Overview
SS321 (AISI 321 Stainless Steel) is a titanium-stabilized austenitic stainless steel belonging to the 300 Series Stainless Steel Family. By adding titanium (Ti), SS321 prevents chromium carbide precipitation during welding and prolonged exposure to elevated temperatures, providing superior resistance to intergranular corrosion.
SS321 is specifically designed for high-temperature applications where welded structures are exposed to temperatures ranging from 425°C to 900°C. It is widely used in aerospace systems, aircraft exhaust components, expansion joints, heat exchangers, pressure vessels, refinery equipment, and thermal processing industries.
Compared with SS304, SS321 offers better high-temperature stability and improved resistance to weld decay. Compared with SS347, SS321 uses titanium stabilization instead of niobium stabilization.
Material Specification
| Property | Value |
|---|---|
| Material Designation | AISI 321 |
| Material Family | Titanium-Stabilized Austenitic Stainless Steel |
| UNS Number | S32100 |
| EN Grade | 1.4541 |
| Density | 7.90–8.00 g/cm³ |
| Magnetic Property | Non-Magnetic (Annealed) |
| Standard Forms | Sheet, Plate, Coil, Pipe, Tube, Bar, Wire |
Chemical Composition
| Element | Content (%) |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 17.0–19.0 |
| Nickel (Ni) | 9.0–12.0 |
| Titanium (Ti) | ≥5 × C (Max 0.70) |
| Carbon (C) | ≤0.08 |
| Manganese (Mn) | ≤2.00 |
| Silicon (Si) | ≤1.00 |
| Phosphorus (P) | ≤0.045 |
| Sulfur (S) | ≤0.030 |
| Nitrogen (N) | ≤0.10 |
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | ≥515 MPa |
| Yield Strength | ≥205 MPa |
| Elongation | ≥40% |
| Hardness | ≤95 HRB |
| Elastic Modulus | 193 GPa |
Elevated Temperature Performance
| Temperature | Yield Strength Retention |
|---|---|
| 400°C | Excellent |
| 600°C | Excellent |
| 800°C | Good |
| 900°C | Good |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.90–8.00 g/cm³ |
| Melting Point | 1400–1455°C |
| Thermal Conductivity | 16.3 W/m·K |
| Electrical Resistivity | 0.72 μΩ·m |
| Thermal Expansion Coefficient | 16.9 × 10⁻⁶/K |
| Specific Heat Capacity | 500 J/kg·K |
Corrosion Resistance
| Environment | Performance |
|---|---|
| Atmospheric Exposure | Excellent |
| Industrial Environment | Excellent |
| High Temperature Oxidation | Excellent |
| Intergranular Corrosion | Outstanding |
| Marine Environment | Good |
| Chloride Environment | Moderate |
The titanium stabilization effectively prevents chromium carbide formation at grain boundaries, making SS321 highly resistant to sensitization and weld decay.
High Temperature Performance
| Service Condition | Temperature |
|---|---|
| Continuous Service | 900°C |
| Intermittent Service | 925°C |
| Oxidation Resistance | Excellent |
| Thermal Cycling Resistance | Excellent |
SS321 is particularly suitable for applications involving repeated heating and cooling cycles.
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | 321 |
| UNS | S32100 |
| EN (Europe) | 1.4541 |
| DIN (Germany) | X6CrNiTi18-10 |
| JIS (Japan) | SUS321 |
| GB/T (China) | 06Cr18Ni11Ti |
| ISO | X6CrNiTi18-10 |
Available Forms
| Product Type | Availability |
|---|---|
| Stainless Steel Sheet | Yes |
| Stainless Steel Plate | Yes |
| Stainless Steel Coil | Yes |
| Stainless Steel Pipe | Yes |
| Stainless Steel Tube | Yes |
| Stainless Steel Bar | Yes |
| Stainless Steel Wire | Yes |
| Aerospace Tubing | Yes |
Typical Applications
Aerospace Industry
- Aircraft Exhaust Systems
- Jet Engine Components
- Exhaust Manifolds
- Thermal Shields
- Aerospace Ducting
Petrochemical Industry
- Refinery Equipment
- Process Piping
- Thermal Reactors
- Heat Recovery Systems
Power Generation
- Boiler Components
- Flue Gas Systems
- Thermal Expansion Joints
- Heat Exchangers
Industrial Heating Equipment
- Furnace Components
- Heat Treatment Equipment
- High Temperature Ducting
- Thermal Processing Systems
Chemical Processing Industry
- Pressure Vessels
- Storage Tanks
- Chemical Reactors
- Expansion Bellows
Automotive Industry
- Turbocharger Components
- Exhaust Systems
- High Temperature Assemblies
Manufacturing Characteristics
| Manufacturing Process | Rating |
|---|---|
| Laser Cutting | Excellent |
| Waterjet Cutting | Excellent |
| CNC Machining | Good |
| Stamping | Excellent |
| Bending | Excellent |
| TIG Welding | Excellent |
| MIG Welding | Excellent |
| Resistance Welding | Excellent |
| Polishing | Excellent |
Advantages
Excellent Resistance to Intergranular Corrosion
Titanium stabilization prevents carbide precipitation.
Outstanding Weldability
Ideal for welded structures operating at elevated temperatures.
Good High-Temperature Strength
Maintains mechanical properties under heat exposure.
Excellent Thermal Cycling Resistance
Suitable for repeated heating and cooling conditions.
Good Corrosion Resistance
Comparable to SS304 in most environments.
Long Service Life
Provides reliable performance in thermal applications.
Limitations
Lower Chloride Resistance Than SS316
Not ideal for marine immersion or aggressive chloride environments.
Higher Cost Than SS304
Due to titanium alloying additions.
Lower Maximum Temperature Than SS310
Not suitable for extreme furnace applications above 1000°C.
Moderate Machinability
More difficult to machine than SS303.
Comparison with Other Stainless Steels
| Property | SS321 | SS304 | SS304L | SS316 | SS347 |
|---|---|---|---|---|---|
| High Temperature Resistance | Excellent | Good | Good | Good | Excellent |
| Intergranular Corrosion Resistance | Outstanding | Moderate | Excellent | Excellent | Outstanding |
| Weldability | Excellent | Excellent | Outstanding | Excellent | Excellent |
| Continuous Service Temperature | 900°C | 870°C | 870°C | 870°C | 900°C |
| Chloride Resistance | Moderate | Moderate | Moderate | Excellent | Moderate |
| Cost | High | Medium | Medium | High | High |
Comparison with Common High-Temperature Materials
| Material | Max Service Temp | Corrosion Resistance | Welded Structure Performance |
|---|---|---|---|
| SS321 | 900°C | Excellent | Outstanding |
| SS304 | 870°C | Excellent | Good |
| SS309 | 1000°C | Excellent | Excellent |
| SS310 | 1100°C | Excellent | Excellent |
| SS347 | 900°C | Excellent | Outstanding |
| Inconel 600 | 1175°C | Outstanding | Outstanding |
Available Surface Finishes
Mill Finishes
- No.1 Finish
- 2B Finish
- BA (Bright Annealed)
- No.4 Finish
Industrial Finishes
- Pickled Finish
- Passivated Surface
- Descaled Surface
Decorative Finishes
- Mirror Polish (8K)
- Hairline Finish
- Satin Finish
- Brushed Finish
- Glass Bead Finish
Frequently Asked Questions (FAQ)
What is SS321 stainless steel?
SS321 is a titanium-stabilized stainless steel designed to resist intergranular corrosion and maintain performance at elevated temperatures.
What is SS321 used for?
Typical applications include:
- Aircraft Exhaust Systems
- Heat Exchangers
- Pressure Vessels
- Expansion Joints
- Petrochemical Equipment
- High Temperature Piping
What is the difference between SS321 and SS304?
| Property | SS321 | SS304 |
|---|---|---|
| Titanium Stabilization | Yes | No |
| High Temperature Performance | Better | Lower |
| Weld Decay Resistance | Excellent | Moderate |
| Thermal Cycling Resistance | Better | Lower |
What is the difference between SS321 and SS347?
| Property | SS321 | SS347 |
|---|---|---|
| Stabilizing Element | Titanium (Ti) | Niobium (Nb) |
| High Temperature Performance | Excellent | Excellent |
| Aerospace Usage | Common | Less Common |
| Welded Structures | Excellent | Excellent |
Is SS321 suitable for aerospace applications?
Yes. SS321 is widely used in aircraft exhaust systems, thermal shields, and high-temperature aerospace structures.
Can SS321 be welded?
Yes. SS321 provides excellent weldability and is commonly used in heavily welded high-temperature equipment.
Is SS321 better than SS304 for high-temperature applications?
Yes. SS321 is specifically designed for elevated-temperature service and resistance to sensitization.
Can SS321 rust?
SS321 offers corrosion resistance similar to SS304 and performs well in most industrial environments.
Why is titanium added to SS321?
Titanium binds with carbon, preventing chromium carbide precipitation and preserving corrosion resistance after welding.
Does GCNOV provide custom manufacturing services for SS321?
Yes. GCNOV provides:
- CNC Machining
- Laser Cutting
- Sheet Metal Fabrication
- Tube Fabrication
- TIG & MIG Welding
- Aerospace Component Manufacturing
- Heat Exchanger Fabrication
- Prototype Development
- Low-Volume Production
- Mass Production