T1 vs T4
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.
T1
Tool Steel
T1 is the original 18-4-1 tungsten high-speed steel from which the whole HSS family descends. It remains in use for lathe tools and cutters in shops worldwide, and as China’s W18Cr4V and Japan’s SKH2.
Standards: DIN 1.3355 · AISI T1 · JIS SKH2 · GB W18Cr4V
T4
Tool Steel
T4 adds about 5% cobalt to the T1 base for extra red hardness in heavy cuts and roughing work. It is a legacy grade, largely replaced by M35/M42 in new tooling but still specified on older drawings.
Standards: DIN — (HS18-0-1-5 family) · AISI T4 · JIS SKH3 (near) · GB W18Cr4VCo5 (near)
Chemical composition compared (%)
| Element | T1 | T4 |
|---|---|---|
| C | 0.65–0.80 | 0.70–0.80 |
| Si | ≤0.40 | ≤0.40 |
| Mn | ≤0.40 | ≤0.40 |
| Cr | 3.75–4.50 | 3.75–4.50 |
| W | 17.25–18.75 | 17.25–18.75 |
| V | 0.90–1.30 | 0.80–1.20 |
| Co | — | 4.25–5.75 |
Properties compared
| Property | T1 | T4 |
|---|---|---|
| Delivery condition | Annealed | Annealed |
| Hardness (hardened) | 62–65 HRC | 63–66 HRC |
| Density | 8.60 g/cm³ | 8.60 g/cm³ |
| Red hardness | The original 18-4-1 benchmark | Higher than T1 (cobalt) |
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: T1 · T4. Substitution decisions for certified parts stay with the design authority.