Zhuojin Pipe Fitting Co., LtdDevelopment and Performance Evaluation of X52NS-825 Metallurgical Composite Steel Pipe for Overseas Oil Field Applications
Literature Overview
This technical paper by Chen Lijuan, Shang Feng, Fan Xuehua, Yu Yong, and Ji Yongbo, published in the journal Steel Pipe (2020, Vol. 49, No. 1, pp. 33-37), documents the development and comprehensive performance evaluation of X52NS/825 metallurgical composite steel pipe for overseas oil field applications. The research addresses the challenge of transporting crude oil containing corrosive media by combining a structural carbon steel base layer with a corrosion-resistant alloy cladding layer through a metallurgical bonding process.
Manufacturing Process and Material Selection
The composite pipe is manufactured using domestic X52NS/825 hot-rolled composite steel plate, where the X52NS grade provides the structural strength for the base layer and the 825 duplex stainless steel provides corrosion resistance for the cladding layer. The pipe is formed using the JCO (J-Circular-Oval) forming process, which involves three sequential forming stages: J-shaping, C-shaping, and final circular ovalization. This forming method is well-suited for large-diameter pipes and provides good dimensional accuracy.
The welding process employs a combination of Plasma Arc Welding (PAW) for the root pass, Submerged Arc Welding (SAW) for the filling passes, and Gas Tungsten Arc Welding (GTAW) for the backing pass. This multi-process welding approach is specifically designed to achieve metallurgical bonding between the composite layers while maintaining the integrity of both the structural and corrosion-resistant layers.
| Component | Specification | Key Properties |
|---|---|---|
| Base layer | X52NS | Yield strength ≥ 360 MPa, structural toughness |
| Cladding layer | 825 duplex SS | PREN ≥ 35, excellent pitting resistance |
| Forming process | JCO | Large diameter, high dimensional accuracy |
| Welding sequence | PAW root + SAW fill + GTAW back | Metallurgical bond, full penetration |
| Composite bond | Hot-rolled metallurgical | High bond strength, no interfacial defects |
Performance Testing and Results
The comprehensive performance evaluation includes chemical composition analysis, tensile testing, Charpy impact testing, hardness measurement, Hydrogen Induced Cracking (HIC) resistance testing, Sulfide Stress Cracking (SSC) resistance testing, pitting corrosion resistance testing, and intergranular corrosion testing. The results demonstrate that all performance parameters significantly exceed the technical standard requirements.
The X52NS base layer exhibits excellent HIC and SSC resistance, which is critical for sour service conditions where hydrogen sulfide and carbon dioxide are present in the crude oil. The 825 duplex stainless steel cladding layer demonstrates superior pitting corrosion resistance and intergranular corrosion resistance, providing long-term protection against chloride-induced corrosion. The metallurgical bond between the layers ensures that the composite structure behaves as a unified member under mechanical loading, with no risk of interfacial delamination.
The welding quality assessment confirms that the PAW+SAW+GTAW combination produces sound welds with full penetration, proper metallurgical bonding at the composite interface, and acceptable weld metal properties. The weld metal chemistry and mechanical properties are compatible with both the base and cladding layers, ensuring uniform corrosion resistance across the entire pipe circumference.
Engineering Application and Study Insights
The development of this metallurgical composite steel pipe represents a significant advancement in corrosion-resistant line pipe technology for oil and gas applications. The use of domestic X52NS/825 composite plate eliminates dependence on imported materials and reduces project costs for overseas oil field developments. The JCO forming process enables the production of large-diameter pipes suitable for trunk line applications, while the multi-process welding approach ensures reliable composite bonding throughout the manufacturing process.
The key engineering insight is that metallurgical composite pipes offer a superior alternative to traditional corrosion-resistant options such as internal coating systems, which can be damaged during installation and maintenance, or fully alloyed pipes, which are prohibitively expensive. The metallurgical bond provides permanent corrosion protection that cannot be compromised by mechanical damage to surface coatings. This technology is particularly well-suited for high-sulfur, high-salinity oil field surface piping systems where long-term reliability is paramount and maintenance access is limited. The comprehensive performance data presented in this study provides a strong technical basis for the specification and approval of X52NS/825 composite steel pipes in critical oil and gas infrastructure projects.