JIS S10C is the lowest-carbon grade in the JIS G4051 machine structural steel series, with a carbon content of 0.08–0.13%. Its near-absence of carbon produces exceptional ductility, outstanding weldability, and excellent cold formability — properties that make it the preferred choice for deep-drawn shells, cold-headed fasteners, welded tubing, and lightly loaded structural parts. Hardening is not a practical option without carburizing. Internationally it matches AISI 1010 (USA) and aligns closely with DIN C10 (Germany).
- International Equivalent Grades
- Chemical Composition
- Mechanical Properties
- Physical Properties
- Heat Treatment Conditions
- Formability & Cold Working
- Weldability
- Common Mistakes
- When to Choose S10C
- FAQ
1. International Equivalent Grades
| Standard | Grade | Region | Match Type |
|---|---|---|---|
| JIS G4051 | S10C | Japan | Reference |
| ASTM / AISI | 1010 | USA | ✅ Exact Match |
| ISO 683-1 | C10 | International | ⚠️ Nearest Equivalent |
| DIN | C10 / 1.0301 | Germany | ⚠️ Nearest Equivalent |
| EN | C10E / 1.1121 | Europe | ⚠️ Nearest Equivalent |
2. Chemical Composition
| Element | JIS S10C | AISI 1010 | DIN C10 |
|---|---|---|---|
| C | 0.08–0.13% | 0.08–0.13% | 0.07–0.13% |
| Si | 0.15–0.35% | 0.10–0.35% | ≤ 0.40% |
| Mn | 0.30–0.60% | 0.30–0.60% | 0.30–0.60% |
| P | ≤ 0.030% | ≤ 0.040% | ≤ 0.035% |
| S | ≤ 0.035% | ≤ 0.050% | ≤ 0.035% |
Sources: JIS G4051:2016, ASTM A29/A29M, DIN EN 10083-2
3. Mechanical Properties
As-normalized (typical)
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| Tensile Strength | 310–390 MPa | 45.0–56.6 ksi |
| Yield Point | ≥ 205 MPa | ≥ 29.7 ksi |
| Elongation (GL=5d) | ≥ 30% | ≥ 30% |
| Reduction of Area | ≥ 60% | ≥ 60% |
| Hardness | 88–143 HB | 88–143 HB |
After carburizing + quench + temper (case surface)
| Property | Case (Surface) | Core |
|---|---|---|
| Hardness | HRC 58–62 | HRC 10–20 (very tough) |
| Effective case depth (HV550 basis) | 0.3–0.8 mm (0.012–0.031 in) | — |
4. Physical Properties
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| Density | 7.87 g/cm³ | 0.284 lb/in³ |
| Young’s Modulus | 207 GPa | 30,000 ksi |
| Thermal Conductivity | 52 W/(m·K) | 361 BTU·in/(hr·ft²·°F) |
| Thermal Expansion (20–100°C / 68–212°F) | 11.9 × 10⁻⁶ /°C | 6.6 × 10⁻⁶ /°F |
| Specific Heat | ~481 J/(kg·K) | 0.115 BTU/(lb·°F) |
5. Heat Treatment Conditions
| Process | Temperature | Cooling | Purpose |
|---|---|---|---|
| Normalizing | 890–930°C (1634–1706°F) | Air cool | Refine grain after forging/rolling |
| Annealing | 860–900°C (1580–1652°F) | Furnace cool | Soften for cold working |
| Gas Carburizing | 900–940°C (1652–1724°F) | Oil quench | Case hardening |
| Tempering (post-carburize) | 150–180°C (302–356°F) | Air cool | Relieve quench stress, maintain case hardness |
6. Formability & Cold Working
S10C is one of the most formable grades in JIS G4051. Its very low carbon content means minimal work hardening rate and high elongation, enabling severe forming operations without intermediate annealing.
- Deep drawing: Excellent — elongation ≥ 30% supports complex drawn shells and cups
- Cold heading: Outstanding — used for cold-headed bolts, rivets, and pins without cracking
- Bending: Can be bent to very tight radii (R = 0.5t or less in annealed condition)
- Cold extrusion: Suitable for forward and backward extrusion of simple shapes
- Work hardening: Lower rate than higher-carbon grades — fewer intermediate anneals needed in multi-stage forming
7. Weldability
S10C offers the best weldability of any JIS G4051 grade. Its carbon equivalent (Ceq ≈ 0.18–0.23) is well below any threshold for preheating or special precautions under normal conditions.
- Preheat: Not required for any section size under normal conditions
- Process: All standard processes (SMAW, GMAW, GTAW, SAW, resistance welding) without restriction
- Filler: ER70S-3 or ER70S-6 for GMAW; match or slightly overmatch strength
- Post-weld treatment: Rarely required; stress relief at 550–600°C (1022–1112°F) for highly restrained joints
8. Common Mistakes
S10C is a bar/rod grade under JIS G4051. Engineers specifying “low-carbon steel sheet for deep drawing” should reference SPCC (cold-rolled) or SPHC (hot-rolled) under JIS G3141/G3131, not S10C. These sheet grades have tighter surface quality and forming property controls suited to sheet metal applications.
S10C cannot be hardened by through-quenching. Engineers who need a hard surface must specify carburizing. Engineers who need bulk strength should select a higher-carbon grade or an alloy steel.
S10C is sometimes used for welded structural brackets. While it welds excellently, its tensile strength (310–390 MPa) is modest. For loaded structural applications, SS400 or SM400 (400+ MPa) typically offer better value with equivalent weldability.
9. When to Choose S10C
- ✅ Deep-drawn shells, cups, and housings requiring maximum ductility
- ✅ Cold-headed bolts, rivets, and pins where cold formability is critical
- ✅ Carburized thin-section parts (needle rollers, thin pins) where maximum core toughness matters more than core strength
- ✅ Welded assemblies requiring the simplest possible weld procedure (no preheat, no special consumables)
- ✅ Cold-extruded shapes where low work hardening rate is advantageous
- ❌ Structural applications requiring tensile strength > 400 MPa — use SS400 or higher grades
- ❌ Parts requiring surface hardness without carburizing — carbon content is too low
- ❌ Sheet and strip applications — specify SPCC or SPHC under the appropriate JIS sheet standard
10. FAQ
Q: Is S10C the same as AISI 1010?
Yes, for all practical purposes. Carbon and manganese ranges are identical. JIS G4051 applies tighter P and S limits (≤0.030% / ≤0.035%) compared to ASTM A29 (≤0.040% / ≤0.050%), making S10C marginally cleaner. The two grades are fully interchangeable in cold forming, welding, and carburizing applications.
Q: How does S10C differ from S15C for carburizing?
S10C produces the toughest core after carburizing — HRC 10–20 — making it ideal for thin-section parts where core fracture under impact is a concern. S15C (C: 0.13–0.18%) gives a slightly stronger core at the cost of marginal toughness reduction. For most carburizing applications, S15C or S20C are the standard choices; S10C is reserved for parts where maximum core ductility is specifically required.
Q: Can S10C be used for structural applications?
In lightly loaded applications, yes. Its normalized tensile strength of 310–390 MPa (45–57 ksi) is adequate for brackets, enclosures, and non-structural frames. For load-bearing structural members, specify SS400 or SM400, which offer guaranteed minimum tensile strength of 400 MPa with similar weldability.
Q: What is the effective case depth achievable on S10C?
Due to the very low core carbon, the concentration gradient from the carburized surface to the core is steep, which can limit the effective case depth achievable with standard cycle times. Typical effective case depth (to HV550) is 0.3–0.8 mm (0.012–0.031 in) for standard gas carburizing at 920°C (1688°F). For deeper cases, longer cycles or higher temperatures are needed, but this risks excessive grain growth in the core.
Q: Is S10C suitable for cold extrusion?
Yes. S10C is one of the preferred grades for cold extrusion due to its low work hardening rate and high ductility. It can be cold extruded in multiple stages with fewer intermediate anneals compared to higher-carbon grades. Ensure the material is in the fully annealed condition before the first extrusion stage.
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