D5 vs D4
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
D5
Tool Steel
D5 is the cobalt-bearing member of the D-family: essentially D2 chemistry plus about 3% cobalt. The cobalt lifts hot hardness and tempering resistance, suiting dies that run warm.
Standards: AISI D5
D4
Tool Steel
D4 is a deep-hardening high-carbon, high-chromium cold work steel with molybdenum and vanadium added to the D3 base chemistry. It keeps D3-class abrasion resistance while hardening through much thicker sections.
Standards: DIN — (X210CrMo12 family) · AISI D4 · JIS SKD2 (near) · GB Cr12Mo (near)
Chemical composition compared (%)
| Element | D5 | D4 |
|---|---|---|
| C | 1.40–1.60 | 2.10–2.35 |
| Si | 0.10–0.60 | 0.10–0.60 |
| Mn | 0.20–0.60 | 0.20–0.60 |
| Cr | 11.00–13.00 | 11.00–13.00 |
| Mo | 0.70–1.20 | 0.70–1.20 |
| V | 0.80–1.20 | 0.80–1.20 |
| Co | 2.50–3.50 | — |
Properties compared
| Property | D5 | D4 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 58–62 HRC | 58–63 HRC |
| Density | 7.80 g/cm³ | 7.70 g/cm³ |
| Hot hardness | Better than D2 | — |
| Wear resistance | — | Extreme |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: D5 · D4. Substitution decisions for certified parts stay with the design authority.