When it comes to choosing the right stainless steel for your project, 316 and 321 are two popular options that often come up. Both offer impressive properties, but they cater to different needs. Let’s dive into a detailed comparison to help you understand which might be the best fit for your specific application.
What Makes Stainless Steel Special?
Stainless steel is prized for its strength, durability, and resistance to corrosion. These qualities make it a go-to material in many industries, from construction to aerospace. However, different grades of stainless steel are designed to handle different conditions. Let’s break down the key differences between 316 and 321 stainless steel.
316 vs. 321 Stainless Steel: Chemical Composition
316 is known for its molybdenum content, which significantly enhances its resistance to chloride-induced corrosion. 321 contains titanium, which stabilizes the steel and prevents carbide precipitation during welding.
| Element | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Chromium | 16-18% | 17-19% |
| Nickel | 10-14% | 9-12% |
| Molybdenum | 2-3% | Not present |
| Carbon | Max 0.08% | Max 0.08% |
| Manganese | 2% | 2% |
| Titanium | Not present | Approx. 0.60% (5 times the carbon content) |
316 vs. 321 Stainless Steel: Physical Property
This table compares key physical properties of 316 and 321 stainless steel, including density, melting point, thermal conductivity, and boiling point, to help determine the best material for specific applications based on strength, temperature resistance, and corrosion resistance.
| Property | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Density | 8.0 g/cm³ | 8.0 g/cm³ |
| Melting Point | 1375°C to 1400°C (2500°F to 2550°F) | 1450°C to 1500°C (2650°F to 2730°F) |
| Thermal Conductivity | 16 W/m·K | 16 W/m·K |
| Modulus of Elasticity | 193 GPa | 193 GPa |
| Thermal Expansion Coefficient | 16 x 10^-6 /°C | 17 x 10^-6 /°C |
| Tensile Strength | 485-620 MPa | 520-750 MPa |
| Yield Strength | 290 MPa | 310 MPa |
| Ductility | 40-50% | 40-50% |
| Hardness (Brinell) | 217 HB | 201 HB |
| Impact Toughness | Excellent (at room temperature) | Excellent (at room temperature) |
| Corrosion Resistance | Superior to 321 in chloride environments | Superior to 316 in high-temperature environments |
| Boiling Point | Approx. 2850°C (5150°F) | Approx. 2850°C (5150°F) |
316 vs. 321 Stainless Steel: Corrosion Resistance
316 stainless steel excels in resisting corrosion, particularly in chloride-rich environments like marine settings, thanks to its 2-3% molybdenum content. This makes it highly resistant to pitting and crevice corrosion. 321 stainless steel, while offering good general corrosion resistance, is less effective in chloride environments compared to 316.
316 vs. 321 Stainless Steel: Heat Resistance
316 stainless steel withstands temperatures up to 870°C (1600°F) with good oxidation resistance. 321 stainless steel, enhanced with titanium, handles temperatures up to 900°C (1650°F), making it ideal for high-heat applications due to superior stability. For high-temperature environments, 321 is the better choice.
316 vs. 321 Stainless Steel: Fabrication and Welding
316 stainless steel is versatile and weldable but can suffer from reduced corrosion resistance due to carbide precipitation. 321 stainless steel, with added titanium, resists carbide precipitation, maintaining strength and corrosion resistance during welding. For welding-intensive applications, 321 is the superior choice.
316 vs. 321 Stainless Steel: Advantages and Disadvantages
| Criteria | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Advantages | – Excellent corrosion resistance, especially in chloride-rich environments. – Good formability and weldability. – Effective in marine and chemical settings due to molybdenum content. | – Superior high-temperature stability due to titanium. – Resists carbide precipitation, maintaining strength and corrosion resistance during welding. – Ideal for high-heat applications. |
| Disadvantages | – Less effective at high temperatures compared to 321. – Susceptible to carbide precipitation during welding, which can reduce corrosion resistance. | – Less corrosion-resistant in chloride environments compared to 316. – Slightly more difficult to form than 316. |
For more comparative information on differences, please watch the following YouTube video. In addition to 316 and 321, we also compared 304.
316 vs. 321 Stainless Steel: Cost
316 stainless steel is generally more expensive due to its higher nickel and molybdenum content. 321 stainless steel is typically less costly, benefiting from titanium stabilization for high-temperature applications but without the added molybdenum.
| Stainless Steel Grade | Cost (per kg) |
|---|---|
| 316 Stainless Steel | $3.00 – $5.00 |
| 321 Stainless Steel | $2.50 – $4.00 |
AISI Standards for 321 vs. 316
AISI 316 offers superior corrosion resistance, especially in chloride environments, with 16-18% chromium, 10-14% nickel, and 2-3% molybdenum. AISI 321, with 17-19% chromium, 9-12% nickel, and titanium, excels in high-temperature applications, resisting intergranular corrosion and maintaining strength at elevated temperatures.
Which is Better 316 and 321 Stainless?
316 Stainless Steel is better for corrosion resistance, especially in marine or chemical environments. 321 Stainless Steel is better for high-temperature applications due to its stability and oxidation resistance.
What Are the Equivalents of 321 Stainless Steel?
321 stainless steel has several equivalents across different standards and countries. Here are some commonly recognized equivalents:
- ASTM/ASME: ASTM A321
- DIN (Germany): 1.4541
- BS (UK): 321S12
- JIS (Japan): SUS321
- UNE (Spain): X6CrNiTi1810
- NF (France): Z7CNCT18-10
- GOST (Russia): 08Cr18Ti
- ISO: ISO 5832-1 (for medical applications)
- AISI (American Iron and Steel Institute): AISI 321
- GB (China): 00Cr18Ni10Ti
These equivalents are used to denote materials with similar properties and applications as 321 stainless steel.
Does 321 Stainless Steel Rust?
321 stainless steel is designed to resist rust and intergranular corrosion, particularly after exposure to temperatures up to 1500°F. Its enhanced oxidation resistance and superior creep and stress rupture properties surpass those of 304/304L. Despite its high resistance, 321 can develop surface rust under extreme conditions or prolonged exposure to aggressive chemicals.
Does 316 Stainless Steel Rust?
316 stainless steel is highly resistant to rust and corrosion due to its molybdenum content, which enhances its protection against chlorides and harsh environments.
What is the Density of 321 Stainless Steel?
The density of 321 stainless steel is approximately 8.0 g/cm³ (or 8000 kg/m³).
What is the Melting Points of 321 Stainless Steel?
The melting point of 321 stainless steel is approximately 1450°C to 1500°C (2650°F to 2730°F). This high melting point contributes to its excellent high-temperature stability and resistance to thermal stress.
Is 321 Stainless Steel Magnetic?
321 stainless steel is generally non-magnetic in its annealed state. However, it can exhibit slight magnetism when cold worked or after certain welding processes. The magnetic properties are not significant in most applications, and it is primarily used for its high-temperature stability and corrosion resistance.
What is 321 Stainless Steel Code?
321 stainless steel is identified by the UNS number S32100 and the SAE number 30321. These codes are used to standardize the material’s specifications across different technical and industrial contexts.
Custom Stainless Steel Parts — BOYI
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Conclusion
Both 316 and 321 stainless steels have their own strengths and are suited for different applications. 316 is excellent for environments exposed to corrosive elements, while 321 shines in high-temperature scenarios. Your choice should be guided by the specific requirements of your project, considering factors like the operating environment and temperature conditions.
If you have any questions or need assistance in choosing the right stainless steel for your application, don’t hesitate to reach out. Understanding the nuances of each type will help you make an informed decision and ensure your project’s success.
316 vs. 321 Stainless Steel: Quick Reference Chart
| Feature/Use | 316 Stainless Steel | 321 Stainless Steel |
|---|---|---|
| Chemical Composition | – 16-18% Chromium (Cr) – 10-14% Nickel (Ni) – 2-3% Molybdenum (Mo) – Balance Iron (Fe) – Max 0.08% Carbon (C) | – 17-19% Chromium (Cr) – 9-12% Nickel (Ni) – Titanium (Ti) – 5 times the carbon content – Balance Iron (Fe) |
| Corrosion Resistance | Excellent resistance to chlorides and marine environments Good general corrosion resistance | Good general corrosion resistance Less resistant to chlorides than 316 Excellent in high-temperature applications |
| Heat Resistance | – Up to around 1600°F (871°C) Not ideal for extremely high temperatures over long periods | Up to 1500°F (816°C) Excellent for high-temperature environments |
| Applications | – Marine equipment – Chemical processing – Medical devices – Food and beverage processing | – Aerospace components – Exhaust systems – Pressure vessels – High-temperature industrial applications |
| Weldability | Good, but may experience carbide precipitation during high-temperature welding | Excellent due to titanium stabilization Less risk of carbide precipitation |
| Mechanical Properties | – Ultimate Tensile Strength: 70,000 psi (485 MPa) – Yield Strength: 30,000 psi (207 MPa) – Modulus of Elasticity: 193-200 GPa | – Ultimate Tensile Strength: 70,000-85,000 psi (485-586 MPa) – Yield Strength: 30,000 psi (207 MPa) – Modulus of Elasticity: 210-220 GPa |
| Unique Features | – Superior resistance to chloride-induced corrosion – Non-magnetic – Good formability and toughness | – High-temperature stability – Good weldability – Ferromagnetic properties |
FAQ
321 is preferable for high-temperature and high-stress applications, while 304 is suitable for general-purpose use
321H offers improved high-temperature strength compared to 321 due to its higher carbon content, making it suitable for more demanding applications.
321 stainless steel can be welded using TIG, MIG, and stick welding methods. TIG is preferred for its precision, while MIG is faster and suitable for thicker sections.
321 stainless steel casting involves melting and pouring 321 stainless steel into molds to create parts. It is used for high-temperature and corrosive environments due to its stability and resistance to intergranular corrosion.
Catalog: Materials Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
