S20C Low Carbon Steel: Composition, Properties & 1020 / C22 Equivalent
S20C is a JIS G 4051 low carbon steel for machine structural use, with carbon 0.18–0.23%, equivalent to AISI/SAE 1020 and GB Grade 20, and close to EN C22E. Slightly stronger than S15C while keeping good cold formability, weldability, and carburizing response — used in pins, bushings, carburized gears, and general structural parts.
Overview
S20C is a low carbon structural steel under JIS G 4051, with carbon 0.18–0.23% — the stronger end of the S-series low carbon steels. About 0.05% more carbon than S15C gives slightly higher strength while cold formability and weldability stay good. Carbon is still too low for quench-and-temper use, so S20C is commonly carburized or used as hot-rolled or normalized for general structural parts.
S20C is a regularly supplied grade, available made to order, with a mill certificate and heat (cast) analysis certificate available for every lot and full chemistry and heat number traceability. See supply specifications below for sizes; please inquire for stock and lead time.
Chemical Composition (JIS G 4051)
| Element | Specification (%) |
|---|---|
| C (Carbon) | 0.18 – 0.23 |
| Si (Silicon) | 0.15 – 0.35 |
| Mn (Manganese) | 0.30 – 0.60 |
| P (Phosphorus) | ≤ 0.030 |
| S (Sulfur) | ≤ 0.035 |
| Ni (Nickel) | ≤ 0.20 |
| Cr (Chromium) | ≤ 0.20 |
| Cu (Copper) | ≤ 0.30 |
| Ni + Cr | ≤ 0.35 |
Mechanical Properties After Heat Treatment (Reference)
| Condition | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HB) |
|---|---|---|---|---|
| Annealed (~860°C, furnace cool) | — | — | — | 114–153 |
| Normalized (870–920°C, air cool) | ≥ 400 | ≥ 245 | ≥ 28 | 116–174 |
Reference values commonly used in the Japanese steel industry after heat treatment (former JIS G 4051 reference values, Ø25 mm test piece) — not guaranteed values for hot-rolled delivery. The current JIS G 4051 does not specify mechanical properties after heat treatment. S20C is too low in carbon for quench-and-temper use; surface hardness and core strength after carburizing depend on carburizing conditions and section size.
Heat Treatment
Carburizing
S20C is a common carbon steel for carburizing, with slightly higher core strength than S15C. Carburize, quench, and low-temperature temper for a wear-resistant surface with a tough core. Carbon steel has low hardenability; choose an alloy carburizing steel such as SCM420 for heavy-load gears or larger carburized sections.
Quench Hardening
With only 0.18–0.23% carbon, direct quench hardening has limited effect, and S20C is not used as a quench-and-temper steel. Choose a medium carbon steel such as S45C when Q+T strength is needed.
Annealing & Normalizing
Process annealing between cold forging or multi-pass cold drawing restores ductility. Normalizing homogenizes the hot-rolled structure, improves the machined surface, and is often used before carburizing.
Welding
Low carbon equivalent gives good weldability, usually without preheating. Do not weld on a carburized case.
International Standard Equivalents
| Standard | Equivalent Grade | Correspondence |
|---|---|---|
| JIS (Japan) | S20C (G 4051) | Reference standard |
| AISI/SAE (USA) | 1020 | Equivalent |
| AISI/SAE (USA) | 1021 | Near equivalent |
| DIN (Germany) | C22 / Ck22 | Near equivalent |
| EN (EU) | C22E (1.1151) | Near equivalent |
| GB (China) | 20 (GB/T 699) | Equivalent |
Composition ranges differ slightly: AISI/SAE 1020 is C 0.18–0.23%, Mn 0.30–0.60% (SAE J403 does not specify Si); 1021 has the same carbon range but higher Mn 0.60–0.90%; EN C22E is C 0.17–0.24%, Mn 0.40–0.70%; GB/T 699 Grade 20 is C 0.17–0.23%, Mn 0.35–0.65%. Where a specific standard is required, follow the standard named on the drawing.
Typical Applications
Machine Components
Pins, bushings, sleeves, mounting bases, and other low-to-medium load parts, plus general carburized parts.
Automotive & Motorcycle Parts
Low-load small structural parts and small carburized parts.
Cold-Forged & Cold-Formed Parts
Cold-forged head parts and cold-bent parts that need slightly more strength than S15C.
Hardware & Welded Parts
Welded brackets, flanges, and general hardware structural parts.
Supply Specifications
| Form | Size Range | Source |
|---|---|---|
| Hot-rolled round bar | Ø 13 – 100 mm | Fengxing |
| Hot-rolled round bar | Ø 14 – 130 mm | CSC |
S20C is a regularly supplied grade, available made to order; a mill certificate and heat (cast) analysis certificate are available for every lot. Please inquire for sizes outside these ranges, stock, and lead time.
Selection Guide
S20C suits parts made by cold forming, welding, or general carburizing that need slightly more strength than S15C. Choose by the main process and load:
Heavier cold forming
About 0.05% less carbon for slightly better cold formability and weldability, with slightly lower strength.
US standard specified, slightly higher Mn wanted
Same carbon range as S20C with higher Mn 0.60–0.90% for slightly higher strength and hardenability.
Carburized parts need high core strength
Cr-Mo carburizing steel with high hardenability for heavy-load gears and shafts.
Part needs Q+T strength
Medium carbon steel that can be quenched and tempered above HB 200 for loaded shafts and structural parts.
For technical consultation or quotations, contact the Double Steel sales team via the inquiry form below or LINE customer service.
Related Grades
For cross-standard composition and mechanical property tables, see the technical reference tables.
FAQ
- What is S20C steel?
- S20C is a JIS G 4051 low carbon steel for machine structural use, with carbon 0.18–0.23%. It is slightly stronger than S15C, with good cold formability, weldability, and carburizing response.
- Are S20C, 1020, C22, and GB Grade 20 the same?
- S20C (JIS G 4051) is generally regarded as equivalent to AISI/SAE 1020 and GB Grade 20, and close to EN C22E (1.1151): 1020 does not specify Si; C22E is C 0.17–0.24%, Mn 0.40–0.70%; Grade 20 is C 0.17–0.23%, Mn 0.35–0.65%. Where certification to a standard is required, follow the standard named on the drawing.
- What is the difference between S20C and 1021?
- Both have carbon 0.18–0.23%, but 1021 has Mn 0.60–0.90%, higher than S20C (0.30–0.60%), for slightly higher strength and hardenability — a near equivalent, not the same grade.
- What is the chemical composition of S20C?
- JIS G 4051 specifies C 0.18–0.23%, Si 0.15–0.35%, Mn 0.30–0.60%, P ≤ 0.030%, S ≤ 0.035%, plus Ni ≤ 0.20%, Cr ≤ 0.20%, Cu ≤ 0.30%, Ni+Cr ≤ 0.35%.
- What is the hardness of S20C?
- It depends on heat treatment (reference values): annealed HB 114–153, normalized HB 116–174. Hardness is not guaranteed for hot-rolled delivery; surface hardness after carburizing depends on carburizing conditions.
- Can S20C be carburized?
- Yes, S20C is a common carbon steel for carburizing, but core strength is limited; use SCM420 for heavy-load carburized parts.
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