SNC415 (JIS G4102) is a nickel-chromium carburizing steel designed for moderate-section gears and shafts. Without molybdenum, it offers a cost-effective alternative to SNCM grades for sections up to 35 mm (1.4 in), delivering excellent case hardness and adequate core toughness at lower material cost.
- International Equivalent Grades
- Chemical Composition
- Mechanical Properties
- Physical Properties
- Heat Treatment Conditions
- Machinability
- Weldability
- Common Mistakes
- When to Choose SNC415
- FAQ
1. International Equivalent Grades
| Standard | Grade | Region | Match Type |
|---|---|---|---|
| JIS G4102 | SNC415 | Japan | Reference |
| ASTM A29/A29M | AISI 3415 | USA | ⚠️ Nearest Equivalent — higher Ni (3.25–3.75%) |
| DIN EN 10084 | 14NiCr10 / 1.5732 | Germany / EU | ✅ Nearest Exact |
| EN 10084 | 14NiCr10 / 1.5762 | Europe | ✅ Nearest Exact |
2. Chemical Composition
| Element | JIS SNC415 | AISI 3415 | DIN 14NiCr10 |
|---|---|---|---|
| C | 0.12–0.18% | 0.10–0.20% | 0.10–0.17% |
| Si | 0.15–0.35% | 0.15–0.35% | ≤ 0.40% |
| Mn | 0.35–0.65% | 0.40–0.60% | 0.40–0.70% |
| P | ≤ 0.030% | ≤ 0.035% | ≤ 0.025% |
| S | ≤ 0.030% | ≤ 0.040% | ≤ 0.035% |
| Ni | 2.00–2.50% | 3.25–3.75% | 2.00–2.50% |
| Cr | 0.60–1.00% | 0.45–0.75% | 0.50–0.80% |
Sources: JIS G4102:2016, ASTM A29/A29M, DIN EN 10084
3. Mechanical Properties
Core Properties — After Carburizing + Quench + Low Temper (Section ≤ 30 mm / 1.2 in)
| Property | Metric | Imperial |
|---|---|---|
| Core tensile strength | 880–1080 MPa | 128–157 ksi |
| Core yield strength | ≥ 685 MPa | ≥ 99.3 ksi |
| Core elongation | ≥ 15% | ≥ 15% |
| Core Charpy impact | ≥ 88 J | ≥ 65 ft·lbf |
| Core hardness | HRC 30–40 | HRC 30–40 |
Case Properties
| Property | Value |
|---|---|
| Surface hardness | HRC 58–64 |
| Effective case depth | 0.5–2.0 mm (0.020–0.079 in) |
4. Physical Properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.85 g/cm³ | 0.284 lb/in³ |
| Young’s modulus | 206 GPa | 29,900 ksi |
| Thermal conductivity | 39 W/(m·K) | 270 BTU·in/(hr·ft²·°F) |
| Thermal expansion (20–100°C) | 11.3 × 10⁻⁶ /°C | 6.3 × 10⁻⁶ /°F |
| Specific heat | ~477 J/(kg·K) | 0.114 BTU/(lb·°F) |
5. Heat Treatment Conditions
| Process | Temperature | Cooling | Purpose |
|---|---|---|---|
| Normalizing | 850–900°C (1562–1652°F) | Air cool | Homogenize microstructure before machining |
| Carburizing | 900–950°C (1652–1742°F) | Oil quench | Enrich surface to 0.7–0.9% C |
| Case hardening quench | 800–840°C (1472–1544°F) | Oil quench | Austenitize and harden case |
| Low tempering | 150–200°C (302–392°F) | Air cool | Relieve quench stress, retain HRC 58–64 |
6. Machinability
- Machinability rating approximately 62% relative to AISI 1212 (free-machining baseline).
- High Ni content reduces work hardening tendency compared to plain carbon steels, enabling consistent surface finish.
- Carbide tooling is preferred; high-speed steel tools are acceptable for roughing in normalized condition.
- Cutting speed: moderate (70–100 m/min / 230–330 ft/min) with coated carbide inserts.
- Perform all critical machining before carburizing — case-hardened surfaces are essentially unmachineable except by grinding.
7. Weldability
- Rating: Restricted — not recommended for welded assemblies after carburizing.
- Preheat: 125–175°C (257–347°F) minimum for sections above 12 mm (0.5 in).
- Process: GMAW or SMAW with low-hydrogen consumables (e.g., E8018-C1 or equivalent Ni-bearing electrode).
- Post-weld heat treatment: Stress relief at 550–620°C (1022–1148°F) if welding is unavoidable; then re-normalize if required.
- Critical rule: Always complete all welding operations before carburizing. Welding a carburized part will destroy the case and introduces severe distortion and cracking risk.
- High Ni content raises sensitivity to heat-affected zone (HAZ) cracking. Weld joint design should minimize restraint.
8. Common Mistakes
Without molybdenum, SNC415’s hardenability drops faster with increasing section size than SNCM grades. For sections beyond 40 mm (1.6 in), the oil-quench cooling rate at the core may be insufficient to achieve the minimum core hardness. Core hardness can fall below HRC 25 at sections over 50 mm (2.0 in), compromising fatigue and bending strength. For sections above 35 mm, verify the Jominy hardenability curve and consider upgrading to SNCM220 or SNCM415.
AISI 3415 contains significantly higher Ni (3.25–3.75%) versus SNC415 (2.00–2.50%). This gap is not trivial — it produces meaningfully different hardenability and heat treatment response. Engineers who substitute AISI 3415 assuming it is a conservative upgrade may find different distortion behavior during carburizing and potentially different core properties after quench. Always verify the Ni content on mill certificates when sourcing from North American suppliers and adjusting heat treatment parameters accordingly.
9. When to Choose SNC415
✅ Choose SNC415 when:
- ✅ Medium-duty carburized gears and shafts with section ≤ 35 mm (1.4 in)
- ✅ Applications where DIN 14NiCr10 / 1.5732 sourcing is preferred for European supply chains
- ✅ Cost is a design driver and molybdenum addition is not required for the section size
- ✅ Gear pins, camshafts, and intermediate shafts in agricultural machinery
- ✅ Direct replacement for 14NiCr10 parts in Japanese production
❌ Avoid SNC415 when:
- ❌ Sections exceed 50 mm (2.0 in) — specify SNCM415 or SNCM815 for better hardenability
- ❌ Through-hardening is required — use SNC836 (higher C) or SNCM439
- ❌ Induction hardening is planned — C content (0.12–0.18%) is too low for effective induction response
10. FAQ
Q: What is the difference between SNC415 and SNCM415?
SNCM415 adds molybdenum (0.15–0.30%) to the Ni-Cr base and has slightly lower Ni (1.60–2.00%) compared to SNC415 (2.00–2.50%). Molybdenum dramatically improves hardenability for large sections by suppressing bainite transformation during oil quench. For sections ≤ 25 mm (1.0 in), both grades achieve similar case and core properties. For sections in the 30–80 mm (1.2–3.1 in) range, SNCM415 with Mo provides better core hardness uniformity. Choose SNC415 when Mo is unnecessary for your section size and cost matters.
Q: Is DIN 14NiCr10 widely available in Europe?
Yes. 14NiCr10 (material number 1.5732) is a standard carburizing grade in European specialty steel supply chains and is well-documented in DIN EN 10084. It is the closest compositional match to SNC415 in Ni (2.00–2.50%) and Cr (0.50–0.80%) ranges and is commonly specified for automotive and industrial gearing in Germany, Italy, and France. European mills offering 16MnCr5 typically also stock 14NiCr10 in bar form.
Q: Can SNC415 be used for induction hardening instead of carburizing?
Not effectively. The carbon content of SNC415 (0.12–0.18%) is too low for a meaningful induction hardening response. The maximum achievable surface hardness after induction hardening would be approximately HRC 35–45 — insufficient for most wear and contact fatigue applications. For induction hardening, specify SNC836 (higher C content for surface response) or SCr440 (medium-carbon Cr steel). SNC415 is purpose-designed for gas or vacuum carburizing, where external carbon is diffused into the surface to achieve HRC 58–64.
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