A36 vs 1018: differences explained
A36 vs 1018: A36 is an ASTM structural spec (≥ 250 MPa yield, loose chemistry, plate/shapes); 1018 is an AISI chemistry grade (0.18 % C, no guaranteed strength, cold-drawn bar ≈ 370 MPa). Same family of mild steel, different rules — table and when each applies.
Overview
'Are A36 and 1018 the same?' is one of the most-asked steel questions in North America, and the honest answer is: they are the same *kind* of steel bought under two different *kinds* of rules. ASTM A36 is a performance specification — it guarantees 250 MPa (36 ksi) minimum yield and 400–550 MPa tensile for structural plate, shapes and bar, and lets carbon float up to 0.25–0.29 %. AISI/SAE 1018 is a chemistry designation — 0.15–0.20 % carbon, 0.6–0.9 % manganese — with no guaranteed strength at all; what you get depends on the condition, and it is almost always sold as cold-drawn bar with about 370 MPa yield.
In a hot-rolled bar the two are practically interchangeable; the difference shows up in what is certified (strength vs chemistry), in the surface and tolerance (A36 mill-scale vs 1018 bright cold-drawn), in weldability (1018's lower carbon is marginally better) and in what a code inspector will accept.
A36 vs 1018 side by side
| Property | A36 | 1018 |
|---|---|---|
| Type of designation | ASTM performance specification (A36/A36M) | AISI/SAE chemistry grade (ASTM A29 / A108) |
| What is guaranteed | yield ≥ 250 MPa, tensile 400–550 MPa, elongation | chemistry only; strength by condition/agreement |
| Carbon | ≤ 0.25–0.29 % (by product/thickness) | 0.15–0.20 % |
| Manganese | 0.60–1.20 % (varies; often unspecified ≤ 20 mm) | 0.60–0.90 % |
| P / S max | 0.030 / 0.030 % | 0.040 / 0.050 % |
| Usual product forms | plate, angles, channels, flats, W/S shapes, hot-rolled bar | cold-drawn rounds, squares, hexes, flats; hot-rolled bar; DOM tube |
| Usual surface | hot-rolled with mill scale | bright cold-drawn (CRS); hot-rolled available |
| Yield strength | ≥ 250 MPa (36 ksi) min; typ. 280–340 | ≈ 370 MPa (54 ksi) cold-drawn; ≈ 220 MPa hot-rolled (not guaranteed) |
| Tensile strength | 400–550 MPa (58–80 ksi) | ≈ 440 MPa cold-drawn; ≈ 400 MPa hot-rolled |
| Elongation | ≥ 20 % (200 mm) / 23 % (50 mm) | ≈ 15 % cold-drawn; ≈ 25 % hot-rolled |
| Hardness (typical) | 119–159 HB | ≈ 126 HB cold-drawn |
| Dimensional tolerance | ASTM A6 (hot-rolled, wide) | ASTM A108 (cold-finished, tight; h10–h11) |
| Weldability | excellent (CE ≈ 0.3–0.4; AWS D1.1 prequalified) | excellent (CE ≈ 0.3); HAZ loses cold-work strength |
| Machinability (vs B1112) | ≈ 72 % (hot-rolled) | ≈ 70–78 % (cold-drawn) |
| Case hardening | possible but not controlled | yes — standard carburizing grade |
| Accepted for structural design (AISC) | yes (Fy = 36 ksi) | no (not a listed structural material) |
| Price basis | per tonne, structural | per kg, cold-finished bar (≈ 1.2–1.5× hot-rolled) |
| EN cross-reference | S235JR / S275JR (near) | C15 / C22 / S235JRC (near) |
| Typical use | structures, base plates, brackets, weldments, plate parts | shafts, pins, spacers, fixtures, machined and carburized parts |
Which should you choose?
Specify A36 when the part is structural, made from plate or shapes, welded, or must satisfy a building/bridge/equipment code: it is what AISC, AWS D1.1 and every fabricator expect, and the strength is certified.
Specify 1018 when the part is machined from bar and needs a bright surface, tight tolerance, or a carburized skin: shafts, pins, spacers, guides, fixtures. Its higher cold-drawn yield is a bonus, not a guarantee.
For a hot-rolled round or flat bar in a non-code application, either name will get you essentially the same steel; write 'A36' for plate and structural shapes and '1018 CRS' for cold-finished bar, and do not claim A36 structural properties for 1018 or 1018 chemistry for A36.
- Structural members, base plates, gussets, stiffeners
- Welded frames and weldments to AWS D1.1
- Plate parts, flame-cut shapes, angles and channels
- Anything requiring a certified minimum yield
- Galvanized or painted structural steelwork
- Machined shafts, pins, dowels, spacers, keys
- Parts needing bright cold-drawn surface and tight tolerance
- Case-hardened (carburized) wear parts
- Fixtures, jigs, prototypes from bar stock
- Cold-headed fasteners and cold-formed parts
Frequently asked questions
Are A36 and 1018 the same steel?
Chemically they overlap (both low-carbon mild steels), but A36 is an ASTM structural specification guaranteeing 250 MPa yield with loose chemistry, while 1018 is an AISI chemistry grade (0.15–0.20 % C) with no guaranteed strength, usually sold cold-drawn. Hot-rolled 1018 and A36 bar behave alike; they are not interchangeable on paper.
Which is stronger, A36 or 1018?
Cold-drawn 1018 is typically stronger (≈ 370 MPa yield, thanks to cold work) than A36's 250 MPa minimum, but 1018's strength is not guaranteed and disappears in weld heat-affected zones. Hot-rolled 1018 is about the same as A36 or slightly weaker.
Can I weld 1018 to A36?
Yes, easily — both are low-carbon steels welded with ER70S-6 / E7018 without preheat. Design the joint on hot-rolled (≈ 220–250 MPa) properties because cold-drawn 1018 softens in the HAZ.
Which is easier to machine?
Cold-drawn 1018 (≈ 70–78 %) is marginally better than hot-rolled A36 (≈ 72 %) and gives a cleaner finish; both are 'gummy' low-carbon steels that benefit from sharp tooling and chip breakers.
Can A36 be case hardened like 1018?
It can be carburized, but A36's chemistry is not controlled for it (carbon may be up to 0.29 %, Mn variable), so results are less predictable. Use 1018 (or 8620 for higher core strength) when a specified case is required.
What do I order for a round bar — A36 or 1018?
For a bright, accurate bar to machine: 1018 CRS. For a hot-rolled bar in a welded structure: A36 (hot-rolled merchant bar is often dual-certified A36/1018-type anyway).
Related comparisons
Verified against ASTM A36/A36M-19; ASTM A29/A29M-20; A108-18. Last checked: September 2026.