Steel S45C · hardness band
Steel S45C QT 34-40 HRC
Properties of the QT 34-40 HRC condition, compared with the other S45C tempers.
Use for wear parts and small-section shafts where strength beats toughness; grinding usually needed after heat treat.
What is S45C QT 34-40 HRC?
S45C QT 34-40 HRC is S45C heat treated to QT 34-40 HRC — use for wear parts and small-section shafts where strength beats toughness; grinding usually needed after heat treat. S45C QT 34-40 HRC has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi). S45C QT 34-40 HRC 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). Normalized is the default condition FabDigit quotes; QT 34-40 HRC is available on request or by drawing note.
Advantages
- High strength — 950 MPa (138 ksi), better than 91% of steel grades
- High electrical conductivity — 10.7 % IACS, better than 91% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
Limitations
- Limited ductility — 11%, worse than 89% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 87% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Difficult to machine — 35/100, worse than 83% of steel grades
S45C QT 34-40 HRC properties
Typical room-temperature values for S45C QT 34-40 HRC — 12 properties are specific to this condition; the rest are grade-level values shared by every S45C temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
S45C QT 34-40 HRC 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
S45C QT 34-40 HRC has a yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S45C QT 34-40 HRC is rated for continuous service to 400°C (752 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
S45C QT 34-40 HRC conducts electricity at 10.7 % IACS, better than 91% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S45C QT 34-40 HRC takes about 26 MJ of energy and emits 2.1 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability8
S45C QT 34-40 HRC's machinability is fair (35/100, worse than 83% of steel grades); weldability poor (20/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other S45C tempers and conditions
S45C is also supplied in 8 other conditions. The full side-by-side table is on the S45C overview.
- NormalizedDefaultDefault stocked condition: uniform fine pearlitic structure, predictable machining and a sound base for later induction or through hardening.380 MPa yield · 187 HB
- QT 34-40 HRCUse for wear parts and small-section shafts where strength beats toughness; grinding usually needed after heat treat.950 MPa yield · 37 HRC
- QT 28-32 HRCMould plate / gear blank condition: highest strength still comfortably machinable with carbide tooling.750 MPa yield · 30 HRC
- CDChoose for close tolerance, bright surface shafting used with little or no machining; note residual stress and lower ductility.600 MPa yield · 207 HB
- QTGeneral strengthened condition per JIS/GB for shafts, gears and connecting parts needing ≥690 MPa with good toughness.550 MPa yield · 22 HRC
- IHChoose when a wear-resistant 50–58 HRC skin (0.5–3 mm case) is needed on a tough normalized or Q&T core, e.g. shaft journals and guide rails.550 MPa yield · 55 HRC
- HRCheapest stock form for weldments and rough machined parts where dimensional and property scatter is acceptable.340 MPa yield · 179 HB
- APick for maximum softness before heavy cold forming, deep drilling or re-hardening.310 MPa yield · 163 HB
Working with S45C QT 34-40 HRC
Is S45C easy to machine?
Good turning/milling at ~57 % of 1212; best chip control at 170–230 HB, use rigid setups and coolant above 300 HB, expect abrasive tool wear from pearlite.
Can S45C be welded?
Weldable but carbon-equivalent ≈0.6: preheat 150–250 °C, low-hydrogen consumables (E7018/ER70S-6) and post-weld stress relief or normalizing to avoid HAZ martensite cracking.
Can S45C be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold bending is limited (generous bend radii, anneal first), and cold-drawn bar should be stress-relieved before heavy machining to control distortion.
What surface finishes work on S45C?
No anodizing; protect by black oxide, phosphate, zinc/nickel or hard-chrome plating, paint or oil — surfaces flash-rust within hours of grinding.
S45C 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 |
|---|---|---|
| CJIS G4051 S45C | 0.42 – 0.48 | 0.45 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.04 | — |
| Curesidual max | ≤ 0.3 | — |
| Niresidual max; Ni+Cr ≤ 0.35 | ≤ 0.2 | — |
| Crresidual max | ≤ 0.2 | — |
| Fe | balance | — |
S45C QT 34-40 HRC — frequently asked
What is S45C QT 34-40 HRC used for?
S45C QT 34-40 HRC is typically used for crankshafts, shafts and industrial bolts. In short: normalized Japanese carbon bar.
What is the yield strength of S45C QT 34-40 HRC?
S45C QT 34-40 HRC has a typical yield strength of 950 MPa (138 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is S45C QT 34-40 HRC easy to machine?
Not especially — machinability is rated fair (35/100, worse than 83% of steel grades). Good turning/milling at ~57 % of 1212; best chip control at 170–230 HB, use rigid setups and coolant above 300 HB, expect abrasive tool wear from pearlite.
Can S45C QT 34-40 HRC be welded?
Not readily — weldability is rated poor (20/100). Weldable but carbon-equivalent ≈0.6: preheat 150–250 °C, low-hydrogen consumables (E7018/ER70S-6) and post-weld stress relief or normalizing to avoid HAZ martensite cracking.
What surface finishes work on S45C QT 34-40 HRC?
No anodizing; protect by black oxide, phosphate, zinc/nickel or hard-chrome plating, paint or oil — surfaces flash-rust within hours of grinding.
Can S45C QT 34-40 HRC be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold bending is limited (generous bend radii, anneal first), and cold-drawn bar should be stress-relieved before heavy machining to control distortion.
What is the maximum service temperature of S45C QT 34-40 HRC?
S45C QT 34-40 HRC 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 S45C Normalized and S45C-CD?
Normalized is the default condition — default stocked condition: uniform fine pearlitic structure, predictable machining and a sound base for later induction or through hardening. CD: choose for close tolerance, bright surface shafting used with little or no machining; note residual stress and lower ductility. Yield strength is 380 MPa in Normalized versus 600 MPa in CD.
Can FabDigit make parts in S45C QT 34-40 HRC?
Yes — S45C QT 34-40 HRC 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
- JIS G 4051 — Carbon steels for machine structural use — JISC (2016)
- EN 10083-2 — Non-alloy quality steels C45 (1.0503) — CEN (2006)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Metals Reference Book / machinability ratings — ASM International (1993)
- Carbon steel LCI datasets (embodied energy/carbon) — worldsteel (2022)
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.