Steel 18Kh2N4MA-A (Solution annealed)
Temper
GOST 18Kh2N4MA (18Х2Н4МА)
Standard machining/delivery condition per GB/T 3077 and GOST 4543 — softest state before carburizing or final quench.
Values for the A condition
Other 18Kh2N4MA tempers and conditions
18Kh2N4MA is listed in 6 conditions; see the grade overview at 18Kh2N4MA.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AThis page Solution annealed | Standard machining/delivery condition per GB/T 3077 and GOST 4543 — softest state before carburizing or final quench. | 700 | 900 | 17 | 25 HRC | — |
Hot rolled | As-rolled or as-forged stock; this steel air-hardens, so the bar arrives hard and must be high-temperature tempered before machining. | 850 | 1,150 | 12 | 36 HRC | 4.9 % IACS |
Q&T 500–560 | Choose when a tough, machinable through-hardened part (shafts, fasteners, non-carburized structural sections) is wanted rather than maximum hardness. | 880 | 1,030 | 16 | 32 HRC | — |
Normalized | Grain-refining pre-treatment; because of the high hardenability the normalized bar is still martensitic and needs tempering. | 900 | 1,200 | 12 | 37 HRC | 4.9 % IACS |
QT200Default quenched (950 °C air + 850 °C oil/air) and tempered 200 °C | The condition in which GOST 4543 / GB/T 3077 specify mechanical properties — maximum core strength for gears and shafts. | 980 | 1,250 | 13 | 39 HRC | — |
Carburized | Final service condition for gears and races: hard wear/contact-resistant case over a tough 36–43 HRC Ni-Cr-Mo core. | 980 | 1,250 | 11 | 60 HRC | — |
What is 18Kh2N4MA-A?
18Kh2N4MA-A is 18Kh2N4MA in the A temper — standard machining/delivery condition per GB/T 3077 and GOST 4543 — softest state before carburizing or final quench. 18Kh2N4MA-A has a yield strength of 700 MPa (102 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 81% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi). 18Kh2N4MA-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). QT200 is the default condition FabDigit quotes; A is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- High embodied carbon — 2.7 kg CO₂/kg, worse than 89% of steel grades
- Difficult to machine — 34/100, worse than 86% 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
18Kh2N4MA-A properties
Typical room-temperature values for 18Kh2N4MA-A; 11 are specific to this condition. Other listed values are 18Kh2N4MA reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18Kh2N4MA-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).
Mechanical15
18Kh2N4MA-A has a yield strength of 700 MPa (102 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 81% of steel grades. Elongation at break is 17% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18Kh2N4MA-A is rated for continuous service to 400°C (752 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical2
18Kh2N4MA-A has an electrical resistivity of 3.5×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 18Kh2N4MA-A takes about 36 MJ of energy and emits 2.7 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 25%.
Manufacturability7
18Kh2N4MA-A's machinability is poor (34/100, worse than 86% of steel grades); weldability poor (22/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18Kh2N4MA-A
Is 18Kh2N4MA easy to machine?
Machine only after high-temperature tempering to ≤269 HB; use rigid setups, coated carbide at moderate speed and heavy positive feed — the 4 % Ni makes the steel gummy and work-hardening.
Can 18Kh2N4MA be welded?
Poor weldability: high hardenability demands 250–350 °C preheat, low-hydrogen or matching filler, and immediate post-weld temper; avoid welding on carburized surfaces.
Can 18Kh2N4MA be formed, bent or molded?
Forge at 1150–850 °C with slow cooling in furnace or ash, then normalize + high-temper; cold forming is impractical beyond minor straightening.
What surface finishes work on 18Kh2N4MA?
Grind the carburized case after heat treatment; protect with oil, phosphate, black oxide or Cd/Zn plating, and bake after plating to avoid hydrogen embrittlement.
18Kh2N4MA 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 | 0.14 – 0.2 | 0.17 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.25 – 0.55 | 0.4 |
| Cr | 1.35 – 1.65 | 1.5 |
| Ni | 4 – 4.4 | 4.2 |
| MoMo grade 18Kh2N4MA | 0.3 – 0.4 | 0.35 |
| WOnly in the tungsten variant 18Kh2N4VA / GB 18Cr2Ni4WA, which replaces Mo with W | 0.8 – 1.2 | 1 |
| Curesidual | ≤ 0.3 | — |
| Shigh-grade (A) quality | ≤ 0.03 | — |
| Phigh-grade (A) quality | ≤ 0.03 | — |
| Fe | balance | — |
18Kh2N4MA-A — frequently asked
What is 18Kh2N4MA-A used for?
18Kh2N4MA-A is typically used for aircraft gears, turbine gearbox gearing, helicopter transmission shafts, high-load pinions and ring gears, splined power-transmission shafts and heavily loaded cams and rollers. In short: strongest core in family; ni-Cr-Mo aerospace gear steel; low machinability, high cost.
What is the yield strength of 18Kh2N4MA-A?
18Kh2N4MA-A has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 18Kh2N4MA-A easy to machine?
Not especially — machinability is rated poor (34/100, worse than 86% of steel grades). Machine only after high-temperature tempering to ≤269 HB; use rigid setups, coated carbide at moderate speed and heavy positive feed — the 4 % Ni makes the steel gummy and work-hardening.
Can 18Kh2N4MA-A be welded?
Not readily — weldability is rated poor (22/100). Poor weldability: high hardenability demands 250–350 °C preheat, low-hydrogen or matching filler, and immediate post-weld temper; avoid welding on carburized surfaces.
What surface finishes work on 18Kh2N4MA-A?
Grind the carburized case after heat treatment; protect with oil, phosphate, black oxide or Cd/Zn plating, and bake after plating to avoid hydrogen embrittlement.
Can 18Kh2N4MA-A be formed, bent or molded?
Forge at 1150–850 °C with slow cooling in furnace or ash, then normalize + high-temper; cold forming is impractical beyond minor straightening.
What is the maximum service temperature of 18Kh2N4MA-A?
18Kh2N4MA-A 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 18Kh2N4MA-QT200 and 18Kh2N4MA-A?
QT200 is the default condition — the condition in which GOST 4543 / GB/T 3077 specify mechanical properties — maximum core strength for gears and shafts. A: standard machining/delivery condition per GB/T 3077 and GOST 4543 — softest state before carburizing or final quench. Yield strength is 980 MPa in QT200 versus 700 MPa in A.
Sources
- GOST 4543 — Alloyed structural steel bars — Gosstandart (2016)
- GB/T 3077 — Alloy structural steels (18Cr2Ni4WA) (2015)
- Marochnik stali i splavov (Steel and Alloy Grade Handbook) — Mashinostroenie (2003)
- 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.