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GB/T 5310 Seamless Steel Tubes for High-Pressure Boilers
Ordering Information
Buyers must specify the following in orders:
- Standard number (GB/T 5310) and version/year.
- Steel grade (e.g., 20G, 15CrMoG, 12Cr1MoVG).
- Dimensions (outer diameter, wall thickness, length).
- Delivery condition (hot-rolled, cold-drawn, heat treatment status).
- Special requirements (e.g., non-destructive testing, hydrostatic pressure).
- Quantity.
Material and Manufacturing Requirements
- Steel grades: Covers carbon, alloy, and stainless steels (e.g., 20G, 12Cr2MoWVTiB).
- Manufacturing process: Tubes are produced by hot-rolling or cold-drawing, followed by heat treatment (annealing, normalizing, or tempering).
- Surface quality: Free from cracks, folds, and other defects.
Chemical Composition and Mechanical Properties
- Chemical composition: Limits for C, Si, Mn, P, S, Cr, Mo, etc., vary by steel grade.
- Mechanical properties: Tensile strength, yield strength, elongation, and hardness requirements specified for each grade.
Test Requirements
5.1 Mandatory Tests
- Hydrostatic test: Every tube must withstand specified pressure without leakage.
- Tensile test: To verify mechanical properties.
- Flattening test or bend test: For ductility evaluation (depending on tube dimensions).
- Impact test: Required for alloy steel grades (e.g., at -20°C).
5.2 Non-Destructive Testing (NDT)
- Ultrasonic testing (UT) or eddy current testing (ET): Full-length inspection for defects.
5.3 Additional Tests
- Grain size analysis (for some grades).
- High-temperature properties (if specified).
Inspection and Certification
- Batch rules: Tubes are inspected in batches (same heat number, dimensions, and heat treatment).
- Certification: Manufacturer provides a compliance certificate with test results (chemical, mechanical, NDT).
Marking & Packaging
- Marking: Includes standard number, steel grade, dimensions, manufacturer’s name, and heat number.
- Packaging: Protected against corrosion (e.g., oiling, capping ends).
Key Updates in Latest Version
- Revised chemical composition limits for improved high-temperature performance.
- Enhanced NDT requirements (e.g., stricter UT criteria).
- Added new steel grades for advanced boiler applications.
Major Steel Grades & Category
9.1 Carbon Steel Grades
- 20G: The most common carbon steel grade for boiler tubes, suitable for temperatures ≤ 450°C.
- 20MnG: Higher manganese content for improved strength.
- 25MnG: Enhanced strength compared to 20MnG.
9.2 Alloy Steel Grades
9.2.1 Mo-Based Alloy Steels
- 15MoG (0.5% Mo)
- 20MoG (0.5% Mo)
9.2.2 Cr-Mo Alloy Steels (Heat-resistant for high-temperature service)
- 12CrMoG (0.5% Cr, 0.5% Mo)
- 15CrMoG (1.0% Cr, 0.5% Mo) – Widely used in power plants.
- 12Cr2MoG (2.25% Cr, 1.0% Mo, similar to ASTM A335 P22).
- 12Cr1MoVG (1.0% Cr, 0.5% Mo, V-added for creep resistance).
9.2.3 High-Cr Heat-Resistant Steels
- 12Cr2MoWVTiB (G102, T/P23): For ultra-high-temperature boilers (≤ 600°C).
- 10Cr9Mo1VNb (G91, T/P91): Advanced creep-resistant steel (≤ 650°C).
- 10Cr9MoW2VNbBN (G92, T/P92): Higher temperature resistance than G91.
- 07Cr2MoW2VNbB (G122): For supercritical boilers.
9.2.4 Stainless Steel Grades
- 07Cr19Ni10 (TP304H): Austenitic stainless steel for corrosion/heat resistance.
- 07Cr25Ni21NbN (TP310HNbN): High-temperature oxidation resistance.
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9.3 Special Notes
- Suffix "G" denotes boiler tube grades (e.g., 20G vs. general 20# steel).
- Higher Cr/Mo content improves oxidation and creep resistance at elevated temperatures.
- Grades like G102, G91, and G92 are critical for advanced power plants (supercritical/ultra-supercritical boilers).
Comparison with International Standards
Some GB/T 5310 grades align with ASTM/EN standards:
- 15CrMoG ≈ ASTM A335 P12 / EN 13CrMo4-5.
- 12Cr1MoVG ≈ ASTM A335 P11.
- 10Cr9Mo1VNb (G91) ≈ ASTM A335 P91.
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