深海用36.5mm厚X70钢板及其大口径直缝埋弧焊管的开发

Development of 36.5mm Thick X70 Steel Plate and Its Large Diameter Longitudinal Submerged Arc Welded Pipe Used for Deep-Sea Pipeline

以低碳高锰铌镍钼系合金为基础进行成分优化设计,辅以两阶段控制轧制+热机械控制工艺,开发出厚36.5mm的X70钢板,测试了其显微组织和力学性能;采用该钢板试制了规格为1 016mm×36.5 mm的直缝埋弧焊管,测试了接头的力学性能和耐腐蚀性能。结果表明:36.5mm厚X70钢板的显微组织主要由针状铁素体组成,其强度和低温韧性优异,屈强比不大于0.80;大口径直缝埋弧焊管接头的力学性能均符合DNV-OS-F101-2013的指标要求,管体(母材)屈强比不大于0.82,伸长率不小于60%,均匀延伸率不小于7.0%,钢管母材及焊接接头具有较好的低温韧性,同时也具有良好的抗氢致开裂和硫化物应力腐蚀开裂性能。

The alloy composition was designed based on the low-carbon-high-manganese-Nb-Ni-Mo alloy,and then the 36.5 mm thick X70 steel plate was developed by the two-stage controlled rolling and thermo-mechanical rolling process.The microstructure and mechanical properties of the steel plate were measured.The longitudinal submerged arc welded pipe of the steel plate with the size of？1 016 mm×36.5 mm was trial-manufactured and the mechanical properties and anti-corrosion performance were tested.The results show that the microstructure of 36.5 mm thick X70 steel plate was mainly composed of acicular ferrite and the strength and low-temperature toughness were excellent with the yield ratio of less than 0.80.The mechanical properties of the longitudinal submerged arc welded pipe joint met the indicators requirements of DNV-OS-F101-2013 standard.The yield ratio of the pipe body （base material）was less than 0.82,the percentage elongation was more than 60% and the uniform extension rate was more than 7.0%.Both the base material and the welded joint of the steel pipe had the relatively excellent low-temperature toughness and the good resistance to hydrogen cracking and to sulfide induced stress corrosion cracking at the same time.