Alloy 347 Stainless Steel Supplier Sheets Plates Pipes Bars

Key Features and Benefits of Alloy 347

At vastmaterial, we specialize in supplying Alloy 347 (UNS S34700), a columbium (niobium) stabilized austenitic stainless steel designed to overcome the limitations of standard 18-8 grades like 304. The addition of columbium is the critical factor here; it stabilizes the carbon, preventing chromium carbide precipitation during welding or exposure to elevated temperatures. This makes 347 stainless steel the premier choice for applications where irregular heating or heavy welding is required without subsequent annealing.

High-Temperature Stability and Corrosion Resistance

The primary advantage of Alloy 347 is its exceptional resistance to intergranular corrosion, particularly in the critical temperature range of 800°F to 1500°F (427°C to 816°C). While standard grades may fail due to sensitization, our stabilized 347 material maintains structural integrity in strong oxidizing environments.

• Superior Creep Strength: Rispetto a 304/304L, Alloy 347 offers significantly higher creep and stress rupture strength, making it ideal for continuous high-heat service.
• Oxidation Resistance: It performs reliably in oxidizing atmospheres, resisting scaling and corrosion even under thermal cycling.
• As-Welded Performance: Because it resists carbide precipitation, heavy sections can be used in the as-welded condition, eliminating the need for costly post-weld heat treatments.

Standard 347 vs. 347H High-Carbon Variants

We offer both standard and high-carbon versions to match specific engineering requirements. While the standard grade is excellent for general corrosion resistance, 347H stainless steel is engineered for extreme temperature environments.

Chemical Composition of Alloy 347

At Haoyu Material, we strictly control the chemistry of our Alloy 347 to ensure it meets the rigorous demands of high-heat environments. The defining feature of this grade is the addition of Columbium (Niobium) and Tantalum. This addition creates a stabilized stainless steel that eliminates carbide precipitation, which is critical for preventing intergranular corrosion during welding or exposure to temperatures between 800°F and 1500°F.

Our material complies with major international standards, including cURL Too many subrequests., ASTM A312, e ASTM A213. As a dedicated provider of leghe per alte temperature solutions, we ensure every batch undergoes strict spectral analysis to verify these elemental ranges.

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Proprietà Meccaniche

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While both grades offer similar performance at room temperature, the distinction becomes vital in high-heat applications.

• Standard Alloy 347: Optimized for intergranular corrosion resistance and general stability. It is the go-to choice for welded structures operating up to 800°F (427°C) where ductility is a priority.
• 347H Stainless Steel: This high-carbon variant (0.04%–0.10% Carbon) is engineered specifically for elevated temperatures. The higher carbon content significantly boosts creep strength and stress-rupture properties at temperatures above 1000°F (537°C). If your application involves continuous high-stress loads in superheaters or refinery piping, 347H provides the necessary structural durability that standard low-carbon grades cannot match.

Physical Properties

Understanding the physical constants of Alloy 347 is critical for engineering components that must withstand extreme thermal cycling. As a stabilized austenitic stainless steel, it offers specific physical characteristics that dictate how it behaves during welding, machining, and high-temperature service.

The material maintains a density of 7.96 g/cm³, which is standard for the austenitic class but essential for calculating component weight in large-scale piping or structural applications. Its melting range sits between 1398°C and 1446°C, allowing it to maintain integrity in environments where other metals might soften or fail.

Key Physical Data Points

• Densità: 7.96 g/cm³
• Melting Range: 1398–1446°C
• Magnetic Permeability: Non-magnetic in the annealed condition (may become slightly magnetic after cold working).

Thermal Expansion and Conductivity

Like many cURL Too many subrequests., Alloy 347 has a higher coefficient of thermal expansion compared to ferritic or martensitic steels. This expansion rate must be carefully calculated when designing expansion joints or welding dissimilar metals to prevent warping.

Conducibilità termica in Alloy 347 is relatively low compared to carbon steel, which helps retain heat in specific processing fluids but requires adjusted parameters during welding to manage heat input. The modulus of elasticity (Young’s Modulus) creates a rigid framework that resists deformation under load, while the electrical resistivity aligns with standard austenitic values, ensuring predictable performance in electrical resistance applications.

Corrosion Resistance Capabilities of Alloy 347

Progettiamo i nostri Alloy 347 to handle aggressive environments where standard stainless steels often fail. The defining characteristic of this grade is its stabilization with Columbium (Niobium), which directly addresses the issue of carbide precipitation. This modification provides superior resistance to intergranular corrosion, even after the material has been exposed to temperatures in the critical sensitization range of 800°F to 1500°F (427°C to 816°C).

For industrial applications requiring long-term reliability, Alloy 347 offers distinct advantages:

• Intergranular Attack: The Columbium addition prevents chromium carbide formation at grain boundaries, maintaining corrosion resistance in as-welded conditions without the need for post-weld annealing.
• Stress Corrosion Cracking: It demonstrates excellent resistance to polythionic acid stress corrosion cracking, a critical factor for equipment used in petroleum refineries and downstream processing.
• Oxidizing Environments: This grade performs exceptionally well in strong oxidizing agents. It maintains stability in nitric acid solutions and dilute phosphoric acid, outperforming standard 304 grades in these specific chemical exposures.

Available Product Forms at vastmaterial

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• cURL Too many subrequests. SUS 347 / SUS 347H.

ASTM and ASME Specifications

Our product forms are manufactured and tested according to the following primary standards:

• ASTM A240 / ASME SA240: Heat-Resisting Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip.
• ASTM A312 / ASME SA312: Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes.
• ASTM A213 / ASME SA213: Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes.
• ASTM A479 / ASME SA479: Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels.

Aerospace Specifications (AMS)

For high-performance aerospace applications requiring superior stability, we also reference:

• AMS 5512: Steel, Corrosion and Heat-Resistant, Sheet, Strip, and Plate.
• AMS 5646: Steel, Corrosion and Heat-Resistant, Bars, Wire, Forgings, Tubing, and Rings.

Industrial Applications for Alloy 347

Alloy 347 is engineered for environments where standard stainless steels fail due to intergranular corrosion or high-temperature creep. Its niobium stabilization makes it the preferred choice for industries requiring long-term stability in the 800°F to 1500°F range.

We supply this grade for critical components across several heavy industries:

• Petroleum Refining: This alloy is standard for fluid catalytic cracking units (FCCU), radiant tubes, and superheaters. It is specifically selected to resist polythionic acid stress corrosion cracking, a common issue during refinery downtime.
• cURL Too many subrequests. The material’s resistance to oxidizing agents makes it ideal for high-pressure settore della produzione di attrezzature, including heat exchangers, reactor vessels, and piping systems handling organic chemicals.
• Produzione di Energia: High-pressure steam piping and boiler tubes utilize Alloy 347 because it offers higher creep and stress rupture strength than 304/304L, ensuring safety in superheated steam environments.
• Aerospace Components: Due to its ability to withstand severe thermal cycling, this grade is widely used for aircraft exhaust manifolds, collector rings, and thrust reversers.
• High-Temperature Furnaces: We provide material for expansion joints and furnace parts that must maintain structural integrity and resist oxidation under continuous high-heat exposure.

Alloy 347 vs. Similar Stainless Grades

Selecting the right stainless steel for your project often comes down to understanding how specific grades handle heat and corrosive environments. At Haoyu Material, we help customers navigate the differences between Alloy 347 and other common austenitic grades like 304, 321, and 316. While they share a similar base chemistry, the addition of stabilizing elements changes their performance limits drastically.

Comparison: 347 vs 304, 321, and 316

The primary distinction of Alloy 347 (UNS S34700) is the addition of Columbium (Niobium). This element stabilizes the steel against carbide precipitation, a common issue in standard grades when exposed to temperatures between 800°F and 1500°F (427°C – 816°C).

• 347 vs. 304: Standard 304 is prone to intergranular corrosion after welding or heat exposure because chromium carbides form at the grain boundaries. Alloy 347 eliminates this risk, making it the superior choice for welded equipment operating in high heat.
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• Method: It can be welded using common fusion and resistance methods. Oxyacetylene welding is generally not recommended due to the risk of carbon pickup.
• Filler Metal: We recommend using AWS E347 or ER347 filler metals. These match the base metal’s chemistry and ensure the weld zone remains stabilized against corrosion.
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Heat Treatment Procedures

While Alloy 347 does not require post-weld annealing for corrosion resistance, heat treatment is often necessary to relieve stresses formed during severe forming or to restore maximum ductility.

• Annealing: Heat to a range of 1800°F – 2000°F (980°C – 1095°C) and follow with a water quench or rapid air cool. This ensures the carbides remain in solution.
• Stabilizing Anneal: For maximum creep strength in high-temperature service, a stabilizing heat treatment at roughly 1550°F – 1650°F may be applied.

At Haoyu Material, we can provide material that has already undergone specific heat treatments or surface finishing (like 2B or BA) to reduce your downstream processing time.

Why Choose vastmaterial for Alloy 347

At vastmaterial, we go beyond simple distribution; we act as a strategic partner for your high-temperature material needs. Sourcing Alloy 347 from us means accessing a supply chain built on reliability, speed, and strict quality adherence. We understand that projects involving 347 stainless steel often face tight deadlines and rigorous specification requirements, which is why we maintain a ready-to-ship inventory of pipes, bars, and sheets.

Our Core Service Capabilities:

• Large Inventory & Fast Delivery: We stock standard sizes of cURL Too many subrequests. to reduce lead times, ensuring your project stays on schedule.
• cURL Too many subrequests. Our facility is equipped for precise cutting, polishing, bending, and surface finishing (2B, BA, No.1) to meet specific fabrication needs.
• Quality Assurance: All materials come with Mill Test Certificates (MTC) per EN 10204 3.1. We also support third-party inspections (TPI) from agencies like SGS or BV.
• cURL Too many subrequests. We offer competitive pricing and handle all export logistics, ensuring secure delivery to your location.

La nostra solida alloy cast steel factory capabilities and quality control systems ensure that every product leaving our warehouse meets international standards (ASTM, ASME, DIN). Whether you require a single prototype piece or a full container load, our technical team provides the support necessary to navigate complex material specifications.

Domande frequenti (FAQ)

What are the differences between 347 and 347H?

The main difference lies in the carbon content. Alloy 347 is the standard stabilized grade, while 347H stainless steel is the high-carbon version (containing 0.04–0.10% carbon). This higher carbon content gives 347H superior creep strength and stress-rupture properties at temperatures above 1000°F (537°C). If your application involves extreme heat over long periods, 347H is often the preferred choice for structural stability.

Is Alloy 347 suitable for welded applications?

Yes, it is excellent for welding. Because Alloy 347 is stabilized with Columbium (Niobium), it resists carbide precipitation that typically occurs during welding in other austenitic grades. This means you can use it in the as-welded condition without needing post-weld annealing. It maintains strong intergranular corrosion resistance even after exposure to welding heat, making it ideal for heavy industrial equipment.

What product forms are available in stock?

At Haoyu Material, we supply a comprehensive range of forms to meet diverse industrial needs. Our inventory includes seamless pipes, welded tubes, round bars, sheets, and plates. We also provide specialized forgings and pipe fittings such as flanges, elbows, and tees. You can explore our full range of prodotti in acciaio inossidabile to find the exact dimensions and finishes required for your project.

What are the standard lead times?

Lead times vary based on the order volume, specific dimensions, and any custom processing requirements like cutting or surface finishing. As a global supplier, we prioritize efficient logistics to ensure fast delivery to international clients. For the most accurate timeline, please send us an inquiry with your specifications, and our team will provide a detailed schedule.