AISI 347H Stainless Steel: Sifat, Fabrikasi & Panduan Aplikasi Perindustrian

AISI 347H stainless steel is a high-carbon, niobium-stabilized austenitic alloy designed for extreme high-temperature and corrosive environments. Its higher carbon content (vs. standard 347) boosts creep resistance, making it a top choice for power plants, penapisan, and chemical facilities. This guide covers everything from its core specs to real-world uses, helping you make informed decisions for high-heat projects.

1. Gambaran Keseluruhan Bahan & Spesifikasi utama

Understanding AISI 347H’s composition and standards is essential to leveraging its full potential. Di bawah adalah pecahan jelas sifat pentingnya.

Komposisi kimia & Piawaian

TheAISI 347H composition termasuk kromium 17-19%, 9-13% nikel, 0.80–1.50% niobium (ditambah tantalum), and a critical347H carbon 0.04–0.10 % —this higher carbon content enhances high-temperature strength. Tidak ada single347H Formula Kimia; sebaliknya, ia mematuhi piawaian global untuk konsistensi:

• 347H UNS S34709 (Sistem penomboran bersatu)
• 347H ASTM A240 / 347H ASME SA-240 (untuk plat, helaian, dan jalur)
• 347H satu 1.4912 setara (Standard Eropah untuk prestasi yang sepadan)

Fizikal & Sifat mekanikal

AISI 347H delivers reliable strength and stability across demanding applications. Metrik utama dianjurkan dalam jadual di bawah:

A Japanese power plant uses347H ASTM A240 plat untuk pengepala dandang -mereka bergantung pada 515 MPa tensile strength to handle 700 °C temperatures and high pressure.

2. Sifat suhu tinggi & Rintangan Creep

AISI 347H’s greatest strength is its performance under sustained high heat. Its higher carbon content and niobium stabilization make it far more creep-resistant than standard 347.

Ciri-ciri suhu tinggi kritikal

• Kekuatan Creep: The 347H 100,000 Jam Kekuatan Creep (penanda aras industri utama) is ~115 MPa at 650 °C—meaning it can operate for decades without deforming. Untuk tugas yang lebih pendek, 347H tegangan masa pendek di 700 ° C. is ~300 MPa.
• Rintangan pengoksidaan: It resists rust and scaling up to 1050 ° C.-347H rintangan pengoksidaan sehingga 1050 ° C. makes it ideal for furnace radiant tubes and flare stacks. The 347H kadar pengoksidaan stim is also low (≤0.15 mm/tahun pada 800 ° C dalam stim tulen).
• Tekanan yang dibenarkan: Per 347H ASME Section II allowable stresses, Ia diluluskan untuk kapal tekanan pada suhu sehingga 870 ° C..
• Service Limit: The 347H had suhu perkhidmatan adalah 870 °C for continuous use and 980 °C for intermittent exposure.

Kajian kes: Penapisan Eropah dipasang347H refinery hydrocracker tubes (beroperasi di 850 ° C.). Selepas 12 tahun, tiub tidak menunjukkan rayapan atau pengoksidaan, Menyelamatkan penapisan $200,000 dalam kos penggantian.

3. Rintangan kakisan & Faedah penstabilan

While AISI 347H is known for high heat resistance, its niobium stabilization also delivers exceptional corrosion protection—even in harsh chemicals.

Ciri-ciri tahan karat utama

• Imuniti kakisan antara: Niobium mengikat dengan karbon untuk membentuk NBC (Niobium Carbide), mencegah pengurangan kromium di sempadan bijian. This gives 347H imuniti kakisan intergranular dan 347H weld decay resistance- Peningkatan utama atas aloi yang tidak stabil seperti 304.
• Pitting & Kakisan tekanan: 347H pitting corrosion vs 316H is competitive—347H resists small holes (pitting) in acidic environments, while 316H excels in chlorides. It also has strong 347H Kakak tekanan klorida retak resistance for marine or chemical applications.
• Prestasi kimia: It handles 347H nitric acid service (menahan asid nitrik cair sehingga 60 ° C.) and has a low 347H caustic corrosion rate (≤0.02 mm/tahun dalam 10% Natrium hidroksida). It also resists 347H polythionic acid cracking (a risk in refineries after shutdowns).

A U.S.. chemical plant switched from 316H to 347H for acid reactor vessels—347H imuniti kakisan intergranular kebocoran dihapuskan, and the higher carbon handled 750 °C operating temperatures.

4. Rawatan haba & Kawalan Mikrostruktur

Proper heat treatment is critical to unlocking AISI 347H’s full potential. Ia memastikan aloi mengekalkan kekuatan, menentang kakisan, and avoids harmful phases like sigma.

Proses rawatan haba utama

• Penyelesaian Penyepuh: Heat to 1050-1100 ° C., Tahan selama 30-60 minit, Kemudian air-quench. This dissolves unwanted carbides and restores a uniform austenitic structure—critical for 347H Rawatan Penyelesaian Karbida.
• Menstabilkan anneal: Heat to 870-900 ° C. to ensure niobium fully reacts with carbon. Langkah ini meningkatkan rintangan kakisan dan menghalang pemekaan.
• Kawalan saiz bijian: The 347H Kawalan Saiz Biji ASTM 7 min (bijirin kasar) diperlukan oleh biji -bijian standard ASME yang meningkatkan rintangan merayap pada suhu tinggi.
• Kerja panas: Gunakan 1150-900 ° C. as the 347H hot working range for forging or rolling. Ini menjadikan mulur material dan mengelakkan retak.

Pertimbangan lain

• Penghindaran pemekaan: Avoid heating to 347H sensitization temperature 425–815 °C for long periods—this prevents chromium depletion.
• Pelepasan tekanan sisa: Panaskan hingga 450-600 ° C untuk mengurangkan tekanan dari kimpalan atau pembentukan. Even after this, 347H intergranular corrosion after PWHT remains minimal.

5. Kimpalan, Fabrikasi & Garis Panduan Pemesinan

Welding and machining AISI 347H require simple adjustments to preserve its high-temperature and corrosion properties.

Petua kimpalan

• Logam pengisi: Gunakan 347H filler metal ER347H (untuk kimpalan TIG/saya) to match the base metal’s carbon and niobium content. 347H carbon matching filler is critical—using standard 347 filler reduces creep resistance.
• Panaskan & Pwht: 347H Panaskan suhu is typically not required for thicknesses up to 25 mm. Untuk bahagian yang lebih tebal, 347H rawatan haba pasca kimpalan (Pwht) (600-650 ° C.) helps restore 347Kekuatan Haz Haz (zon yang terjejas haba) dan melegakan tekanan.
• Kebolehkalasan: 347H weldability rating is “excellent”—it has low 347H hot cracking susceptibility when using proper parameters.

Pemesinan & Membentuk

• Kelajuan & Suapan: 347H kelajuan dan makanan pemesinan should be 10–15% lower than carbon steel. Contohnya, use 80–100 m/min speed with 347H coated carbide tool life (TiAlN coatings last 2x longer than uncoated tools).
• Kebolehbaburan & Penyimpangan: 347H cold working limits allow moderate bending and forming. Untuk 347H distortion control techniques, Gunakan pengapit semasa kimpalan dan penyejukan perlahan. Untuk kapal tekanan, follow 347H joint design for pressure vessels (kimpalan tebal untuk kekuatan).

6. Borang produk, Saiz & Rantaian bekalan

AISI 347H is available in a wide range of forms to fit nearly any high-temperature project.

Borang produk biasa

• Plat: 347H stainless steel plate thickness chart ranges from 3 mm ke 200 mm, termasuk 347H Plat Kapal Tekanan (certified to ASME SA-240).
• Paip & Tiub: 347H pipe schedule dimensions include Schedule 40 untuk jadual 160; 347H seamless tube ASTM A312 is used for boiler and superheater tubes.
• Bar & Kelengkapan: 347H round bar stockists offer 10–300 mm diameter bars; 347H FITTINGS FORGED (siku, Tees) suit high-pressure piping.
• Borang khusus: 347H coil slit widths (10–1250 mm), 347H flat bar tolerances (± 0.1 mm), dan 347H hollow bar suppliers (Untuk bahagian ringan).

Petua Rantaian Bekalan

Bekerja dengan347H round bar stockists and global distributors for quick access to common sizes. For unique parts, choose suppliers offering347H custom forgings (Mis., furnace components).

7. Aplikasi industri & Gunakan kes

AISI 347H’s versatility makes it a top choice for high-heat, high-corrosion industries. Here are key applications:

• Penjanaan kuasa: 347H Boiler Tubes, 347H Superheater Headers, dan 347Header loji kuasa h handle 700–850 °C steam and pressure.
• Penapisan: 347H refinery hydrocracker tubes dan 347Petua Stack H Flare resist high heat and chemical exposure.
• Pemprosesan kimia: 347H Kerangka penukar haba dan 347H gegelung retak etilena operate reliably in acidic, high-temperature environments.
• Kegunaan lain: 347H furnace radiant tubes (1000 ° C Haba sekejap) dan 347H manifold pengedaran wap (corrosion-resistant steam flow).

Contoh sebenar: A U.S.. power plant replaced 321H boiler tubes with347H Boiler Tubes—the 347H tubes showed 50% less creep after 8 tahun, extending maintenance intervals.

Perspektif Teknologi Yigu

Di Yigu Technology, we recommend AISI 347H for clients needing high-temperature creep resistance and corrosion protection. Kami sumber347H ASTM A240 plat dan347H seamless tube ASTM A312 dari kilang yang disahkan, ensuring compliance with ASME standards. For power and refinery clients, Kami mengutamakan347H 100,000 Jam Kekuatan Creep verification. Our team advises on welding (menggunakan347H filler metal ER347H) and heat treatment to maximize performance. For long-term high-heat projects, AISI 347H is a cost-effective, reliable choice.

Soalan Lazim

1. Apa perbezaan antara Aisi 347 and 347H?
   347H has a higher carbon content (0.04–0.10% vs. 347’s ≤0.08%), boosting 347H Kekuatan suhu tinggi and creep resistance. Both use niobium for corrosion protection, but 347H is better for long-term high-heat service (Mis., boiler tubes), manakala 347 suits lower-heat applications.
2. Do I need preheat for welding AISI 347H?
   Tidak-347H Panaskan suhu is not required for thicknesses up to 25 mm. Untuk bahagian yang lebih tebal (>25 mm), a 100–150 °C preheat reduces cracking risk. Always use 347H filler metal ER347H and optional PWHT to restore HAZ strength.
3. Can AISI 347H resist sulfuric acid?
   Ya--347H sulfuric acid performance is strong in dilute solutions (≤20% concentration, ≤60 °C). It resists pitting and intergranular corrosion, making it suitable for chemical tanks and piping handling mild sulfuric acid. For concentrated acid, consider 317L.