轧制方向对新型125KSI高钢级油套管性能的影响

Influence of Rolling Direction on Performance of New 125KSI High-grade Steel Oil Casing

利用室温拉伸试验、冲击试验、断裂韧性试验检验了超深井用新型125KSI高钢级油套管中沿扎向和垂直于扎向的强度、塑性、冲击韧性和断裂韧性。通过OM、SEM和EDS技术,对显微组织、晶粒长宽比和夹杂物分布进行了分析,讨论了显微组织对油套管各种性能的影响。结果表明,油套管材的微观组织由板条状回火马氏体和均匀弥散分布的细小Al_(2)O_(3)-MnS类混合夹杂物组成,晶粒为8.5级。轧制后,沿管道轧制方向的晶粒长宽比增加,导致强度增加,塑性降低且平行于管道轧向的冲击韧性下降;沿管道轧制方向的夹杂物分布更加集中,导致临界距离变小,裂纹扩展方向垂直于轧制方向的断裂韧性降低。

The tensile test,impact test and fracture toughness test at room temperature were used to test the strength,plasticity,impact toughness and fracture toughness of new 125KSI high-grade oil casing for ultra-deep wells along the tie direction and perpendicular to the tie direction.Using OM,SEM and EDS technology,the microstructure,grain aspect ratio and inclusion distribution were analyzed,and the influence of microstructure characteristics on the different properties of the oil casing was discussed.The results show that the microstructure of the tubing and casing is composed of lath-like tempered martensite and fine Al_(2)O_(3)-MnS mixed inclusions uniformly dispersed,with a grain size of 8.5.After rolling,the grain aspect ratio along the rolling direction increases,which leads to the increase of strength,the decrease of plasticity and the decrease of impact toughness paralleling to the rolling direction.The inclusion distribution along the rolling direction of the pipeline is more concentrated,which can lead to the decrease of the critical distance and the fracture toughness of the crack propagation direction perpendicular to the rolling direction.