Steel En25 Nitrided
Finish state
Choose when wear resistance and fatigue life at journals or gear flanks matter; core stays at the Q&T condition.
Values for the Nitrided condition
Other En25 tempers and conditions
En25 is listed in 10 conditions; see the grade overview at En25.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
softened for machining/forming | Softest condition; pick for heavy machining or cold work before final hardening and tempering. | 440 | 700 | 22 | 210 HB | — |
Hot rolled | Mill-condition stock bought for subsequent forging and full heat treatment by the customer. | 560 | 880 | 16 | 25 HRC | 7.2 % IACS |
air cooled from austenitizing temperature | Uniform grain structure for forgings and stock prior to final heat treatment. | 570 | 850 | 18 | 24 HRC | 7.2 % IACS |
TDefault Q&T Condition T | Most commonly stocked hardened-and-tempered band: best balance of strength, toughness and machinability. | 700 | 930 | 15 | 28 HRC | — |
NitridedThis page Q&T + Gas Nitrided case | Choose when wear resistance and fatigue life at journals or gear flanks matter; core stays at the Q&T condition. | 820 | 1,000 | 12 | 58 HRC | 7.2 % IACS |
Q&T Condition V | Higher-strength band for gear blanks and heavily loaded axles. | 850 | 1,070 | 13 | 34 HRC | — |
Solution heat treated (unstable) | For high-duty transmission and aerospace parts where strength dominates over machinability. | 930 | 1,150 | 12 | 37 HRC | — |
Q&T Condition X | High-strength band for crankshafts, torsion bars and landing-gear-type components. | 1,010 | 1,230 | 11 | 40 HRC | — |
Q&T Condition Y | Near-maximum tempered strength; check notch sensitivity and hydrogen embrittlement risk if plated. | 1,090 | 1,300 | 10 | 42 HRC | — |
Q&T Condition Z | Maximum-strength low-temper condition for special high-stress parts; toughness and machinability are marginal. | 1,330 | 1,620 | 8 | 49 HRC | — |
What is En25 Nitrided?
En25 Nitrided is En25 supplied in the Nitrided condition — choose when wear resistance and fatigue life at journals or gear flanks matter; core stays at the Q&T condition. En25 Nitrided has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi). En25 Nitrided 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). T is the default condition FabDigit quotes; Nitrided is available on request or by drawing note.
Advantages
- Good corrosion resistance — 22/100, better than 90% of steel grades
- High service temperature — 480°C (896 °F), better than 88% of steel grades
- High strength — 820 MPa (119 ksi), better than 87% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Difficult to machine — 10/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
En25 Nitrided properties
Typical room-temperature values for En25 Nitrided; 21 are specific to this condition. Other listed values are En25 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
En25 Nitrided 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
En25 Nitrided has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En25 Nitrided is rated for continuous service to 480°C (896 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
En25 Nitrided conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of En25 Nitrided takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 35%.
Manufacturability7
En25 Nitrided's machinability is not recommended (10/100, worse than 99% of steel grades); weldability not recommended (5/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En25 Nitrided
Is En25 easy to machine?
Machine in the annealed or condition-T state with rigid setups, sharp carbide and generous coolant; above ~340 HB expect reduced speeds and consider grinding for finish features.
Can En25 be welded?
Weldable only with care: preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the last tempering temperature; avoid welding on finished Q&T parts.
Can En25 be formed, bent or molded?
Hot forge at 1050–1200 °C then normalize; cold forming is impractical except mild straightening in the annealed condition.
What surface finishes work on En25?
Not anodizable — protect with black oxide, phosphate + oil, hard chrome, zinc or cadmium plating (bake to relieve hydrogen at high strength), or nitride for wear surfaces.
En25 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 | 0.27 – 0.35 | 0.31 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.45 – 0.7 | 0.58 |
| Ni | 2.3 – 2.8 | 2.55 |
| Cr | 0.5 – 0.8 | 0.65 |
| Mo | 0.45 – 0.65 | 0.55 |
| P | ≤ 0.04 | — |
| Smax; 826M31 typically 0.035 max, resulphurised variants excluded | ≤ 0.04 | — |
| Fe | balance | — |
En25 Nitrided — frequently asked
What is En25 Nitrided used for?
En25 Nitrided is typically used for heavy-duty shafts, gears, aircraft components and axles. In short: 4340-class Ni-Cr-Mo steel; high strength with core toughness; deep-hardening large sections.
What is the yield strength of En25 Nitrided?
En25 Nitrided has a typical yield strength of 820 MPa (119 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is En25 Nitrided easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine in the annealed or condition-T state with rigid setups, sharp carbide and generous coolant; above ~340 HB expect reduced speeds and consider grinding for finish features.
Can En25 Nitrided be welded?
Not readily — weldability is rated not recommended (5/100). Weldable only with care: preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the last tempering temperature; avoid welding on finished Q&T parts.
What surface finishes work on En25 Nitrided?
Not anodizable — protect with black oxide, phosphate + oil, hard chrome, zinc or cadmium plating (bake to relieve hydrogen at high strength), or nitride for wear surfaces.
Can En25 Nitrided be formed, bent or molded?
Hot forge at 1050–1200 °C then normalize; cold forming is impractical except mild straightening in the annealed condition.
What is the maximum service temperature of En25 Nitrided?
En25 Nitrided is rated for continuous use to about 480°C (896 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between En25-T and En25-Z?
T is the default condition — most commonly stocked hardened-and-tempered band: best balance of strength, toughness and machinability. Z: maximum-strength low-temper condition for special high-stress parts; toughness and machinability are marginal. Yield strength is 700 MPa in T versus 1,330 MPa in Z.
Sources
- BS 970-1: Wrought steels for mechanical and allied engineering purposes (826M31 / En25) — BSI (1996)
- 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)
- 826M31 (En25) Ni-Cr-Mo through-hardening steel bar datasheet — European alloy-steel bar stockholders (2022)
- GB/T 3077 (40CrNiMoA comparable grade) — 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.