GB/T 5310 Seamless Steel Tubes for High-Pressure Boilers

 1. Scope  

GB/T 5310 specifies the technical requirements, test methods, inspection rules, and marking for seamless steel tubes used in high-pressure boilers (e.g., superheaters, heat exchangers, pipelines). It applies to tubes for environments with high-temperature and high-pressure conditions.

 2. 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.  

 3. 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.  

 4. 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.  

 5. 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).  

 6. 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).  

 7. Marking and Packaging  

- Marking: Includes standard number, steel grade, dimensions, manufacturer’s name, and heat number.  

- Packaging: Protected against corrosion (e.g., oiling, capping ends).  

 8. 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.  

9. 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.  

 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).  

10. 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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