Steel 45SCD6 QT-1800
Heat-treated state · default condition
EN 45SCD6
QT-1800 = q&T ~1800 MPa
Standard hardened-and-tempered spring condition: best balance of elastic limit, relaxation resistance and toughness.
Values for the QT-1800 condition
Other 45SCD6 tempers and conditions
45SCD6 is listed in 8 conditions; see the grade overview at 45SCD6.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Supply condition for machining, cold coiling of heavy wire or upsetting before final hardening. | 460 | 780 | 18 | 225 HB | — |
Normalized | Grain-refined intermediate condition after hot forging, before quench and temper. | 620 | 980 | 13 | 30 HRC | 6 % IACS |
Hot rolled | Mill supply form for spring makers who do their own annealing and hardening. | 640 | 1,020 | 12 | 31 HRC | 6 % IACS |
Cold drawn | Close-tolerance, decarb-free bar for torsion bars and machined spring components before hardening. | 800 | 950 | 9 | 30 HRC | 6 % IACS |
Q&T ~1500 MPa | Tougher temper for thick torsion bars and stabiliser bars where impact and notch tolerance matter. | 1,330 | 1,500 | 10 | 46 HRC | — |
QT-1800DefaultThis page Q&T ~1800 MPa | Standard hardened-and-tempered spring condition: best balance of elastic limit, relaxation resistance and toughness. | 1,600 | 1,800 | 8 | 51 HRC | — |
Q&T + shot peened (and pre-set) spring | Final production state of coil springs and torsion bars — compressive surface stress lifts fatigue life markedly. | 1,620 | 1,800 | 8 | 51 HRC | 5 % IACS |
Q&T ~2000 MPa | Maximum-strength temper for lightweight high-stress valve and suspension springs; low toughness, very decarb/defect sensitive. | 1,800 | 2,000 | 6 | 54 HRC | — |
What is 45SCD6 QT-1800?
45SCD6 QT-1800 is 45SCD6 heat treated to QT-1800 — standard hardened-and-tempered spring condition: best balance of elastic limit, relaxation resistance and toughness. 45SCD6 QT-1800 has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi). 45SCD6 QT-1800 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- High strength — 1,600 MPa (232 ksi), better than 98% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Limited formability — 10/100, worse than 95% of steel grades
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
45SCD6 QT-1800 properties
Typical room-temperature values for 45SCD6 QT-1800; 13 are specific to this condition. Other listed values are 45SCD6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
45SCD6 QT-1800 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
45SCD6 QT-1800 has a yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
45SCD6 QT-1800 is rated for continuous service to 250°C (482 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
45SCD6 QT-1800 conducts electricity at 5 % IACS, worse than 82% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 45SCD6 QT-1800 takes about 30 MJ of energy and emits 2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
45SCD6 QT-1800's machinability is poor (20/100, worse than 97% of steel grades); weldability not recommended (12/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 45SCD6 QT-1800
Is 45SCD6 easy to machine?
Machine only in the annealed condition (~225 HB) with carbide tooling; after quench-and-temper at 48–55 HRC use grinding or CBN, and avoid grinding burns that cause re-tempering or cracks.
Can 45SCD6 be welded?
Not recommended for load-carrying springs — high carbon equivalent gives hard, crack-prone HAZ; if unavoidable, preheat 300–350 °C, low-hydrogen filler and immediate post-weld temper.
Can 45SCD6 be formed, bent or molded?
Hot coil/forge at 900–1050 °C, or cold coil in annealed state then harden (austenitize ~880 °C, oil quench, temper 400–480 °C to target strength); presetting and shot peening are standard finishing steps.
What surface finishes work on 45SCD6?
Protect with phosphate + oil, zinc-flake or powder coating; avoid electroplating on the high-strength temper or bake at 190–220 °C within 4 h to relieve hydrogen; control furnace atmosphere to prevent surface decarburisation that kills fatigue life.
45SCD6 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 |
|---|---|---|
| CAFNOR 45SCD6 ≈ EN 46SiCrMo6 (1.8062) | 0.42 – 0.5 | 0.46 |
| Siraises elastic limit and relaxation resistance | 1.3 – 1.6 | 1.45 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mohardenability + temper resistance | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Curesidual limit typical of spring steel practice | ≤ 0.25 | — |
| Fe | balance | — |
45SCD6 QT-1800 — frequently asked
What is 45SCD6 QT-1800 used for?
45SCD6 QT-1800 is typically used for torsion bars, heavy springs and suspension components. In short: 1800 MPa spring steel; high fatigue resistance; not for welded assemblies.
What is the yield strength of 45SCD6 QT-1800?
45SCD6 QT-1800 has a typical yield strength of 1,600 MPa (232 ksi) and a tensile strength of 1,800 MPa (261 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 45SCD6 QT-1800 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine only in the annealed condition (~225 HB) with carbide tooling; after quench-and-temper at 48–55 HRC use grinding or CBN, and avoid grinding burns that cause re-tempering or cracks.
Can 45SCD6 QT-1800 be welded?
Not readily — weldability is rated not recommended (12/100). Not recommended for load-carrying springs — high carbon equivalent gives hard, crack-prone HAZ; if unavoidable, preheat 300–350 °C, low-hydrogen filler and immediate post-weld temper.
What surface finishes work on 45SCD6 QT-1800?
Protect with phosphate + oil, zinc-flake or powder coating; avoid electroplating on the high-strength temper or bake at 190–220 °C within 4 h to relieve hydrogen; control furnace atmosphere to prevent surface decarburisation that kills fatigue life.
Can 45SCD6 QT-1800 be formed, bent or molded?
Hot coil/forge at 900–1050 °C, or cold coil in annealed state then harden (austenitize ~880 °C, oil quench, temper 400–480 °C to target strength); presetting and shot peening are standard finishing steps.
What is the maximum service temperature of 45SCD6 QT-1800?
45SCD6 QT-1800 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 45SCD6 QT-1800 and 45SCD6-A?
QT-1800 is the default condition — standard hardened-and-tempered spring condition: best balance of elastic limit, relaxation resistance and toughness. A: supply condition for machining, cold coiling of heavy wire or upsetting before final hardening. Yield strength is 1,600 MPa in QT-1800 versus 460 MPa in A.
Sources
- EN 10089 — Hot rolled steels for quenched and tempered springs (46SiCrMo6, 1.8062) — CEN (2002)
- NF A 35-571 — Aciers pour ressorts (désignation AFNOR 45SCD6) — AFNOR (1990)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (Spring Steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Spring steel bar 46SiCrMo6 datasheet — Saarstahl / Ovako (2021)
- EN 13906-1 — Cylindrical helical springs, design and calculation — CEN (2013)
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.