Overview
SS347 (AISI 347 Stainless Steel) is a niobium-stabilized (columbium-stabilized) austenitic stainless steel belonging to the 300 Series Stainless Steel Family. By adding Niobium (Nb/Cb), SS347 prevents chromium carbide precipitation during welding and prolonged high-temperature service, providing exceptional resistance to intergranular corrosion.
SS347 is specifically developed for applications involving continuous exposure to temperatures between 425°C and 900°C, where conventional stainless steels such as SS304 may become sensitized. It is widely used in aerospace systems, petrochemical plants, refinery equipment, pressure vessels, heat exchangers, boilers, and thermal processing industries.
Compared with SS321, SS347 generally offers better creep strength and stress rupture properties at elevated temperatures, making it a preferred choice for long-term high-temperature service.
Material Specification
| Property | Value |
|---|---|
| Material Designation | AISI 347 |
| Material Family | Niobium-Stabilized Austenitic Stainless Steel |
| UNS Number | S34700 |
| EN Grade | 1.4550 |
| Density | 7.95–8.00 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) | 9.0–13.0 |
| Niobium + Tantalum (Nb+Ta) | ≥10 × C (Max 1.00) |
| 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 Strength
| Temperature | Performance |
|---|---|
| 500°C | Excellent |
| 650°C | Excellent |
| 800°C | Very Good |
| 900°C | Good |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.95–8.00 g/cm³ |
| Melting Point | 1400–1455°C |
| Thermal Conductivity | 16.3 W/m·K |
| Electrical Resistivity | 0.73 μΩ·m |
| Thermal Expansion Coefficient | 17.2 × 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 niobium stabilization prevents carbide precipitation and ensures excellent corrosion resistance after welding and prolonged thermal exposure.
High Temperature Performance
| Service Condition | Temperature |
|---|---|
| Continuous Service | 900°C |
| Intermittent Service | 925°C |
| Oxidation Resistance | Excellent |
| Thermal Fatigue Resistance | Excellent |
| Creep Resistance | Excellent |
SS347 generally exhibits superior creep strength compared with SS321 during long-term elevated-temperature service.
International Equivalent Grades
| Standard | Equivalent Grade |
|---|---|
| ASTM / AISI (USA) | 347 |
| UNS | S34700 |
| EN (Europe) | 1.4550 |
| DIN (Germany) | X6CrNiNb18-10 |
| JIS (Japan) | SUS347 |
| GB/T (China) | 06Cr18Ni11Nb |
| ISO | X6CrNiNb18-10 |
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 |
| Pressure Vessel Plate | Yes |
Typical Applications
Aerospace Industry
- Aircraft Exhaust Systems
- Jet Engine Components
- Thermal Shields
- Aerospace Ducting
- High Temperature Assemblies
Petrochemical Industry
- Refinery Equipment
- Cracking Units
- Process Piping
- Thermal Reactors
Power Generation
- Boiler Tubes
- Superheater Components
- Heat Recovery Systems
- Exhaust Ducting
Chemical Processing Industry
- Pressure Vessels
- Heat Exchangers
- Storage Tanks
- Process Equipment
Industrial Heating Equipment
- Furnace Components
- Heat Treatment Fixtures
- Thermal Chambers
- Expansion Bellows
Nuclear Industry
- Reactor Components
- Heat Transfer Systems
- Containment Equipment
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
Outstanding Resistance to Intergranular Corrosion
Maintains corrosion resistance after welding and thermal exposure.
Excellent High-Temperature Strength
Suitable for prolonged elevated-temperature service.
Superior Creep Resistance
Better long-term thermal performance than SS321 in many applications.
Excellent Weldability
Ideal for pressure vessels and large fabricated structures.
Good Oxidation Resistance
Performs reliably in thermal processing environments.
Long Service Life
Provides excellent durability under demanding industrial conditions.
Limitations
Higher Cost Than SS304
Niobium alloying increases material cost.
Lower Chloride Resistance Than SS316
Not optimized for aggressive marine environments.
Lower Maximum Temperature Than SS310
For temperatures above 1000°C, SS310 is preferred.
Moderate Machinability
More difficult to machine than free-machining grades such as SS303.
Comparison with Other Stainless Steels
| Property | SS347 | SS321 | SS304 | SS316 | SS310 |
|---|---|---|---|---|---|
| Intergranular Corrosion Resistance | Outstanding | Outstanding | Moderate | Excellent | Excellent |
| High Temperature Strength | Excellent | Very Good | Good | Good | Outstanding |
| Creep Resistance | Excellent | Good | Moderate | Good | Excellent |
| Weldability | Excellent | Excellent | Excellent | Excellent | Excellent |
| Continuous Service Temperature | 900°C | 900°C | 870°C | 870°C | 1100°C |
| Chloride Resistance | Moderate | Moderate | Moderate | Excellent | Moderate |
Comparison with Common High-Temperature Materials
| Material | Max Service Temp | Creep Resistance | Corrosion Resistance |
|---|---|---|---|
| SS347 | 900°C | Excellent | Excellent |
| SS321 | 900°C | Very Good | Excellent |
| SS309 | 1000°C | Excellent | Excellent |
| SS310 | 1100°C | Outstanding | Excellent |
| Inconel 600 | 1175°C | Outstanding | Outstanding |
| Inconel 625 | 980°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 SS347 stainless steel?
SS347 is a niobium-stabilized austenitic stainless steel designed to resist sensitization and intergranular corrosion in welded and high-temperature applications.
What is SS347 used for?
Typical applications include:
- Pressure Vessels
- Heat Exchangers
- Aerospace Exhaust Systems
- Petrochemical Equipment
- Boilers
- Thermal Processing Equipment
What is the difference between SS347 and SS321?
| Property | SS347 | SS321 |
|---|---|---|
| Stabilizing Element | Niobium (Nb) | Titanium (Ti) |
| Creep Resistance | Better | Good |
| High Temperature Strength | Higher | Slightly Lower |
| Aerospace Applications | Common | Common |
What is the difference between SS347 and SS304?
| Property | SS347 | SS304 |
|---|---|---|
| High Temperature Stability | Excellent | Moderate |
| Weld Decay Resistance | Outstanding | Moderate |
| Intergranular Corrosion Resistance | Excellent | Lower |
Is SS347 suitable for pressure vessels?
Yes. SS347 is widely used in pressure vessels, boilers, and thermal processing systems.
Can SS347 be welded?
Yes. SS347 provides excellent weldability and is commonly selected for heavily welded high-temperature equipment.
Is SS347 better than SS321?
For long-term elevated-temperature service and creep resistance, SS347 is often preferred. For aerospace exhaust systems, both are commonly used.
Why is niobium added to SS347?
Niobium binds with carbon, preventing chromium carbide precipitation and maintaining corrosion resistance after welding.
Is SS347 suitable for high-temperature service?
Yes. SS347 is designed specifically for temperatures between 425°C and 900°C.
Does GCNOV provide custom manufacturing services for SS347?
Yes. GCNOV provides:
- CNC Machining
- Laser Cutting
- Sheet Metal Fabrication
- Pressure Vessel Components
- Heat Exchanger Fabrication
- TIG & MIG Welding
- Aerospace Component Manufacturing
- Prototype Development
- Low-Volume Production
- Mass Production