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.

• 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: 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.

• 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).

• Ultrasonic testing (UT) or eddy current testing (ET): Full-length inspection for defects.

• Grain size analysis (for some grades).
• High-temperature properties (if specified).

• 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: Includes standard number, steel grade, dimensions, and heat number.
• Packaging: Protected against corrosion (e.g., oiling, capping ends).

• 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.

20G Most common, for temperatures ≤ 450°C.
20MnG, 25MnG Enhanced strength.

Mo-Based: 15MoG, 20MoG

Cr-Mo Alloy: 12CrMoG, 15CrMoG, 12Cr2MoG, 12Cr1MoVG

High-Cr Heat-Resistant: 12Cr2MoWVTiB (G102), 10Cr9Mo1VNb (G91), 10Cr9MoW2VNbBN (G92), 07Cr2MoW2VNbB (G122)

Stainless Steel: 07Cr19Ni10 (TP304H), 07Cr25Ni21NbN (TP310HNbN)

• Suffix "G" denotes boiler tube grades.
• Higher Cr/Mo improves oxidation and creep resistance.

• 15CrMoG ≈ ASTM A335 P12 / EN 13CrMo4-5
• 12Cr1MoVG ≈ ASTM A335 P11
• 10Cr9Mo1VNb (G91) ≈ ASTM A335 P91