S55C Steel (JIS ~1055): Properties and Key Applications
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Table Of Content
Table Of Content
S55C steel, classified as a medium-carbon alloy steel, is recognized for its balanced properties that make it suitable for a variety of engineering applications. This steel grade is primarily composed of carbon (approximately 0.50-0.60% by weight), with additional alloying elements such as manganese, silicon, and phosphorus. The presence of carbon enhances its hardness and strength, while manganese contributes to improved toughness and wear resistance.
Comprehensive Overview
S55C steel is categorized under the JIS (Japanese Industrial Standards) and is equivalent to the AISI 1055 grade. Its medium carbon content allows for a good balance between strength and ductility, making it a versatile choice for various applications, including automotive components, machinery parts, and structural applications.
Key Characteristics:
- Hardness and Strength: S55C exhibits good hardness and tensile strength, making it suitable for applications requiring high wear resistance.
- Ductility: While it is stronger than low-carbon steels, it retains sufficient ductility for forming and machining processes.
- Heat Treatability: This steel can be heat treated to enhance its mechanical properties further.
Advantages:
- High strength-to-weight ratio.
- Good machinability and weldability.
- Suitable for heat treatment processes to achieve desired hardness.
Limitations:
- Moderate corrosion resistance compared to stainless steels.
- Requires careful control during heat treatment to avoid brittleness.
Historically, S55C has been widely used in the manufacturing of components that require a combination of strength and toughness, such as gears, axles, and shafts. Its market position remains strong due to its adaptability in various engineering sectors.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | G10550 | USA | Closest equivalent to S55C |
| AISI/SAE | 1055 | USA | Similar properties, minor compositional differences |
| ASTM | A29/A29M | USA | General specification for carbon steel |
| EN | C55E | Europe | Equivalent with slight differences in composition |
| DIN | C55 | Germany | Comparable grade with similar applications |
| JIS | S55C | Japan | Primary designation for this steel grade |
| GB | Q345B | China | Similar strength but lower carbon content |
The differences between these equivalent grades often lie in their specific carbon content and the presence of other alloying elements, which can affect their mechanical properties and suitability for particular applications.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.50 - 0.60 |
| Mn (Manganese) | 0.60 - 0.90 |
| Si (Silicon) | 0.15 - 0.40 |
| P (Phosphorus) | ≤ 0.030 |
| S (Sulfur) | ≤ 0.030 |
The primary role of carbon in S55C is to enhance hardness and strength, while manganese improves toughness and wear resistance. Silicon contributes to deoxidation during steelmaking and enhances strength, while phosphorus and sulfur are kept to low levels to avoid brittleness and improve ductility.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric - SI Units) | Typical Value/Range (Imperial Units) | Reference Standard for Test Method |
|---|---|---|---|---|
| Tensile Strength | Quenched & Tempered | 600 - 800 MPa | 87 - 116 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Quenched & Tempered | 400 - 600 MPa | 58 - 87 ksi | ASTM E8 |
| Elongation | Quenched & Tempered | 10 - 15% | 10 - 15% | ASTM E8 |
| Reduction of Area | Quenched & Tempered | 40 - 50% | 40 - 50% | ASTM E8 |
| Hardness (Rockwell C) | Annealed | 20 - 30 HRC | 20 - 30 HRC | ASTM E18 |
| Impact Strength (Charpy) | -20°C | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The combination of high tensile and yield strength makes S55C suitable for applications subjected to significant mechanical loading. Its moderate elongation indicates that while it is strong, it can still undergo some deformation before failure, which is crucial for structural integrity.
Physical Properties
| Property | Condition/Temperature | Value (Metric - SI Units) | Value (Imperial Units) |
|---|---|---|---|
| Density | - | 7.85 g/cm³ | 0.284 lb/in³ |
| Melting Point | - | 1425 - 1540 °C | 2600 - 2800 °F |
| Thermal Conductivity | 20°C | 45 W/m·K | 31.2 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | - | 0.46 J/g·K | 0.11 BTU/lb·°F |
| Electrical Resistivity | - | 0.0000017 Ω·m | 0.0000017 Ω·in |
| Coefficient of Thermal Expansion | 20 - 100 °C | 11.5 x 10⁻⁶ /K | 6.36 x 10⁻⁶ /°F |
The density of S55C indicates it is relatively heavy, which contributes to its strength. The melting point range suggests it can withstand high temperatures before transitioning to a liquid state, making it suitable for applications involving heat. The thermal conductivity is moderate, which is beneficial in applications where heat dissipation is necessary.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Atmospheric | - | - | Fair | Susceptible to rust without protection |
| Chlorides | 3-5 | 20-60 °C (68-140 °F) | Poor | Risk of pitting corrosion |
| Acids | 10-20 | 20-40 °C (68-104 °F) | Poor | Not recommended for acidic environments |
| Alkalis | 5-10 | 20-60 °C (68-140 °F) | Fair | Moderate resistance, but can corrode over time |
| Organics | - | - | Good | Generally resistant to organic solvents |
S55C steel exhibits moderate corrosion resistance, particularly in atmospheric conditions. However, it is susceptible to pitting in chloride environments and should not be used in acidic conditions. Compared to stainless steels, S55C's corrosion resistance is limited, making it less suitable for applications in harsh environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 300 | 572 | Suitable for moderate temperature applications |
| Max Intermittent Service Temp | 400 | 752 | Can withstand short-term exposure to higher temperatures |
| Scaling Temperature | 600 | 1112 | Risk of oxidation above this temperature |
| Creep Strength considerations | 400 | 752 | Begins to lose strength at elevated temperatures |
S55C steel maintains its mechanical properties at moderate temperatures, making it suitable for applications that experience thermal cycling. However, care must be taken to avoid prolonged exposure to temperatures above 400 °C (752 °F), as this can lead to oxidation and loss of strength.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| MIG | ER70S-6 | Argon + CO2 mix | Good for thin sections |
| TIG | ER70S-2 | Argon | Suitable for clean joints |
| Stick (SMAW) | E7018 | - | Requires preheat |
S55C steel is generally considered weldable, but preheating is recommended to minimize the risk of cracking. Post-weld heat treatment can also enhance the properties of the weld. Care should be taken to choose appropriate filler metals to match the base material's properties.
Machinability
| Machining Parameter | S55C | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | S55C is less machinable than 1212 |
| Typical Cutting Speed (Turning) | 30 m/min | 50 m/min | Adjust speeds based on tooling |
S55C exhibits moderate machinability, which can be improved with proper cutting tools and conditions. It is advisable to use high-speed steel or carbide tools for optimal performance.
Formability
S55C steel can be cold and hot formed, but care must be taken to avoid excessive work hardening. The minimum bend radius should be considered during forming processes to prevent cracking.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 600 - 700 / 1112 - 1292 | 1 - 2 hours | Air | Softening, improving ductility |
| Quenching | 800 - 900 / 1472 - 1652 | 30 minutes | Oil or Water | Hardening |
| Tempering | 200 - 600 / 392 - 1112 | 1 hour | Air | Reducing brittleness, improving toughness |
Heat treatment processes significantly affect the microstructure and properties of S55C steel. Quenching increases hardness, while tempering reduces brittleness, making the steel more suitable for dynamic applications.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Automotive | Gears | High tensile strength, wear resistance | Required for durability |
| Machinery | Shafts | Toughness, machinability | Essential for performance |
| Construction | Structural components | Strength, ductility | Supports load-bearing needs |
Other applications include:
- Tooling and dies
- Fasteners
- Agricultural equipment
S55C is chosen for these applications due to its combination of strength, toughness, and machinability, making it ideal for components that must withstand significant mechanical stress.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | S55C | AISI 1045 | AISI 4140 | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength | Moderate strength | High strength | S55C offers a balance of strength and ductility |
| Key Corrosion Aspect | Fair | Fair | Good | S55C is less resistant than 4140 in corrosive environments |
| Weldability | Good | Moderate | Fair | S55C is easier to weld than 4140 |
| Machinability | Moderate | Good | Fair | S55C is less machinable than 1045 |
| Formability | Good | Good | Fair | S55C can be formed easily compared to 4140 |
| Approx. Relative Cost | Moderate | Moderate | Higher | Cost-effective for many applications |
| Typical Availability | Common | Common | Less common | S55C is widely available in various forms |
When selecting S55C steel, considerations such as cost-effectiveness, availability, and specific mechanical properties are crucial. Its moderate corrosion resistance makes it suitable for many applications, but for environments with high corrosive potential, alternative grades may be more appropriate. Additionally, S55C's weldability and machinability make it a practical choice for manufacturers looking for a versatile steel grade.
In summary, S55C steel is a medium-carbon alloy steel that offers a balanced combination of strength, toughness, and machinability, making it suitable for various engineering applications. Its properties can be tailored through heat treatment, and while it has limitations in corrosion resistance, it remains a popular choice in the industry.
