P91 Heat Resistant Steel: Panduan untuk Hartanah, Penggunaan & Pembuatan

If you work in power generation, penapisan minyak, or aerospace—industries where extreme heat is a constant challenge—P91 heat resistant steel adalah bahan yang perlu anda ketahui. As a chromium-molybdenum-vanadium (Cr-Mo-V) aloi, it’s engineered to stay strong, resist creep, and withstand oxidation at temperatures up to 650°C. This guide will break down everything you need to choose, gunakan, and maximize P91 for your high-temperature projects.

1. Material Properties of P91 Heat Resistant Steel

P91’s performance stems from its precise composition and tailored properties, meeting standards like ASTM A335 (untuk paip lancar) and ASTM A182 (for forged components). Mari kita pecahkan mereka dengan jelas.

Komposisi kimia

TheKomposisi kimia of P91 is optimized for high-temperature resilience—with chromium, Molybdenum, and vanadium as key alloying elements. Di bawah adalah kerosakan biasa (Per Piawaian ASTM):

Sifat fizikal

These traits determine how P91 behaves in extreme heat and real-world conditions:

• Ketumpatan: 7.85 g/cm³ (Sama seperti keluli struktur yang paling banyak, simplifying weight calculations for large components)
• Titik lebur: ~1450–1490°C (stable at operating temps far below its melting point)
• Kekonduksian terma: 32 W/(m · k) (slower than carbon steel, which helps retain strength at high temps)
• Pekali pengembangan haba: 13.5 × 10⁻⁶/° C. (low enough to handle temperature swings in power plants)
• Resistiviti elektrik: 0.60 × 10⁻⁶ Ω · m (not used for electrical parts, but useful for safety planning)

Sifat mekanikal

P91’s mechanical strength is tailored for high-heat, high-pressure environments. Here are its key metrics (after quenching and tempering):

• Kekuatan tegangan: 690 MPa min (handles pulling forces even at 600°C)
• Kekuatan hasil: 415 MPa min (maintains shape under load—vital for boiler tubes)
• Kekerasan: 200-250 HB (resists wear without being too brittle for welding)
• Kesan ketangguhan: ≥ 40 J pada -20 ° C. (performs reliably in cold startup/shutdown cycles)
• Kemuluran: ≥ 20% pemanjangan (can bend or form without cracking, Walaupun selepas rawatan haba)
• Rintangan Keletihan: Excellent for cyclic stress (ideal for turbine components that heat/cool repeatedly)
• Kekuatan patah: Tinggi (prevents sudden failure in high-pressure, high-temp systems)

Sifat utama lain

• Excellent high-temperature strength: Mengekalkan 80% of its room-temperature strength at 600°C.
• Good creep resistance: Deforms less than 0.1% selepas 100,000 hours at 600°C (critical for long-lasting power plant parts).
• Rintangan pengoksidaan yang baik: Forms a protective chromium oxide layer that prevents rust at 650°C+.
• Kebolehkalasan yang baik: Works with standard methods (TIG, Saya) when preheated (200-300 ° C.) and post-weld heat-treated.
• Kebolehbaburan: Boleh digulung panas, dipalsukan, atau diekstrusi menjadi bentuk yang kompleks (Mis., bilah turbin, reactor tubes).

2. Applications of P91 Heat Resistant Steel

P91’s ability to withstand extreme heat makes it indispensable across industries that rely on high-temperature equipment. Begini cara menyelesaikan masalah dunia nyata:

Penjanaan kuasa

The top use for P91 ispenjanaan kuasa—where it’s trusted for components that face constant heat and pressure:

• Turbin stim: P91 is used for rotor shafts and casings (handles 565°C steam and 16 Tekanan MPA).
• Komponen Loji Kuasa: Tiub dandang, superheater tubes, and headers (resist creep and oxidation).
• Kajian kes: A coal-fired power plant in China replaced its carbon steel boiler tubes with P91. The P91 tubes lasted 15 tahun (vs. 5 years for carbon steel) dan mengurangkan kos penyelenggaraan oleh 60%. Even at 600°C, they showed no signs of creep or thinning.

Petroleum and Chemical Industry

P91 excels in harsh chemical and refining environments:

• Oil refining equipment: Hydrocracker reactors and heater tubes (resist sulfur corrosion and 600°C+ temps).
• Reaktor kimia: Handles acidic or high-pressure reactions (Mis., ethylene production).
• Penukar haba: Transfers heat without deforming (ideal for processing crude oil).
• Kajian kes: A refinery in Texas used P91 for its hydrocracker reactor tubes. The tubes operated at 580°C and 12 MPA untuk 12 years—no corrosion, no creep, and no need for replacement (unlike the previous stainless steel tubes, yang gagal selepas 7 tahun).

Aeroangkasa

Dalam aeroangkasa, P91 is used for components that face extreme heat during flight:

• Komponen enjin pesawat: Turbine disks and combustion chambers (handle 650°C exhaust gas).
• Bilah turbin gas: For industrial gas turbines (resist creep and oxidation at high speeds).

Automotif

For high-performance and heavy-duty vehicles:

• Sistem ekzos: P91 is used for exhaust manifolds in racing cars and trucks (resists 900°C exhaust heat).
• Komponen enjin: Turbocharger housings (handles 800°C+ temps without warping).

Marin

For offshore and shipboard equipment:

• Komponen kapal: Marine diesel engine parts (resist saltwater corrosion and engine heat).
• Offshore structures: Piping for offshore oil rigs (handles 550°C well fluids and salt spray).

3. Manufacturing Techniques for P91 Heat Resistant Steel

Producing P91 requires precision to unlock its high-temperature properties. Berikut adalah pecahan langkah demi langkah proses:

Proses pembuatan keluli

Two main methods are used to produce P91, depending on volume and component type:

1. Relau arka elektrik (EAF): The most common method for P91. Keluli sekerap cair, Kemudian elemen aloi (Cr, Mo, V) are added to hit precise composition targets. EAF offers tight control over chemistry—critical for P91’s creep resistance.
2. Relau oksigen asas (Bof): Used for large-volume production (Mis., seamless pipes). Molten iron is mixed with alloys, then oxygen is blown in to remove impurities. Faster than EAF but less flexible for small batches.

Rawatan haba

Heat treatment is non-negotiable for P91—it’s how the steel gains its high-temperature strength. Key processes:

• Menormalkan: Heats to 1040–1080°C, holds for 1–2 hours, then air-cools. Refines grain structure and prepares the steel for tempering.
• Pelindapkejutan dan pembajaan: After normalizing, the steel is quenched (water-cooled) to 200°C, then tempered at 730–780°C for 2–4 hours. This process forms a “tempered martensite” structure that boosts Rintangan Creep dan ketangguhan.
• Penyepuhlindapan: Memanaskan hingga 800-850 ° C., menyejukkan perlahan. Reduces stress after forming (used for precision parts like turbine blades).

Proses membentuk

P91 is shaped into final products using techniques that preserve its strength:

• Rolling panas: Heats to 1100–1200°C, rolls into pipes, plat, atau bar. The main method for boiler tubes and structural parts.
• Rolling sejuk: Used for thin-walled pipes or precision components (Mis., small heat exchanger tubes). Requires post-heat treatment to restore toughness.
• Menunaikan: Hammers or presses hot steel into complex shapes (Mis., turbine disks, reactor flanges). Improves grain alignment, enhancing creep resistance.
• Penyemperitan: Pushes heated steel through a die to make hollow parts (Mis., superheater tubes). Fast for custom shapes.
• Setem: Rarely used for P91—most high-temp components need thickness, which stamping can’t provide.

Rawatan permukaan

To boost durability in harsh environments:

• Galvanizing: Dips dalam zink cair. Ideal for above-ground parts (Mis., power plant structural supports) terdedah kepada hujan.
• Lukisan: Applies high-temp ceramic paint. Used for components like turbine casings to add extra oxidation resistance.
• Tembakan letupan: Blasts with metal balls to remove rust, skala, or dirt. Prepares surfaces for welding or coating.
• Salutan: Uses aluminide or chromide coatings for extreme temps (Mis., Bilah turbin aeroangkasa). These coatings extend oxidation resistance to 700°C+.

4. P91 Heat Resistant Steel vs. Bahan lain

How does P91 compare to other common heat-resistant materials? Mari kita pecahkan untuk membantu anda memilih:

P91 vs. Keluli karbon (Mis., A36)

P91 vs. Kekuatan tinggi rendah aloi (HSLA) Keluli (Mis., X80)

• Komposisi kimia: P91 has Cr, Mo, V (untuk rintangan haba); X80 has Mn, Dalam (for pressure resistance).
• Sifat: P91 excels at high temps (600° C+); X80 excels at room-temp pressure (14 MPA+) but weakens above 350°C.
• Aplikasi: P91 = power plants; X80 = oil/gas pipelines (temp bilik, tekanan tinggi).

P91 vs. Keluli tahan karat (Mis., 316)

P91 vs. Aloi aluminium (Mis., 6061)

• Berat: Aluminium adalah 1/3 lebih ringan, but P91 is 4x stronger at 500°C.
• Prestasi Temp Tinggi: Aluminum melts at 660°C and weakens above 150°C; P91 works at 650°C.
• Kos: P91 is cheaper for high-temp parts (aluminum alloys for heat resistance are expensive).
• Aplikasi: P91 = industrial heat systems; aluminum = lightweight, low-temp parts (Mis., bingkai pesawat).

5. Yigu Technology’s Perspective on P91 Heat Resistant Steel

Di Yigu Technology, we’ve supplied P91 heat resistant steel for power plants and refineries globally. We see P91 as a “long-term investment” material: while it costs more upfront than carbon steel, its 15–20 year lifespan (vs. 5 years for carbon steel) cuts total ownership costs by 50%. Untuk pelanggan, P91’s creep resistance and oxidation resistance eliminate unplanned downtime—critical for power plants that run 24/7. We optimize P91’s heat treatment (quenching/tempering) to match each project’s temp needs and provide welding guidelines to avoid issues. For high-temperature projects where reliability matters, P91 is our top recommendation.

FAQ About P91 Heat Resistant Steel

1. Can P91 be used for low-temperature applications?

While P91 works at low temps (it has good impact toughness at -20°C), it’s overkill. For low-temp projects (Mis., residential piping), mild carbon steel or stainless steel is cheaper and more workable. P91 should be reserved for high-temp (400° C+) use to justify its cost.

2. Is post-weld heat treatment (Pwht) required for P91?

Yes—PWHT is mandatory. P91’s high Cr-Mo content makes it prone to residual stress and cracking after welding. Pwht (heating to 730–780°C for 2–4 hours) relieves stress and restores creep resistance. Skipping PWHT will lead to premature failure.

3. How long does P91 last in power plant boiler tubes?

With proper maintenance (regular inspections, pembersihan), P91 boiler tubes last 15–20 years. This is 3x longer than carbon steel tubes (5 tahun) and 2x longer than stainless steel tubes (10 tahun). We recommend ultrasonic testing every 3 years to check for creep or thinning.