D2
1.2379 / X153CrMoV12 · EN ISO 4957 · 1.2379
D2 (1.2379 / X153CrMoV12) is a tool steel (High-Chromium Cold Work family) to EN ISO 4957 (1.2379). Supplied hardened in service; for analysis treat it as elastic (E = 210 GPa) with a hardness- or fracture-based limit. It is formulated for hardness, wear resistance and dimensional stability in tooling.
Bilinear material model — nonlinear FEA
This grade is supplied hardened in service and is not represented as a bilinear material — it has a negligible uniform-plastic range. Model it as elastic (E = 210 GPa) with an appropriate fracture / hardness-based limit.
Ratings — engineering judgement
Weldabilitypoor
Essentially not weldable in service — very high carbon and chromium crack readily; any repair needs matched consumables, high preheat and immediate temper by a specialist.
Formabilitypoor
Not a forming material; shaped by machining/grinding in the annealed state, then hardened.
Machinabilitypoor
Machine in the annealed condition; the high carbide content is abrasive on tooling, and finishing is done by grinding after hardening.
Corrosion resistancemoderate
~12 % chromium gives mild (“semi-stainless”) corrosion and staining resistance — better than plain tool steels, well short of true stainless.
Hardenabilityexcellent
Air-hardening (hardens on still-air cooling), giving high hardness with minimal distortion — a key reason it is favoured for accurate tooling.
Toughnesslow
Low toughness — the hard chromium carbides that give wear resistance also make it chip rather than bend. Not for shock/impact tooling (use A2 or S7 there).
Expert notes
D2 is the default cold-work tool steel — the one specified for blanking and forming dies, punches, shear blades and thread-rolling tools that have to keep an edge over long production runs. Its high carbon and ~12 % chromium form a dense field of hard carbides that give outstanding abrasive-wear resistance and good compressive strength.
It air-hardens, which is a big practical advantage: hardening on still-air cooling gives ~58–62 HRC with little distortion, so accurate tools hold size through heat treatment. The ~12 % chromium also makes it “semi-stainless” — it resists staining and light corrosion far better than plain tool steels, though it is not a true stainless.
The trade-off is toughness. Those same carbides make D2 chip and crack rather than bend — it does not like shock or interrupted impact. For impact tooling step across to A2 (tougher cold-work) or S7 (shock-resisting). It is also hard to grind and effectively unweldable once in service.
Because it is used fully hardened with negligible uniform plasticity, there is no meaningful bilinear model — treat it as elastic (E ≈ 210 GPa) up to a hardness- or fracture-based limit, not a yield-and-hardening curve.
Physical properties
| Density | 7700 | kg/m³ |
| Elastic modulus | 210 | GPa |
| Shear modulus | 81 | GPa |
| Poisson's ratio | 0.30 | |
| Thermal expansion | 10.5 | ×10⁻⁶/°C |
| Thermal conductivity | 20 | W/(m·K) |
| Specific heat | 460 | J/(kg·K) |
| Magnetic | Yes |
Chemical composition (wt %)
Available forms
Equivalent grades
| Standard | Grade | Note |
|---|---|---|
| EN ISO 4957 | X153CrMoV12 / 1.2379 | |
| AISI | D2 | |
| JIS | SKD11 | |
| BS 4659 | BD2 |
Historical designations
| Standard | Grade | Note |
|---|---|---|
| BS 4659 | BD2 | British tool-steel designation. |
| Werkstoff Nr. | 1.2379 | German material number — very widely used name. |
Common applications
- Blanking, piercing and forming dies
- Punches and shear blades
- Thread-rolling dies
- Industrial knives and slitters
- Gauges and wear parts
History
D2 is the classic high-carbon high-chromium cold-work tool steel, developed in the early 20th century for long-run dies and the mainstay of cold-work tooling ever since.
- 1920High-carbon high-chromium die steels developed for long-run blanking
- 1950AISI D2 established as the standard cold-work die steel