Steel S20CK CARB
Heat-treated state
JIS S20CK
CARB = carburized, quenched and tempered
The service condition: hard wear-resistant case on a tough low-carbon core for pins, bushings and light gears.
Values for the CARB 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 |
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 |
CARBThis page 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 CARB?
S20CK CARB is S20CK heat treated to CARB — the service condition: hard wear-resistant case on a tough low-carbon core for pins, bushings and light gears. S20CK CARB has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). S20CK CARB 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; CARB is available on request or by drawing note.
Advantages
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10.5 % IACS, better than 89% 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 CARB properties
Typical room-temperature values for S20CK CARB; 14 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 CARB 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 CARB has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S20CK CARB is rated for continuous service to 180°C (356 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
S20CK CARB conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of S20CK CARB 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 CARB'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 CARB
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 CARB — frequently asked
What is S20CK CARB used for?
S20CK CARB 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 CARB?
S20CK CARB has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is S20CK CARB 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 CARB 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 CARB?
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 CARB 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 CARB?
S20CK CARB 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.