Steel SNC815-CH (Carburized and hardened)
Heat-treated state
JIS SNC815
Final service condition for gears and pinions: hard wear-resistant case over a tough, high-hardenability Ni-Cr core.
Values for the CH condition
Other SNC815 tempers and conditions
SNC815 is listed in 6 conditions; see the grade overview at SNC815.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stock condition: softest, most machinable state for gear blanking prior to carburizing. | 450 | 700 | 22 | 14 HRC | 34 W/m·K |
Hot rolled | Cheapest mill condition for large forging/machining blanks that will be normalized or annealed before carburizing. | 540 | 830 | 17 | 23 HRC | 33 W/m·K |
Normalized | Grain refinement and structure homogenisation of forgings before carburizing; also used to stabilise machining distortion. | 620 | 900 | 18 | 26 HRC | 33 W/m·K |
Cold drawn | Bright, close-tolerance small-diameter bar for shafts and pinions machined with minimal stock removal. | 690 | 830 | 12 | 23 HRC | 33 W/m·K |
Quenched and tempered | Direct-hardened condition (no carburizing) or the reference core property set used for JIS acceptance testing. | 930 | 1,150 | 14 | 37 HRC | — |
CHThis page Carburized and hardened | Final service condition for gears and pinions: hard wear-resistant case over a tough, high-hardenability Ni-Cr core. | 1,000 | 1,250 | 12 | 61 HRC | — |
What is SNC815-CH?
SNC815-CH is SNC815 heat treated to CH — final service condition for gears and pinions: hard wear-resistant case over a tough, high-hardenability Ni-Cr core. SNC815-CH has a yield strength of 1,000 MPa (145 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 92% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). SNC815-CH has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). A is the default condition FabDigit quotes; CH is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- High strength — 1,000 MPa (145 ksi), better than 92% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
SNC815-CH properties
Typical room-temperature values for SNC815-CH; 16 are specific to this condition. Other listed values are SNC815 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SNC815-CH has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical17
SNC815-CH has a yield strength of 1,000 MPa (145 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 92% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNC815-CH is rated for continuous service to 180°C (356 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SNC815-CH conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of SNC815-CH takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
SNC815-CH's machinability is not recommended (8/100, worse than 100% of steel grades); weldability not recommended (5/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SNC815-CH
Is SNC815 easy to machine?
Machine in the annealed/spheroidized state with sharp coated carbide, moderate speed and heavy flood coolant; the high-Ni matrix is gummy and work-hardens, so avoid dwelling and finish-grind after carburizing.
Can SNC815 be welded?
Poor weldability due to high hardenability — if unavoidable use low-hydrogen or matching Ni filler with 200–300 °C preheat and immediate post-weld temper; never weld carburized surfaces.
Can SNC815 be formed, bent or molded?
Hot forge at 1100–1200 °C and normalize afterwards; cold forming is limited to gentle bending of annealed bar.
What surface finishes work on SNC815?
Protect with oil, phosphate, black oxide or zinc plating; shot-peen carburized gear roots for fatigue life and bake after any electroplating to avoid hydrogen embrittlement.
SNC815 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.12 – 0.18 | 0.15 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.35 – 0.65 | 0.5 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Ni | 3 – 3.5 | 3.25 |
| Cr | 0.6 – 1 | 0.8 |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SNC815-CH — frequently asked
What is SNC815-CH used for?
SNC815-CH is typically used for heavy-duty gears, aircraft gearbox components, pinion and bull gears, highly loaded drive shafts, splined couplings and bearing races and rollers. In short: deep case, tough core; high-nickel carburizing steel; aerospace gear grade.
What is the yield strength of SNC815-CH?
SNC815-CH has a typical yield strength of 1,000 MPa (145 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 92% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is SNC815-CH easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine in the annealed/spheroidized state with sharp coated carbide, moderate speed and heavy flood coolant; the high-Ni matrix is gummy and work-hardens, so avoid dwelling and finish-grind after carburizing.
Can SNC815-CH be welded?
Not readily — weldability is rated not recommended (5/100). Poor weldability due to high hardenability — if unavoidable use low-hydrogen or matching Ni filler with 200–300 °C preheat and immediate post-weld temper; never weld carburized surfaces.
What surface finishes work on SNC815-CH?
Protect with oil, phosphate, black oxide or zinc plating; shot-peen carburized gear roots for fatigue life and bake after any electroplating to avoid hydrogen embrittlement.
Can SNC815-CH be formed, bent or molded?
Hot forge at 1100–1200 °C and normalize afterwards; cold forming is limited to gentle bending of annealed bar.
What is the maximum service temperature of SNC815-CH?
SNC815-CH is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SNC815-A and SNC815-CH?
A is the default condition — standard stock condition: softest, most machinable state for gear blanking prior to carburizing. CH: final service condition for gears and pinions: hard wear-resistant case over a tough, high-hardenability Ni-Cr core. Yield strength is 450 MPa in A versus 1,000 MPa in CH.
Sources
- JIS G 4053 — Low-alloyed structural steels (Ni-Cr case hardening steels) — JISC (2016)
- SAE J404 / ASTM A29 — Alloy steel bar chemical compositions (E3310) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
- MatWeb / JIS-equivalent alloy steel datasheets — MatWeb LLC (2024)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.