X70厚壁海底管线钢管研制

根据我国南海深海管线用钢管的技术要求，开发出了厚壁X70钢级φ765.2 mm×31.8 mm海底管线钢管。通过对钢管进行检测:钢管管体纵向和横向屈服强度≥550 MPa，抗拉强度≥660 MPa，屈强比最低达到0.81，焊缝抗拉强度达695 MPa，均匀延伸率达到了7.6%，断后伸长率达到54%；在-20 ℃下管体冲击功平均值为340 J，焊接接头冲击功平均值最低为168 J；在0 ℃下管体CTOD特征值δm最高达到0.688 mm，焊接接头最小为0.222 mm，热影响区最小为0.280 mm。钢管管体母材、热影响区、焊缝部位的抗氢致开裂、硫化物应力腐蚀及盐雾腐蚀性能良好。试验结果表明研制的X70钢管具有优良的强塑性、低温韧性、断裂韧性及耐腐蚀性能，适用于海洋服役环境的油气输送。

Research and Development of X70 Steel Pipe withHeavy Wall Thickness Used in Submarine Pipeline

According to the requirements of steel pipe used in deep sea pipeline of the south China，the X70 grade φ765.2 mm×31.8 mm submarine pipeline with heavy wall thickness was developed successfully. Through the test of steel pipe. The longitudinal and the transverse yield strength both are greater than or equal to 550 MPa，the tensile strength is not less than 666 MPa，the yield ratio shows the lowest 0.81，the tensile strength of the weld reaches 695 MPa. And the uniform elongation reaches 7.6% and the percentages elongation after fracture reaches 54% of the pipe body. The average impact energy of pipe body is 340 J and in weld the lowest value is 168 J under -20 ℃. The CTOD characteristic value δm is up to 0.688 mm in the pipe body at 0 ℃，the smallest is 0.222 mm in welded joint，and the smallest is 0.280 mm in HAZ. The resistance to hydrogen induced cracking，sulfide stress corrosion performance and salt spray corrosion is good on the base materials，steel pipe weld and heat affected zone of the pipe.