Stainless Steel, Austenitic
S34700 (347) Stainless Steel Sheet
Columbium stabilizes this alloy making it immune to chromium carbide precipitation.
Alloy 347 is recommended for welded applications that can not tolerate a post anneal. The alloy can operate between 800-1600°F.
347 stainless steel is a high-performance austenitic stainless steel with niobium stabilization that ensures excellent corrosion resistance, mechanical strength, and high-temperature stability. It is widely used in chemical, industrial, aerospace, food processing, and high-temperature applications.
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347 Stainless Steel Related Specifications
| System / Standard | Country / Region | Grade / Designation |
| AISI | USA | 347 |
| UNS | International | S34700 |
| EN / W.Nr. | Europe | 1.4550 |
| EN Name | Europe | X6CrNiNb18-10 |
| ASTM A240 | USA | 347 (plate, sheet, strip) |
| ASTM A182 | USA | F347 (forgings, flanges, fittings) |
| ASTM A213 | USA | TP347 (boiler / HX tubes) |
| ASTM A312 | USA | TP347 (seamless pipe) |
| GB | China | 06Cr18Ni11Nb |
| JIS | Japan | SUS347 |
| BS | UK | 347S31 |
| AFNOR | France | Z6CNb18-10 |
Properties
Chemical Composition
S34700 Sheet
ASTM A240
| Chemical Element | % Present |
| Carbon (C) | 0.00 - 0.08 |
| Chromium (Cr) | 17.00 - 19.00 |
| Nickel (Ni) | 9.00 - 13.00 |
| Manganese (Mn) | 0.00 - 2.00 |
| Phosphorous (P) | 0.00 - 0.04 |
| Sulphur (S) | 0.00 - 0.03 |
| Silicon (Si) | 0.00 - 0.75 |
| Niobium (Columbium) (Nb) | 0.00 - 1.00 |
| Iron (Fe) | Balance |
Mechanical Properties
Sheet
ASTM A240
| Mechanical Property | Value |
| Proof Stress | 205 Min MPa |
| Tensile Strength | 515 Min MPa |
| Elongation A50 mm | 40 Min % |
General Physical Properties
| Physical Property | Value |
| Density | 7.96 g/cm³ |
Applications of 347 Stainless Steel
347 stainless steel is a stabilized austenitic stainless steel containing niobium (columbium), which improves resistance to intergranular corrosion after exposure to high temperatures. Its excellent mechanical properties and corrosion resistance make it suitable for a wide range of high-temperature and industrial applications.
1. High-Temperature Applications
Furnace components and heat exchangers
Boiler parts, superheater and evaporator tubes
Exhaust stacks and high-temperature ducting
Industrial ovens and kilns
2. Chemical and Petrochemical Industry
Processing equipment and piping in moderately corrosive environments
Pressure vessels and tanks for chemical storage
Heat-resistant piping carrying steam or hot liquids
3. Food and Beverage Processing
Equipment exposed to elevated temperatures
Heat exchangers and evaporators
Components requiring good corrosion resistance and stability at high temperature
4. Aerospace and Automotive
Exhaust systems and turbochargers
High-temperature components in engines and power plants
5. Industrial Equipment
Springs, fasteners, and structural components for high-temperature service
Mechanical equipment exposed to heat and corrosion simultaneously
6. Architectural Applications
Structures and components exposed to outdoor weather and moderate corrosive conditions
Decorative elements requiring durability and stability at elevated temperatures
Summary
347 stainless steel is ideal for high-temperature and industrial applications, where intergranular corrosion resistance, mechanical strength, and stability at elevated temperatures are critical. Common industries include chemical processing, food and beverage, aerospace, automotive, and industrial equipment.
Characteristics of 347 Stainless Steel
347 stainless steel is a stabilized austenitic stainless steel containing niobium (columbium), which enhances resistance to intergranular corrosion after exposure to high temperatures. It offers good mechanical properties, excellent corrosion resistance, and high-temperature stability, making it suitable for demanding applications.
1. High-Temperature Stability
Excellent resistance to intergranular corrosion after exposure to temperatures of 425–870°C (800–1600°F)
Niobium stabilization prevents chromium carbide precipitation during welding and heat exposure
Suitable for furnace parts, heat exchangers, and boiler components
2. Corrosion Resistance
Good resistance to oxidation, atmospheric corrosion, and mild chemical attack
Performs better than 304 and similar to 321 in high-temperature corrosive environments
Low susceptibility to pitting and crevice corrosion in moderately aggressive media
3. Mechanical Properties
High strength and toughness, even at elevated temperatures
Can be cold-worked to improve strength
Excellent ductility for forming, bending, and shaping
4. Weldability
Easily welded using conventional methods: TIG, MIG, SMAW, or resistance welding
Niobium stabilization reduces risk of sensitization in the heat-affected zone
Suitable for welded components in chemical, food, and high-temperature applications
5. Formability and Fabrication
Good cold and hot workability
Can be rolled, drawn, or pressed into complex shapes
Suitable for sheets, plates, tubes, and structural components
6. Heat Resistance
Can withstand continuous service up to 870°C (1600°F)
Resistant to scaling and oxidation in oxidizing atmospheres
Summary
347 stainless steel combines high-temperature stability, excellent corrosion resistance, and strong mechanical properties. Its niobium stabilization prevents intergranular corrosion, making it ideal for high-temperature industrial equipment, chemical processing, aerospace, and food processing applications.
Additional Information
Fabrication
Fabrication of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel designed to resist intergranular corrosion during welding and high-temperature service. It combines excellent corrosion resistance, good weldability, and mechanical strength, making it suitable for a wide range of fabrication processes in industrial and high-temperature applications.
1. Forming
347 stainless steel has good cold formability in the annealed condition.
Can be bent, deep-drawn, stamped, and roll-formed.
Because of work-hardening, intermediate annealing may be required during extensive forming operations to restore ductility.
2. Cutting and Shearing
Can be cut with standard techniques such as shearing, sawing, and laser cutting.
Tools must be sharp to minimize work-hardening at the cut edges.
3. Machining
347 is moderately difficult to machine due to austenitic toughness and work-hardening tendency.
Use carbide tooling for better performance, proper feed rates, and cooling lubricants to control heat and tool wear.
4. Welding
Excellent weldability with conventional processes: TIG, MIG, SMAW.
Titanium stabilization prevents intergranular corrosion near the weld.
Filler metals such as 347 or 308L are commonly used.
Post-weld annealing is typically not required for corrosion resistance, but stress relief may be applied in high-temperature applications.
5. Cold Working
Cold working increases strength significantly due to work-hardening.
Extensive cold work reduces ductility; annealing may be required to restore formability for further fabrication.
6. Hot Working
Hot working is typically performed between 1010–1175°C (1850–2150°F).
Proper temperature control ensures uniform mechanical properties and prevents grain growth.
7. Surface Finishing
Can be supplied in a range of finishes (2B, BA, or polished).
Work-hardened areas may require additional finishing for aesthetics or corrosion resistance.
Summary
347 stainless steel is versatile and easily fabricated, offering excellent weldability, corrosion resistance, and strength. Its titanium stabilization makes it particularly suitable for welding and high-temperature applications, while its workability allows for forming, machining, and finishing across a wide range of industrial uses.
Weldability
Weldability of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel that offers excellent weldability. Its titanium content prevents the formation of chromium carbides during welding, reducing the risk of intergranular corrosion in the heat-affected zone (HAZ). This makes 347 highly suitable for welded structures and components exposed to elevated temperatures.
1. Compatible Welding Processes
TIG (GTAW) – Preferred for precision welding and thin sections.
MIG (GMAW) – Common for thicker sections and high-productivity applications.
Shielded Metal Arc Welding (SMAW) – Suitable for field and maintenance welding.
Resistance welding – Spot and seam welding can be used effectively.
2. Titanium Stabilization Benefits
Titanium reacts with carbon to form stable titanium carbides.
Prevents chromium carbide precipitation, avoiding sensitization in the HAZ.
Ensures corrosion resistance is maintained after welding, even without post-weld annealing.
3. Filler Material Selection
Filler metals matching 347 are commonly used for optimum corrosion resistance.
ER347 or 308L filler rods are suitable depending on base material thickness and application.
Low-carbon fillers reduce carbide precipitation risk in general austenitic stainless steel applications.
4. Heat Input and Distortion
347 has high thermal expansion, which can lead to distortion if not controlled.
Use low to moderate heat input to reduce warping and maintain dimensional stability.
Adequate fixturing and sequence planning help minimize residual stresses.
5. Post-Weld Treatment
Usually, post-weld annealing is not required because titanium stabilization protects against intergranular corrosion.
Stress relief may be applied for high-temperature service or when dimensional stability is critical.
6. Applications Related to Weldability
High-temperature boilers and furnace components
Chemical and petrochemical processing equipment
Heat exchangers
Pressure vessels and piping systems requiring welded assemblies
Summary
347 stainless steel exhibits excellent weldability due to its titanium stabilization, allowing it to maintain corrosion resistance in welded areas without the need for extensive post-weld heat treatment. Proper filler selection, heat control, and welding technique ensure strong, durable, and corrosion-resistant welds suitable for high-temperature and industrial applications.
Machinability
Machinability of 347 Stainless Steel
347 stainless steel, a titanium-stabilized austenitic stainless steel, has moderate machinability similar to other austenitic grades such as 304 and 321. While it is tougher and more work-hardening than carbon steels, careful tooling and machining practices allow for efficient processing and good surface finishes.
1. Work-Hardening Behavior
347 stainless steel exhibits work-hardening during cutting, which increases tool wear if not properly managed.
Continuous, consistent cutting helps prevent excessive hardening on the surface.
2. Tooling Recommendations
Carbide tooling is preferred for higher productivity and tool life.
High-speed steel (HSS) tools can be used at slower cutting speeds with careful feed control.
Positive rake angles reduce cutting forces and heat generation.
3. Cutting Speeds and Feeds
Slower cutting speeds than those used for carbon steels are recommended.
Use moderate to heavy feeds to keep the tool engaged and minimize work-hardening.
4. Cooling and Lubrication
Austenitic stainless steels have low thermal conductivity, so heat control is critical.
Flood coolant or high-performance cutting oils help reduce heat, improve surface finish, and extend tool life.
5. Chip Formation
Chips are typically tough and stringy, making them difficult to evacuate.
Use chip breakers or insert geometries designed for stainless steel to manage chips effectively.
6. Surface Finish
Good surface finishes can be achieved with proper tool geometry, cutting parameters, and cooling.
Avoid dwell or pauses on the workpiece, as these can create hardened spots and reduce finish quality.
Summary
347 stainless steel has moderate machinability compared with other austenitic grades. Success in machining relies on sharp tools, controlled cutting parameters, proper cooling, and feed rates to counteract work-hardening and achieve high-quality finished components.
Corrosion Resistance
Corrosion Resistance of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel with excellent corrosion resistance. The titanium stabilization prevents chromium carbide precipitation during welding, reducing the risk of intergranular corrosion, particularly in the heat-affected zone (HAZ). This makes 347 ideal for welded assemblies and high-temperature applications.
1. General Corrosion Resistance
Performs well in atmospheric, industrial, and mildly corrosive environments.
Resistant to oxidation at moderate elevated temperatures.
Suitable for general chemical, petrochemical, and process equipment.
2. Intergranular Corrosion Resistance
Titanium binds with carbon to form stable titanium carbides.
Prevents chromium depletion at grain boundaries, which avoids sensitization.
Especially beneficial in welded areas where intergranular corrosion is a concern.
3. Resistance to Chlorides
Exhibits moderate resistance to chloride-induced pitting and crevice corrosion.
Not as resistant as Mo-bearing grades like 316, but better than carbon steels or unstabilized austenitic grades in welded components.
4. High-Temperature Corrosion
Suitable for use in continuous service up to ~870°C (1600°F) in oxidizing atmospheres.
Titanium stabilization provides good resistance to carbide precipitation and oxidation during high-temperature service.
5. Comparison to Other Austenitic Grades
Better corrosion resistance than 304 in welded conditions due to titanium stabilization.
Slightly less corrosion-resistant than 316 in chloride-rich environments.
Superior intergranular corrosion resistance compared to unstabilized 321 or 304 stainless steels.
6. Applications Leveraging Corrosion Resistance
Heat exchangers and furnace components
Chemical and petrochemical equipment
Pressure vessels and piping systems
Components exposed to elevated temperatures or welding
Summary
347 stainless steel combines excellent general corrosion resistance with superior resistance to intergranular corrosion, making it highly suitable for welded and high-temperature applications. Titanium stabilization ensures reliable long-term performance, especially in industrial and chemical environments.
Cold Working
Cold Working of 347 Stainless Steel
347 stainless steel is an austenitic, titanium-stabilized stainless steel with good cold-working properties. Cold working increases the material’s strength and hardness while reducing ductility. The titanium stabilization helps maintain corrosion resistance, even in heavily worked conditions.
1. Work-Hardening Behavior
347 stainless steel work-hardens during cold deformation, although slightly less aggressively than 301 or 304.
Strength increases significantly with deformation, but ductility decreases.
2. Common Cold Working Processes
Rolling: For sheets, strips, and plates.
Drawing: For wires, tubes, and rods.
Bending and Forming: For clips, springs, and structural components.
Stamping and Deep Drawing: For complex parts.
3. Mechanical Properties Control
Cold working allows precise adjustment of tensile strength, yield strength, and hardness.
Extensive cold working may require intermediate annealing to restore ductility for further forming.
4. Effect on Corrosion Resistance
Titanium stabilization prevents chromium carbide precipitation, maintaining corrosion resistance even after significant cold work.
Unlike unstabilized austenitic grades, 347 maintains resistance to intergranular corrosion in welded or heavily worked areas.
5. Post-Forming Considerations
In highly cold-worked parts, solution annealing can be performed to relieve residual stresses and restore formability if required.
Cold working may also induce some magnetism due to martensitic transformation, though minimal in 347 compared to 301.
6. Applications Utilizing Cold Work
Springs and clips
Structural components requiring high strength
Industrial equipment requiring formability and corrosion resistance
Tubes, rods, and wire for chemical and high-temperature service
Summary
347 stainless steel exhibits good cold-working characteristics, allowing it to achieve higher strength through work hardening while maintaining corrosion resistance thanks to titanium stabilization. Proper management of deformation and occasional annealing enables high-performance components for industrial and high-temperature applications.
Heat Treatment
Heat Treatment of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel. Unlike martensitic or precipitation-hardening grades, it is not hardened by conventional heat treatment. Heat treatment is mainly used to restore ductility, relieve stresses, and maintain corrosion resistance, especially after cold working or welding.
1. Annealing / Solution Treatment
Purpose:
Relieve stresses from cold working or forming
Restore ductility
Dissolve any unwanted precipitates
Typical Temperature: 1010–1120°C (1850–2050°F)
Cooling: Rapid air or water quenching to preserve a fully austenitic structure
Effect:
Returns mechanical properties to annealed condition
Maintains corrosion resistance due to titanium stabilization
2. Stress Relief
Purpose: Reduce residual stresses from forming, bending, or welding
Temperature Range: 450–650°C (840–1200°F)
Effect: Minimizes distortion and reduces the risk of stress corrosion cracking without significantly changing mechanical properties
3. Cold-Worked Condition Considerations
Cold working increases strength but reduces ductility.
Intermediate annealing may be performed between forming operations to restore ductility and workability.
Repeated cold work and annealing allow precise control over strength and hardness.
4. Post-Weld Heat Treatment
Welding 347 stainless steel typically does not require post-weld annealing for corrosion resistance, thanks to titanium stabilization.
Stress relief annealing may be applied in high-temperature service or where dimensional stability is critical.
5. Limitations
Heat treatment does not significantly increase hardness; 347 relies on cold working for strength enhancement.
Prolonged high-temperature exposure above ~500°C can reduce the effects of prior cold work.
Summary
Heat treatment of 347 stainless steel is focused on stress relief, ductility restoration, and maintaining corrosion resistance, rather than hardening. Solution annealing and controlled stress relief help ensure optimal mechanical and chemical performance for welded, cold-worked, and high-temperature components.
Heat Resistance
Heat Resistance of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel with good high-temperature properties. It is specifically designed for applications requiring resistance to carbide precipitation and oxidation at elevated temperatures.
1. Continuous Service Temperature
Suitable for continuous service in oxidizing atmospheres up to ~870°C (1600°F).
Titanium stabilization prevents intergranular corrosion and maintains strength during long-term exposure to elevated temperatures.
2. Intermittent Exposure
Can tolerate intermittent exposure up to ~925°C (1700°F) without significant scaling or degradation.
Useful for components subject to occasional thermal cycling or transient heating.
3. Oxidation Resistance
Forms a protective chromium oxide layer that resists scaling in oxidizing environments.
Not suitable for prolonged exposure to strongly oxidizing or sulfidizing atmospheres at extreme temperatures; for these, specialized high-temperature grades such as 310 are recommended.
4. Thermal Effects on Mechanical Properties
Retains good tensile strength and ductility at elevated temperatures.
High-temperature exposure does not significantly reduce corrosion resistance, due to titanium stabilization.
Prolonged exposure above 900°C can lead to grain growth, which may reduce toughness.
5. Applications Related to Heat Resistance
Boiler and furnace components
Heat exchangers
Chemical and petrochemical processing equipment
High-temperature piping and welded assemblies
6. Comparison to Other Austenitic Grades
Heat resistance is better than 304 in welded or high-temperature applications.
Slightly lower high-temperature strength than 310 but more corrosion-resistant than unstabilized 304 in the HAZ.
Titanium stabilization ensures reliability in long-term service at elevated temperatures.
Summary
347 stainless steel provides excellent high-temperature performance up to ~870°C for continuous service. Its titanium stabilization prevents carbide precipitation, maintaining corrosion resistance and mechanical strength in welded and heat-exposed components, making it ideal for industrial and high-temperature applications.
Hot Working
Heat Resistance of 347 Stainless Steel
347 stainless steel is a titanium-stabilized austenitic stainless steel with good high-temperature properties. It is specifically designed for applications requiring resistance to carbide precipitation and oxidation at elevated temperatures.
1. Continuous Service Temperature
Suitable for continuous service in oxidizing atmospheres up to ~870°C (1600°F).
Titanium stabilization prevents intergranular corrosion and maintains strength during long-term exposure to elevated temperatures.
2. Intermittent Exposure
Can tolerate intermittent exposure up to ~925°C (1700°F) without significant scaling or degradation.
Useful for components subject to occasional thermal cycling or transient heating.
3. Oxidation Resistance
Forms a protective chromium oxide layer that resists scaling in oxidizing environments.
Not suitable for prolonged exposure to strongly oxidizing or sulfidizing atmospheres at extreme temperatures; for these, specialized high-temperature grades such as 310 are recommended.
4. Thermal Effects on Mechanical Properties
Retains good tensile strength and ductility at elevated temperatures.
High-temperature exposure does not significantly reduce corrosion resistance, due to titanium stabilization.
Prolonged exposure above 900°C can lead to grain growth, which may reduce toughness.
5. Applications Related to Heat Resistance
Boiler and furnace components
Heat exchangers
Chemical and petrochemical processing equipment
High-temperature piping and welded assemblies
6. Comparison to Other Austenitic Grades
Heat resistance is better than 304 in welded or high-temperature applications.
Slightly lower high-temperature strength than 310 but more corrosion-resistant than unstabilized 304 in the HAZ.
Titanium stabilization ensures reliability in long-term service at elevated temperatures.
Summary
347 stainless steel provides excellent high-temperature performance up to ~870°C for continuous service. Its titanium stabilization prevents carbide precipitation, maintaining corrosion resistance and mechanical strength in welded and heat-exposed components, making it ideal for industrial and high-temperature applications.
