A8 vs H42
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.
A8
Tool Steel
A8 is an air-hardening 5% chromium cold work steel with tungsten and molybdenum, positioned between A2 and the hot work family. Its secondary-hardening response suits cold work tools that run warm, such as extrusion backers and warm-heading dies.
Standards: AISI A8
H42
Tool Steel
H42 is chemically a molybdenum high-speed steel (close to the M2 family) that ASTM classes with the hot work steels because of its high working hardness and hot strength. It is used for hot punches and extrusion tools needing near-HSS edge retention.
Standards: AISI H42
Chemical composition compared (%)
| Element | A8 | H42 |
|---|---|---|
| C | 0.50–0.60 | 0.55–0.70 |
| Si | 0.75–1.10 | ≤0.45 |
| Mn | 0.20–0.50 | ≤0.40 |
| Cr | 4.75–5.25 | 3.75–4.50 |
| Mo | 1.15–1.65 | 4.50–5.50 |
| W | 2.00–2.50 | 5.75–6.75 |
| V | — | 1.75–2.25 |
Properties compared
| Property | A8 | H42 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 52–58 HRC | — |
| Density | 7.85 g/cm³ | 8.10 g/cm³ |
| Working hardness | — | 48–58 HRC |
| Class note | — | Molybdenum high-speed composition classed as hot 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: A8 · H42. Substitution decisions for certified parts stay with the design authority.