1040 Steel
A hardenable medium-carbon steel
Typical values for the temper in the title
1040 contains about 0.4% carbon. It is stronger than low-carbon steels, and can be hardened by quench and temper or by induction. It is used for shafts, forgings and moderately loaded machine parts.
It is very close to 1045, with slightly less carbon, so slightly softer and slightly more weldable.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 620 MPa | |
| Yield strength Rp0.2 | 415 MPa | |
| Elongation A | 25% | |
| Hardness | 179 HB | |
| Modulus of elasticity E | 200 GPa | |
| Density ρ | 7.85 g/cm³ | |
| Machinability | 60% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| C carbon | 0.37–0.44 | sets strength and hardenability |
| Mn manganese | 0.60–0.90 | strength and hardenability |
| P phosphorus | max 0.040 | |
| S sulfur | max 0.050 | |
| Fe iron | balance |
Ranges per SAE J403 and ASTM A29. P max 0.040, S max 0.050 (except free-machining grades). Equivalents in other standards are close in composition, not identical.
Conditions and heat treatment
The properties of carbon steel depend strongly on the condition and heat treatment. The values at the top of the page are for the typical condition.
| Condition | Properties | When to choose it |
|---|---|---|
| Normalized | uniform structure, medium strength | base condition for parts |
| Quenched and tempered (Q&T) | high strength and good toughness | shafts and loaded parts |
| Induction hardened | very hard surface (around 50–60 HRC), soft core | shafts, rails and wear surfaces |
Applications
- Shafts and axles
- Forgings
- Moderately loaded machine parts
- Bolts and automotive parts
- Induction-hardened parts
Fabrication
Heat treatment
Quenched in water or oil and tempered. Hardenability is limited: in large diameters the center does not reach full hardness. So for thick parts, alloy steel is chosen.
Welding
Possible, but requires preheat and sometimes post-weld treatment, because the weld zone hardens and may crack.
Machining
Reasonable, and better normalized or annealed.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 1045 | 570–700 / 310–450 MPa | Medium | slightly more carbon, more common · material page |
| 1018 | 400 / 220 MPa | Excellent | low carbon, more weldable · material page |
| 4140 | 655–1000 / 415–835 MPa | Medium — Preheat 150C | much higher hardenability · material page |
Common mistakes
Expecting full hardness at the center of a thick shaft
Hardenability is limited. For thick parts, 4140 or 4340.
Welding without preheat
The weld zone hardens and may crack.
Leaving it unprotected
Carbon steel rusts. Paint, plating or oil are needed.
Equivalents, standards and supply
| EN | C40 |
|---|---|
| DIN | Ck40 |
| JIS | S40C |
| Standards | ASTM A29 / SAE J403 / EN 10083-2 |
| Forms | rod · plate · forging |
| Producers | TimkenSteel · Ovako · ArcelorMittal |
Learn more
Values are typical and for comparison only, and depend strongly on condition and diameter. For design, rely on the standard and on the mill certificate. Sources: SAE J403 and J404, ASTM A29, A322 and A519 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026