Steel 20Cr2Ni4-HR (Hot rolled)
Supply condition
Cheapest mill condition; this steel air-hardens, so hot-rolled bar is hard and must be softened before machining.
Values for the HR 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 | — |
HRThis page 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 | — |
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-HR?
20Cr2Ni4-HR is 20Cr2Ni4 supplied in the HR condition — cheapest mill condition; this steel air-hardens, so hot-rolled bar is hard and must be softened before machining. 20Cr2Ni4-HR has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 86% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi). 20Cr2Ni4-HR 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; HR is available on request or by drawing note.
Advantages
- High strength — 800 MPa (116 ksi), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 28/100, worse than 91% of steel grades
- High embodied carbon — 2.7 kg CO₂/kg, worse than 89% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 22/100, worse than 81% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
20Cr2Ni4-HR properties
Typical room-temperature values for 20Cr2Ni4-HR; 22 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-HR 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-HR has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 86% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
20Cr2Ni4-HR is rated for continuous service to 300°C (572 °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-HR 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-HR 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-HR's machinability is poor (28/100, worse than 91% of steel grades); weldability poor (22/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Cr2Ni4-HR
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-HR — frequently asked
What is 20Cr2Ni4-HR used for?
20Cr2Ni4-HR 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-HR?
20Cr2Ni4-HR has a typical yield strength of 800 MPa (116 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 86% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20Cr2Ni4-HR easy to machine?
Not especially — machinability is rated poor (28/100, worse than 91% 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-HR be welded?
Not readily — weldability is rated poor (22/100). 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-HR?
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-HR 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-HR?
20Cr2Ni4-HR is rated for continuous use to about 300°C (572 °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.