Steel C40-CD (Cold drawn)
Supply condition
EN C40 · AISI/SAE 1040 · JIS S40C · GB 40
Pick for close tolerance, straight bright bar with raised yield strength and good chip control on screw machines.
Values for the CD condition
Other C40 tempers and conditions
C40 is listed in 11 conditions; see the grade overview at C40.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold heading, deep drawing or fine machining where a spheroidized carbide structure is needed. | 320 | 500 | 33 | 143 HB | 10.5 % IACS |
Hot rolled | Lowest-cost as-rolled stock for non-critical parts that will be machined and later heat treated. | 320 | 550 | 25 | 156 HB | — |
Annealed | Softest condition, for maximum cold formability and easy rough machining before heat treatment. | 350 | 520 | 30 | 149 HB | 52 W/m·K |
+NDefault Normalized | Default stock condition: uniform fine ferrite–pearlite grain, balanced strength/toughness, good base for machining or later Q&T. | 375 | 590 | 28 | 170 HB | — |
Q&T | Use when maximum toughness and easy machining are wanted from a tempered martensitic structure. | 435 | 620 | 28 | 192 HB | — |
Quenched and tempered | Standard EN delivery condition for shafts and machine parts needing ~650–800 MPa with useful toughness. | 500 | 720 | 18 | 18 HRC | — |
Induction hardened | Select for shaft journals, splines and slideways needing a hard wear surface over a tough tempered core. | 500 | 720 | 16 | 54 HRC | 9 % IACS |
CDThis page Cold drawn | Pick for close tolerance, straight bright bar with raised yield strength and good chip control on screw machines. | 530 | 620 | 12 | 180 HB | — |
Q&T 25–30 HRC (≈255–290 HB) | Common shaft/gear-blank hardness band: good strength with parts still readily machinable. | 700 | 880 | 17 | 28 HRC | — |
Q&T 28–32 HRC (≈270–310 HB) | Typical specified band for medium-duty shafts, couplings and gear blanks in small sections. | 780 | 950 | 15 | 30 HRC | — |
Q&T 32–36 HRC (≈300–340 HB) | Upper practical Q&T band for C40 in thin sections where wear and strength outweigh toughness. | 900 | 1,080 | 13 | 34 HRC | — |
What is C40-CD?
C40-CD is C40 supplied in the CD condition — pick for close tolerance, straight bright bar with raised yield strength and good chip control on screw machines. C40-CD has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 69% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). C40-CD 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). +N is the default condition FabDigit quotes; CD is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
C40-CD properties
Typical room-temperature values for C40-CD; 11 are specific to this condition. Other listed values are C40 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
C40-CD 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
C40-CD has a yield strength of 530 MPa (76.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 69% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
C40-CD is rated for continuous service to 400°C (752 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
C40-CD conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of C40-CD takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
C40-CD's machinability is good (60/100, better than 83% of steel grades); weldability fair (40/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C40-CD
Is C40 easy to machine?
Machines well at 55–65 % of 1212; best in the annealed/normalized or cold-drawn state — above ~30 HRC use carbide and reduce speed; sulphurized oil improves finish.
Can C40 be welded?
Weldable with care only: CE ≈ 0.55, so preheat 150–250 °C, use low-hydrogen electrodes and post-weld stress relief/temper to avoid HAZ martensite cracking.
Can C40 be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold bending needs generous radii (≥2t) and is best in the annealed or spheroidized condition.
What surface finishes work on C40?
No inherent corrosion protection — apply phosphate+oil, black oxide, zinc plating, hard chrome or paint; grinds and polishes to a fine finish but rusts quickly if left bare.
C40 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 |
|---|---|---|
| CEN 10083-2 C40; AISI 1040 = 0.37–0.44 | 0.37 – 0.44 | 0.4 |
| Si | ≤ 0.4 | 0.25 |
| MnAISI 1040: 0.60–0.90 | 0.5 – 0.8 | 0.65 |
| PC40E ≤0.030 | ≤ 0.05 | — |
| SC40E ≤0.035 | ≤ 0.05 | — |
| Crresidual | ≤ 0.4 | — |
| Niresidual | ≤ 0.4 | — |
| Moresidual; Cr+Ni+Mo ≤0.63 | ≤ 0.1 | — |
| CuGB/T 699 residual limit | ≤ 0.25 | — |
| Fe | balance | — |
C40-CD — frequently asked
What is C40-CD used for?
C40-CD is typically used for shafts, gears, spindles, connecting rods and bolts. In short: workhorse quench-and-temper carbon steel; stronger than mild steel; cheaper than alloy 4140.
What is the yield strength of C40-CD?
C40-CD has a typical yield strength of 530 MPa (76.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 69% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is C40-CD easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines well at 55–65 % of 1212; best in the annealed/normalized or cold-drawn state — above ~30 HRC use carbide and reduce speed; sulphurized oil improves finish.
Can C40-CD be welded?
With care — weldability is rated fair (40/100). Weldable with care only: CE ≈ 0.55, so preheat 150–250 °C, use low-hydrogen electrodes and post-weld stress relief/temper to avoid HAZ martensite cracking.
What surface finishes work on C40-CD?
No inherent corrosion protection — apply phosphate+oil, black oxide, zinc plating, hard chrome or paint; grinds and polishes to a fine finish but rusts quickly if left bare.
Can C40-CD be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold bending needs generous radii (≥2t) and is best in the annealed or spheroidized condition.
What is the maximum service temperature of C40-CD?
C40-CD 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 C40 +N and C40-CD?
+N is the default condition — default stock condition: uniform fine ferrite–pearlite grain, balanced strength/toughness, good base for machining or later Q&T. CD: pick for close tolerance, straight bright bar with raised yield strength and good chip control on screw machines. Yield strength is 375 MPa in +N versus 530 MPa in CD.
Sources
- EN 10083-2 Steels for quenching and tempering – Non-alloy steels (C40, 1.0511) — CEN (2006)
- ASTM A29/A29M & SAE J403 (AISI 1040) — ASTM / SAE (2020)
- JIS G4051 Carbon steels for machine structural use (S40C) — JSA (2016)
- ASM Handbook Vol.1: Properties and Selection – Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook, 31st ed. (machinability ratings, heat treatment) — Industrial Press (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.