Steel 37CrNi3A-QT430
Heat-treated state
EN 37CrNi3A
QT430 = q&T
Aerospace high-strength condition (~1450–1650 MPa) for landing-gear axles and highly loaded pins; watch hydrogen embrittlement and notch sensitivity.
Values for the QT430 condition
Other 37CrNi3A tempers and conditions
37CrNi3A is listed in 7 conditions; see the grade overview at 37CrNi3A.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for rough machining, deep hole drilling and cold straightening before hardening. | 460 | 750 | 19 | 235 HB | — |
Hot rolled | Raw mill bar or forging stock before machining and heat treatment; not for load-bearing service. | 560 | 900 | 14 | 30 HRC | 6 % IACS |
Normalized | Grain-refined, uniform structure for large forgings prior to final Q&T, or a moderate-strength delivery condition. | 620 | 880 | 16 | 27 HRC | 5.9 % IACS |
Q&T | Choose when impact toughness and low-temperature performance matter more than peak strength (heavy sections, cold climates). | 860 | 1,000 | 16 | 31 HRC | — |
Q&T + gas nitrided case | For journals and splines needing wear resistance and high surface fatigue strength without distorting the tempered core. | 1,000 | 1,150 | 12 | 60 HRC | 5.7 % IACS |
QT500Default Q&T | The standard supply/qualification condition: ≥1130 MPa with ≥47 J impact — general aircraft shafts, axles and structural fittings. | 1,030 | 1,180 | 13 | 37 HRC | — |
QT430This page Q&T | Aerospace high-strength condition (~1450–1650 MPa) for landing-gear axles and highly loaded pins; watch hydrogen embrittlement and notch sensitivity. | 1,350 | 1,550 | 10 | 46 HRC | — |
What is 37CrNi3A-QT430?
37CrNi3A-QT430 is 37CrNi3A heat treated to QT430 — aerospace high-strength condition (~1450–1650 MPa) for landing-gear axles and highly loaded pins; watch hydrogen embrittlement and notch sensitivity. 37CrNi3A-QT430 has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 37CrNi3A-QT430 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). QT500 is the default condition FabDigit quotes; QT430 is available on request or by drawing note.
Advantages
- High strength — 1,350 MPa (196 ksi), better than 95% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
- Low electrical conductivity — 5.7 % IACS, worse than 80% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
37CrNi3A-QT430 properties
Typical room-temperature values for 37CrNi3A-QT430; 14 are specific to this condition. Other listed values are 37CrNi3A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
37CrNi3A-QT430 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
37CrNi3A-QT430 has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
37CrNi3A-QT430 is rated for continuous service to 350°C (662 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 75% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
37CrNi3A-QT430 conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 37CrNi3A-QT430 takes about 36 MJ of energy and emits 2.6 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 25%.
Manufacturability7
37CrNi3A-QT430's machinability is poor (25/100, worse than 93% of steel grades); weldability poor (25/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 37CrNi3A-QT430
Is 37CrNi3A easy to machine?
Rough machine annealed (≤269 HB) and finish after Q&T; use rigid setups, carbide inserts and reduced speeds above 40 HRC, grind for final tolerance.
Can 37CrNi3A be welded?
Poor weldability — preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the part's tempering temperature; avoid welding fully hardened parts.
Can 37CrNi3A be formed, bent or molded?
Hot forge 1150–850 °C with slow cool or immediate anneal; cold forming limited to light straightening in the annealed state.
What surface finishes work on 37CrNi3A?
Not corrosion resistant — Cd or Zn-Ni plate, chrome plate on journals, or phosphate + primer; bake 190 °C ≥ 8 h after plating to avoid hydrogen embrittlement, and shot peen fatigue-critical fillets.
37CrNi3A 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 | 0.34 – 0.41 | 0.37 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.3 – 0.6 | 0.45 |
| Cr | 1.2 – 1.6 | 1.4 |
| Ni | 3 – 3.5 | 3.25 |
| Curesidual | ≤ 0.2 | — |
| Phigh-grade (A) limit | ≤ 0.03 | — |
| Shigh-grade (A) limit; aerospace melts often ≤0.010 | ≤ 0.03 | — |
| Fe | balance | — |
37CrNi3A-QT430 — frequently asked
What is 37CrNi3A-QT430 used for?
37CrNi3A-QT430 is typically used for landing gear axles, aircraft structural shafts and high-strength pins. In short: most machinable of family; nitridable Ni-Cr grade; moderate 1030 MPa strength.
What is the yield strength of 37CrNi3A-QT430?
37CrNi3A-QT430 has a typical yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 37CrNi3A-QT430 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Rough machine annealed (≤269 HB) and finish after Q&T; use rigid setups, carbide inserts and reduced speeds above 40 HRC, grind for final tolerance.
Can 37CrNi3A-QT430 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability — preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the part's tempering temperature; avoid welding fully hardened parts.
What surface finishes work on 37CrNi3A-QT430?
Not corrosion resistant — Cd or Zn-Ni plate, chrome plate on journals, or phosphate + primer; bake 190 °C ≥ 8 h after plating to avoid hydrogen embrittlement, and shot peen fatigue-critical fillets.
Can 37CrNi3A-QT430 be formed, bent or molded?
Hot forge 1150–850 °C with slow cool or immediate anneal; cold forming limited to light straightening in the annealed state.
What is the maximum service temperature of 37CrNi3A-QT430?
37CrNi3A-QT430 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 37CrNi3A-QT500 and 37CrNi3A-A?
QT500 is the default condition — the standard supply/qualification condition: ≥1130 MPa with ≥47 J impact — general aircraft shafts, axles and structural fittings. A: softest condition for rough machining, deep hole drilling and cold straightening before hardening. Yield strength is 1,030 MPa in QT500 versus 460 MPa in A.
Sources
- GB/T 3077 (Alloy structural steels) (2015)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- (China Aeronautical Materials Handbook) (2002)
- MMPDS-analogue data for 4340 / 34CrNiMo6 Q&T steels — Battelle / FAA (2023)
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.