Abstract: X70 and X80 steel grade longitudinally submerged arc welding pipe was developed to satisfy the demand by the country’s highstrength pipeline construction projects. Based on the research efforts to design chemical components of raw materials and develop the key technology for pipe molding and welding and the related materials, the products of X70 and X80 longitudinally submerged arc welding pipe can be used in the geologically-harsh areas, such as fault zones, earthquake and landslide regions, and deepwater zones. The “ferrite + bainite” diphase microstructure with the large deformation characteristics was developed on the basis of the research on the low-carbon multi -microalloying component design method, rolling controlled technology and special online cooling technology. As a result, the X70 and X80 steel grade large deformation plates were successfully developed in China for the first time and used in large quantities for China-Burma pipeline, breaking the long-term technological blockade and monopoly of the high-end design-based-on-strain longitudinally submerged arc steel pipe products by European, American and Japanese steel pipe enterprises. The products are equal to their foreign counterparts in terms of functions and even economically better.

Key words: X70 steel grade, X80 steel grade, design based on strain, diphase microstructure, forming process technology

摘要： 针对国家重点高强度管道建设工程的需要, 通过对原料化学成分设计、制管成型与焊接关键技术、匹配 焊接材料的研制开发, 使生产的X70、X80 直缝埋弧焊管产品已经延伸到了断裂带、地震、滑坡等恶劣地质, 并向着深 海领域纵深方向发展。通过对低碳多元微合金化成分设计方法技术、控制轧制和特殊的在线冷却技术等研究, 实现了 具有大变形特点的“铁素体+贝氏体” 双相组织, 在国内首次成功开发出了国产X70、X80 级大变形板材, 并在中缅管 道实现了批量化应用, 打破了欧美、日本等钢管企业长期以来在基于应变直缝埋弧钢管高端产品的技术封锁与垄断。 与国外同类产品相比性能相当, 且经济性更好。

关键词: X70 钢级; X80 钢级; 基于应变设计; 双相组织; 成型工艺技术