Submerged arc welded steel pipes, as an important product in the modern industrial pipeline field, demonstrate the deep integration of materials science and welding technology through their diverse manufacturing processes and application scenarios. Among them, double-sided submerged arc-welded straight seam steel pipes, with their unique structural performance and technological advantages, occupy an irreplaceable position in long-distance transportation pipelines and building support structures. The manufacturing process of this type of steel pipe integrates automated welding technology and precision forming processes, achieving high strength and high sealing performance of the weld seam through double-sided submerged arc welding, making it a key material for ensuring the safety of energy transmission.
First, Analysis of the Core Processes of Double-Sided Submerged Arc Welded Straight Seam Steel Pipes.
The manufacturing of double-sided submerged arc welded straight seam steel pipes begins with the precision processing of high-quality hot-rolled steel plates. First, the steel plate is processed to the required width using a milling machine, and then subjected to multiple progressive pressing processes on a JCOE forming machine to form an open pipe blank. The core welding stage employs a double-sided submerged arc welding process: first, a pre-welded seam is welded to the inner wall of the pipe blank, then the main weld seam is completed through submerged arc welding on the outer wall, and finally, a supplementary weld is performed on the inner wall. This layered welding method allows for weld penetration to reach over 70% of the plate thickness, significantly improving joint strength. During welding, the arc beneath the flux layer melts the metal at a high temperature of 1600℃, forming a protective slag layer that effectively isolates air, preventing porosity and slag inclusions.
Compared to ordinary straight seam steel pipes, double-sided submerged arc welding creates a fine needle-like ferrite structure in the weld area, increasing its impact toughness by over 30%. Online ultrasonic testing and X-ray inspection ensure that the internal quality of the weld meets international standards such as API 5L or GB/T 9711. Typical products, such as X80 grade steel pipes, have a yield strength of up to 555 MPa and can withstand transmission pressures exceeding 15 MPa, widely used in national pipeline projects such as the West-East Gas Pipeline.
Second, a technical and economic comparison with spiral welded steel pipes.
Although double-sided submerged arc spiral welded steel pipes (such as L485M steel grade according to GB/T 9711 standard) have advantages in continuous production and large diameter, straight seam welded steel pipes are superior in pressure-bearing stability and dimensional accuracy. Because the weld seam of spiral steel pipes is distributed in a spiral pattern, the circumferential stress decomposition under high-pressure conditions may cause weak points, while the longitudinal weld seam of straight seam welded steel pipes is stressed in the same direction as the principal stress, and the burst pressure is usually 10%-15% higher. Comparative tests in an oil pipeline project showed that the fatigue life of straight seam welded steel pipes of the same specification reached 2 million cycles, about 1.5 times higher than that of spiral welded steel pipes. From a production cost perspective, the material utilization rate of straight seam welded steel pipes with a diameter of less than 1420mm can reach 96%, while spiral welded steel pipes have about 5% scrap material loss due to plate width limitations. However, in the field of ultra-large diameter (such as 3000mm and above), spiral steel pipes do not require customized ultra-wide steel plates, and their economic advantages begin to emerge. It is worth noting that straight seam steel pipes are easier to automate with diameter expansion processes. Mechanical expansion allows roundness deviations to be controlled within 0.5%D, which is crucial for ensuring pipe connection accuracy.
Third, innovative processes and special application scenarios.
In recent years, straight seam submerged arc welded pipe technology has made continuous breakthroughs: In the South China Sea subsea pipeline project, X65 grade straight seam steel pipes with a double-layer FBE+PP anti-corrosion coating, by adding 0.06% Nb micro-alloying element, achieved an impact energy of over 220J at -40℃. In polar pipeline construction, X100 grade steel pipes produced using TMCP (Thermomechanical Control Process) reduced wall thickness by 15% while maintaining excellent crack resistance.
Special fields such as nuclear power plant pipes require compliance with the Z-direction performance indicators in the RCC-M standard. A nuclear power plant’s containment vessel straight seam steel pipes used specially formulated low-sulfur phosphorus steel plates (S≤0.002%), combined with a multi-pass narrow-gap welding process, achieved a thickness-direction area reduction rate exceeding 75%. In the field of coal slurry transportation, composite straight seam steel pipes with a 6mm thick ceramic lining exhibit wear resistance eight times higher than ordinary steel pipes, achieving a service life of 15 years in a coal preparation plant in Shanxi.
Fourth, Industry Development Trends and Challenges.
With the advancement of intelligent manufacturing, leading domestic enterprises have achieved full-process digitalization of straight seam steel pipe production. A factory’s MES system can monitor over 200 parameters in real time, including welding current (fluctuations controlled within ±15A) and linear energy (18-22kJ/cm), increasing the product qualification rate to 99.92%. However, in terms of raw materials, high-end pipeline steel still relies on imports; for example, 80% of X90/X100 grade steel plates need to be purchased from other companies.
Environmental requirements are also driving technological innovation. The application of a new generation of low-smoke welding flux has reduced dust concentration in welding workshops from 15mg/m³ to 3mg/m³. In the future, with the increasing demand for hydrogen energy pipeline construction, the research and development of hydrogen-embrittlement-resistant straight seam steel pipes will become a key focus. Currently, L415H grade steel products with a hydrogen-induced cracking (HIC) sensitivity index of ≤2% have been trial-produced domestically. However, in the field of deep-sea pipelines above 1500 meters, the challenge of controlling welding residual stress in thick-walled straight seam steel pipes (≥40mm) still needs to be addressed.
From land to sea, from conventional energy to new energy transmission, double-sided submerged arc welded straight seam steel pipes continue to demonstrate their core value as the lifeblood of industry. Their technological evolution reflects both the transformation of Chinese manufacturing from scale expansion to quality improvement and foreshadows the infinite possibilities brought about by the integration of new materials and processes. In the context of carbon neutrality, this pipeline product, which combines high strength and long service life, will undoubtedly play an even more crucial role in the restructuring of global energy infrastructure.
Post time: Nov-18-2025