1018 Mild Steel vs 1045 Steel
1018 and 1045 are both plain-carbon steels separated mainly by carbon content. 1018 is low-carbon (~0.18% C) mild steel — ~440 MPa tensile / 370 MPa yield, ductile, weldable, and easy to work. 1045 is medium-carbon (~0.45% C) — stronger at ~625 MPa tensile / 530 MPa yield and heat-treatable to higher hardness, but harder to weld. Weldable general parts versus stronger, hardenable shafts.
The verdict
Choose 1018 for weldable general-purpose parts, carburized components, and machined work where good weldability and ductility matter. Choose 1045 for shafts, axles, and medium-strength components needing higher strength (~530 MPa yield vs 370 MPa) or through-hardening by heat treatment.
Side-by-side data
| Property | 1018 Mild Steel | 1045 Steel |
|---|---|---|
| Category | Steel | Steel |
| Density (g/cm³) | 7.87 | 7.87 |
| Tensile strength (MPa) | 440 | 625 |
| Yield strength (MPa) | 370 | 530 |
| Elongation (%) | 15 | 12 |
| Hardness | 126 HB | 170 HB |
| Max service temp (°C) | 400 | 400 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 51 | 49 |
| Typically used for | General low-carbon parts, weldable | Shafts & medium-strength components |
Which should you choose?
Choose 1018 Mild Steel when…
- Parts must be welded without preheat or cracking concerns
- Good ductility and formability are needed (15% elongation)
- Carburizing/case-hardening a tough low-carbon core
- General machined parts, pins, and brackets at low cost (~1.0 index)
- Cold-formed or bent components requiring forgiving workability
- Strength demands are moderate (~370 MPa yield is sufficient)
Choose 1045 Steel when…
- Making shafts, axles, and medium-strength load-bearing components
- Higher strength is required (~530 MPa yield vs 1018's 370 MPa)
- Through-hardening by quench-and-temper is planned (~0.45% C)
- Higher surface hardness from flame or induction hardening is wanted
- Wear resistance matters more than weldability
- Parts see fatigue or rotational loads beyond mild steel capacity
Key differences that matter
- Carbon drives the difference: 1018 ~0.18% C vs 1045 ~0.45% C
- Strength: 1045 ~625 MPa tensile / 530 MPa yield vs 1018 ~440 MPa / 370 MPa — 1045 is ~43% higher yield
- 1018 welds readily; 1045's higher carbon makes welding harder and often requires preheat/post-heat to avoid cracking
- 1045 is through-hardenable by quench-and-temper and responds well to flame/induction hardening; 1018 is typically carburized instead
- Ductility: 1018 15% elongation vs 1045 12% — 1018 is more forgiving in forming
- Both have poor corrosion resistance (1.5/5) and need coating or plating outdoors
- Cost and machinability are similar (1018 ~1.0 index, 1045 ~1.1); 1018 machines slightly easier (3.5 vs 3.0)
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Open the Material SelectorGet a Quote →Frequently asked questions
What is the difference between 1018 and 1045 steel?
The key difference is carbon content: 1018 has about 0.18% carbon and 1045 about 0.45%. That makes 1045 stronger (~530 vs 370 MPa yield) and through-hardenable by quench-and-temper, while 1018 is more ductile and far easier to weld. 1018 suits weldable general parts; 1045 suits shafts and hardenable components.
Can 1045 steel be welded?
Yes, but with care. Its higher carbon content (~0.45%) makes 1045 prone to hardening and cracking in the heat-affected zone, so preheating and slow cooling or post-weld stress relief are usually required. 1018, with much lower carbon, welds easily without these precautions and is the better choice for heavily welded assemblies.
Which steel is stronger, 1018 or 1045?
1045 is stronger. In as-supplied condition it offers about 625 MPa tensile and 530 MPa yield, versus roughly 440 MPa tensile and 370 MPa yield for 1018 — about 43% more yield strength. 1045 can also be quench-and-tempered for substantially higher strength and hardness, which 1018's low carbon cannot match.
Can 1018 steel be hardened?
1018 can't be effectively through-hardened because its low carbon (~0.18%) won't form enough martensite. Instead, it's case-hardened by carburizing, which adds carbon to the surface to create a hard, wear-resistant case over a tough core. For through-hardening, choose a medium-carbon steel like 1045 or an alloy steel like 4140.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.