Steel S20CK-CN (Carbonitrided and tempered)
Heat-treated state
JIS S20CK
Lower-cost thin-case alternative for small stamped or turned parts needing wear resistance only at the surface.
Values for the CN condition
Other S20CK tempers and conditions
S20CK is listed in 8 conditions; see the grade overview at S20CK.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Use for cold-heading and deep upsetting of pins and fasteners before carburizing. | 230 | 385 | 36 | 110 HB | 10.8 % IACS |
Solution annealed | Softest condition for maximum cold formability and stress-free machining of blanks. | 240 | 400 | 34 | 115 HB | 11 % IACS |
HRDefault Hot rolled | Standard mill-supplied condition for bars and wire rod before machining and carburizing. | 260 | 430 | 28 | 125 HB | — |
Normalized | Pick for uniform fine-grain structure and consistent carburizing/machining response after forging. | 280 | 450 | 30 | 131 HB | 10.5 % IACS |
CNThis page Carbonitrided and tempered | Lower-cost thin-case alternative for small stamped or turned parts needing wear resistance only at the surface. | 380 | 560 | 20 | 58 HRC | 10 % IACS |
Water quenched and tempered | Direct quench-and-temper of thin sections when moderate strength is wanted without a carburized case. | 390 | 560 | 22 | 170 HB | 10.2 % IACS |
Carburized, quenched and tempered | The service condition: hard wear-resistant case on a tough low-carbon core for pins, bushings and light gears. | 420 | 620 | 20 | 60 HRC | — |
Cold drawn | Choose for close-tolerance bright bar with higher strength and better surface for turned parts. | 430 | 520 | 15 | 155 HB | — |
What is S20CK-CN?
S20CK-CN is S20CK heat treated to CN — lower-cost thin-case alternative for small stamped or turned parts needing wear resistance only at the surface. S20CK-CN has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 68% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). S20CK-CN has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F). HR is the default condition FabDigit quotes; CN is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
S20CK-CN properties
Typical room-temperature values for S20CK-CN; 21 are specific to this condition. Other listed values are S20CK reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
S20CK-CN has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F).
Mechanical14
S20CK-CN has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 68% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S20CK-CN is rated for continuous service to 180°C (356 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
S20CK-CN conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of S20CK-CN 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
S20CK-CN's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (20/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with S20CK-CN
Is S20CK easy to machine?
Machine soft (HB 110–155) before carburizing; gummy chips and built-up edge — use sharp positive-rake tools, good coolant, avoid finishing after case hardening except by grinding.
Can S20CK be welded?
Excellent weldability in the soft condition (CE ≈ 0.30, no preheat below ~25 mm); never weld through a carburized case — mask or remove case first.
Can S20CK be formed, bent or molded?
Very good cold formability for bending, heading and deep drawing in the annealed/spheroidized state; forge at 1050–1200 °C followed by normalizing.
What surface finishes work on S20CK?
No anodizing; protect with zinc or nickel plating, black oxide, phosphate-and-oil or paint — carburized surfaces should be baked after plating to avoid hydrogen embrittlement.
S20CK 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 | 0.18 – 0.23 | 0.2 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.3 – 0.6 | 0.45 |
| Prestricted for K (case-hardening) grades | ≤ 0.03 | — |
| Srestricted for K (case-hardening) grades | ≤ 0.03 | — |
| Curesidual | ≤ 0.25 | — |
| Niresidual; Ni+Cr ≤ 0.30 | ≤ 0.2 | — |
| Crresidual; Ni+Cr ≤ 0.30 | ≤ 0.2 | — |
| Fe | balance | — |
S20CK-CN — frequently asked
What is S20CK-CN used for?
S20CK-CN is typically used for pins, small shafts and light gears. In short: general-purpose carburizing steel; very good cold formability; weldable before case hardening.
What is the yield strength of S20CK-CN?
S20CK-CN has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is S20CK-CN easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine soft (HB 110–155) before carburizing; gummy chips and built-up edge — use sharp positive-rake tools, good coolant, avoid finishing after case hardening except by grinding.
Can S20CK-CN be welded?
Not readily — weldability is rated poor (20/100). Excellent weldability in the soft condition (CE ≈ 0.30, no preheat below ~25 mm); never weld through a carburized case — mask or remove case first.
What surface finishes work on S20CK-CN?
No anodizing; protect with zinc or nickel plating, black oxide, phosphate-and-oil or paint — carburized surfaces should be baked after plating to avoid hydrogen embrittlement.
Can S20CK-CN be formed, bent or molded?
Very good cold formability for bending, heading and deep drawing in the annealed/spheroidized state; forge at 1050–1200 °C followed by normalizing.
What is the maximum service temperature of S20CK-CN?
S20CK-CN is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between S20CK-HR and S20CK-CD?
HR is the default condition — standard mill-supplied condition for bars and wire rod before machining and carburizing. CD: choose for close-tolerance bright bar with higher strength and better surface for turned parts. Yield strength is 260 MPa in HR versus 430 MPa in CD.
Sources
- JIS G 4051 — Carbon steels for machine structural use — JISC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes (carburizing) — ASM International (2013)
- GB/T 699 — Quality carbon structural steels (20 grade cross-reference) — SAC (2015)
- Mysteel / SMM carbon steel bar spot price references (2025)
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.