55NiCrMoV7
1.2714Nickel-chromium-molybdenum-vanadium hot work tool steel with outstanding toughness. 1.7% Ni provides superior shock resistance and toughness at working temperatures. Hardened to 44–50 HRC. Used where maximum impact resistance is needed: hammer dies, forging dies, drop forge inserts, hot shear blades, plastic mold base plates and large press tools. The standard material for heavy forging dies in the automotive and aerospace forging industry.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | L6 | T61206 | REF |
| 🇯🇵 | JIS | Japan | SKT4 | — | 85% |
Sources: ASTM A681, JIS G4404
Chemical composition comparison (wt%)
Side-by-side: 55NiCrMoV7 (EN) (EN ISO 4957) vs SKT4 (JIS)
| Element | 55NiCrMoV7 (EN) | SKT4 (JIS) | Overlap |
|---|---|---|---|
| C | 0.5–0.6% | — | — |
| Si | 0.1–0.4% | — | — |
| Mn | 0.6–0.9% | — | — |
| Cr | 0.8–1.2% | — | — |
| Mo | 0.35–0.55% | — | — |
| Ni | 1.5–1.8% | — | — |
| V | 0.05–0.15% | — | — |
Mechanical properties
Annealed
| Property | Value | Unit |
|---|---|---|
| Hardness HB | ≤ 248 | HB |
Hardened + Tempered
| Property | Value | Unit |
|---|---|---|
| Hardness HRC | 44–50 | HRC |
| Tensile Strength | 1400–1700 | MPa |
General
| Property | Value | Unit |
|---|---|---|
| Density | 7.85 | g/cm³ |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| Soft annealing | 650–700 °C | Furnace cooling | — | Cool 20°C/h, max 248 HB |
| Hardening | 840–880 °C | Oil/Air | — | Preheat 400-500°C, oil quench for large sections |
| Tempering | 400–600 °C | Air | — | Double temper, 400°C→50 HRC, 550°C→44 HRC |
Compatibility verdict
55NiCrMoV7 and SKT4: 85% composition match
Close equivalents but NOT identical.
Related materials
P20 / 40CrMnMo7
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
1.2767Nickel cold-work tool steel with exceptional toughness from ~4% Ni content. Excellent through-hardenability, polishability, and impact resistance. Used for plastic injection molds (high-gloss), embossing dies, scrap shear blades, punches, cutlery dies, and bending tools.
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