Steel En52-QT750
Heat-treated state · default condition
QT750 = q&T
Standard service condition for exhaust valves and hot bolts — best balance of hot strength, scaling resistance and toughness.
Values for the QT750 condition
Other En52 tempers and conditions
En52 is listed in 5 conditions; see the grade overview at En52.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest supply condition for machining or cold straightening before hardening. | 480 | 780 | 22 | 21 HRC | 2.4 % IACS |
Hot rolled | Mill bar or forged valve blanks bought for subsequent hardening and tempering. | 600 | 900 | 18 | 29 HRC | 2.3 % IACS |
Q&T | Choose when maximum ductility/toughness and dimensional stability at high running temperature matter more than strength. | 660 | 900 | 21 | 25 HRC | 2.3 % IACS |
QT750DefaultThis page Q&T | Standard service condition for exhaust valves and hot bolts — best balance of hot strength, scaling resistance and toughness. | 750 | 1,000 | 17 | 30 HRC | — |
Q&T + gas nitrided valve stem/seat | Surface-treated condition for wear resistance on valve stems and seating faces; core properties as QT750. | 750 | 1,000 | 14 | 30 HRC | 2.3 % IACS |
What is En52-QT750?
En52-QT750 is En52 heat treated to QT750 — standard service condition for exhaust valves and hot bolts — best balance of hot strength, scaling resistance and toughness. En52-QT750 has a yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Elongation at break is 17% and the elastic modulus is 215 GPa (31.2 Msi). En52-QT750 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- High service temperature — 750°C (1,382 °F), better than 100% of steel grades
- Good corrosion resistance — 35/100, better than 97% of steel grades
- High strength — 750 MPa (109 ksi), better than 84% of steel grades
Limitations
- Low electrical conductivity — 2.3 % IACS, worse than 98% of steel grades
- Poor heat conductor — 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
En52-QT750 properties
Typical room-temperature values for En52-QT750; 10 are specific to this condition. Other listed values are En52 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
En52-QT750 has a density of 7.7 g/cm³ (0.278 lb/in³), lighter than 95% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
En52-QT750 has a yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Elongation at break is 17% and the elastic modulus is 215 GPa (31.2 Msi).
Thermal6
En52-QT750 is rated for continuous service to 750°C (1,382 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
En52-QT750 conducts electricity at 2.3 % IACS, worse than 98% of steel grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), better than 97% of steel grades.
Sustainability4
Producing a kilogram of En52-QT750 takes about 36 MJ of energy and emits 2.6 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 30%.
Manufacturability8
En52-QT750's machinability is poor (32/100, worse than 87% of steel grades); weldability poor (25/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En52-QT750
Is En52 easy to machine?
Machine in the annealed or high-tempered condition with rigid setups, sharp carbide tooling and generous coolant; the Si-rich matrix is abrasive and work-hardens, so keep speeds moderate and feeds steady.
Can En52 be welded?
Poor weldability — air-hardening martensitic steel; if unavoidable use 300–400 °C preheat, matching or austenitic filler, and temper immediately after welding, otherwise expect HAZ cracking.
Can En52 be formed, bent or molded?
Hot-work only: forge/extrude valve blanks at 1050–1150 °C and finish above 900 °C, then slow cool or anneal; cold forming is impractical.
What surface finishes work on En52?
Nitride or chromize stems and seat faces for wear and scuffing resistance; the surface polishes well but has no useful passive film, so oil, phosphate or plate parts exposed to moisture.
En52 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 | 0.4 – 0.5 | 0.45 |
| Sihigh Si for scaling resistance | 3 – 3.75 | 3.3 |
| Mn | 0.2 – 0.6 | 0.4 |
| Cr | 7.5 – 9.5 | 8.5 |
| Niresidual | ≤ 0.5 | 0.2 |
| Moresidual | ≤ 0.3 | — |
| P | ≤ 0.04 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
En52-QT750 — frequently asked
What is En52-QT750 used for?
En52-QT750 is typically used for engine exhaust valves, valve stems and seat faces, high-temperature fasteners, furnace and burner hardware, exhaust manifold studs and nuts and turbocharger linkage pins. In short: 750 °C valve steel; highest service temperature here; hot hardness, abrasive to cut.
What is the yield strength of En52-QT750?
En52-QT750 has a typical yield strength of 750 MPa (109 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 84% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is En52-QT750 easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Machine in the annealed or high-tempered condition with rigid setups, sharp carbide tooling and generous coolant; the Si-rich matrix is abrasive and work-hardens, so keep speeds moderate and feeds steady.
Can En52-QT750 be welded?
Not readily — weldability is rated poor (25/100). Poor weldability — air-hardening martensitic steel; if unavoidable use 300–400 °C preheat, matching or austenitic filler, and temper immediately after welding, otherwise expect HAZ cracking.
What surface finishes work on En52-QT750?
Nitride or chromize stems and seat faces for wear and scuffing resistance; the surface polishes well but has no useful passive film, so oil, phosphate or plate parts exposed to moisture.
Can En52-QT750 be formed, bent or molded?
Hot-work only: forge/extrude valve blanks at 1050–1150 °C and finish above 900 °C, then slow cool or anneal; cold forming is impractical.
What is the maximum service temperature of En52-QT750?
En52-QT750 is rated for continuous use to about 750°C (1,382 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between En52-QT750 and En52-A?
QT750 is the default condition — standard service condition for exhaust valves and hot bolts — best balance of hot strength, scaling resistance and toughness. A: softest supply condition for machining or cold straightening before hardening. Yield strength is 750 MPa in QT750 versus 480 MPa in A.
Sources
- BS 970 (En-series / 401S45 valve steel) — BSI (1955)
- DIN 17480 / EN 10090 — Valve steels for internal combustion engines (X45CrSi9-3, 1.4718) — DIN/CEN (1998)
- GB/T 1222 — Spring and valve steels (4Cr9Si2) — SAC (2016)
- JIS G 4311 — Heat-resisting steel bars (SUH1) — JISC (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- 1.4718 / X45CrSi9-3 valve steel bar datasheet — European specialty steel producers (2020)
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.