Steel 30NiCrMo16-QT1250
Heat-treated state
EN 30NiCrMo16 · AISI/SAE 4340
QT1250 = q&T 1240–1420 MPa
Chosen when high fatigue strength is needed but fracture toughness and SCC margin must stay high.
Values for the QT1250 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 | — |
QT1250This page 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 | — |
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-QT1250?
30NiCrMo16-QT1250 is 30NiCrMo16 heat treated to QT1250 — chosen when high fatigue strength is needed but fracture toughness and SCC margin must stay high. 30NiCrMo16-QT1250 has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi). 30NiCrMo16-QT1250 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; QT1250 is available on request or by drawing note.
Advantages
- High strength — 1,200 MPa (174 ksi), better than 94% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Limited formability — 8/100, worse than 97% of steel grades
- Difficult to machine — 25/100, worse than 93% 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-QT1250 properties
Typical room-temperature values for 30NiCrMo16-QT1250; 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-QT1250 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-QT1250 has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
30NiCrMo16-QT1250 is rated for continuous service to 350°C (662 °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-QT1250 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-QT1250 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-QT1250's machinability is poor (25/100, worse than 93% 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-QT1250
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-QT1250 — frequently asked
What is 30NiCrMo16-QT1250 used for?
30NiCrMo16-QT1250 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-QT1250?
30NiCrMo16-QT1250 has a typical yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 30NiCrMo16-QT1250 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% 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-QT1250 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-QT1250?
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-QT1250 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-QT1250?
30NiCrMo16-QT1250 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 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.