SAE 1040 Steel

SAE 1040 (AISI 1040) is a medium-carbon, non-alloy engineering steel containing approximately 0.40% carbon. Because it offers a balanced profile of strength, toughness and machinability, it is preferred in many applications such as machine parts, shafts, bolts and forgings. Its closest equivalents in European standards are C40 (1.0511) and C40E / Ck40 (1.1186), which has lower phosphorus and sulfur content. In this article, we cover the technical properties of 1040 steel and when it should be chosen.

What does the SAE 1040 designation mean?

In the SAE/AISI numbering system, the first two digits indicate the steel group and the last two digits indicate the carbon content. 10xx refers to the non-alloy carbon steel group, and 40 indicates approximately 0.40% carbon. To learn more about this system, see our article What Is the AISI Standard?

SAE 1040 chemical composition

The chemical composition of SAE 1040 and its European equivalent C40 are compared in the table below:

As shown, SAE 1040 and C40 have exactly the same carbon range, with only a small difference in the manganese range.

SAE 1040 mechanical properties

The values below are typical/approximate and may vary depending on section size:

Cold drawing significantly increases yield strength while reducing elongation. For this reason, cold drawn 1040 steel is an advantage for shafts that require dimensional accuracy and strength.

SAE 1040 heat treatment

The main heat treatments applied to SAE 1040 steel are:

• Normalizing: Held at approximately 860–900 °C and air cooled, producing a uniform, fine-grained structure.
• Soft annealing: Applied to improve machinability.
• Hardening: Quenched in water or oil from approximately 820–860 °C. Since the hardening depth is limited, it is effective in small and medium cross-sections.
• Tempering: Carried out after quenching at 400–650 °C, depending on the desired balance of hardness and toughness.
• Surface hardening: Suitable for flame or induction hardening, producing a hard case with a tough core on wear-exposed surfaces.

Heat treatment temperatures vary depending on cross-section, furnace and desired properties. Exact values should be determined together with your heat treatment specialist.

Where is SAE 1040 used?

Typical applications of SAE 1040 include:

• Transmission shafts, axles and pins
• Bolts, studs and fasteners
• Forged parts such as crankshafts and connecting rods
• Light and medium-duty gears
• Hydraulic and pneumatic system components
• Automotive and agricultural machinery components

SAE 1040 or C45?

1040 and C45 (close to SAE 1045) are often considered alternatives to each other.

If wear resistance and surface hardness are the priority, C45 can be chosen; if formability and toughness matter more, 1040 can be preferred. For details on C45, see our article C45 Steel Properties.

SAE 1040 international equivalents

Grades equivalent to SAE 1040 in different standards are as follows:

What to consider when buying SAE 1040

• Heat treatment: Determine whether the part will be heat treated; hardenability requirements should be checked against the section size.
• Production method: Choose between hot rolled and cold drawn products based on your machining needs.
• Welding: If the part will be welded, plan the preheating and welding procedure.
• Standard and certification: Specify the standard designation (SAE 1040 / C40 / Ck40) and certificate type in your request for quotation.

Machinability of SAE 1040

Thanks to its medium-carbon structure, SAE 1040 shows balanced performance in machining operations such as turning, milling and drilling. Although its machinability is not as high as that of free-cutting steels, it is sufficient for most general machine parts.

Hot rolled and normalized material is easier to machine; with cold drawn material, cutting parameters need to be adjusted for its higher hardness. In series production, soft annealed material can be chosen to improve machinability.

Which product form should you choose?

• Hot rolled round bar: Raw material for shafts to be turned, forgings and pressed parts
• Cold drawn round bar: Pins, axles and precision shafts that go directly into assembly
• Flat and square bar: Keys, slides, connecting parts and wear plates
• Hexagon bar: Series production of nuts, fittings and fasteners

Choosing the right form directly affects both machining time and material waste. If you are unsure, you can share your part drawing with our sales team to determine the most economical form together.

SAE 1040 steel supply from Uyar Çelik

Uyar Çelik supplies SAE 1018, 1020, 1030, 1040, 1050 and 1060 grades in accordance with ASTM/SAE standards, in hot rolled flat, square, round and hexagon sections.

With 6–12 meter standard lengths and custom length cutting options, we offer solutions tailored to your production schedule.

Frequently asked questions

What is the equivalent of SAE 1040?

Its closest European equivalents are C40 (1.0511) and C40E/Ck40 (1.1186) in EN 10083-2, and its Japanese equivalent is S40C.

Can 1040 steel be hardened?

Yes. Thanks to its medium-carbon structure, it can be hardened by quenching and tempering, and it is also suitable for induction surface hardening.

Can 1040 steel be welded?

Yes, but due to its carbon content, preheating and controlled cooling are recommended to prevent the risk of cracking.

Conclusion

SAE 1040 is a medium-carbon engineering steel equivalent to C40 and Ck40, offering a balanced profile of strength, toughness and machinability. It is a strong option for forged parts and fasteners where formability and toughness are key, while choosing the right product form and heat treatment determines the part’s performance.

Get a quote for SAE 1040 and other carbon steels: +90 (212) 485 98 98 or visit our contact page.