Steel En47 QT36-40
Hardness band
QT36-40 = q&T 36–40 HRC
Balanced strength/toughness for torsion bars and medium-duty springs.
Values for the QT36-40 condition
Other En47 tempers and conditions
En47 is listed in 10 conditions; see the grade overview at En47.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest condition, used for cold heading, deep drawing or heavy cold forming of blanks. | 400 | 660 | 25 | 11 HRC | 8.5 % IACS |
Solution annealed | Pick for machining, cold bending or blanking of spring blanks before hardening. | 450 | 750 | 20 | 225 HB | — |
Hot rolled | Cheapest mill condition for stock that will be forged or fully heat treated afterwards. | 600 | 950 | 14 | 29 HRC | — |
Normalized | Uniform fine-grain structure after forging; a good base condition before hardening. | 650 | 1,000 | 15 | 31 HRC | — |
Cold drawn | Close tolerance bright bar for machined parts that will be hardened later. | 700 | 860 | 10 | 24 HRC | 7.8 % IACS |
Q&T 28–32 HRC | Tough machinable condition for shafts, tools and lightly loaded torsion members. | 880 | 1,000 | 15 | 30 HRC | — |
QT36-40This page Q&T 36–40 HRC | Balanced strength/toughness for torsion bars and medium-duty springs. | 1,120 | 1,250 | 12 | 38 HRC | — |
Q&T 40–44 HRC | Common leaf-spring and heavy coil-spring hardness with useful residual toughness. | 1,270 | 1,400 | 10 | 42 HRC | — |
QT44-48Default Q&T 44–48 HRC | Standard working hardness of En47 springs and torsion bars — best strength/relaxation compromise. | 1,450 | 1,600 | 8 | 46 HRC | — |
Q&T 48–52 HRC | Maximum spring load capacity, chisels and punches; toughness and notch tolerance drop sharply. | 1,620 | 1,800 | 6 | 50 HRC | — |
What is En47 QT36-40?
En47 QT36-40 is En47 heat treated to QT36-40 — balanced strength/toughness for torsion bars and medium-duty springs. En47 QT36-40 has a yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi). En47 QT36-40 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). QT44-48 is the default condition FabDigit quotes; QT36-40 is available on request or by drawing note.
Advantages
- High strength — 1,120 MPa (162 ksi), better than 93% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Difficult to machine — 36/100, worse than 81% of steel grades
En47 QT36-40 properties
Typical room-temperature values for En47 QT36-40; 13 are specific to this condition. Other listed values are En47 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
En47 QT36-40 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
En47 QT36-40 has a yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
En47 QT36-40 is rated for continuous service to 380°C (716 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
En47 QT36-40 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 En47 QT36-40 takes about 27 MJ of energy and emits 2.3 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
En47 QT36-40's machinability is fair (36/100, worse than 81% of steel grades); weldability poor (20/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En47 QT36-40
Is En47 easy to machine?
Machine in the annealed/spheroidized state (~60 % of 1212); above 40 HRC use carbide or CBN with rigid setups, or finish by grinding.
Can En47 be welded?
Poor weldability (CE ≈ 0.9): preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper — avoid welding on finished springs.
Can En47 be formed, bent or molded?
Cold form or coil only when annealed or as pre-tempered spring strip/wire; hot form at 950–1100 °C, then harden 830–860 °C oil quench and temper 380–520 °C to the target hardness.
What surface finishes work on En47?
No corrosion resistance bare — shot peen then phosphate + oil, powder coat or zinc plate with 190–220 °C bake to avoid hydrogen embrittlement; decarburised skin must be ground off before service.
En47 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 | 0.45 – 0.55 | 0.5 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.9 – 1.2 | 1.05 |
| V0.15 % minimum in BS 970 En47; EN 10089 50CrV4 specifies 0.10–0.25 % | 0.15 – 0.25 | 0.18 |
| P | ≤ 0.04 | — |
| Smax (0.025 max for spring quality) | ≤ 0.04 | — |
| Fe | balance | — |
En47 QT36-40 — frequently asked
What is En47 QT36-40 used for?
En47 QT36-40 is typically used for coil springs, torsion bars and valve springs. In short: high-duty Cr-V spring steel; 50CrV4 / 6150 equivalent; hardest grade in family.
What is the yield strength of En47 QT36-40?
En47 QT36-40 has a typical yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is En47 QT36-40 easy to machine?
Not especially — machinability is rated fair (36/100, worse than 81% of steel grades). Machine in the annealed/spheroidized state (~60 % of 1212); above 40 HRC use carbide or CBN with rigid setups, or finish by grinding.
Can En47 QT36-40 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability (CE ≈ 0.9): preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper — avoid welding on finished springs.
What surface finishes work on En47 QT36-40?
No corrosion resistance bare — shot peen then phosphate + oil, powder coat or zinc plate with 190–220 °C bake to avoid hydrogen embrittlement; decarburised skin must be ground off before service.
Can En47 QT36-40 be formed, bent or molded?
Cold form or coil only when annealed or as pre-tempered spring strip/wire; hot form at 950–1100 °C, then harden 830–860 °C oil quench and temper 380–520 °C to the target hardness.
What is the maximum service temperature of En47 QT36-40?
En47 QT36-40 is rated for continuous use to about 380°C (716 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between En47 QT44-48 and En47-SA?
QT44-48 is the default condition — standard working hardness of En47 springs and torsion bars — best strength/relaxation compromise. SA: softest condition, used for cold heading, deep drawing or heavy cold forming of blanks. Yield strength is 1,450 MPa in QT44-48 versus 400 MPa in SA.
Sources
- BS 970-1: Wrought steels for mechanical and allied engineering purposes (En47 / 735A50) — BSI (1991)
- EN 10089: Hot-rolled steels for quenched and tempered springs (50CrV4, 1.8159) — CEN (2002)
- EN 10270-2: Steel wire for mechanical springs — oil hardened and tempered wire — CEN (2011)
- ASTM A689 / SAE J404 (AISI 6150 alloy spring steel) — ASTM / SAE (2015)
- GB/T 1222 (50CrVA) — SAC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture (spring steels) — ASM International (1996)
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.