1021 Low Carbon Steel: Composition, Properties & S20C Equivalent
AISI/SAE 1021 (SAE J403) is a low carbon steel with C 0.18–0.23% and Mn 0.60–0.90%, close to JIS G 4051 S20C, EN C22E and GB Grade 20. It has more manganese than 1020 for slightly higher strength and hardenability, while keeping good cold heading, weldability and carburizing response.
Overview
1021 has the same carbon range as 1020 (0.18–0.23%) but manganese raised to 0.60–0.90%, giving slightly higher strength and hardenability than 1020 while cold heading, welding and carburizing stay good. It is common on US drawings for cold-headed parts, carburized parts and general structural parts.
JIS S20C, widely used in Taiwan, has the same carbon range as 1021 but only Mn 0.30–0.60%, so the two are near equivalents; when a drawing specifies 1021, check that manganese falls within 0.60–0.90%. 1021 is still too low in carbon for Q+T use; carburized parts that need higher core strength should move to alloy case-hardening steels such as SCM420.
Chemical Composition (SAE J403, Long Products)
| Element | Spec Range (%) |
|---|---|
| C (Carbon) | 0.18 – 0.23 |
| Mn (Manganese) | 0.60 – 0.90 |
| P (Phosphorus) | ≤ 0.040 |
| S (Sulfur) | ≤ 0.050 |
P and S are the SAE J403 limits for long products such as bar and wire rod; flat-rolled products (sheet, strip) are limited to P ≤ 0.030% and S ≤ 0.035%. For comparison, JIS G 4051 S20C is C 0.18–0.23%, Si 0.15–0.35%, Mn 0.30–0.60%, P ≤ 0.030%, S ≤ 0.035% — the same carbon range, but lower manganese.
Mechanical Properties (Reference)
| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Reduction of Area (%) | Hardness (HB) |
|---|---|---|---|---|---|
| Hot rolled | 420 | 230 | 24 | 48 | 116 |
| Cold drawn | 470 | 390 | 15 | 40 | 131 |
Estimated typical values for hot-rolled and cold-drawn bars per SAE J1397 — not guaranteed values. SAE J403 specifies chemistry only, not mechanical properties. Actual values depend on size, cold-drawing reduction and processing.
Heat Treatment & Processing
Hardening
With low carbon, direct quench hardening has little effect; 1021 is not used as a Q+T steel. Choose a medium-carbon grade where strength is needed.
Carburizing
1021 is a common carbon-steel carburizing base; its higher manganese gives slightly better hardenability than 1020. After carburizing, quenching and tempering the surface is wear resistant and the core tough. Carbon steel hardenability is still limited, so core strength is lower than alloy case-hardening steels such as SCM420.
Annealing & Normalizing
Process annealing between cold heading or multi-pass drawing restores ductility; normalizing homogenizes the as-rolled structure and improves machined finish.
Welding
Low carbon equivalent gives good weldability, normally without preheat; carburized cases should not be welded afterwards.
International Standard Equivalents
| Standard | Equivalent Grade | Correspondence |
|---|---|---|
| AISI/SAE (USA) | 1021 (SAE J403) | Reference standard |
| UNS | G10210 | Identical |
| JIS (Japan) | S20C (G 4051) | Near equivalent |
| EN (Europe) | C22E (1.1151) | Near equivalent |
| GB (China) | 20 (Grade 20) | Near equivalent |
S20C has the same carbon range as 1021 but Mn 0.30–0.60%, and also specifies Si 0.15–0.35% and S ≤ 0.035%. 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%. All three have lower manganese than 1021. Where a drawing names a specific standard, follow that standard.
Typical Applications
Cold-Headed Fasteners
Screws, bolt blanks and cold-headed parts that need slightly more strength than 1010 or 1015.
Carburized Parts
Pins, sleeves, lightly loaded gears and small shafts with a carburized wear surface.
Welded & Structural Parts
Welded brackets, flanges and general structural parts.
Automotive & Motorcycle Parts
Low-load small structural parts machined from bar, made mainly by cold heading or welding.
Supply Specifications
| Form | Size Range | Source |
|---|---|---|
| Hot-rolled round bar | Ø 13 – 100 mm | Fengxing |
| Hot-rolled round bar | Ø 14 – 130 mm | CSC |
1021 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.
Material Selection Guide
1021 suits cold-headed, welded or carburized parts that need slightly more strength than 1015. Pick by the main process and load:
JIS specified, or high manganese not needed
Same carbon range with lower Mn 0.30–0.60%, plus specified silicon and a tighter sulfur limit.
Heavier cold-forming deformation
Lower carbon and manganese for better cold heading, with slightly lower strength.
Carburized parts needing high core strength
Cr-Mo case-hardening steel with high hardenability for heavily loaded 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 a quotation, contact the Double Steel sales team via the inquiry form below or LINE.
Related Grades
For cross-standard composition and mechanical property tables, see the technical reference tables.
FAQ
- What is 1021 steel?
- AISI/SAE 1021 (SAE J403) is a low carbon steel: C 0.18–0.23%, Mn 0.60–0.90%, P ≤ 0.040%, S ≤ 0.050%, with good cold heading, weldability and carburizing response.
- What is the difference between 1021 and 1020?
- Both have carbon 0.18–0.23%, but 1021 has Mn 0.60–0.90%, higher than 1020 (0.30–0.60%), for slightly higher strength and hardenability.
- Is 1021 the same as S20C?
- Not exactly — they are near equivalents. Carbon ranges match, but S20C has Mn 0.30–0.60%, lower than 1021, and also specifies Si 0.15–0.35% and S ≤ 0.035%. When a drawing specifies 1021, check the manganese content.
- What are the hardness and strength of 1021?
- SAE J1397 estimates: hot rolled about 420 MPa tensile and HB 116; cold drawn about 470 MPa tensile, 390 MPa yield and HB 131.
- Can 1021 be carburized?
- Yes — 1021 is a common carbon-steel carburizing base. Core strength is limited, so heavily loaded carburized parts should use SCM420.
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