Steel En25 Annealed
Temper
Softest condition; pick for heavy machining or cold work before final hardening and tempering.
Values for the Annealed 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 |
|---|---|---|---|---|---|---|
AnnealedThis page 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 | — |
What is En25 Annealed?
En25 Annealed is En25 in the Annealed temper — softest condition; pick for heavy machining or cold work before final hardening and tempering. En25 Annealed has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi). En25 Annealed 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; Annealed is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 25/100, worse than 77% of steel grades
En25 Annealed properties
Typical room-temperature values for En25 Annealed; 11 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 Annealed 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 Annealed has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En25 Annealed 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 Annealed 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 Annealed 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 Annealed's machinability is good (58/100, better than 75% of steel grades); weldability poor (25/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En25 Annealed
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 Annealed — frequently asked
What is En25 Annealed used for?
En25 Annealed 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 Annealed?
En25 Annealed has a typical yield strength of 440 MPa (63.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 50% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is En25 Annealed easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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 Annealed 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 Annealed?
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 Annealed 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 Annealed?
En25 Annealed 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.
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.