GB/T 5310 "Seamless Steel Tubes for High-Pressure Boilers"
1. What is the scope of application of the GB/T 5310 standard?
A: This standard applies to seamless steel tubes for boilers with high pressure and above (such as power plant boilers and industrial boilers), covering key pressure-bearing components such as superheaters, reheaters, and headers.
Typical materials: 20G, 15CrMoG, 12Cr1MoVG, etc.
Parameter range: Working pressure ≥ 9.8 MPa, temperature ≤ 620°C (depending on the material).
Additional information: It is not applicable to low-temperature or non-pressure pipelines (such as GB/T 8163 general fluid transport pipes).
2. What are the chemical composition and mechanical property requirements of the steel tubes?
A: Core indicators fall into two categories:
Chemical composition:
Carbon (C), silicon (Si), and manganese (Mn) contents are strictly controlled (e.g., 20G steel requires C ≤ 0.24%);
Alloy steels must indicate the content of elements such as chromium (Cr), molybdenum (Mo), and vanadium (V) (e.g., 12Cr1MoVG requires Cr: 1.00-1.50%).
Mechanical properties:
Tensile strength (e.g., 20G ≥ 410 MPa), yield strength (≥ 245 MPa);
Elongation (≥ 24%), and impact energy (≥ 40 J, low-temperature impact at -20°C).
Note: Different grades have significant performance differences, so material selection must be based on the design temperature.
3. What are the manufacturing processes and testing requirements for steel pipes? A: The standard stipulates:
Manufacturing process: Hot-rolled or cold-drawn seamless steel must be used; welding is prohibited;
Heat treatment: Normalizing and tempering (alloy steel) or full annealing (carbon steel);
Inspection items:
100% ultrasonic testing (UT) or eddy current testing (ET);
Hydraulic pressure test (test pressure = 2 times the design pressure);
Sampling metallographic examination (grain size ≥ Grade 5).
Exception: Steel pipes with an outer diameter of ≤25.4mm are exempt from the hydrostatic test and eddy current testing is used instead.
4. What are the differences between GB/T 5310 and international standards such as ASME SA-106/SA-213? A: The main differences include:
Material Comparison: For example, 20G ≈ SA-106B, but the Cr-Mo steel composition requirements are more stringent;
Test Methods: ASME requirements focus more on high-temperature endurance strength testing, while GB/T 5310 emphasizes room-temperature mechanical properties;
Acceptance Rules: ASME allows for negotiation and relaxation of some defects, while GB/T 5310 is generally more rigid.
Recommendation: For export projects, the dominant standard should be selected based on the contractual agreement.
5. How is steel pipe acceptance and storage conducted according to this standard?
A: Key Steps:
Acceptance Documents: Check the quality certificate (must include the furnace number, heat treatment batch, and test report);
Appearance Inspection: No defects such as cracks, folds, or scars, and wall thickness deviation ≤±10%;
Storage Requirements: Moisture-proof and rust-proof (apply with anti-rust oil). Alloy steel pipes should be stored separately to avoid mixing.
