347 stainless steel is an austenitic heat-resistant alloy with 17% chromium and 10% nickel. It contains niobium, offering excellent intergranular corrosion resistance. Used in high-temperature applications like aircraft and petrochemical industries.
347 stainless steel is an austenitic stainless steel with a higher alloy content than standard 304 and 316 stainless steels. The composition of 347 stainless steel typically includes the following key elements:
| Element | Composition Range |
|---|---|
| Chromium (Cr) | 17.0 – 20.0% |
| Nickel (Ni) | 9.0 – 13.0% |
| Manganese (Mn) | 2.0% maximum |
| Silicon (Si) | 0.75% maximum |
| Carbon (C) | 0.08% maximum |
| Phosphorus (P) | 0.045% maximum |
| Sulfur (S) | 0.03% maximum |
| Niobium (Columbium) (Nb/Cb) | 10xC – 1.10% |
The addition of niobium (columbium) sets 347 stainless steel apart from other austenitic grades. Niobium stabilizes the steel against intergranular corrosion, which makes it suitable for high-temperature applications.
| Performance Characteristics | Description |
|---|---|
| Corrosion Resistance | Excellent resistance to corrosion in various environments, including pitting and crevice corrosion. |
| Intergranular Corrosion Resistance | Superior resistance to intergranular corrosion due to niobium stabilization, making it suitable for high-temperature applications. |
| High-Temperature Performance | Demonstrates high strength and oxidation resistance at elevated temperatures, with continuous service up to 870°C (1600°F). |
| Weldability | Easily weldable using common welding techniques, with reduced risk of sensitization and intergranular corrosion during welding. |
| Creep Resistance | Exhibits good resistance to creep deformation under prolonged exposure to high temperatures. |
| Heat Resistance | Offers excellent heat resistance, making it suitable for applications in high-temperature environments. |
| Stability | Stabilized against the formation of harmful chromium carbides at grain boundaries during exposure to high temperatures. |
347 stainless steel offers several advantageous properties due to its specific composition:
Corrosion Resistance: 347 stainless steel provides excellent resistance to corrosion in a wide range of environments. Its high chromium and nickel content contribute to its resistance against general corrosion, as well as pitting and crevice corrosion.
Intergranular Corrosion Resistance: The addition of niobium (columbium) in 347 stainless steel enhances its resistance to intergranular corrosion. This makes it an ideal choice for applications involving exposure to high temperatures, such as welding and heat treatment.
High-Temperature Performance: 347 stainless steel exhibits superior high-temperature strength and oxidation resistance. It can withstand temperatures up to 870°C (1600°F) in continuous service and higher temperatures in intermittent exposures.
Weldability: 347 stainless steel is readily weldable using common welding techniques, such as shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW/TIG), and gas metal arc welding (GMAW/MIG). Its niobium content minimizes sensitization during welding, reducing the risk of intergranular corrosion.
Creep Resistance: Creep refers to the deformation of a material under prolonged exposure to high temperatures. 347 stainless steel demonstrates good creep resistance, making it suitable for applications that require prolonged mechanical integrity at elevated temperatures.
Heat Resistance: Due to its high nickel and chromium content, 347 stainless steel offers excellent heat resistance and is well-suited for use in high-temperature applications like aerospace components and industrial furnace parts.
Stability: The niobium stabilization in 347 stainless steel prevents the formation of harmful chromium carbides at grain boundaries, ensuring the material remains stable and corrosion-resistant during exposure to high temperatures.
Due to its impressive combination of corrosion resistance, high-temperature performance, and weldability, 347 stainless steel is commonly used in applications involving elevated temperatures, such as aircraft exhaust systems, chemical processing equipment, and high-temperature furnace components.
347 stainless steel is highly versatile and finds numerous applications in high-temperature and corrosive environments due to its exceptional performance characteristics. Some typical applications include:
Aircraft Exhaust Systems: 347 stainless steel’s high-temperature strength and oxidation resistance make it suitable for use in aircraft exhaust systems, where components are exposed to hot gases and high temperatures during engine operation.
Chemical Processing Equipment: In chemical processing industries, 347 stainless steel is employed for manufacturing reactor vessels, heat exchangers, and other equipment that handle corrosive chemicals at elevated temperatures.
High-Temperature Furnace Components: Furnace parts, such as radiant tubes, muffles, and burner nozzles, benefit from 347 stainless steel’s heat resistance and creep resistance in high-temperature furnace environments.
Oil and Gas Industry: 347 stainless steel is used in downhole tools and equipment for oil and gas exploration and production, where resistance to corrosive downhole environments and high temperatures is vital.
Petrochemical Industry: For refining and processing petrochemicals, 347 stainless steel is employed in pipes, fittings, and equipment that come into contact with aggressive chemicals and elevated temperatures.
Heat Exchangers: 347 stainless steel is suitable for constructing heat exchangers that transfer heat between hot and cold fluids in various industrial processes.
Power Generation: In power plants, 347 stainless steel is utilized for boiler tubes, superheaters, and other components exposed to high temperatures and steam.
Pulp and Paper Industry: 347 stainless steel finds applications in digesters and bleach towers, where it provides resistance to corrosive chemicals and high-temperature liquors.
Waste Incineration: 347 stainless steel is used in waste incineration plants for components that handle high-temperature combustion processes and corrosive by-products.
Automotive Components: Some automotive components, such as exhaust systems and catalytic converters, utilize 347 stainless steel for its high-temperature resistance and corrosion resistance.
Due to its superior corrosion resistance, stability against intergranular corrosion, and high-temperature strength, 347 stainless steel offers reliability and longevity in challenging environments. Its application versatility makes it a valuable material choice across a wide range of industries that require excellent performance under harsh conditions.
The addition of niobium to 347 stainless steel significantly enhances its performance compared to other austenitic stainless steel grades. Niobium, also known as columbium, is a key alloying element that provides several beneficial effects:
Intergranular Corrosion Resistance: Niobium stabilizes 347 stainless steel against sensitization and the formation of harmful chromium carbides at grain boundaries during welding and exposure to high temperatures. This makes 347 stainless steel highly resistant to intergranular corrosion, a common issue in other austenitic stainless steel grades.
High-Temperature Performance: The presence of niobium imparts superior high-temperature strength and oxidation resistance to 347 stainless steel. This allows it to maintain its mechanical properties and structural integrity at elevated temperatures, making it ideal for applications in high-temperature environments.
Creep Resistance: Niobium contributes to the creep resistance of 347 stainless steel, which refers to the material’s ability to resist deformation under prolonged exposure to high temperatures and constant loads. This property is particularly important in applications involving high-temperature service.
Weldability: Niobium minimizes sensitization during welding, reducing the risk of intergranular corrosion in the heat-affected zone. As a result, 347 stainless steel exhibits excellent weldability, making it easier to fabricate and join components without compromising their corrosion resistance.
Corrosion Resistance: Niobium, along with the high chromium and nickel content in 347 stainless steel, contributes to its excellent overall corrosion resistance in various environments, including those containing corrosive chemicals and high temperatures.
Stability: The addition of niobium ensures the stability of 347 stainless steel, even after prolonged exposure to high temperatures, preventing the material from undergoing phase transformations or embrittlement.
Due to these advantageous properties, 347 stainless steel is well-suited for applications in corrosive and high-temperature environments, where it outperforms other austenitic stainless steel grades. Its ability to resist intergranular corrosion and maintain mechanical strength at elevated temperatures makes it a reliable and durable choice for various industries, including aerospace, chemical processing, power generation, and petrochemicals.
The advantages of using 347 stainless steel in applications involving sensitizing temperatures and intergranular corrosion resistance are significant and make it a preferred choice for various industries. Here are the key advantages:
Intergranular Corrosion Resistance: One of the primary advantages of using 347 stainless steel is its exceptional resistance to intergranular corrosion. This resistance is achieved through the addition of niobium, which stabilizes the steel’s microstructure, preventing the formation of harmful chromium carbides at grain boundaries. As a result, 347 stainless steel remains highly resistant to intergranular corrosion, even after exposure to sensitizing temperatures, making it ideal for applications in corrosive environments.
Sensitizing Temperature Resistance: Sensitization is a phenomenon in stainless steels where chromium carbides precipitate at grain boundaries during exposure to certain temperatures. This can lead to a depletion of chromium near the grain boundaries, causing intergranular corrosion susceptibility. However, the niobium stabilization in 347 stainless steel prevents sensitization and maintains its corrosion resistance, even at sensitizing temperatures.
High-Temperature Performance: 347 stainless steel exhibits excellent high-temperature strength and oxidation resistance. It can withstand sensitizing temperatures without losing its mechanical properties, making it suitable for use in applications where components are exposed to elevated temperatures for prolonged periods.
Weldability: 347 stainless steel offers superior weldability due to its niobium content, which minimizes sensitization during welding. This ensures that the welded joints retain their intergranular corrosion resistance, making it easier to fabricate components without compromising their overall performance.
Chemical Resistance: Apart from intergranular corrosion resistance, 347 stainless steel provides good overall resistance to a wide range of corrosive chemicals, including organic acids, inorganic acids, and various aqueous environments.
Versatility: Due to its combination of intergranular corrosion resistance, high-temperature performance, and general corrosion resistance, 347 stainless steel is versatile and finds applications in industries such as chemical processing, petrochemicals, power generation, and aerospace.
Long-Term Reliability: The intergranular corrosion resistance and stability of 347 stainless steel ensure that components made from this material have a longer service life and require less maintenance, reducing overall operational costs.
In summary, the advantages of using 347 stainless steel lie in its ability to resist intergranular corrosion and sensitization at elevated temperatures. These properties make it an excellent choice for applications involving corrosive environments, sensitizing temperatures, and demanding conditions, providing long-term reliability and performance.
When welding and fabricating components made of 347 stainless steel, several considerations are crucial to ensure optimal results and maintain the material’s intergranular corrosion resistance and mechanical properties. Here are the key considerations:
Preventing Sensitization: 347 stainless steel is sensitive to sensitization, which can occur during prolonged exposure to temperatures in the range of 800°C to 1500°C (1472°F to 2732°F). To prevent sensitization, it is essential to use low heat inputs during welding and avoid prolonged exposure to sensitizing temperatures.
Welding Heat Input: Controlling the heat input during welding is critical to avoid overheating the material and causing intergranular carbide precipitation. Low heat inputs, such as pulsed welding or using low amperage settings, help minimize the risk of sensitization and maintain the material’s intergranular corrosion resistance.
Use of Low Carbon Fillers: When selecting welding fillers, it is advisable to choose those with low carbon content to avoid the formation of harmful chromium carbides at grain boundaries. Filler metals with stabilized columbium or niobium are often recommended for welding 347 stainless steel.
Post-Weld Heat Treatment (PWHT): In some applications, a post-weld heat treatment may be employed to re-stabilize the material and eliminate any sensitization that occurred during welding. PWHT is typically performed at temperatures between 1050°C to 1150°C (1922°F to 2102°F) for a specified duration, followed by controlled cooling.
Avoiding Contamination: To maintain the corrosion resistance of 347 stainless steel, it is essential to avoid contamination during fabrication and welding processes. This includes preventing contact with carbon steel tools or surfaces that could introduce carbon into the material and compromise its intergranular corrosion resistance.
Proper Shielding Gas: The use of appropriate shielding gas during welding is crucial to protect the weld pool from atmospheric contamination. Inert gases like argon or helium are commonly used for gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes.
Grinding and Surface Preparation: Proper surface preparation is essential to remove any contaminants, such as oils, grease, or scale, before welding. Grinding surfaces to be welded helps ensure proper fusion and prevents the introduction of contaminants into the weld zone.
Welding Technique: Employing suitable welding techniques, such as back purging or using double-sided welding for thicker components, can help enhance the quality of the weld and reduce the risk of defects.
Avoiding Overmatching: Overmatching the filler metal strength to that of the base material can lead to brittleness and reduce the material’s corrosion resistance. It is essential to select filler metals with strength levels that closely match the base metal.
By adhering to these considerations, fabricators and welders can successfully work with 347 stainless steel, preserving its intergranular corrosion resistance and ensuring the longevity and reliability of fabricated components.
When selecting 347 stainless steel supplier, several factors should be considered to ensure you receive high-quality materials and reliable services. Here are the key factors to keep in mind:
Quality and Certification: Look for suppliers who provide 347 stainless steel products that meet international quality standards, such as ASTM A240 or ASME SA240. Ensure that the supplier is certified and can provide material certifications and test reports to verify the composition and properties of the stainless steel.
Experience and Reputation: Choose suppliers with a proven track record and extensive experience in supplying 347 stainless steel products to various industries. Check for customer reviews, testimonials, and references to gauge the supplier’s reputation and reliability.
Stock Availability: Verify the supplier’s stock availability to ensure they can meet your immediate and future requirements promptly. A reputable supplier should maintain a substantial inventory of 347 stainless steel products in various sizes and forms.
Customization Capabilities: If you require custom-sized or shaped components, ensure the supplier has the capability to provide custom fabrication services and meets your specific requirements.
On-Time Delivery: Timely delivery of materials is crucial to keep your projects on schedule. Choose a supplier with a proven track record of delivering products on time and handling logistics efficiently.
Technical Support: A reliable supplier should have a knowledgeable technical support team that can provide assistance with material selection, welding guidelines, and any technical inquiries related to 347 stainless steel.
Competitive Pricing: While cost should not be the sole determining factor, consider suppliers offering competitive pricing without compromising material quality and services.
Packaging and Handling: Ensure the supplier provides proper packaging and handling to protect the stainless steel products during transportation and storage, reducing the risk of damage or contamination.
Certifications and Compliance: Check if the supplier complies with industry standards and regulations, such as ISO 9001, to ensure they follow best practices in their manufacturing and supply processes.
Customer Service: Opt for a supplier with excellent customer service, as it indicates their commitment to addressing your inquiries and concerns promptly and professionally.
Supply Chain Resilience: Assess the supplier’s supply chain resilience and contingency plans to minimize potential disruptions in material availability.
Sustainability: If environmental considerations are important to your organization, inquire about the supplier’s sustainability practices and commitment to eco-friendly processes.
By thoroughly evaluating these factors and selecting a reputable and reliable supplier, you can ensure a smooth and successful procurement process for 347 stainless steel products, meeting your project’s requirements and quality standards.
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