Steel 35NCD16-QT1790
Heat-treated state · default condition
EN 35NCD16
QT1790 = q&T 1790–1980 MPa
The classic aerospace condition for landing gear legs and pistons — maximum practical strength with acceptable K_IC.
Values for the QT1790 condition
Other 35NCD16 tempers and conditions
35NCD16 is listed in 9 conditions; see the grade overview at 35NCD16.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Delivery condition for rough machining and deep forming before the final quench-and-temper cycle. | 600 | 860 | 18 | 23 HRC | — |
Normalized | Intermediate forging/bar condition giving a uniform fine grain before final hardening. | 800 | 1,050 | 15 | 33 HRC | 6 % IACS |
Q&T 1080–1230 MPa | Toughest quench-and-temper class — pick when impact energy and SCC resistance outrank strength. | 980 | 1,150 | 15 | 36 HRC | — |
Q&T 1230–1420 MPa | General high-strength shafting and structural fittings with good toughness reserve. | 1,130 | 1,320 | 14 | 41 HRC | — |
Q&T 1420–1620 MPa | Balanced class for actuator bodies, torsion bars and heavy sections needing through-hardening. | 1,300 | 1,520 | 13 | 45 HRC | — |
Q&T 1620–1810 MPa | Ultra-high-strength class where damage tolerance is still specified alongside high load capacity. | 1,460 | 1,700 | 12 | 49 HRC | — |
QT1790DefaultThis page Q&T 1790–1980 MPa | The classic aerospace condition for landing gear legs and pistons — maximum practical strength with acceptable K_IC. | 1,620 | 1,900 | 11 | 53 HRC | — |
Q&T + gas nitrided surface | Choose for sliding/bearing surfaces on gear pistons: hard nitrided case with unchanged Q&T core (nitride below the tempering temperature). | 1,620 | 1,900 | 10 | 53 HRC | 5.7 % IACS |
Q&T 1930–2130 MPa | Peak-strength condition for the most weight-critical parts; toughness and SCC resistance are marginal, shot peening plus strict hydrogen control are mandatory. | 1,700 | 2,000 | 9 | 55 HRC | — |
What is 35NCD16-QT1790?
35NCD16-QT1790 is 35NCD16 heat treated to QT1790 — the classic aerospace condition for landing gear legs and pistons — maximum practical strength with acceptable K_IC. 35NCD16-QT1790 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi). 35NCD16-QT1790 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).
Advantages
- High strength — 1,620 MPa (235 ksi), better than 98% of steel grades
- 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
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited formability — 12/100, worse than 92% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
35NCD16-QT1790 properties
Typical room-temperature values for 35NCD16-QT1790; 13 are specific to this condition. Other listed values are 35NCD16 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
35NCD16-QT1790 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
35NCD16-QT1790 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
35NCD16-QT1790 is rated for continuous service to 200°C (392 °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
35NCD16-QT1790 conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 35NCD16-QT1790 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
35NCD16-QT1790's machinability is poor (25/100, worse than 93% of steel grades); weldability poor (20/100); formability not recommended (12/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 35NCD16-QT1790
Is 35NCD16 easy to machine?
Rough machine in the annealed state (~240 HB); finish at 50+ HRC with rigid setups, coated carbide or CBN, low speed and heavy flood coolant, and avoid grinding burn on final ground diameters.
Can 35NCD16 be welded?
Poor weldability at high strength: only fusion weld before final heat treatment, with 250–350 °C preheat, low-hydrogen consumables and immediate post-weld temper; welded joints are not used in landing-gear primary structure.
Can 35NCD16 be formed, bent or molded?
Hot forge at 1150–850 °C then normalize; cold forming is impractical except mild straightening in the annealed condition — all shaping is done before quench and temper.
What surface finishes work on 35NCD16?
Shot peen highly stressed surfaces, then cadmium, zinc-nickel or hard-chrome plate with mandatory hydrogen-embrittlement relief bake (190–200 °C, 8–23 h); never leave the steel bare in service.
35NCD16 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 | 0.32 – 0.39 | 0.35 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| Nigives deep hardenability and low-temperature toughness | 3.6 – 4.1 | 3.85 |
| Cr | 1.6 – 2 | 1.8 |
| Mosuppresses temper embrittlement | 0.25 – 0.45 | 0.35 |
| Vresidual | ≤ 0.05 | — |
| Curesidual | ≤ 0.25 | — |
| Paerospace melt limit | ≤ 0.02 | — |
| Saerospace melt limit | ≤ 0.01 | — |
| Fe | balance | — |
35NCD16-QT1790 — frequently asked
What is 35NCD16-QT1790 used for?
35NCD16-QT1790 is typically used for aircraft landing gear, high-strength shafts and aerospace fasteners. In short: above 1900 MPa tensile; landing-gear grade steel; low ductility, no welding.
What is the yield strength of 35NCD16-QT1790?
35NCD16-QT1790 has a typical yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,900 MPa (276 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 35NCD16-QT1790 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Rough machine in the annealed state (~240 HB); finish at 50+ HRC with rigid setups, coated carbide or CBN, low speed and heavy flood coolant, and avoid grinding burn on final ground diameters.
Can 35NCD16-QT1790 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability at high strength: only fusion weld before final heat treatment, with 250–350 °C preheat, low-hydrogen consumables and immediate post-weld temper; welded joints are not used in landing-gear primary structure.
What surface finishes work on 35NCD16-QT1790?
Shot peen highly stressed surfaces, then cadmium, zinc-nickel or hard-chrome plate with mandatory hydrogen-embrittlement relief bake (190–200 °C, 8–23 h); never leave the steel bare in service.
Can 35NCD16-QT1790 be formed, bent or molded?
Hot forge at 1150–850 °C then normalize; cold forming is impractical except mild straightening in the annealed condition — all shaping is done before quench and temper.
What is the maximum service temperature of 35NCD16-QT1790?
35NCD16-QT1790 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 35NCD16-QT1790 and 35NCD16-A?
QT1790 is the default condition — the classic aerospace condition for landing gear legs and pistons — maximum practical strength with acceptable K_IC. A: delivery condition for rough machining and deep forming before the final quench-and-temper cycle. Yield strength is 1,620 MPa in QT1790 versus 600 MPa in A.
Sources
- NF A35-565 / AIR 9160 — 35NCD16 aerospace alloy steel — AFNOR / BNAE (1990)
- 35NCD16 high-strength Ni-Cr-Mo steel bar and forging data — Aubert & Duval (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- MMPDS — 4340 and ultra-high-strength steel allowables (analogous grade) — 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.