Steel SNCM420
JIS SNCM420
SNCM420 is a high-alloy nickel-chromium-molybdenum case-hardening steel (JIS G 4103) comparable to SAE 9310 and overlapping 8620 practice, used where deep case depth and high core toughness are both required.
Reference datasheet — SNCM420 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
SNCM420 tempers and conditions
SNCM420 is supplied in 8 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard as-supplied bar condition: softest state for gear cutting, hobbing and deep machining before carburizing. | 455 | 700 | 22 | 197 HB | — |
Normalized | Use to homogenize forgings and refine grain before carburizing; better chip control than annealed. | 560 | 830 | 18 | 235 HB | — |
Hot rolled | Cheapest mill condition for rough-turned blanks that will be normalized or annealed by the gear shop. | 570 | 870 | 16 | 24 HRC | 7.5 % IACS |
Cold drawn | Pick for small-diameter shafts and pins needing tight tolerance and good surface straight off the bar. | 660 | 820 | 12 | 22 HRC | 7.5 % IACS |
Quenched and tempered | Through-hardened condition used for the JIS acceptance test and for uncarburized shafts requiring ≥980 MPa. | 900 | 1,080 | 17 | 34 HRC | — |
Deep carburized (>1.5 mm case) + double quench & temper | For large module wind-turbine and marine gears needing deep case depth and refined grain from a second quench. | 980 | 1,230 | 13 | 60 HRC | 7 % IACS |
Carburized, hardened & tempered | Standard gear condition: 0.6–1.5 mm effective case at 58–62 HRC over a 30–40 HRC tough core; grind after treatment. | 1,000 | 1,250 | 12 | 60 HRC | — |
Aircraft quality | Choose for aerospace transmission gears and bearings where AMS-class inclusion cleanliness and maximum bending fatigue life are required. | 1,030 | 1,280 | 15 | 60 HRC | 7 % IACS |
What is SNCM420?
SNCM420 is a high-alloy nickel-chromium-molybdenum case-hardening steel (JIS G 4103) comparable to SAE 9310 and overlapping 8620 practice, used where deep case depth and high core toughness are both required. It is the standard choice for heavily loaded aerospace and industrial gearing and is available annealed, normalized, hot-rolled, cold-drawn, Q&T, carburized to 58–62 HRC, deep-case carburized and in air-melt/VAR quality. Default values are 455 MPa yield, 700 MPa tensile, 22 % elongation, 197 HB (92 HRB), machinability 60, weldability 40 and formability 50. Welding is restricted to the uncarburized condition and the steel offers no corrosion resistance on its own. SNCM420 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). SNCM420 has a yield strength of 455 MPa (66 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 54% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
What is SNCM420 used for?
- Aircraft gears
- High-load gearbox gears and pinions
- Helicopter transmission components
- Racing and motorsport gearsets
- Heavy-duty drive shafts
- Bearing races
- Planetary carriers and ring gears
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
SNCM420 properties
Typical room-temperature values for SNCM420-A; bars are the position among steel grades.
Physical3
SNCM420 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).
Mechanical16
SNCM420 has a yield strength of 455 MPa (66 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 54% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNCM420 is rated for continuous service to 250°C (482 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
SNCM420 conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of SNCM420 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
SNCM420's machinability is good (60/100, better than 83% of steel grades); weldability fair (40/100); formability fair (50/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. SNCM420 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SNCM420
Is SNCM420 easy to machine?
Cut gear teeth and finish all features in the annealed/normalized state (~60 % of 1212); after carburizing only grinding, honing or hard-turning with CBN is practical.
Can SNCM420 be welded?
Weldable only before carburizing with low-hydrogen consumables, 200–300 °C preheat and immediate stress relief/temper; welding carburized surfaces is not permitted.
Can SNCM420 be formed, bent or molded?
Hot forge at 1150–1200 °C down to ~900 °C then normalize; cold heading and light cold forming are possible in the spheroidize-annealed condition.
SNCM420 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 | 0.17 – 0.23 | 0.2 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.4 – 0.7 | 0.55 |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Ni | 1.6 – 2 | 1.8 |
| Cr | 0.4 – 0.65 | 0.5 |
| Mo | 0.15 – 0.3 | 0.22 |
| Curesidual, max | ≤ 0.3 | |
| Fe | balance |
What surface finishes work on SNCM420?
Grind after case hardening to remove distortion and any high-carbon surface layer; protect with black oxide, manganese phosphate, zinc or hard chrome — avoid processes that risk hydrogen embrittlement, or bake within 4 h at 190 °C.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel SNCM420 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does SNCM420 cost?
SNCM420 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
SNCM420 — frequently asked
What is SNCM420 used for?
SNCM420 is typically used for aircraft gears, high-load gearbox gears and pinions, helicopter transmission components, racing and motorsport gearsets, heavy-duty drive shafts and bearing races. In short: SAE 9310 gear equivalent; deep case, high core toughness; aerospace VAR quality available.
What is the yield strength of SNCM420?
SNCM420 has a typical yield strength of 455 MPa (66 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 54% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SNCM420 easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Cut gear teeth and finish all features in the annealed/normalized state (~60 % of 1212); after carburizing only grinding, honing or hard-turning with CBN is practical.
Can SNCM420 be welded?
With care — weldability is rated fair (40/100). Weldable only before carburizing with low-hydrogen consumables, 200–300 °C preheat and immediate stress relief/temper; welding carburized surfaces is not permitted.
What surface finishes work on SNCM420?
Grind after case hardening to remove distortion and any high-carbon surface layer; protect with black oxide, manganese phosphate, zinc or hard chrome — avoid processes that risk hydrogen embrittlement, or bake within 4 h at 190 °C.
Can SNCM420 be formed, bent or molded?
Hot forge at 1150–1200 °C down to ~900 °C then normalize; cold heading and light cold forming are possible in the spheroidize-annealed condition.
What is the maximum service temperature of SNCM420?
SNCM420 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SNCM420-A and SNCM420 AQ-VAR?
A is the default condition — standard as-supplied bar condition: softest state for gear cutting, hobbing and deep machining before carburizing. AQ-VAR: choose for aerospace transmission gears and bearings where AMS-class inclusion cleanliness and maximum bending fatigue life are required. Yield strength is 455 MPa in A versus 1,030 MPa in AQ-VAR.
How much does SNCM420 cost?
SNCM420 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- JIS G 4053 — Low-alloyed structural steels for machine structural use — JSA (2016)
- SAE J404 — Chemical Compositions of SAE Alloy Steels (4320/8620/9310) — SAE International (2020)
- AMS 6265 — Steel Bars, Forgings, Tubing 3.2Ni-1.2Cr-0.12Mo, premium aircraft quality — SAE International (2019)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4A/4D — Steel Heat Treating and Carburizing — ASM International (2013)
- GB/T 3077 — Alloy structural steels (20CrNi2Mo comparison) — SAC (2015)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.