Analysis of the National Standard for Seamless Steel Pipes for Petroleum Cracking

First, the Standard Positioning and Implementation Background of Seamless Steel Pipes for Petroleum Cracking
GB/T 9948-2025 is my country's new national standard for seamless steel pipes for petroleum cracking units, which will officially come into effect on January 1, 2026. This standard integrates four existing standards, including GB/T 9948-2013 and GB/T 6479-2013, unifying and upgrading the standards for seamless steel pipes used in petrochemical and chemical plants. This marks a new step forward in my country's technical specifications for high-end steel pipe manufacturing.

Second, the Scope of Application and Core Applications of Seamless Steel Pipes for Petroleum Cracking
This standard applies to furnace tubes, heat exchangers, pipelines, and pressure vessels in petroleum refineries, covering the full range of pipe requirements from catalytic cracking units to delayed coking units. Typical applications include:
Reactor temperature control system: Utilizes 12Cr1MoVG steel pipes, capable of withstanding temperatures up to 620°C and pressures up to 15 MPa;
Regenerator flue gas ducting: Utilizes 1Cr5Mo steel pipes, offering excellent H₂S corrosion resistance;
Heat exchanger tube bundle: Utilizes 35CrMo steel pipes, offering both high-temperature strength and thermal fatigue resistance;
High-pressure reactor: Utilizes 12Cr2MoWVTiB steel pipes, capable of withstanding extreme operating conditions up to 650°C and 25 MPa.

Third, the material system and technical requirements for seamless steel pipes for petroleum cracking.
Material Classification
The standard covers three categories: high-quality carbon structural steel, alloy structural steel, and stainless heat-resistant steel. Specifically, they include:
Carbon structural steel: 20G, 20MnG, 25MnG (suitable for low-temperature, low-pressure conditions);
Alloy structural steel: 15MoG, 12CrMoG, 12Cr2MoG, 12Cr1MoVG (improved by adding elements such as Mo, Cr, and V for high-temperature strength and creep resistance);
Stainless heat-resistant steel: 1Cr18Ni9, 1Cr18Ni11Nb (used in highly corrosive environments). Key Performance Indicators: Tensile Strength: ≥410 MPa (carbon steel) to ≥560 MPa (alloy steel);
Yield Strength: ≥245 MPa (carbon steel) to ≥415 MPa (high-alloy steel);
Endurance Strength: ≥100 MPa at 600°C for 100,000 hours;
Oxidation Resistance: Oxidation Rate ≤0.1 g/(m²·h) at 650°C;
Microstructure Stability: Grain Size ≤ Grade 6 to prevent microstructure coarsening after long-term high-temperature use.

Dimensional Tolerances
Hot-rolled tubes: OD 22-530 mm, wall thickness 20-70 mm, OD tolerance ±1.0%, wall thickness tolerance ±10% (minimum ±0.5 mm);
Cold-drawn tubes: OD 10-108 mm, wall thickness 2.0-13.0 mm, OD tolerance ±0.3 mm (D≤50 mm) or ±0.8% (D>50 mm), wall thickness tolerance ±10%.

Fourth, Manufacturing Process and Quality Control of Seamless Steel Pipes for Petroleum Cracking
Heat Treatment System: Carbon Steel: Normalizing (900-930°C) + Tempering (670-720°C); Alloy Steel: Quenching (930-960°C) + Tempering (680-720°C); Stainless Steel: Solution Treatment (≥1040°C) followed by Rapid Cooling. Inspection Rules: Individual pipe inspection: Hydrostatic test (pressure ≥20 MPa), expansion test (expansion ratio ≥15%), flattening test (no cracks after flattening); Non-destructive Testing: Ultrasonic testing (in accordance with GB/T 5777-2019), Eddy Current Testing (in accordance with GB/T 7735-2016); Additional Testing: Intergranular Corrosion Test (per GB/T 4334-2020 Method E), High-Temperature Endurance Strength Test (600°C/100 MPa/100,000 hours).

Fifth, Standard Upgrades and Industry Impact on Seamless Steel Pipes for Petroleum Cracking
Technology Upgrades
New steel grades 12Cr2Mo1VR (H-grade) and 10Cr9Mo1VNbN (ultra-supercritical grade) have been added, with yield strengths reaching 550 MPa and 620 MPa, respectively, a 23% increase over the 2013 high-grade standard. A "controlled rolling and controlled cooling + online heat treatment" process has been introduced, achieving a grain size of Grade 8 or finer. Steel pipes with wall thicknesses greater than 50 mm utilize electromagnetic stirring continuous casting technology, with the segregation band width not exceeding 15% of the wall thickness.
Inspection Enhancements
Phase-controlled Array Ultrasonic Testing (PAUT) has replaced traditional manual UT, increasing the defect detection rate to 99.5%. New hydrogen-induced cracking (HIC) testing requirements have been added for pipes used in hydrogenation reactors, with a crack sensitivity rate (CSR) of <2%. Industry Impact
Supply-side reforms eliminated approximately 15% of outdated production capacity, increasing the market share of the top five steel mills to 63%. Import substitution increased the localization rate of high-end steel pipes, such as P91/P92, from 45% to 82%. Cost optimization reduced initial procurement costs by 8-12%, but overall costs decreased by 19-25%.