1018 steel (G10180): properties, composition, equivalents
1018 steel (AISI/SAE 1018, UNS G10180): 0.18 % C, 0.75 % Mn low-carbon bar. Cold-drawn ≈ 370 MPa (54 ksi) yield / 440 MPa (64 ksi) tensile; hot-rolled ≈ 220/400 MPa. Composition, properties, case hardening, 1018 vs A36 vs 4140, C15/C20/S15C equivalents.
What is 1018?
AISI 1018 is the general-purpose low-carbon steel of North American machine shops: 0.15–0.20 % carbon and 0.6–0.9 % manganese, UNS G10180, sold overwhelmingly as cold-drawn bar ('1018 CRS') in rounds, squares, hexes and flats with a smooth, close-tolerance surface. Cold drawing raises the yield from about 220 MPa (hot-rolled) to 350–400 MPa and gives a bright finish that often needs no further machining — which is why 1018 is the default for shafts, spacers, pins, keys, fixtures, brackets and prototype parts that will not be heat-treated.
Its other role is case hardening: the low carbon core stays tough while carburizing produces a 58–62 HRC skin, so 1018 is used for pins, gears and cam followers in light service. Through-hardening is not possible. Weldability is excellent (CE ≈ 0.3) and it forms, bends and machines easily, though the low carbon makes it 'gummy' with built-up edge on tools.
There is no exact EN grade: C15 (lower Mn) is the case-hardening match, S235JRC or C22 the bright-bar substitute; JIS S17C/S20C, GB 20 and BS 080A17 are near or identical. When a drawing says 1018 for a plate, the buyer usually receives A36 or A1011 CS.
1018 chemical composition
| Element | Mass % | Note |
|---|---|---|
| C | 0.15 – 0.2 | |
| Mn | 0.6 – 0.9 | |
| P | ≤ 0.04 | |
| S | ≤ 0.05 |
SAE J403 / ASTM A29 (G10180). Si is not specified for 10xx bar (typically 0.15–0.30). Compare EN C15 (C 0.12–0.18, Mn 0.30–0.60), C20 / C22 (C 0.17–0.24, Mn 0.40–0.70) — 1018 sits between them with higher Mn.
1018 mechanical properties
| Thickness / condition | Yield strength ReH / Rp0.2 MPa (ksi) | Tensile strength Rm MPa (ksi) | Elongation A % | Hardness |
|---|---|---|---|---|
| Cold drawn (as drawn), 16–22 mm — typical | ≈ 370 (≈ 53.7) | ≈ 440 (≈ 63.8) | 15 | ≈ 126 HB |
| Cold drawn, 22–32 mm — typical | ≈ 345 (≈ 50.0) | ≈ 420 (≈ 60.9) | 15 | ≈ 121 HB |
| Cold drawn, 32–50 mm — typical | ≈ 310 (≈ 45.0) | ≈ 400 (≈ 58.0) | 15 | ≈ 116 HB |
| Cold drawn + stress relieved (A108 SR) — typical | ≈ 400 (≈ 58.0) | ≈ 450 (≈ 65.3) | 18 | ≈ 130 HB |
| Hot rolled — typical | ≈ 220 (≈ 31.9) | ≈ 400 (≈ 58.0) | 25 | ≈ 116 HB |
| Normalized (925 °C) — typical | ≈ 235 (≈ 34.1) | ≈ 420 (≈ 60.9) | 28 | ≈ 121 HB |
| Annealed (870 °C) — typical | ≈ 205 (≈ 29.7) | ≈ 385 (≈ 55.8) | 30 | ≈ 111 HB |
| Carburized & hardened — surface | — | — | — | 58–62 HRC (case), core ≈ 20 HRC |
AISI 1018 is specified by chemistry; mechanical values are typical (ASM / A108 guidance) and vary with bar size and reduction. ASTM A108 gives no strength minimums unless a special condition (e.g. SR) is ordered.
Impact toughness
1018 requires a minimum Charpy V-notch energy of 80 J at 20 °C (typical, hot rolled / normalized). Very tough in the ductile range; cold-drawn bar is less tough (≈ 30–40 J). Transition temperature around −20 to 0 °C for as-rolled material.
1018 equivalent grades
| Grade | System | Match | Why / differences |
|---|---|---|---|
| 080A17 | BS (superseded British) | Identical | BS 970 080A17: C 0.15–0.20, Mn 0.70–0.90. |
| 1020 | AISI / SAE | Near | C 0.18–0.23, Mn 0.30–0.60: slightly higher carbon, lower Mn; used interchangeably for many parts. |
| 1015 / 1010 | AISI / SAE | Near | Lower-carbon cold-heading grades. |
| C15 / C15E | EN (European) | Near | C 0.12–0.18, Mn 0.30–0.60 — lower Mn; the case-hardening equivalent. C16E (1.1148) and C20/C22 are also quoted. |
| S235JRC / C22 | EN (European) | Near | EN 10277 bright bar S235JRC (1.0122) is the general-purpose cold-drawn substitute; C22 (C 0.17–0.24) the closer chemistry. |
| C15 | EN (European) | Near | C 0.15–0.20, Mn 0.60–0.90; the US stock grade most often supplied against a C15 request. |
| 20 | GB/T (China) | Near | GB/T 699 grade 20 (20#): C 0.17–0.23, Mn 0.35–0.65 — slightly higher C, lower Mn. |
| 20 / 18kp | GOST (Russia/CIS) | Near | GOST 1050 Steel 20: C 0.17–0.24, Mn 0.35–0.65. |
| S15C / S17C / S20C | JIS (Japan) | Near | JIS G4051 S17C (C 0.15–0.20, Mn 0.30–0.60) is closest on carbon; S20C on strength. |
| 12L14 | AISI / SAE | Functional | Free-machining leaded steel for high-volume screw-machine parts (not weldable, not case-hardenable). |
| A36 | ASTM / ASME | Functional | Structural plate/shape with guaranteed 250 MPa yield — the alternative for welded structures; 1018 is a bar product with no guaranteed properties. |
Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 1018 →
Old and superseded designations
| Old name | Standard | Note |
|---|---|---|
| C1018 | AISI (pre-1960s prefix) | C = basic open-hearth; still used in catalogues. |
| G10180 | UNS | |
| 080A17 / 080M15 | BS 970 | |
| C15 / C20 | EN 10084 / 10083 | Bracketing European grades. |
| St 37-3 K (bright bar) | DIN 1652 (withdrawn) | German bright-bar equivalent, now EN 10277 S235JRC / C15. |
Product forms and tolerance standards
Product forms: cold-finished (cold-drawn) bar — round, square, hex, flat (ASTM A108): the signature form ('1018 CRS'), hot-rolled bar (A29 / A575 / A576), seamless DOM tube (A513 type 5), welded tube (A513), forgings, wire, cold-heading wire (A510), plate and sheet are usually A36 / A1011 / A1008 rather than '1018'.
Dimensional tolerances: cold-finished bar: ASTM A108 (typ. −0.05 mm on rounds ≤ 25 mm; h10–h11); hot-rolled bar: ASTM A29 / A6; DOM tube: ASTM A513.
Key property values
1018 steel yield strength
Cold-drawn ≈ 370 MPa (54 ksi) in 16–22 mm rounds (decreasing to ≈ 310 MPa at 50 mm); stress-relieved cold-drawn ≈ 400 MPa; hot-rolled ≈ 220 MPa (32 ksi); annealed ≈ 205 MPa.
1018 tensile strength
Cold-drawn ≈ 440 MPa (64 ksi); hot-rolled ≈ 400 MPa (58 ksi); annealed ≈ 385 MPa; carburized core ≈ 500–600 MPa.
1018 hardness
Cold-drawn ≈ 126 HB (≈ 71 HRB); hot-rolled ≈ 116 HB; annealed ≈ 111 HB. Carburized case 58–62 HRC (0.5–1.5 mm typical); through-hardening not possible (as-quenched ≈ 35–40 HRC in very thin sections only).
Heat treatment
Anneal 870–900 °C, furnace cool. Normalize 900–925 °C (1650–1700 °F), air. Stress relieve cold-drawn bar 500–600 °C (A108 condition SR). Carburize 900–930 °C, direct or single quench in water/brine from 790–820 °C (oil for distortion-sensitive parts), temper 150–200 °C. Ac1 ≈ 725 °C, Ac3 ≈ 845 °C.
Machinability
≈ 70–78 % of B1112 (cold-drawn) — good but gummy; sharp tools, positive rake, higher feeds to avoid built-up edge. 1117/1141 or 12L14 are the free-machining alternatives; 1018 machines better than 1020 hot-rolled thanks to the cold-drawn surface.
Physical properties
Density 7.87 g/cm³ (0.284 lb/in³), E = 205 GPa (29.7 × 10⁶ psi), expansion 11.7 × 10⁻⁶/K (20–100 °C), conductivity 51.9 W/m·K, specific heat 486 J/kg·K.
Weldability
Excellent weldability by all processes (CE ≈ 0.30): MIG (ER70S-6), TIG, stick (E6013/E7018), resistance and laser, no preheat, no PWHT. Cold-drawn bar loses its cold-work strength in the HAZ (reverts to ≈ 220 MPa yield) — design welded 1018 assemblies on hot-rolled properties. Do not weld carburized surfaces.
Machining, forming and heat treatment
Good machinability with HSS or carbide; typical turning 60–90 m/min HSS, 150–250 m/min carbide. Chip control is poor (long stringy chips) — use chip breakers. Cold forming, bending (1 t radius), swaging and cold heading are excellent in the annealed or hot-rolled condition; cold-drawn bar has reduced ductility and may crack on sharp bends. Surface treatments: carburizing/carbonitriding, zinc/nickel/chrome plating, black oxide, phosphate.
Typical applications
- Shafts, spacers, pins, dowels, keys, studs for machinery and fixtures
- Prototype and low-stress machined parts, jigs and tooling bodies
- Case-hardened pins, gears, ratchets, cam followers in light service
- Hydraulic and pneumatic cylinder tubes (DOM, A513 type 5)
- Cold-headed bolts and rivets, tie rods, anchor bolts
- Welded brackets, frames and general fabrication (hot-rolled)
- Chain links, agricultural and lawn-equipment parts
1018 compared with related grades
Frequently asked questions
What is the difference between 1018 and A36?
1018 is an AISI bar grade defined by chemistry (0.15–0.20 % C) and sold mainly cold-drawn with ~370 MPa yield; A36 is an ASTM structural specification for plate and shapes with a guaranteed 250 MPa minimum yield and looser chemistry (C ≤ 0.25–0.29 %). Use 1018 for machined bar parts, A36 for welded structures and plate.
Which is stronger, 1018 or 4140?
4140 by a wide margin: even annealed 4140 (≈ 415 MPa yield) exceeds cold-drawn 1018 (≈ 370 MPa), and heat-treated 4140 reaches 900–1600 MPa. 1018 cannot be through-hardened. Choose 1018 for cheap, weldable, low-stress parts; 4140 for strength.
Can 1018 be hardened?
Only on the surface by carburizing or carbonitriding (58–62 HRC case). Its 0.18 % carbon is too low for through-hardening; quenching alone gives at most 35–40 HRC in very thin sections.
What does 1018 CRS mean?
Cold-Rolled Steel — strictly cold-drawn bar (ASTM A108): pickled hot-rolled bar pulled through a die, giving a bright surface, tight tolerance and higher yield strength (≈ 370 MPa vs 220 MPa hot-rolled).
Is 1018 weldable?
Yes, one of the most weldable steels — no preheat, any process, ER70S-6 or E7018. The heat-affected zone loses the strength gained by cold drawing, so welded joints should be designed on hot-rolled strength.
What is 1018 equivalent to in EN?
No exact match. C15/C15E (1.0401/1.1141) for case-hardening use, C22 or S235JRC (EN 10277 bright bar) for general machining. JIS S17C/S20C, GB 20 and BS 080A17 are the closest.
Related grades
Verified against ASTM A29/A29M-20 (SAE J403 chemistry); ASTM A29/A29M-20 Table 1 (G10180); ASTM A108-18 (cold-finished bar); ASM Handbook Vol. 1 (typical properties). Last checked: September 2026.