Both are plain-carbon bar steels, but 1045 carries more than double the carbon of 1018. That single difference decides strength, hardness, machinability, weldability and cost. Here is how to pick the right one for your part.
Choose 1018 when the part is welded, formed or machined and strength demand is modest — studs, pins, brackets, weldments and carburised wear parts. Choose 1045 when the part must carry real load or be through-hardened — shafts, axles, gears, spindles and keyed components. 1018 is easier to weld, form and machine; 1045 is stronger and hardenable. If 1045 still isn't strong enough, the next step is an alloy grade such as EN19 / 4140.
| Property | 1018 | 1045 |
|---|---|---|
| Type | Low-carbon (mild) steel | Medium-carbon steel |
| Carbon (C) | 0.15–0.20% | 0.43–0.50% |
| Manganese (Mn) | 0.60–0.90% | 0.60–0.90% |
| Silicon (Si) | 0.30% max | 0.15–0.35% |
| Sulphur (S) | 0.050% max | 0.050% max |
| Phosphorus (P) | 0.040% max | 0.040% max |
| Tensile strength | 400–480 MPa (as-rolled) | 620–720 MPa (normalised); higher when Q&T |
| Yield strength | 220–310 MPa | 340–460 MPa (normalised) |
| Elongation | 15–25% | 15–20% |
| Hardness | 110–150 HB | 180–230 HB (normalised) |
| Through-hardening | No — carbon too low | Yes — quench & temper |
| Case hardening | Yes — carburise readily | Surface-hardenable by induction/flame |
| Machinability | Good (best cold-drawn) | Moderate; harder on tooling |
| Weldability | Excellent — no preheat needed | Limited — preheat & post-heat advised |
| Relative cost | Lower | Slightly higher |
| Equivalents | 070M20, S20C, C15–C18 | C45 (1.0503), S45C, 080M46 |
| Typical use | Studs, pins, brackets, weldments | Shafts, axles, gears, spindles |
Q&T = quenched and tempered. Actual values for a heat are confirmed on the mill test certificate.
The number in each designation points to carbon content: 1018 carries about 0.18% carbon, 1045 about 0.45%. Carbon is the single biggest lever on a plain-carbon steel's behaviour. More carbon means more strength and hardness potential, but less ductility, harder machining and tougher welding.
At 0.18% carbon, 1018 stays soft and forgiving. It welds without preheat, cold-forms and cold-heads well, and machines cleanly in the cold-drawn condition. What it cannot do is reach high hardness by quenching — there simply isn't enough carbon to form a hard martensitic structure through the section. The practical answer for a hard surface on 1018 is carburising, which adds carbon to the skin.
At 0.45% carbon, 1045 crosses into medium-carbon territory. It responds to quench-and-temper heat treatment and can be surface-hardened by induction or flame, so it suits parts that carry load or wear. The trade is that welding needs preheat and slow cooling to avoid cracking, and machining wears tooling faster than 1018.
Ambhe Ferro is an engineering-steel manufacturer with two factories in MIDC Murbad, near Kalyan — about 80 km from Mumbai Port and JNPT. We roll and finish 1018 and 1045 steel at our units and dispatch quickly across the Mumbai–Pune–Nashik corridor and pan-India. Regular dispatches go to buyers in Mumbai, Navi Mumbai, Thane, Vasai–Virar, Pune, Pimpri-Chinchwad, Chakan, Nashik, Ahmednagar, Aurangabad, Kolhapur, Nagpur, Rajkot, Ahmedabad and Bengaluru; exports are arranged on request. Order as hot-rolled rounds, bright bars, hexagons or RCS against your size and tonnage, with a heat-wise mill test certificate on every dispatch. MOQ is 5 MT per size.
Tell us the grade, form, size, and tonnage. Ambhe Ferro responds with pricing, availability, and lead time — and a mill test certificate on every heat.
