Steel EN24T
BS EN24T · AISI/SAE 4340
EN24T is a nickel-chromium-molybdenum through-hardening alloy steel close to AISI 4340, supplied in the quenched and tempered 'T' condition at roughly 265 HB (26 HRC) with 560 MPa yield and 900 MPa tensile.
Values for the HR condition
EN24T tempers and conditions
EN24T is supplied in 13 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
soft, spheroidised/full annealed for machining | Pick when the part must be heavily machined or cold worked before its own hardening cycle. | 460 | 700 | 22 | 210 HB | — |
HRDefault Hot rolled | Cheapest mill condition for parts that will be fully heat treated after rough machining. | 560 | 900 | 16 | 26 HRC | 7.8 % IACS |
Quenched and tempered | The standard stocked EN24T condition — best all-round strength/toughness balance and still machinable. | 750 | 930 | 17 | 29 HRC | — |
Q&T + gas/plasma nitrided case | Add when wear resistance and fatigue life of a Q&T core are needed without distortion from re-hardening. | 750 | 930 | 15 | 55 HRC | 7.8 % IACS |
Cold rolled | Flat product with tight thickness and improved surface for machined plates and blanks. | 780 | 940 | 14 | 30 HRC | 7.8 % IACS |
Cold drawn | Choose for bright, straight, close-tolerance shafting that needs little finish machining. | 800 | 950 | 14 | 30 HRC | 7.8 % IACS |
air cooled from ~870 °C | Grain refinement before final hardening; this air-hardening grade comes out hard, so a subcritical temper is usually added. | 800 | 1,150 | 12 | 36 HRC | — |
Q&T Condition U | One step above T when slightly higher strength is needed with almost the same toughness. | 820 | 1,000 | 15 | 31 HRC | 7.8 % IACS |
Q&T Condition V | Typical for heavier-duty shafts, gears and high-tensile fasteners. | 900 | 1,075 | 14 | 34 HRC | — |
Q&T Condition W | High-strength condition for aircraft/heavy-vehicle components; machining becomes noticeably harder. | 1,000 | 1,150 | 13 | 36 HRC | — |
Q&T Condition X | Used where very high tensile strength is required and toughness/machinability can be traded away. | 1,070 | 1,230 | 12 | 40 HRC | — |
Q&T Condition Y | Near the practical strength ceiling for machined parts; grinding often replaces turning. | 1,150 | 1,300 | 11 | 42 HRC | — |
Q&T Condition Z | Maximum-strength low-temper condition for small sections only; low toughness and high hydrogen-embrittlement risk. | 1,320 | 1,600 | 8 | 48 HRC | — |
What is EN24T?
EN24T is a nickel-chromium-molybdenum through-hardening alloy steel close to AISI 4340, supplied in the quenched and tempered 'T' condition at roughly 265 HB (26 HRC) with 560 MPa yield and 900 MPa tensile. Engineers specify it as ready-to-machine bar and forgings for heavily loaded shafts and forged parts, and it can be nitrided for wear surfaces. Weldability is poor (CE ≈ 0.9–1.0), cold forming is impractical once Q&T, and it has no corrosion resistance, so plating or paint is required. 4140/EN19 is the cheaper choice when the extra strength is not needed. EN24T 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). EN24T has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
What is EN24T used for?
- Drive shafts
- Forged industrial parts
- Gearbox shafts and pinions
- High-strength bolts and studs
- Crankshafts
- Axles and torsion bars
- Machine spindles
- Tool holders
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
EN24T properties
Typical room-temperature values for EN24T-HR; bars are the position among steel grades.
Physical3
EN24T 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
EN24T has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
EN24T is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
EN24T conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of EN24T takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 35%.
Manufacturability7
EN24T's machinability is fair (46/100, worse than 59% of steel grades); weldability poor (30/100); formability poor (25/100).
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. EN24T is highlighted; hover a dot for its name, or open the interactive family chart.
Working with EN24T
Is EN24T easy to machine?
Machinable in T condition with carbide at ~90–140 m/min, rigid setups and positive rake; above ~350 HB switch to CBN/ceramic or grind.
Can EN24T be welded?
Poor weldability (CE ≈ 0.9–1.0): use low-hydrogen consumables, preheat 250–350 °C, interpass control and immediate PWHT/temper below the original tempering temperature.
Can EN24T be formed, bent or molded?
Hot forge 1100–1200 °C finishing above 900 °C then slow cool or normalise; cold forming is not practical in Q&T conditions.
Manufacturability
The process limits FabDigit applies to EN24T. Every EN24T part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better46 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair25 / 100 |
|---|---|
| Weldability | Better30 / 100 |
EN24T 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 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.45 – 0.7 | 0.6 |
| Ni | 1.3 – 1.7 | 1.5 |
| Cr | 1 – 1.4 | 1.2 |
| Mo | 0.2 – 0.35 | 0.28 |
| P | ≤ 0.04 | |
| Smax; 817M40S variant is resulphurised for machinability | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on EN24T?
Not anodizable — protect with zinc/nickel plating, black oxide, phosphate or paint; bake 190–210 °C after plating to avoid hydrogen embrittlement, 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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel EN24T in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does EN24T cost?
EN24T is a standard-cost steel ($$), cheaper than about 61% 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.
EN24T — frequently asked
What is EN24T used for?
EN24T is typically used for drive shafts, forged industrial parts, gearbox shafts and pinions, high-strength bolts and studs, crankshafts and axles and torsion bars. In short: Q&T Ni-Cr-Mo bar.
What is the yield strength of EN24T?
EN24T has a typical yield strength of 560 MPa (81.2 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 73% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is EN24T easy to machine?
Reasonably — machinability is rated fair (46/100, worse than 59% of steel grades). Machinable in T condition with carbide at ~90–140 m/min, rigid setups and positive rake; above ~350 HB switch to CBN/ceramic or grind.
Can EN24T be welded?
Not readily — weldability is rated poor (30/100). Poor weldability (CE ≈ 0.9–1.0): use low-hydrogen consumables, preheat 250–350 °C, interpass control and immediate PWHT/temper below the original tempering temperature.
What surface finishes work on EN24T?
Not anodizable — protect with zinc/nickel plating, black oxide, phosphate or paint; bake 190–210 °C after plating to avoid hydrogen embrittlement, or nitride for wear surfaces.
Can EN24T be formed, bent or molded?
Hot forge 1100–1200 °C finishing above 900 °C then slow cool or normalise; cold forming is not practical in Q&T conditions.
What is the maximum service temperature of EN24T?
EN24T 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 EN24T-HR and EN24T-CD?
HR is the default condition — cheapest mill condition for parts that will be fully heat treated after rough machining. CD: choose for bright, straight, close-tolerance shafting that needs little finish machining. Yield strength is 560 MPa in HR versus 800 MPa in CD.
How much does EN24T cost?
EN24T is a standard-cost steel ($$), cheaper than about 61% 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.
Can FabDigit make parts in EN24T?
Yes — EN24T is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- BS 970-1: Wrought steels — 817M40 (EN24) mechanical condition T–Z — BSI (1991)
- EN 10083-3 / GB/T 3077 — 40CrNiMoA (34CrNiMo6 family) alloy structural steel — CEN / SAC (2015)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys (4340) — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- Machinery's Handbook — machinability ratings — Industrial Press (2020)
- 817M40 / EN24T engineering steel datasheets — West Yorkshire Steel / Interlloy / Smiths Metal Centres (2023)
- 40CrNiMoA — Mysteel / 1688 (2026)
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.