Steel 20KhN3A N+T
Heat-treated state
GOST 20KhN3A (20ХН3А)
N+T = normalized and tempered
Use when a stress-relieved, easily machined but stronger-than-annealed blank is wanted.
Values for the N+T condition
Other 20KhN3A tempers and conditions
20KhN3A is listed in 8 conditions; see the grade overview at 20KhN3A.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for maximum machinability and best condition before carburizing of complex gear blanks. | 430 | 700 | 21 | 197 HB | — |
Hot rolled | Cheapest mill supply for forging stock or parts that will be fully heat treated later. | 520 | 820 | 16 | 22 HRC | 6.2 % IACS |
N+TThis page Normalized and tempered | Use when a stress-relieved, easily machined but stronger-than-annealed blank is wanted. | 560 | 780 | 19 | 19 HRC | 6.3 % IACS |
Normalized | Grain-refining condition used to homogenize forgings before carburizing or final Q&T. | 620 | 900 | 16 | 26 HRC | 6.2 % IACS |
Q&TDefault Quenched and tempered | Standard through-hardened condition quoted in GOST 4543 — best all-round core strength/toughness for shafts and gear cores. | 780 | 980 | 14 | 31 HRC | — |
Cold drawn | Choose for close-tolerance bright bar and small turned parts where no further hot heat treatment is planned. | 780 | 950 | 10 | 28 HRC | 6.1 % IACS |
Carburized and hardened | The intended service condition: hard wear-resistant case with tough high-strength core for heavily loaded gears and splines. | 950 | 1,200 | 11 | 60 HRC | — |
Oil quenched + low temper 180–250 °C | Highest core strength/hardness for pins, small shafts and fasteners where toughness demand is moderate. | 1,100 | 1,350 | 10 | 42 HRC | — |
What is 20KhN3A N+T?
20KhN3A N+T is 20KhN3A heat treated to N+T — use when a stress-relieved, easily machined but stronger-than-annealed blank is wanted. 20KhN3A N+T has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of steel grades. Elongation at break is 19% and the elastic modulus is 210 GPa (30.5 Msi). 20KhN3A N+T 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). Q&T is the default condition FabDigit quotes; N+T is available on request or by drawing note.
Limitations
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
20KhN3A N+T properties
Typical room-temperature values for 20KhN3A N+T; 23 are specific to this condition. Other listed values are 20KhN3A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20KhN3A N+T 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
20KhN3A N+T has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of steel grades. Elongation at break is 19% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20KhN3A N+T is rated for continuous service to 400°C (752 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical2
20KhN3A N+T has an electrical resistivity of 2.75×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 20KhN3A N+T takes about 34 MJ of energy and emits 2.6 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
20KhN3A N+T's machinability is fair (52/100, better than 52% of steel grades); weldability poor (32/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20KhN3A N+T
Is 20KhN3A easy to machine?
Machine in the annealed/normalized state (≈180–230 HB) with coated carbide, moderate speed and rigid setups; leave 0.3–0.6 mm stock for post-carburizing grinding since the case cannot be turned.
Can 20KhN3A be welded?
Poor weldability — CE ≈ 0.7; if unavoidable use low-hydrogen electrodes, 250–350 °C preheat, interpass control and immediate 550–650 °C post-weld temper; never weld after carburizing.
Can 20KhN3A be formed, bent or molded?
Hot forge 1180–850 °C with slow cooling and a subsequent normalize/anneal; cold forming limited to light straightening or thread rolling in the annealed condition.
What surface finishes work on 20KhN3A?
No anodizing (ferrous); protect with oil, manganese phosphate, black oxide, zinc or hard chrome plating — bake after plating to avoid hydrogen embrittlement in high-strength conditions; case-hardened surfaces are finish-ground and can be shot peened for fatigue.
20KhN3A 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 – 0.24 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.3 – 0.6 | 0.45 |
| Cr | 0.6 – 0.9 | 0.75 |
| Ni | 2.75 – 3.15 | 2.95 |
| Shigh-quality grade ('A') restriction | ≤ 0.03 | 0.01 |
| Phigh-quality grade ('A') restriction | ≤ 0.03 | 0.01 |
| Curesidual | ≤ 0.3 | 0.15 |
| Moresidual, not intentionally added | ≤ 0.15 | 0.05 |
| Fe | balance | — |
20KhN3A N+T — frequently asked
What is 20KhN3A N+T used for?
20KhN3A N+T is typically used for heavy-duty gears, gearbox and pinion shafts, ring gears and bevel pinions, splined and keyed drive shafts, crown wheels for axle drives and cams and gear-type couplings. In short: higher core strength; ni-Cr heavy gear steel; 400 C service limit.
What is the yield strength of 20KhN3A N+T?
20KhN3A N+T has a typical yield strength of 560 MPa (81.2 ksi) and a tensile strength of 780 MPa (113 ksi) — stronger than 73% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 20KhN3A N+T easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machine in the annealed/normalized state (≈180–230 HB) with coated carbide, moderate speed and rigid setups; leave 0.3–0.6 mm stock for post-carburizing grinding since the case cannot be turned.
Can 20KhN3A N+T be welded?
Not readily — weldability is rated poor (32/100). Poor weldability — CE ≈ 0.7; if unavoidable use low-hydrogen electrodes, 250–350 °C preheat, interpass control and immediate 550–650 °C post-weld temper; never weld after carburizing.
What surface finishes work on 20KhN3A N+T?
No anodizing (ferrous); protect with oil, manganese phosphate, black oxide, zinc or hard chrome plating — bake after plating to avoid hydrogen embrittlement in high-strength conditions; case-hardened surfaces are finish-ground and can be shot peened for fatigue.
Can 20KhN3A N+T be formed, bent or molded?
Hot forge 1180–850 °C with slow cooling and a subsequent normalize/anneal; cold forming limited to light straightening or thread rolling in the annealed condition.
What is the maximum service temperature of 20KhN3A N+T?
20KhN3A N+T is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20KhN3A Q&T and 20KhN3A-A?
Q&T is the default condition — standard through-hardened condition quoted in GOST 4543 — best all-round core strength/toughness for shafts and gear cores. A: pick for maximum machinability and best condition before carburizing of complex gear blanks. Yield strength is 780 MPa in Q&T versus 430 MPa in A.
Sources
- GOST 4543 — Alloyed structural steel bars, technical requirements — Gosstandart / Rosstandart (2016)
- Marochnik stalei i splavov (Steel and Alloy Grades Handbook) — Mashinostroenie (2003)
- 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)
- GB/T 3077 — Alloy structural steels (20CrNi3 comparable grade) — SAC (2015)
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.