Steel EN24 · hardness band
Steel EN24 Q&T-U
Properties of the Q&T-U condition, compared with the other EN24 tempers.
One step above T when slightly higher strength is required with near-equal toughness.
What is EN24 Q&T-U?
EN24 Q&T-U is EN24 heat treated to Q&T-U — one step above T when slightly higher strength is required with near-equal toughness. EN24 Q&T-U has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 86% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi). EN24 Q&T-U has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). HR is the default condition FabDigit quotes; Q&T-U is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 800 MPa (116 ksi), better than 86% of steel grades
Limitations
- Limited ductility — 14%, worse than 75% of steel grades
EN24 Q&T-U properties
Typical room-temperature values for EN24 Q&T-U — 8 properties are specific to this condition; the rest are grade-level values shared by every EN24 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
EN24 Q&T-U has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
EN24 Q&T-U has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 86% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
EN24 Q&T-U 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
EN24 Q&T-U conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of EN24 Q&T-U takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
EN24 Q&T-U's machinability is fair (50/100, worse than 53% of steel grades); weldability poor (30/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other EN24 tempers and conditions
EN24 is also supplied in 11 other conditions. The full side-by-side table is on the EN24 overview.
- HRDefaultCheapest raw stock for parts that will be heat treated after rough machining.520 MPa yield · 22 HRC
- Q&T-ZMaximum-strength condition for small sections and tooling; low ductility and high notch/hydrogen sensitivity.1,400 MPa yield · 49 HRC
- Q&T-YNear-top standard strength band for highly stressed bolts, rods and aerospace fittings.1,130 MPa yield · 42 HRC
- Q&T-XUsed where high yield strength dominates; watch notch sensitivity and plating hydrogen embrittlement.1,070 MPa yield · 40 HRC
- Q&T-WHigh-strength condition for aerospace/heavy machine parts; machining becomes noticeably harder.990 MPa yield · 36 HRC
- Q&T-VCommon for high-duty gears, torsion bars and heavy-duty shafting.900 MPa yield · 34 HRC
- NormalizedUniform grain and high strength without quench distortion; usually followed by tempering for stock relief.860 MPa yield · 39 HRC
- Q&T-UOne step above T when slightly higher strength is required with near-equal toughness.800 MPa yield · 31 HRC
- Q&TThe standard stock condition (EN24T): best strength/toughness/machinability compromise for shafts, gears and general engineering parts.740 MPa yield · 28 HRC
- CDBright, size-accurate bar for shafts machined to near-final size before hardening; best surface of the untreated forms.720 MPa yield · 26 HRC
- AnnealedSoftest condition for deep machining, cold forming or thread rolling before hardening.470 MPa yield · 217 HB
Working with EN24 Q&T-U
Is EN24 easy to machine?
Machinable at 248–302 HB with rigid setups, carbide tooling and generous coolant; above ~350 HB use coated carbide/CBN, low feeds and consider grinding for finishing.
Can EN24 be welded?
Restricted weldability — preheat 250–350 °C, low-hydrogen consumables (or matching Ni-Cr-Mo filler), and temper immediately after welding; cracking risk high in the hardened conditions.
Can EN24 be formed, bent or molded?
Hot forge 1150–850 °C then normalise or anneal; cold forming only in the annealed condition and limited to gentle bends.
What surface finishes work on EN24?
No anodising; protect by black oxide, phosphating, zinc or hard chrome plating, nitriding for surface wear — bake plated parts above 1000 MPa strength to relieve hydrogen.
EN24 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 – 0.4 | 0.25 |
| Mn | 0.45 – 0.7 | 0.58 |
| Ni | 1.3 – 1.7 | 1.5 |
| Cr | 1 – 1.4 | 1.2 |
| Mo | 0.2 – 0.35 | 0.27 |
| S0.015–0.040 for 817M40; 0.050 max for free-machining 816M40 variant | ≤ 0.04 | 0.02 |
| P | ≤ 0.04 | 0.02 |
| Fe | balance | — |
EN24 Q&T-U — frequently asked
What is EN24 Q&T-U used for?
EN24 Q&T-U is typically used for drive shafts, industrial axles and forgings. In short: workhorse Q&T English bar.
What is the yield strength of EN24 Q&T-U?
EN24 Q&T-U has a typical yield strength of 800 MPa (116 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 86% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is EN24 Q&T-U easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machinable at 248–302 HB with rigid setups, carbide tooling and generous coolant; above ~350 HB use coated carbide/CBN, low feeds and consider grinding for finishing.
Can EN24 Q&T-U be welded?
Not readily — weldability is rated poor (30/100). Restricted weldability — preheat 250–350 °C, low-hydrogen consumables (or matching Ni-Cr-Mo filler), and temper immediately after welding; cracking risk high in the hardened conditions.
What surface finishes work on EN24 Q&T-U?
No anodising; protect by black oxide, phosphating, zinc or hard chrome plating, nitriding for surface wear — bake plated parts above 1000 MPa strength to relieve hydrogen.
Can EN24 Q&T-U be formed, bent or molded?
Hot forge 1150–850 °C then normalise or anneal; cold forming only in the annealed condition and limited to gentle bends.
What is the maximum service temperature of EN24 Q&T-U?
EN24 Q&T-U 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 EN24-HR and EN24-CD?
HR is the default condition — cheapest raw stock for parts that will be heat treated after rough machining. CD: bright, size-accurate bar for shafts machined to near-final size before hardening; best surface of the untreated forms. Yield strength is 520 MPa in HR versus 720 MPa in CD.
Can FabDigit make parts in EN24 Q&T-U?
Yes — EN24 Q&T-U is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- BS 970-1: Wrought steels — 817M40 (EN24) — BSI (1991)
- GB/T 3077 Alloy structural steels — 40CrNiMoA — SAC (2015)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels (AISI 4340) — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- MMPDS-17 typical properties, 4340 steel — Battelle/FAA (2022)
- EN24T / 817M40 hardened & tempered bar datasheets — West Yorkshire Steel / Interlloy (2023)
- 40CrNiMoA — Mysteel / 1688 (2026)
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.