A2 vs A4
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.
A2
Tool Steel
A2 is an air-hardening 5% chromium cold work steel with much better toughness than D2 and far less distortion than oil-hardening grades. It is the default upgrade from O1 where die size or intricate shapes make quench cracking a risk.
Standards: DIN 1.2363 · AISI A2 · JIS SKD12 · GB Cr5Mo1V
A4
Tool Steel
A4 is an air-hardening medium-alloy cold work steel using high manganese plus about 1% chromium and molybdenum for deep hardening. It offers A2-like dimensional stability with simpler chemistry and lower cost.
Standards: AISI A4 · GB Cr5Mo1V (near)
Chemical composition compared (%)
| Element | A2 | A4 |
|---|---|---|
| C | 0.95–1.05 | 0.95–1.05 |
| Si | 0.10–0.50 | 0.10–0.50 |
| Mn | 0.40–1.00 | 1.80–2.20 |
| Cr | 4.75–5.50 | 0.90–1.20 |
| Mo | 0.90–1.40 | 0.90–1.40 |
| V | 0.15–0.50 | — |
Properties compared
| Property | A2 | A4 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 57–62 HRC | 56–61 HRC |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Toughness | Good for cold work | — |
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: A2 · A4. Substitution decisions for certified parts stay with the design authority.