AISI 1045 Carbon Steel Properties and Applications

AISI 1045 Carbon Steel is a widely used medium-carbon steel known for its good balance of strength, toughness, and wear resistance. Understanding its characteristics is essential for proper material selection in various industrial applications.

1. 1045 Steel Chemical Composition

The designation “1045” indicates a plain carbon steel with a nominal carbon content of 0.45%. Key compositional ranges according to major standards are:

• Carbon (C): Typically 0.43% – 0.50% (e.g., ASTM A29, SAE J403). Some specifications allow 0.42% – 0.50%.
• Manganese (Mn): Generally 0.60% – 0.90%. Some standards may specify 0.50% – 0.80%.
• Silicon (Si): Often specified as 0.15% – 0.35% or a maximum of 0.40%. Note: Merchant quality bars may not have a specified silicon content.
• Phosphorus (P) & Sulfur (S): These are impurities kept at low levels, typically max 0.040% for P and max 0.050% for S, although stricter limits (e.g., 0.035% max) may apply depending on the standard.
• Other Elements: Some standards (like JIS G4051) may specify maximum limits for elements like Cu (0.30%), Ni (0.20%), and Cr (0.20%).

2. 1045 Steel International Equivalent Grades

For global sourcing and specification, it’s useful to know the equivalent grades for 1045 steel:

• ISO: C45E4
• EN (Europe): C45E (1.1191)
• DIN (Germany): C45 (1.0503)
• JIS (Japan): S45C (occasionally S48C)
• BS (UK): IC45 / 080A47
• GB (China): 45 (also 45H, ML45)
• GOST (Russia): 45 (also 45H)
• Other: NF C45 (France), AFNOR CC45 (France), UNI C45 / F.114 (Italy), SS 1650 (Sweden), UNE F.114 (Spain), ASTM 1045H (specified hardenability).

3. 1045 Steel Mechanical Properties

The mechanical properties of 1045 steel depend highly on its condition (how it’s processed and heat-treated).

As-Processed Conditions

Hot-Rolled: In this common supply condition, typical properties are:

• Tensile Strength: ~585 MPa (85 ksi)
• Yield Strength: ~310 MPa (45 ksi)
• Elongation: ~17%
• Reduction of Area: ~35%
• Hardness: ~170-229 HBW

Cold-Drawn: Cold drawing increases strength and hardness but generally reduces ductility. Example values might be:

• Tensile Strength: ~725 MPa (105 ksi)
• Yield Strength: ~585 MPa (85 ksi)

4. 1045 Steel Heat Treatment

Heat treatment is crucial for tailoring 1045 steel’s properties:

4.1 Normalizing: Heating to 850-870°C and air cooling refines the grain structure. This results in improved uniformity, higher strength, and better elongation than the as-rolled state. Typical hardness after normalizing is 170-217 HBW.

4.2 Hardening (Quenching) & Tempering: For maximum strength and hardness:

4.2.1 Quenching: Heat 820-870°C and rapidly cool in water or oil. Water quenching provides faster cooling and can achieve greater hardening depth, especially in thicker sections.

4.2.2 Tempering: Reheat the quenched steel to 550-650°C, hold, and cool rapidly. This process reduces brittleness and achieves the final desired balance of hardness and toughness. Typical properties after Quenching and Tempering (Q&T):

• Tensile Strength: > 686 MPa
• Yield Strength: > 490 MPa
• Elongation: > 17%
• Reduction of Area: > 45%
• Hardness: 201-269 HBW

5. Hardenability Considerations

Hardenability refers to the depth to which steel can be hardened during quenching. As a plain carbon steel, 1045 has lower hardenability compared to alloy steels like 4145. This means achieving high hardness throughout the core is only possible in relatively thin sections. For instance, achieving HRC 45 might only be possible within the outer 3-6.5 mm bar quenched under specific conditions. This is a key limitation to consider for larger components requiring high core strength and hardness.

6. 1045 Steel Applications

Thanks to its versatility and cost-effectiveness, 1045 steel and its equivalents (like S45C) are used in numerous applications requiring good strength and wear resistance, including:

• Axles, shafts, and spindles
• Gears and studs
• Bolts and connecting rods
• Hydraulic clamps
• Backup plates for cold work and plastic molds
• Drill jig fixing plates
• Plastic molds and mold bases
• Standard die set components

The normalized or lightly cold-drawn condition is often suitable for applications needing tensile strengths in the 60-75 kgf/mm² range.

7. Selecting 1045 Steel

When specifying 1045 steel, it is vital to define the required condition (e.g., hot-rolled, normalized, quenched and tempered) and reference the appropriate standard (ASTM, EN, JIS, etc.). This ensures the material meets the necessary chemical composition and mechanical properties for your specific application. Factors like component size and required hardness depth are critical in determining if 1045 is the best choice or if an alloy steel with higher hardenability is needed.

At Aobo Steel, with our extensive experience in tool and alloy steels, we can help you select the right grade and condition for your requirements. Contact us to discuss your specific needs.

FAQs

1. What is 1045 steel good for?

1045 steel is a dependable and cost-effective choice for many applications requiring a good balance of strength, toughness, and wear resistance. Its versatility is further enhanced by its amenability to various heat treatments, allowing for property optimization. From tooling components like mold parts and jig plates to machinery elements such as pins, rollers, and even gears and axles in less demanding applications, 1045 steel offers a pragmatic solution. However, exploring alloy steel alternatives might be a more suitable approach for components with substantial cross-sections demanding deep and uniform hardening.

2. Is 1045 stronger than 4140?

For smaller parts or those with less stringent strength requirements, 1045 steel may offer a more economical solution. However, for larger, more critical components demanding high strength and consistent performance across their entire cross-section, 4140 steel would be the more appropriate selection.