 °F). Do not forge below 926 °C (1700 °F) to avoid cracking.
Annealing Annealing is carried out by heating to 871 – 898 °C (1600 – 1650 °F) followed by slow furnace cooling at a maximum rate of 4,4 °C/h (40 °F/h).
Quenching Preheat slowly to 815 °C (1500 °F), then raise the temperature to 1010 °C (1850 °F) and hold for 20 to 45 minutes before cooling in still air (air quenching).
Tempering Tempering can be performed at 204 °C (400 °F) to obtain a Rockwell C hardness of 61 – 62, or at 537 °C (1000 °F) to reach approximately 57 HRC, taking advantage of secondary hardening.
Applications by Industry
Section titled “Applications by Industry”D2 steel is used in components that require exceptional resistance to abrasive wear and good cold toughness. Its typical applications, grouped by industrial sector, include:
| Industry | Representative Applications |
|---|---|
| Automotive | Punches, stamping dies, cutting dies, cold rolling rolls. |
| Aerospace | Gages, precision tooling, shear blades for sheet metal. |
| Tool and Die Making | Cold extrusion dies, plastic injection molds, mold inserts. |
| Cutlery and Instruments | Industrial knives, cutting blades for paper and plastic, cutting discs. |
| Hand Tools | Coining dies, threading dies, taps. |
| Food and Packaging | Crusher blades, thin sheet cutting tools. |
Comparison with Similar Materials
Section titled “Comparison with Similar Materials”The following table compares D2 steel with other commonly used cold work steels, highlighting differences in quenching medium, typical maximum hardness, and wear resistance.
| Steel | Quenching Medium | Maximum Hardness (HRC) | Wear Resistance | Toughness |
|---|---|---|---|---|
| D2 | Air / pressurized gas | 62 | Very high (high chromium carbide fraction) | Medium |
| D3 | Oil | 63 | Very high (similar to D2, but more brittle) | Low |
| A2 | Air | 61 | High (chromium and molybdenum carbides) | Medium‑high |
| O1 | Oil | 62 | Medium‑high (tungsten and chromium) | Medium |
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the main difference between D2 and D3?
Section titled “What is the main difference between D2 and D3?”D2 steel contains molybdenum and is air-hardening, while D3 lacks molybdenum and requires oil quenching, making it more prone to distortion and brittleness.
Can D2 be oil quenched instead of air?
Section titled “Can D2 be oil quenched instead of air?”It is not recommended. D2 is designed for air quenching; using oil can increase the risk of cracking and distortion without significantly improving hardness.
What hardness does D2 achieve after tempering at 200 °C?
Section titled “What hardness does D2 achieve after tempering at 200 °C?”After tempering at 204 °C (400 °F), a Rockwell C hardness of 61 to 62 HRC is obtained, an optimal condition for maximum wear applications.
Is it possible to weld D2 steel?
Section titled “Is it possible to weld D2 steel?”Welding of D2 is difficult due to its high carbon and chromium content. Preheating to 300‑400 °C and using low-hydrogen electrodes is required, along with post-weld heat treatment to avoid cracking.
Is D2 suitable for hot work?
Section titled “Is D2 suitable for hot work?”It is not designed for hot work. Above 200 °C (390 °F), its hardness begins to decrease rapidly; therefore, H-group steels are recommended for hot work applications.
How does it compare to A2 steel?
Section titled “How does it compare to A2 steel?”D2 offers clearly superior wear resistance due to its higher chromium and carbon content, but A2 exhibits better toughness and machinability, making it preferred when impacts are frequent.
Sources Consulted
Section titled “Sources Consulted”- azom.com: https://www.azom.com/article.aspx?ArticleID=6214
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/engineering-materials-properties-d_1225.html
- steelnumber.com: https://www.steelnumber.com/en/equivalent_steel_iron_eu.php?zname_id=638