202 Stainless Steel: Properties and Key Applications
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Table Of Content
Table Of Content
202 Stainless Steel is classified as an austenitic stainless steel, primarily known for its excellent corrosion resistance and good mechanical properties. It is characterized by a high chromium content, typically around 17-20%, and a nickel content of about 4-6%. The addition of these alloying elements significantly enhances its resistance to oxidation and corrosion, while also improving its formability and weldability.
Comprehensive Overview
202 Stainless Steel is often used in applications where a combination of strength, corrosion resistance, and aesthetic appeal is required. Its unique composition allows it to maintain structural integrity in various environments, making it a popular choice in the manufacturing of kitchen equipment, architectural applications, and automotive components.
Advantages and Limitations
| Advantages | Limitations |
|---|---|
| Excellent corrosion resistance | Lower corrosion resistance compared to 304 stainless steel |
| Good formability and weldability | Susceptible to stress corrosion cracking in chloride environments |
| Cost-effective alternative to 304 stainless steel | Limited high-temperature strength compared to other grades |
| Aesthetic appeal with a bright finish | Not suitable for cryogenic applications |
Historically, 202 Stainless Steel has gained traction as a cost-effective alternative to 304 stainless steel, particularly in regions where nickel prices are volatile. Its market position is strong, especially in the Asian markets, where it is commonly used in the production of consumer goods and architectural elements.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S20200 | USA | Closest equivalent to AISI 304 with minor compositional differences |
| AISI/SAE | 202 | USA | Lower nickel content than 304, making it more cost-effective |
| ASTM | A240 | USA | Standard specification for stainless steel plates |
| EN | 1.4373 | Europe | Similar properties to AISI 202 |
| JIS | SUS202 | Japan | Comparable to AISI 202 with slight variations in composition |
The differences between 202 and its equivalents, such as 304, primarily lie in their nickel content and resultant corrosion resistance. While 202 is more economical, it may not perform as well in highly corrosive environments.
Key Properties
Chemical Composition
| Element (Symbol) | Percentage Range (%) |
|---|---|
| Chromium (Cr) | 17.0 - 20.0 |
| Nickel (Ni) | 4.0 - 6.0 |
| Manganese (Mn) | 7.0 - 9.0 |
| Carbon (C) | ≤ 0.15 |
| Silicon (Si) | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.03 |
The primary role of chromium is to enhance corrosion resistance, while nickel improves toughness and ductility. Manganese contributes to strength and helps stabilize the austenitic structure.
Mechanical Properties
| Property | Condition/Temper | Typical Value/Range (Metric - SI Units) | Typical Value/Range (Imperial Units) | Reference Standard for Test Method |
|---|---|---|---|---|
| Tensile Strength | Annealed | 520 - 750 MPa | 75 - 109 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | 210 - 310 MPa | 30 - 45 ksi | ASTM E8 |
| Elongation | Annealed | 40 - 50% | 40 - 50% | ASTM E8 |
| Hardness (Rockwell B) | Annealed | 80 - 90 HRB | 80 - 90 HRB | ASTM E18 |
| Impact Strength (Charpy, -20°C) | Annealed | 40 - 60 J | 30 - 44 ft-lbf | ASTM E23 |
The mechanical properties of 202 Stainless Steel make it suitable for applications requiring moderate strength and good ductility. Its tensile strength and yield strength allow it to withstand various mechanical loads, while its elongation indicates good formability.
Physical Properties
| Property | Condition/Temperature | Value (Metric - SI Units) | Value (Imperial Units) |
|---|---|---|---|
| Density | Room Temperature | 7.93 g/cm³ | 0.286 lb/in³ |
| Melting Point | - | 1400 - 1450 °C | 2552 - 2642 °F |
| Thermal Conductivity | Room Temperature | 16.2 W/m·K | 112 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temperature | 500 J/kg·K | 0.12 BTU/lb·°F |
| Electrical Resistivity | Room Temperature | 0.72 µΩ·m | 0.000012 Ω·in |
The density and melting point of 202 Stainless Steel indicate its suitability for high-temperature applications, while its thermal conductivity and specific heat capacity make it effective for thermal management in various engineering applications.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 0 - 3 | 20 - 60 (68 - 140) | Fair | Susceptible to pitting corrosion |
| Sulfuric Acid | 0 - 10 | 20 - 40 (68 - 104) | Poor | Not recommended |
| Acetic Acid | 0 - 5 | 20 - 60 (68 - 140) | Good | Moderate resistance |
| Atmospheric | - | - | Excellent | Good resistance |
202 Stainless Steel exhibits good resistance to atmospheric corrosion and mild organic acids, but it is susceptible to pitting in chloride environments. Compared to 304 stainless steel, which offers superior resistance to chlorides, 202 may not be the best choice for marine applications or environments with high chloride exposure.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 800 | 1472 | Suitable for intermittent use |
| Max Intermittent Service Temp | 870 | 1598 | Limited oxidation resistance |
| Scaling Temperature | 900 | 1652 | Risk of scaling at high temps |
At elevated temperatures, 202 Stainless Steel maintains its strength but may experience oxidation. It is not recommended for continuous service above 800 °C due to potential scaling and loss of mechanical properties.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| TIG | ER202 | Argon | Good results with proper technique |
| MIG | ER202 | Argon/CO2 mixture | Preheat may be required |
| Stick | E202 | - | Not commonly used |
202 Stainless Steel is generally considered to be weldable using standard techniques. However, preheating may be necessary to avoid cracking, especially in thicker sections. Post-weld heat treatment can enhance the properties of the weld.
Machinability
| Machining Parameter | 202 Stainless Steel | Benchmark Steel (AISI 1212) | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Moderate machinability |
| Typical Cutting Speed (Turning) | 30 - 40 m/min | 60 - 80 m/min | Use carbide tools |
Machining 202 Stainless Steel can be challenging due to its work hardening characteristics. Optimal cutting speeds and tooling are essential to achieve desired surface finishes and dimensional tolerances.
Formability
202 Stainless Steel exhibits good formability, making it suitable for cold and hot forming processes. It can be easily bent and shaped, but care must be taken to avoid excessive work hardening, which can lead to cracking.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 1050 - 1150 / 1922 - 2102 | 1 - 2 hours | Air or water | Relieve stresses, improve ductility |
| Solution Treatment | 1000 - 1100 / 1832 - 2012 | 30 minutes | Rapid cooling | Stabilize austenitic structure |
Heat treatment processes such as annealing can significantly improve the ductility and toughness of 202 Stainless Steel. The metallurgical transformations during these treatments enhance its performance in various applications.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Food Processing | Kitchen Equipment | Corrosion resistance, formability | Hygiene and durability |
| Architecture | Decorative Panels | Aesthetic appeal, corrosion resistance | Visual appeal and longevity |
| Automotive | Exhaust Systems | High-temperature resistance, strength | Performance and durability |
| Construction | Handrails and Balustrades | Strength, aesthetic appeal | Safety and design flexibility |
Other applications include:
-
- Medical devices
-
- Chemical processing equipment
-
- Consumer goods (e.g., cutlery, cookware)
The selection of 202 Stainless Steel for these applications is primarily due to its balance of cost, mechanical properties, and corrosion resistance.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | 202 Stainless Steel | Alternative Grade 1 (304) | Alternative Grade 2 (316) | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | Moderate Strength | High Strength | High Strength | 304 and 316 outperform in strength |
| Key Corrosion Aspect | Fair in Chlorides | Excellent | Excellent | 304 and 316 are better for marine use |
| Weldability | Good | Excellent | Good | 304 has better overall weldability |
| Machinability | Moderate | Good | Moderate | 304 is easier to machine |
| Formability | Good | Excellent | Good | 202 is suitable for various shapes |
| Approx. Relative Cost | Lower | Higher | Higher | Cost-effective for non-critical uses |
| Typical Availability | Common | Very Common | Common | 304 is widely available |
When selecting 202 Stainless Steel, considerations such as cost-effectiveness, availability, and specific application requirements are crucial. While it offers a good balance of properties, alternatives like 304 and 316 may be more suitable for applications requiring higher corrosion resistance or strength.
In summary, 202 Stainless Steel serves as a versatile and cost-effective material for various applications, particularly where moderate corrosion resistance and good mechanical properties are essential. Its unique characteristics make it a valuable choice in many industries, although careful consideration of its limitations is necessary for optimal performance.