GB/T5310-2023 High-Pressure Boiler Seamless Steel Tubes in Technology, Application, and Quality Control Details

First, Background and Significance of the Standard's Evolution

The development of my country's high-pressure boiler seamless steel tube standards has evolved from imported and assimilated standards to independent innovation. The early GB5310 standard primarily referenced the Soviet GOCT standard system. With advancements in domestic metallurgical processes, the 2017 version has aligned with international standards such as ASTM A335 and EN 10216. The 2023 version further optimizes material purity and high-temperature performance. For example, the upper limit of phosphorus and sulfur content for 20G steel has been reduced from 0.030% to 0.025%, and creep strength specifications have been added for heat-resistant alloy steels such as 12Cr1MoVG. These improvements have increased the service life of domestically produced steel tubes in supercritical units above 600°C by approximately 15%, providing material support for efficient coal-fired power generation technology under the "dual carbon" goal.

Second, Analysis of Core Technical Requirements

1. Material Chemical Composition Control: The new standard implements more precise range control for essential elements such as C, Si, and Mn. For example, the chromium content of P91 steel has been adjusted to 8.0%-9.5% (previously 8.0%-10.0%). Particularly noteworthy are the addition of restrictions on residual elements such as As and Sn, requiring As ≤ 0.010% and Sn ≤ 0.015%, effectively suppressing embrittlement during long-term high-temperature operation.

2. Mechanical Performance Improvements: Compared to the 2017 version, the 2023 standard raises the lower limit of tensile strength for 20G steel pipe from 410 MPa to 430 MPa, and the yield strength from 245 MPa to 265 MPa. For bainitic heat-resistant steels such as 12Cr2MoWVTiB (Steel 102), a new technical requirement for 100,000-hour rupture strength at 650°C of ≥ 80 MPa has been added, bringing this performance level to the same level as Japan's STBA26. 3. Process Control Innovation: For the first time, the use of an external furnace refining (LF+VD) process is explicitly required to ensure that the gas content [H] ≤ 2 ppm and [O] ≤ 20 ppm. For steel pipes with a diameter ≥ 219 mm, electromagnetic ultrasonic automatic flaw detection is mandatory, increasing the defect detection sensitivity from 2 mm to 1.6 mm. These improvements ensure that the internal quality of the steel pipes reaches the level of nuclear power pipes.

Third, Typical Application Scenarios and Selection Recommendations

1. Subcritical Units (16-18 MPa/540°C): 15CrMoG steel pipe is recommended, with an allowable stress of 78 MPa at 580°C. A power plant has demonstrated that the life of economizer tubes using the new standard 15CrMoG has been extended from 80,000 hours to 100,000 hours.

2. Supercritical Units (25 MPa/600°C): 12Cr1MoVG or P22 materials are preferred. Notably, the new standard adjusts the allowable stress of 12Cr1MoVG at 600°C from 46MPa to 49MPa, reducing tube wall thickness by 7% under equivalent operating conditions.

3. Double-reheat ultra-supercritical units (32MPa/630°C): High-alloy materials such as P91/P92 must be used. The 2023 edition adds a mandatory requirement for P92 steel to maintain an endurance strength of ≥100MPa at 630°C and 100,000 hours, laying the material foundation for advanced 700°C ultra-supercritical technology.

Fourth, Key Points for Quality Acceptance

1. Dimensional Tolerance Control: The new standard tightens the wall thickness tolerance for hot-rolled tubes from ±12.5% to ±10%, and increases the ovality requirement for cold-drawn tubes from ≤1.5% to ≤1.2%. During acceptance, particular attention should be paid to the newly added "wall thickness measurement for each tube." 2. Heat Treatment System Verification: For martensitic steels such as P91, complete "normalizing + tempering" temperature-time curve records are required, and the post-tempering hardness must be controlled within the 180-250 HB range. Data from a testing agency indicates that approximately 8% of non-conforming products inspected in 2023 were due to deviations in the heat treatment process.

3. Application of New Inspection Technologies: The standard introduces TOFD (Time-of-Flight Diffraction) inspection requirements for the first time, requiring 100% longitudinal defect inspection for steel pipes used in main steam lines. Practice has shown that this method can detect cracks ≥0.5mm in depth, increasing sensitivity by 40% compared to traditional UT inspection.

Fifth, Market Impact and Industry Trends

According to statistics from the China Special Steel Association, the production of high-pressure boiler tubes reached 2.8 million tons in 2024, of which approximately 65% complied with the GB/T5310-2023 standard. Major manufacturers have completed production line upgrades, increasing the yield rate of their P91 steel tubes from 85% to 92%. However, it's worth noting that in specialty materials like 12Cr2MoWVTiB, domestic production capacity still faces a gap of approximately 200,000 tons/year. With the implementation of the new standard, the industry is developing in three key directions: First, steel pipe manufacturers are accelerating the construction of "smart factories." For example, one company is using a manufacturing execution system (MES) to achieve full traceability of composition, process, and performance. Second, downstream users are gradually establishing "full lifecycle" management systems, feeding service data back into the selection process. Third, testing agencies are developing machine learning-based nondestructive evaluation technologies, such as using acoustic emission signals to predict remaining life. It is foreseeable that the implementation of GB/T5310-2023 will propel my country's high-pressure boiler tube quality into the international top tier. However, attention must also be paid to practical challenges in standard implementation, such as insufficient testing capabilities among small and medium-sized enterprises and the continued need to import some specialized materials. With the development of 700°C ultra-supercritical technology, the standard will face even more stringent revisions, requiring continuous collaborative innovation across industry, academia, research, and application.