1018 and 1045 are common carbon steels that differ mainly in carbon content. That single difference drives their strength, hardness, and how they are best used.
| Property | undefined | undefined |
|---|---|---|
| Carbon content | 0.18% | 0.45% |
| Yield strength (cold drawn) | 370 MPa (54 ksi) | 530 MPa (77 ksi) |
| Tensile (cold drawn) | 440 MPa (64 ksi) | 625 MPa (91 ksi) |
| Hardness | About 126 HB | 170 to 200 HB |
| Weldability | Excellent | Fair, preheat helps |
| Heat treatment | Case-harden only | Through-hardenable |
| Typical use | Shafts, pins, weldments | Gears, axles, bolts |
Which should you choose
Choose 1018 when you need a mild, weldable, easily machined steel for general parts, or a core that can be case-hardened for a tough skin.
Choose 1045 when you need more strength and the ability to through-harden by heat treatment, as in gears and high-load shafts.
Carbon drives the trade-off. More carbon means more strength and hardenability but poorer weldability. 1018 welds easily; 1045 is stronger and heat-treatable.
Compare data sheets: 1018 Steel and 1045 Steel.