O1 / 100MnCrW4
1.2510Oil-hardening cold-work tool steel. Good balance of wear resistance, toughness, and machinability at moderate cost. Very predictable heat treatment response. The standard choice for hand tools, gauges, jigs, fixtures, taps, reamers, and general precision tooling.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | AISI O1 | T31501 | REF |
| 🇪🇺 | EN | Europe | 100MnCrW4 | 1.2510 | 100% |
| 🇯🇵 | JIS | Japan | SKS3 | — | 90% |
Sources: ASTM A681, EN ISO 4957, JIS G4404
Chemical composition comparison (wt%)
Side-by-side: O1 / 100MnCrW4 (EN) (EN ISO 4957) vs SKS3 (JIS)
| Element | O1 / 100MnCrW4 (EN) | SKS3 (JIS) | Overlap |
|---|---|---|---|
| C | 0.9–1.05% | — | — |
| Si | 0.1–0.4% | — | — |
| Mn | 1–1.2% | — | — |
| Cr | 0.5–0.7% | — | — |
| V | 0.05–0.15% | — | — |
| W | 0.5–0.7% | — | — |
Mechanical properties
Hardened Tempered
| Property | Value | Unit |
|---|---|---|
| Hardness HRC | 57–62 | HRC |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.83 | g/cm3 |
Annealed
| Property | Value | Unit |
|---|---|---|
| Hardness HB | ≤ 225 | HB |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 780–820 °C | oil | 15-30 min | OIL hardening — the defining feature. Low distortion. |
| tempering | 180–300 °C | air | 1 hour x2 | Double temper recommended. 200°C for max hardness. |
| annealing | 740–780 °C | furnace | 2-4 hours | Slow furnace cool ≤20°C/hour to 600°C |
Compatibility verdict
O1 / 100MnCrW4 and SKS3: 90% composition match
Close equivalents but NOT identical.
Related materials
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1.2311Pre-hardened plastic mold steel (usually delivered at 28-34 HRC). The most widely used mold base steel globally. Good machinability in pre-hardened condition, good polishability. Used for injection molds, die-casting dies, extrusion tooling, and structural mold components.
M2 / HS6-5-2
1.3343The most widely used high-speed steel worldwide. W-Mo-Cr-V composition gives excellent red hardness (cuts at temperatures up to 600°C). Used for twist drills, end mills, taps, reamers, bandsaw blades, and general-purpose cutting tools. The benchmark HSS grade.
X45NiCrMo4
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