Steel 20Cr2Ni4A-A (Solution annealed)
Temper
GB 20Cr2Ni4A
Softest commercial condition — the state most bar stock is bought in for gear blanking and rough machining before carburizing.
Values for the A condition
Other 20Cr2Ni4A tempers and conditions
20Cr2Ni4A is listed in 7 conditions; see the grade overview at 20Cr2Ni4A.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page Solution annealed | Softest commercial condition — the state most bar stock is bought in for gear blanking and rough machining before carburizing. | 500 | 800 | 18 | 240 HB | — |
Hot rolled | Raw mill condition of large bar and forgings before softening; hard and unstable, always heat treated before machining. | 650 | 950 | 14 | 31 HRC | 6 % IACS |
Normalized and tempered | Pre-treatment that refines grain and homogenizes large forgings while giving a machinable, dimensionally stable blank for carburizing. | 700 | 900 | 16 | 29 HRC | 6 % IACS |
Cold drawn | Small-diameter bright bar with close tolerance and better surface for automatic-lathe parts that will be carburized afterwards. | 750 | 900 | 10 | 28 HRC | 5.9 % IACS |
Q&T with 500–580 °C temper | Choose when maximum core toughness and machinability are wanted on heavy shafts that will not be carburized. | 930 | 1,080 | 15 | 35 HRC | — |
Carburized and hardened | The working condition for heavy-duty gears and bearing rings — hard wear-resistant case with compressive residual stress over a tough Ni-Cr core. | 1,100 | 1,300 | 10 | 60 HRC | — |
QTDefault Quenched and tempered | The GB/T 3077 double-quench + low-temper condition that defines the grade's spec properties; used for high-strength shafts and as the core condition of carburized parts. | 1,120 | 1,250 | 12 | 40 HRC | — |
What is 20Cr2Ni4A-A?
20Cr2Ni4A-A is 20Cr2Ni4A in the A temper — softest commercial condition — the state most bar stock is bought in for gear blanking and rough machining before carburizing. 20Cr2Ni4A-A has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 63% of steel grades. Elongation at break is 18% and the elastic modulus is 208 GPa (30.2 Msi). 20Cr2Ni4A-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). QT is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- High embodied carbon — 2.8 kg CO₂/kg, worse than 90% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Poor heat conductor — 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades
- Low electrical conductivity — 5.7 % IACS, worse than 80% of steel grades
20Cr2Ni4A-A properties
Typical room-temperature values for 20Cr2Ni4A-A; 11 are specific to this condition. Other listed values are 20Cr2Ni4A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20Cr2Ni4A-A has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
20Cr2Ni4A-A has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 63% of steel grades. Elongation at break is 18% and the elastic modulus is 208 GPa (30.2 Msi).
Thermal6
20Cr2Ni4A-A is rated for continuous service to 200°C (392 °F). It conducts heat at 32 W/m·K (18.5 BTU/hr·ft·°F), worse than 82% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
20Cr2Ni4A-A conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of 20Cr2Ni4A-A takes about 36 MJ of energy and emits 2.8 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 30%.
Manufacturability7
20Cr2Ni4A-A's machinability is fair (40/100, worse than 77% of steel grades); weldability poor (20/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20Cr2Ni4A-A
Is 20Cr2Ni4A easy to machine?
Machine in the annealed or normalized+tempered state (≤269 HB) with rigid setups and coated carbide; the Q&T or carburized condition needs CBN/grinding only.
Can 20Cr2Ni4A be welded?
Poor weldability (CE ≈ 0.9) — preheat 250–350 °C, low-hydrogen or matched Ni-Cr filler, and immediate post-weld temper; avoid welding carburized surfaces.
Can 20Cr2Ni4A be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling to avoid white-spot/flake cracking; cold forming is limited to light straightening.
What surface finishes work on 20Cr2Ni4A?
Carburized surfaces are ground and shot-peened for fatigue; corrosion protection by oiling, phosphating, black oxide or plating (bake after plating to avoid hydrogen embrittlement).
20Cr2Ni4A 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 – 3.65 | 3.45 |
| PA grade = high-grade quality steel, low P/S | ≤ 0.03 | — |
| SA grade = high-grade quality steel | ≤ 0.03 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
20Cr2Ni4A-A — frequently asked
What is 20Cr2Ni4A-A used for?
20Cr2Ni4A-A is typically used for large industrial gears, heavy machinery pinions and high-load carburized shafts. In short: deep-case carburizing steel; high core toughness; difficult to machine and weld.
What is the yield strength of 20Cr2Ni4A-A?
20Cr2Ni4A-A has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 63% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 20Cr2Ni4A-A easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine in the annealed or normalized+tempered state (≤269 HB) with rigid setups and coated carbide; the Q&T or carburized condition needs CBN/grinding only.
Can 20Cr2Ni4A-A be welded?
Not readily — weldability is rated poor (20/100). Poor weldability (CE ≈ 0.9) — preheat 250–350 °C, low-hydrogen or matched Ni-Cr filler, and immediate post-weld temper; avoid welding carburized surfaces.
What surface finishes work on 20Cr2Ni4A-A?
Carburized surfaces are ground and shot-peened for fatigue; corrosion protection by oiling, phosphating, black oxide or plating (bake after plating to avoid hydrogen embrittlement).
Can 20Cr2Ni4A-A be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling to avoid white-spot/flake cracking; cold forming is limited to light straightening.
What is the maximum service temperature of 20Cr2Ni4A-A?
20Cr2Ni4A-A is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20Cr2Ni4A-QT and 20Cr2Ni4A-A?
QT is the default condition — the GB/T 3077 double-quench + low-temper condition that defines the grade's spec properties; used for high-strength shafts and as the core condition of carburized parts. A: softest commercial condition — the state most bar stock is bought in for gear blanking and rough machining before carburizing. Yield strength is 1,120 MPa in QT versus 500 MPa in A.
Sources
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating (carburizing steels) — ASM International (1991)
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.