Steel En25
En25 is a high-strength Ni-Cr-Mo through-hardening steel to BS 970, broadly comparable to 4340, available annealed, normalized, hot-rolled, nitrided and in the T to Z tempered condition bands.
Reference datasheet — En25 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the T condition
En25 tempers and conditions
En25 is supplied in 10 conditions, soft to hard. T is the default FabDigit quotes; the values on this page are for it.
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 | — |
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 | — |
Supply forms, finishes and certifications
Ways En25 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
U | Q&T Condition U | Coating |
What is En25?
En25 is a high-strength Ni-Cr-Mo through-hardening steel to BS 970, broadly comparable to 4340, available annealed, normalized, hot-rolled, nitrided and in the T to Z tempered condition bands. It is specified for heavily stressed shafts, axles and gears that need high strength together with good core toughness in large sections. Typical tempered properties are 700 MPa yield, 930 MPa tensile, 15% elongation and 275 HB (28 HRC), with a machinability rating of 45. It has no inherent corrosion resistance, is difficult to weld, and at high strength requires hydrogen-embrittlement control after plating; En26 is the higher-hardenability alternative. En25 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). En25 has a yield strength of 700 MPa (102 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
What is En25 used for?
- heavy-duty shafts
- gears
- aircraft components
- axles
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- Limited formability — 20/100, worse than 80% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
En25 properties
Typical room-temperature values for En25-T; bars are the position among steel grades.
Physical3
En25 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 has a yield strength of 700 MPa (102 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 81% of steel grades. Elongation at break is 15% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En25 is rated for continuous service to 400°C (752 °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 conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of En25 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's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (25/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. En25 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with En25
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel En25 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 4340
How much does En25 cost?
En25 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
En25 — frequently asked
What is En25 used for?
En25 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?
En25 has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is En25 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% 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 be welded?
Not readily — weldability is rated poor (25/100). 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?
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 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?
En25 is rated for continuous use to about 400°C (752 °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.
How much does En25 cost?
En25 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.