Steel S20CK
JIS S20CK
S20CK is a JIS plain carbon carburizing steel with slightly higher carbon than S15CK, used for general-purpose case-hardened parts.
Reference datasheet — S20CK is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the HR condition
S20CK tempers and conditions
S20CK is supplied in 8 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
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 |
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?
S20CK is a JIS plain carbon carburizing steel with slightly higher carbon than S15CK, used for general-purpose case-hardened parts. The default condition gives 260 MPa yield, 430 MPa tensile, 28% elongation and about 125 HB (70 HRB), with machinability 58, weldability 90 and formability 80 on a 100-point scale; it is stocked hot rolled, normalized, annealed, spheroidized, cold drawn, carburized and carbonitrided. Hardenability is shallow and there is no corrosion resistance, so highly loaded gears should move to an alloyed grade such as SCM415 or 15CrNi6. S20CK 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). S20CK has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 92% of steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi).
What is S20CK used for?
- pins
- small shafts
- light gears
Advantages
- Forms and bends easily — 80/100, better than 93% of steel grades
- 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
- Readily welded — 90/100, better than 90% of steel grades
- Ductile — tolerates forming and impact — 28%, better than 89% of steel grades
Limitations
- Low strength — 260 MPa (37.7 ksi), worse than 92% of steel grades
S20CK properties
Typical room-temperature values for S20CK-HR; bars are the position among steel grades.
Physical3
S20CK 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 has a yield strength of 260 MPa (37.7 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 92% of steel grades. Elongation at break is 28% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
S20CK is rated for continuous service to 400°C (752 °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 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 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's machinability is good (58/100, better than 75% of steel grades); weldability excellent (90/100); formability very good (80/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. S20CK is highlighted; hover a dot for its name, or open the interactive family chart.
Working with S20CK
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
How much does S20CK cost?
S20CK is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
S20CK — frequently asked
What is S20CK used for?
S20CK 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?
S20CK has a typical yield strength of 260 MPa (37.7 ksi) and a tensile strength of 430 MPa (62.4 ksi) — weaker than 92% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is S20CK easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% 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 be welded?
Yes — weldability is rated excellent (90/100). 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?
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 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?
S20CK 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 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.
How much does S20CK cost?
S20CK is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.