Liaoyang Steel Pipe Company overcomes production bottlenecks for ultra-thick-walled steel pipes using a two-step process

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Liaoyang Steel Pipe Company overcomes production challenges for ultra-thick-walled pipes using a two-step process On March 21, with the successful production of ultra-thick-walled pipes with a diameter of 2220 millimeters and a wall thickness of 28 millimeters, the two-step process developed by China National Petroleum Corporation’s Liaoyang Steel Pipe Company – namely online internal welding using \"gas shielded welding for pre-welding + submerged arc welding for final welding\" – was declared a success. This marks a significant breakthrough by the company in welding technology for the production of steel pipes with extremely large diameters and thick walls. It is reported that the traditional spiral submerged arc welding process is limited by factors such as heat input and metallurgical reactions; as a result, it cannot ensure long-term stability during the welding process when producing steel pipes with wall thicknesses over 25 millimeters, which affects both the quality and efficiency of welding. Drawing on the advanced welding techniques of leading companies in the industry, the technical team at Liaoyang Steel Pipe Company proposed a phased welding approach that involves \"pre-welding for shaping + final welding for reinforcement.\" In the first step, Ar-MAG gas shielded welding is used to create a basic weld layer; in the second step, high-toughness submerged arc welding is employed to complete the full welding process and achieve a gradient metallurgical structure. “This welding method offers stable quality, good weld shape, and high tensile strength. ”Meng Deqiang, deputy general manager of Liaoyang Petroleum Steel Pipe Manufacturing Co., Ltd., said. To ensure the smooth progress of production, the pipe manufacturing branch took proactive measures, focusing on making thorough preparations for the gas shielded welding equipment. First, it planned in advance the installation, debugging, and workflow integration for this equipment; second, it purchased the necessary key devices based on production requirements; third, it designed and modified specialized components tailored to the characteristics of the existing equipment. Multiple special meetings were held to thoroughly analyze the equipment and process-related challenges in production, and detailed solutions were developed. In the early stages of production, since Liaoyang Steel Pipe Company was using the two-step process for the first time, there were no existing empirical data available for reference. Therefore, aspects such as the calibration of the pre-welding device, the ratio and flow rate of the shielding gas, the output current and voltage, and the location of the weld points all had to be determined from scratch. Technicians, skill experts, and key production staff from the pipe manufacturing branch focused on the front line to verify the precision of the upgraded equipment and conduct simulated tests to assess the feasibility of the manufacturing process. After production started, challenges arose one after another, but everyone stepped up to meet them. “The output volume of the mixed gas is fine-tuned little by little, and the extension amount of the welding wire is tested step by step... Through repeated attempts, the process is continuously optimized, and as the shape of the weld gradually takes form, the final process plan is determined. “The geometric dimensions of the steel pipe meet the standard requirements. ”“The weld morphology is normal. ”“The internal quality of the weld is perfect. ”“Welding inspection passed. ”After all the test parameters met the required standards, the two-step online welding process for internal welding at Liaoyang Steel Pipe Company was successfully tested for the first time. This not only verified the company’s capability for mass production and provided valuable experience, but also ensured the feasibility of producing steel pipes with extremely large diameters and thick walls in the future, thus supporting key projects related to water transmission pipelines.