Steel 30NiCrMo16-QT1550
Heat-treated state
EN 30NiCrMo16 · AISI/SAE 4340
QT1550 = q&T 1500–1650 MPa
Intermediate aerospace strength level for shafts, torsion bars and highly loaded fittings.
Values for the QT1550 condition
Other 30NiCrMo16 tempers and conditions
30NiCrMo16 is listed in 8 conditions; see the grade overview at 30NiCrMo16.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Delivery condition for bar/billet that will be machined then heat treated by the user. | 550 | 820 | 18 | 20 HRC | — |
normalized and tempered (forging/pre-machining condition) | Intermediate condition for large forgings before final quench and temper; better machinability than Q&T. | 750 | 1,000 | 15 | 31 HRC | — |
+QT 980–1180 MPa | EN 10083-3 heavy-section Q&T class for large shafts and forgings where toughness matters more than strength. | 900 | 1,080 | 13 | 34 HRC | — |
+QT 1080–1230 MPa | Standard European Q&T delivery condition for bar; best strength/toughness balance for machine parts. | 980 | 1,150 | 12 | 36 HRC | — |
Q&T 1240–1420 MPa | Chosen when high fatigue strength is needed but fracture toughness and SCC margin must stay high. | 1,200 | 1,350 | 14 | 42 HRC | — |
QT1550This page Q&T 1500–1650 MPa | Intermediate aerospace strength level for shafts, torsion bars and highly loaded fittings. | 1,400 | 1,580 | 13 | 47 HRC | — |
QT1800Default Q&T 1790–1930 MPa | The classic aerospace ultra-high-strength condition for landing gear and structural forgings; requires plating + hydrogen bake. | 1,620 | 1,860 | 12 | 53 HRC | — |
Q&T 1930–2070 MPa | Highest practical strength level; use only where weight is critical and notch/hydrogen control is guaranteed. | 1,720 | 1,980 | 9 | 55 HRC | — |
What is 30NiCrMo16-QT1550?
30NiCrMo16-QT1550 is 30NiCrMo16 heat treated to QT1550 — intermediate aerospace strength level for shafts, torsion bars and highly loaded fittings. 30NiCrMo16-QT1550 has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,580 MPa (229 ksi) — stronger than 96% of steel grades. Elongation at break is 13% and the elastic modulus is 205 GPa (29.7 Msi). 30NiCrMo16-QT1550 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). QT1800 is the default condition FabDigit quotes; QT1550 is available on request or by drawing note.
Advantages
- High strength — 1,400 MPa (203 ksi), better than 96% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited formability — 8/100, worse than 97% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
30NiCrMo16-QT1550 properties
Typical room-temperature values for 30NiCrMo16-QT1550; 13 are specific to this condition. Other listed values are 30NiCrMo16 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30NiCrMo16-QT1550 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
30NiCrMo16-QT1550 has a yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,580 MPa (229 ksi) — stronger than 96% of steel grades. Elongation at break is 13% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
30NiCrMo16-QT1550 is rated for continuous service to 300°C (572 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
30NiCrMo16-QT1550 conducts electricity at 6.8 % IACS, worse than 76% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of 30NiCrMo16-QT1550 takes about 36 MJ of energy and emits 2.6 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 30%.
Manufacturability7
30NiCrMo16-QT1550's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (15/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 30NiCrMo16-QT1550
Is 30NiCrMo16 easy to machine?
Rough machine in the annealed or ≤35 HRC condition; above 45 HRC use rigid setups with coated carbide/CBN at low speed, or finish by grinding, and always stress-relieve before final grinding.
Can 30NiCrMo16 be welded?
Poor weldability — high carbon equivalent means preheat 250–350 °C, low-hydrogen filler, and immediate post-weld temper; welding is normally avoided on flight-critical Q&T parts.
Can 30NiCrMo16 be formed, bent or molded?
Hot forge at 1050–1150 °C with slow cooling to avoid quench cracks; cold forming is impractical, all shaping is by hot work or machining.
What surface finishes work on 30NiCrMo16?
Bare surface rusts quickly — use Cd, Zn-Ni or hard chrome plating (with 190 °C hydrogen bake-out within 4 h), shot peen highly stressed fillets, and phosphate + epoxy primer for non-plated areas.
30NiCrMo16 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 | 0.26 – 0.34 | 0.3 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| Nihigh Ni gives deep hardenability and low-temperature toughness | 3.6 – 4.1 | 3.9 |
| Cr | 1.6 – 2 | 1.8 |
| Mo | 0.4 – 0.6 | 0.5 |
| Paerospace grades typically ≤0.015 | ≤ 0.03 | — |
| Saerospace / VAR grades typically ≤0.010 | ≤ 0.04 | — |
| Fe | balance | — |
30NiCrMo16-QT1550 — frequently asked
What is 30NiCrMo16-QT1550 used for?
30NiCrMo16-QT1550 is typically used for landing gear forgings, aircraft structural shafts and high-strength bolts. In short: european 4340 equivalent; widest quench-and-temper range; hardest condition, 53 HRC.
What is the yield strength of 30NiCrMo16-QT1550?
30NiCrMo16-QT1550 has a typical yield strength of 1,400 MPa (203 ksi) and a tensile strength of 1,580 MPa (229 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 30NiCrMo16-QT1550 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Rough machine in the annealed or ≤35 HRC condition; above 45 HRC use rigid setups with coated carbide/CBN at low speed, or finish by grinding, and always stress-relieve before final grinding.
Can 30NiCrMo16-QT1550 be welded?
Not readily — weldability is rated poor (15/100). Poor weldability — high carbon equivalent means preheat 250–350 °C, low-hydrogen filler, and immediate post-weld temper; welding is normally avoided on flight-critical Q&T parts.
What surface finishes work on 30NiCrMo16-QT1550?
Bare surface rusts quickly — use Cd, Zn-Ni or hard chrome plating (with 190 °C hydrogen bake-out within 4 h), shot peen highly stressed fillets, and phosphate + epoxy primer for non-plated areas.
Can 30NiCrMo16-QT1550 be formed, bent or molded?
Hot forge at 1050–1150 °C with slow cooling to avoid quench cracks; cold forming is impractical, all shaping is by hot work or machining.
What is the maximum service temperature of 30NiCrMo16-QT1550?
30NiCrMo16-QT1550 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 30NiCrMo16-QT1800 and 30NiCrMo16-A?
QT1800 is the default condition — the classic aerospace ultra-high-strength condition for landing gear and structural forgings; requires plating + hydrogen bake. A: delivery condition for bar/billet that will be machined then heat treated by the user. Yield strength is 1,620 MPa in QT1800 versus 550 MPa in A.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels (30NiCrMo16-6, 1.6747) — CEN (2006)
- AIR 9160 / NF A35-565 aerospace Ni-Cr-Mo steels (35NCD16 family) — AFNOR/BNAE (1990)
- Ni-Cr-Mo ultra-high-strength steel bar and forgings (35NCD16 / 30NiCrMo16) — 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 — AISI 4340 alloy steel design allowables — Battelle/FAA (2019)
- GB/T 3077 (40CrNiMoA / 30CrNi4MoA analogues) — 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.