Steel Pipe & Tube & High Pressure Boiler Tube,20G、15CrMoG、12Cr1MoVG、P91
Detailed Description of High Pressure Boiler Tubes
High pressure boiler tubes are seamless steel pipes specially used for high-pressure and ultra-high-pressure boilers and high-temperature & high-pressure working conditions. They are mainly applied to manufacture superheaters, reheaters, main steam pipes, economizers and other components. Operating long-term under high temperature of 450℃–650℃ and high pressure above 9.8MPa, the products feature excellent high-temperature strength, oxidation resistance, structural stability and creep resistance.
1. Applicable Standards
Domestic Standard: GB/T 5310-2023 (Implemented on April 1, 2024, replacing GB/T 5310-2017)
International Common Standards: ASTM A335 (P11/P12/P22/P91/P92), DIN 17175, EN 10216-2
2. Materials & Chemical Compositions (Main Grades)
2.1 Carbon Steel
20G: C 0.17–0.24, Mn 0.35–0.65. Applicable for working temperature ≤500℃ and pressure ≤10MPa, widely used for low-pressure headers and main steam pipes.
2.2 Chromium-Molybdenum Steel (Medium & High Temperature Service)
15CrMoG: C 0.12–0.18, Cr 0.80–1.10, Mo 0.45–0.60. Suitable for temperature ≤550℃ and pressure 16–25MPa, applied to superheaters and reheaters.
12Cr1MoVG: C 0.08–0.15, Cr 0.90–1.20, Mo 0.25–0.35, V 0.15–0.30. Designed for temperature ≤580℃ and pressure 25–31.5MPa, ideal for main steam pipes of supercritical units.
2.3 High-Alloy Heat Resistant Steel (Ultra-Supercritical Service)
P91 (10Cr9Mo1VNb): Cr 8.0–9.5, Mo 0.85–1.05, V 0.18–0.25. Applicable for working temperature ≤620℃, used for ultra-supercritical power generation units.
P92: Cr 8.5–9.5, W 1.5–2.0, V 0.18–0.25. It possesses superior stress rupture strength at 650℃, adopted for main steam pipes and reheat pipelines.
3. Dimensions & Dimensional Tolerance
3.1 Size Range (In accordance with GB/T 5310)
Hot Rolled Tubes: Outer diameter 22–530mm, Wall thickness 20–70mm
Cold Drawn / Cold Rolled Tubes: Outer diameter 10–108mm, Wall thickness 2.0–13.0mm
3.2 Dimensional Deviation (High Precision)
Outer diameter: ±1.0% (hot rolled), ±0.5% (cold drawn)
Wall thickness: ±12.5% (hot rolled), ±10% (cold drawn)
Standard length: 6–12m; Custom fixed length available with tolerance ±5mm
4. Production Process
Smelting: Electric furnace smelting plus LF/VD refining. Strict control: S ≤0.015%, P ≤0.025%.
Pipe Forming: Continuous casting round billet → Heating → Hot rolling piercing → Shell tube → Cold rolling / Cold drawing → Finishing.
Heat Treatment (Core Process)
20G: Normalizing at 900–930℃
15CrMoG: Normalizing + Tempering at 680–720℃
12Cr1MoVG: Normalizing + Tempering at 720–760℃ to realize grain refinement and stable structure.
Finishing: Straightening, cropping, non-destructive testing, hydrostatic test, anti-corrosion treatment and packaging.
5. Main Mechanical Properties (Ambient Temperature, GB/T 5310)
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 20G | 410–550 | ≥245 | ≥24 |
| 15CrMoG | 440–640 | ≥235 | ≥21 |
| 12Cr1MoVG | 470–640 | ≥255 | ≥21 |
| P91 | ≥585 | ≥415 | ≥20 |
High Temperature Performance: The stress rupture strength of 12Cr1MoVG is no less than 120MPa at 580℃. P91 and P92 maintain excellent creep strength at 600–650℃.
6. Technological Properties & Inspection
Hydrostatic Test: Each pipe is tested individually. Test pressure is calculated by formula P=2SR/D. Hold pressure for no less than 5 seconds without leakage.
Non-Destructive Testing: 100% Ultrasonic Testing (UT) and Eddy Current Testing (ET) to eliminate cracks, inclusions and laminations.
Flattening & Flaring Test: No cracks when flattened to 2/3 of the original outer diameter; Flaring rate ≥15% (30° cone mandrel).
Metallographic Examination: Grain size grade ≥8; Maximum decarburized layer ≤0.5mm.
7. Main Applications
Power Station Boilers: Superheaters, reheaters, main steam pipes, headers and economizers for 300MW–1000MW supercritical and ultra-supercritical units.
Industrial Boilers: Heating surfaces and steam pipelines of high-pressure steam boilers, waste heat boilers and waste incineration boilers.
Petrochemical Industry: High-temperature & high-pressure reactors, heat exchangers, cracking furnace tubes and pipelines for hydrogenation units.
Other Fields: Conventional island of nuclear power plants, waste heat boilers for gas turbines and high-temperature & high-pressure transmission pipelines.
8. Quality & Packaging
Surface Quality: No cracks, folds, scabs or heavy oxide scales on inner and outer surfaces. Minor grinding is permitted on the premise that the remaining wall thickness is not less than 90% of the nominal value.
Packaging: Both ends equipped with plastic pipe caps. Bundled (each bundle ≤5 tons) and wrapped with moisture-proof woven bags. Complete quality documents including heat number, batch number, chemical composition, mechanical properties and NDT reports are attached.
Marking: Each pipe is marked with standard number, material grade, dimension, heat number, batch number, manufacturer and production date.
9. Selection Guidelines
Temperature Matching: Select 20G for temperature ≤500℃; 15CrMoG for 500–550℃; 12Cr1MoVG for 550–580℃; P91/P92 for temperature above 600℃.
Pressure Matching: Select 20G for pressure ≤10MPa; 15CrMoG for 10–25MPa; 12Cr1MoVG for 25–32MPa; P91/P92 for pressure above 32MPa.
Working Condition Adaptation: High-chromium alloys such as P92 are recommended for environments with sulfur or chlorine corrosion. Materials with good fatigue resistance are preferred for units with frequent start-stop operation.
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