In precision manufacturing, consistent machining performance is the foundation of quality and efficiency. For parts that undergo both turning and milling, material stability and cutting smoothness are critical. S45C carbon steel bars, known for their balanced strength, hardness, and machinability, offer excellent performance in high-speed cutting applications. Whether in CNC machining or conventional lathes, S45C delivers both dimensional stability and cost efficiency, making it one of the most popular medium-carbon steels for mechanical components.
1. Overview of S45C Carbon Steel
S45C, also known as AISI 1045 or C45, is a medium-carbon steel containing approximately 0.45% carbon. It offers high tensile strength, moderate toughness, and excellent mechanical properties after heat treatment. This material can be normalized, quenched, or tempered depending on the desired strength level. Its balanced composition makes it suitable for shafts, gears, bolts, and other wear-resistant components.
2. Chemical Composition and Mechanical Properties
| Element | Composition (%) | Function |
|---|---|---|
| C | 0.42–0.48 | Increases hardness and strength |
| Si | 0.15–0.35 | Improves elasticity and strength |
| Mn | 0.60–0.90 | Enhances toughness and hardenability |
| P | ≤0.030 | Improves machinability |
| S | ≤0.035 | Improves cutting smoothness |
| Fe | Balance | Base element |
| Property | Condition | Typical Value |
|---|---|---|
| Tensile Strength (MPa) | Normalized | 570–700 |
| Yield Strength (MPa) | Normalized | 330–450 |
| Elongation (%) | Normalized | 15–25 |
| Hardness (HB) | Annealed | 160–190 |
| Machinability | — | Excellent |
3. Machining Advantages of S45C
S45C carbon steel is designed for stable and smooth cutting. Its uniform structure and moderate carbon content allow it to perform well under both turning and milling operations.
Key advantages include:
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Excellent cutting stability: Consistent hardness and uniform grain reduce vibration and chatter.
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Good surface finish: Produces clean, smooth surfaces under both wet and dry machining.
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Versatile heat treatment: Can be adjusted for strength and wear resistance without losing machinability.
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Balanced hardness: Avoids tool wear caused by overly hard materials.
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Cost-effective: Offers great strength-to-price ratio compared to alloy steels.
4. Application Performance in Turning and Milling
When used in CNC or automatic lathes, S45C maintains dimensional precision throughout the cutting process. Its stable thermal conductivity reduces heat accumulation, which minimizes deformation during long machining cycles. During milling, its fine grain structure provides consistent chip formation, preventing tool edge buildup.
Machining Recommendations:
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Cutting Speed: 80–120 m/min (carbide tools)
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Feed Rate: 0.1–0.3 mm/rev for turning
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Coolant: Recommended to improve surface finish and extend tool life
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Tool Material: Carbide or coated HSS tools for long runs
5. Heat Treatment Options for Enhanced Stability
S45C’s machinability and strength can be optimized through different heat treatments.
| Heat Treatment | Temperature (°C) | Resulting Property |
|---|---|---|
| Annealing | 800–850°C, slow cool | Soft structure for easy machining |
| Normalizing | 850–880°C, air cool | Balanced hardness and ductility |
| Quenching & Tempering | 820°C + 500–600°C | High strength with toughness |
| Surface Hardening | 850–900°C (flame or induction) | Improved wear resistance, stable core |
These treatments allow flexibility based on part requirements—soft for machining, or hardened for service durability.
6. Typical Applications
S45C carbon steel bars are widely used in mechanical engineering, automotive, and mold manufacturing industries. Common applications include:
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Shafts and axles requiring high torsional strength.
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Gear parts where precision and wear resistance are critical.
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Bolts and fasteners under repetitive stress.
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Machine components such as couplings and bearing housings.
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Tool bases and fixtures requiring rigidity and durability.
7. Why Choose Tongyi Metal’s S45C Bars
Tongyi Metal’s S45C round bars are produced through controlled rolling, heat treatment, and precision grinding to achieve outstanding surface finish and internal stability. Advantages include:
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Uniform hardness with stable core strength.
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Precision straightness (≤0.03 mm/m).
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Mirror-like surface roughness after polishing.
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Optional grinding and cutting customization.
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Full material traceability with Mill Test Certificate (MTC).
S45C carbon steel bars combine machinability, strength, and stability, making them ideal for parts that require both turning and milling. Their smooth cutting performance and predictable hardness response allow manufacturers to maintain precision and efficiency. With Tongyi Metal’s refined production control, S45C bars deliver reliable performance in every machining process—helping you achieve smoother cuts, longer tool life, and consistent part quality.
