Steel 20Cr2Ni4 CARB
Heat-treated state
CARB = carburized, hardened and low tempered
The service condition for gears: gas-carburize 920–930 °C, double quench (or direct quench + sub-zero), temper 160–200 °C for maximum contact and bending fatigue strength.
Values for the CARB condition
Other 20Cr2Ni4 tempers and conditions
20Cr2Ni4 is listed in 7 conditions; see the grade overview at 20Cr2Ni4.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard stock condition for bar and forgings: soft enough to rough-machine gear blanks before carburizing. | 680 | 880 | 16 | 22 HRC | — |
Normalized and tempered | Normalize ~890 °C then temper 630–670 °C to break up the air-hardened structure and stabilise machining before carburizing. | 750 | 950 | 15 | 26 HRC | — |
Hot rolled | Cheapest mill condition; this steel air-hardens, so hot-rolled bar is hard and must be softened before machining. | 800 | 1,100 | 12 | 34 HRC | 6.6 % IACS |
Cold drawn | Small-diameter bright bar for shafts and pins where a close-tolerance blank is wanted before case hardening. | 800 | 950 | 11 | 28 HRC | 6.6 % IACS |
quenched and tempered to a machinable core hardness | Tempered high (≈550–600 °C) for large shafts, gear blanks and nitriding bases needing toughness plus good machinability. | 860 | 1,000 | 16 | 32 HRC | — |
CARBThis page Carburized, hardened and low tempered | The service condition for gears: gas-carburize 920–930 °C, double quench (or direct quench + sub-zero), temper 160–200 °C for maximum contact and bending fatigue strength. | 1,080 | 1,250 | 11 | 61 HRC | — |
Double quenched (880 °C + 780 °C oil) and tempered 200 °C | The standard's property-qualification condition; also used for through-hardened high-strength shafts and fasteners. | 1,130 | 1,250 | 12 | 40 HRC | — |
What is 20Cr2Ni4 CARB?
20Cr2Ni4 CARB is 20Cr2Ni4 heat treated to CARB — the service condition for gears: gas-carburize 920–930 °C, double quench (or direct quench + sub-zero), temper 160–200 °C for maximum contact and bending fatigue strength. 20Cr2Ni4 CARB has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi). 20Cr2Ni4 CARB 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; CARB is available on request or by drawing note.
Advantages
- High strength — 1,080 MPa (157 ksi), better than 93% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 8/100, worse than 100% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- High embodied carbon — 2.7 kg CO₂/kg, worse than 89% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
20Cr2Ni4 CARB properties
Typical room-temperature values for 20Cr2Ni4 CARB; 13 are specific to this condition. Other listed values are 20Cr2Ni4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20Cr2Ni4 CARB 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).
Mechanical14
20Cr2Ni4 CARB has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
20Cr2Ni4 CARB is rated for continuous service to 150°C (302 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical2
20Cr2Ni4 CARB has an electrical resistivity of 2.6×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 20Cr2Ni4 CARB takes about 36 MJ of energy and emits 2.7 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 30%.
Manufacturability7
20Cr2Ni4 CARB's machinability is not recommended (8/100, worse than 100% of steel grades); weldability poor (30/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Cr2Ni4 CARB
Is 20Cr2Ni4 easy to machine?
Machine only after normalize + high temper or full anneal (≤269 HB); the high-Ni matrix work-hardens and smears, so use rigid setups, positive-rake coated carbide, moderate speed and heavy coolant, and leave 0.2–0.4 mm grinding stock for post-carburizing distortion.
Can 20Cr2Ni4 be welded?
Low carbon makes it weldable but the alloy is air-hardening: preheat 200–300 °C, use low-hydrogen consumables, keep interpass heat, and stress-relieve/temper afterwards; never weld carburized or hardened parts.
Can 20Cr2Ni4 be formed, bent or molded?
Forge at 1150–1200 °C down to about 850 °C followed by controlled slow cooling plus anneal; cold forming is limited to light straightening and thread rolling in the softened condition.
What surface finishes work on 20Cr2Ni4?
Case-hardened surfaces are finish-ground and optionally shot-peened or superfinished for fatigue life; unhardened areas need phosphate, black oxide, Zn/Ni plating or oil since the steel has no corrosion resistance (bake after plating to avoid hydrogen embrittlement).
20Cr2Ni4 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 | 0.17 – 0.37 | 0.27 |
| Mn | 0.3 – 0.6 | 0.45 |
| Cr | 1.25 – 1.65 | 1.45 |
| Ni | 3.25 – 3.75 | 3.5 |
| P≤0.025 for high-quality 'A' grade (20Cr2Ni4A) | ≤ 0.03 | — |
| S≤0.025 for high-quality 'A' grade | ≤ 0.03 | — |
| Curesidual | ≤ 0.25 | — |
| Moresidual only; SAE 9310 by contrast specifies 0.08–0.15 Mo | ≤ 0.15 | — |
| Fe | balance | — |
20Cr2Ni4 CARB — frequently asked
What is 20Cr2Ni4 CARB used for?
20Cr2Ni4 CARB is typically used for aircraft transmission gears, helicopter and rotorcraft gearbox gears, heavy-duty industrial gearboxes, accessory drive gears, high-load pinions and ring gears and marine reduction gears. In short: 9310-class aerospace gear steel; deepest hardenability, highest cost; toughest core in family.
What is the yield strength of 20Cr2Ni4 CARB?
20Cr2Ni4 CARB has a typical yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20Cr2Ni4 CARB easy to machine?
Not especially — machinability is rated not recommended (8/100, worse than 100% of steel grades). Machine only after normalize + high temper or full anneal (≤269 HB); the high-Ni matrix work-hardens and smears, so use rigid setups, positive-rake coated carbide, moderate speed and heavy coolant, and leave 0.2–0.4 mm grinding stock for post-carburizing distortion.
Can 20Cr2Ni4 CARB be welded?
Not readily — weldability is rated poor (30/100). Low carbon makes it weldable but the alloy is air-hardening: preheat 200–300 °C, use low-hydrogen consumables, keep interpass heat, and stress-relieve/temper afterwards; never weld carburized or hardened parts.
What surface finishes work on 20Cr2Ni4 CARB?
Case-hardened surfaces are finish-ground and optionally shot-peened or superfinished for fatigue life; unhardened areas need phosphate, black oxide, Zn/Ni plating or oil since the steel has no corrosion resistance (bake after plating to avoid hydrogen embrittlement).
Can 20Cr2Ni4 CARB be formed, bent or molded?
Forge at 1150–1200 °C down to about 850 °C followed by controlled slow cooling plus anneal; cold forming is limited to light straightening and thread rolling in the softened condition.
What is the maximum service temperature of 20Cr2Ni4 CARB?
20Cr2Ni4 CARB is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20Cr2Ni4-A and 20Cr2Ni4-QT200?
A is the default condition — standard stock condition for bar and forgings: soft enough to rough-machine gear blanks before carburizing. QT200: the standard's property-qualification condition; also used for through-hardened high-strength shafts and fasteners. Yield strength is 680 MPa in A versus 1,130 MPa in QT200.
Sources
- SAE J404 / AMS 6265 (9310 carburizing steel) — SAE International (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes (carburizing) — ASM International (2013)
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.