Steel EN24T · hardness band
Steel EN24T Q&T-Z
Properties of the Q&T-Z condition, compared with the other EN24T tempers.
Maximum-strength low-temper condition for small sections only; low toughness and high hydrogen-embrittlement risk.
What is EN24T Q&T-Z?
EN24T Q&T-Z is EN24T heat treated to Q&T-Z — maximum-strength low-temper condition for small sections only; low toughness and high hydrogen-embrittlement risk. EN24T Q&T-Z has a yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi). EN24T Q&T-Z 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). HR is the default condition FabDigit quotes; Q&T-Z is available on request or by drawing note.
Advantages
- High strength — 1,320 MPa (191 ksi), better than 95% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to weld — 10/100, worse than 99% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Limited service temperature — 220°C (428 °F), worse than 88% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 83% of steel grades
EN24T Q&T-Z properties
Typical room-temperature values for EN24T Q&T-Z — 13 properties are specific to this condition; the rest are grade-level values shared by every EN24T temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
EN24T Q&T-Z 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 Q&T-Z has a yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
EN24T Q&T-Z is rated for continuous service to 220°C (428 °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 Q&T-Z conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of EN24T Q&T-Z 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 Q&T-Z's machinability is poor (20/100, worse than 97% of steel grades); weldability not recommended (10/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other EN24T tempers and conditions
EN24T is also supplied in 12 other conditions. The full side-by-side table is on the EN24T overview.
- HRDefaultCheapest mill condition for parts that will be fully heat treated after rough machining.560 MPa yield · 26 HRC
- Q&T-ZMaximum-strength low-temper condition for small sections only; low toughness and high hydrogen-embrittlement risk.1,320 MPa yield · 48 HRC
- Q&T-YNear the practical strength ceiling for machined parts; grinding often replaces turning.1,150 MPa yield · 42 HRC
- Q&T-XUsed where very high tensile strength is required and toughness/machinability can be traded away.1,070 MPa yield · 40 HRC
- Q&T-WHigh-strength condition for aircraft/heavy-vehicle components; machining becomes noticeably harder.1,000 MPa yield · 36 HRC
- Q&T-VTypical for heavier-duty shafts, gears and high-tensile fasteners.900 MPa yield · 34 HRC
- Q&T-UOne step above T when slightly higher strength is needed with almost the same toughness.820 MPa yield · 31 HRC
- CDChoose for bright, straight, close-tolerance shafting that needs little finish machining.800 MPa yield · 30 HRC
- NormalizedGrain refinement before final hardening; this air-hardening grade comes out hard, so a subcritical temper is usually added.800 MPa yield · 36 HRC
- Q&TThe standard stocked EN24T condition — best all-round strength/toughness balance and still machinable.750 MPa yield · 29 HRC
- AnnealedPick when the part must be heavily machined or cold worked before its own hardening cycle.460 MPa yield · 210 HB
Working with EN24T Q&T-Z
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.
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.
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 | — |
EN24T Q&T-Z — frequently asked
What is EN24T Q&T-Z used for?
EN24T Q&T-Z 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 Q&T-Z?
EN24T Q&T-Z has a typical yield strength of 1,320 MPa (191 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is EN24T Q&T-Z easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% 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 Q&T-Z be welded?
Not readily — weldability is rated not recommended (10/100). 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 Q&T-Z?
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 Q&T-Z 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 Q&T-Z?
EN24T Q&T-Z is rated for continuous use to about 220°C (428 °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.
Can FabDigit make parts in EN24T Q&T-Z?
Yes — EN24T Q&T-Z 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) 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.