SKS3 Cold Work Die Steel
JIS SKS3 · AISI O1 (approximate) · DIN 90MnCrV8 (1.2842, approximate)
SKS3 is a JIS-classified (G4404) oil-hardening cold work tool steel widely used in Japanese toolmaking traditions. Compared to high-chromium grades like SKD11/D2, SKS3 occupies the middle ground: it offers better toughness and easier machinability than D2, while delivering significantly higher hardness and wear resistance than plain carbon tool steels.
Material Properties
SKS3 achieves hardness of 60–63 HRC in the fully hardened condition, with better impact toughness than SKD11 at equivalent hardness levels. The steel's moderate alloy content means it is responsive to tempering: hardness can be adjusted from 58–63 HRC to suit the required balance between hardness and toughness. Machinability in the annealed condition (≤217 HB) is good. The oil quench provides more uniform cooling than water, reducing distortion and cracking risk — particularly important for complex punch and die profiles.
The alloy additions of chromium, tungsten, and manganese in SKS3 provide improved hardenability, allowing section sizes up to 50–75 mm to achieve through-hardening in oil quench without the distortion associated with water quenching. The tungsten addition contributes to fine carbide formation, improving edge retention in cutting and blanking applications.
SKS3 is particularly popular in jig and gauge manufacture, precision cold punching, and fine cutting tools where a balance of wear resistance, toughness, and dimensional stability is required. Its oil-hardening characteristic makes it more forgiving in heat treatment than air-hardening grades, which is valued in small job shops and toolrooms.
Chemical Composition (%)
| Element | Content (%) |
|---|---|
| C | 0.90 – 1.00 |
| Si | ≤ 0.35 |
| Mn | 0.90 – 1.20 |
| Cr | 0.50 – 1.00 |
| W | 0.50 – 1.00 |
| V | 0.10 – 0.25 |
| P | ≤ 0.030 |
| S | ≤ 0.030 |
Mechanical Properties
| Property | Value |
|---|---|
| Hardness (Annealed) | ≤ 217 HB |
| Hardness (After Hardening) | 60 – 63 HRC |
| Toughness (relative) | Good (higher than SKD11) |
| Density | ~7.85 g/cm³ |
Heat Treatment
Annealing
Heat to 780–820°C, hold 2–4 hours, furnace cool slowly to ≤500°C, then air cool. Target: ≤217 HB.
Hardening
Austenitise at 800–840°C (typically 820°C), soak 20–40 min depending on section. Quench in warm oil (40–60°C).
Tempering
Temper immediately after quench at 150–180°C for maximum hardness (60–63 HRC) or 180–220°C for improved toughness (57–61 HRC). Hold 1–2 hrs.
Typical Applications
Frequently Asked Questions
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Cold Work Die Steel
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