AISI SAE 1040 Alloy Steel Bar 1040 Round Bars 1040 Rods

Product Description

AISI/SAE 1040 Carbon Steel

AISI 1040 (UNS G10400) is a medium-carbon structural steel characterized by its versatility and reliability. While frequently grouped with "alloy steels" in trade discussions, it is technically an unalloyed carbon steel. It contains approximately 0.40% carbon, providing a significant increase in strength and hardness over mild steels (like 1018 or 1020) while maintaining reasonable ductility and excellent machinability.

It is one of the most commonly used grades for general-purpose engineering, specifically for components that require more strength than low-carbon steels can provide but do not justify the cost of high-alloy alternatives.

International Equivalents

As a global "workhorse" grade, 1040 has direct equivalents in nearly every major international standard:

Typical Chemical Composition

The balance of carbon and manganese allows the material to respond well to heat treatment, including induction hardening.

• Carbon (C): 0.37% – 0.44%

• Manganese (Mn): 0.60% – 0.90%

• Phosphorus (P): $\le$ 0.040%

• Sulfur (S): $\le$ 0.050%

• Iron (Fe): Balance

Mechanical Properties

The properties of AISI 1040 vary significantly depending on the supply condition. It is most frequently used in the Normalized or Cold Drawn state.

Key Performance Attributes

• Heat Treatability: 1040 can be through-hardened by quenching and tempering, though its hardenability is limited to relatively small sections (typically under 25mm for through-hardening). For larger sections, it is an excellent candidate for induction or flame hardening to achieve a high surface hardness while maintaining a tough core.

• Machinability: Rated at approximately 60% of AISI 1212 (the standard for free-machining steel). It produces consistent chips and a high-quality surface finish.

• Weldability: Considered "fair." Because of the medium carbon content, pre-heating to 150–250°C and post-weld stress relieving are recommended to prevent hydrogen-induced cracking in the heat-affected zone (HAZ).

Common Applications for Round Bars & Rods

AISI 1040 is the primary choice for parts subjected to moderate mechanical loads:

1. Automotive Components: Forged connecting rods, crankshafts, and steering knuckles.

2. Machinery Parts: Shafts, axles, spindles, and lightly stressed gears.

3. Fasteners: High-strength bolts, studs, and heavy-duty nuts (typically Grade 8.8 equivalent).

4. Agricultural Equipment: Tines, pins, and structural supports for heavy machinery.

Supply Condition & Finish

• Cold Drawn Bars: Preferred for high-precision CNC machining due to tighter dimensional tolerances and improved surface finish.

• Hot Rolled / Normalized: Used when the material will undergo significant subsequent forging or when internal stresses must be minimized.

• Peeled & Polished: Often specified for long-length shafts to ensure the removal of surface decarburization and defects.