论文部分内容阅读
在天然气管线脆性断裂止裂的研究中,由于落锤撕裂试验(Drop weight tear test,DWTT)采用了全板厚试样,其试验状态接近管道在实际情况下的应力应变状态,能充分显示管材断裂的真实状况及其止裂能力,所以,DWTT已经成为评价管线钢脆性断裂止裂能力的重要方法,并以试样的断口纤维率(Shear-area percentage,SA)大小作为衡量标准。在不同的工业生产条件下轧制X70管线钢,并对它们进行落锤撕裂试验、疲劳试验、拉伸试验及冲击试验,探讨X70管线钢显微组织中多边形铁素体体积分数和大小对DWTT断口纤维率的影响。研究结果表明,当多边形铁素体作为第二相存在时,断口纤维率随着多边形铁素体体积分数的增加呈现出先上升后下降的特点;当多边形铁素体作为主要基体组织存在时,断口纤维率主要受多边形铁素体晶粒大小的影响,并且晶粒越细断口纤维率越高。
In the research of brittle fracture and cracking prevention of natural gas pipeline, the full thickness specimen is adopted in the Drop Weight Tear Test (DWTT), and its test state is close to the stress-strain state of the pipeline under actual conditions and can fully display Therefore, DWTT has become an important method to evaluate the brittle fracture arrestability of pipeline steel. The shear strain rate (Shear-area percentage, SA) of the sample is taken as the standard. X70 pipeline steel was rolled under different industrial production conditions, and the drop weight tear test, the fatigue test, the tensile test and the impact test were carried out to investigate the volume fraction and size of the polygonal ferrite in the X70 pipeline steel microstructure Effect of DWTT Fracture Fiber Rate. The results show that when the polygonal ferrite exists as the second phase, the fracture fiber ratio increases firstly and then decreases with the increase of the volume fraction of polygonal ferrite. When the polygonal ferrite is present as the main matrix, the fracture The fiber rate is mainly affected by the polygonal ferrite grain size, and the finer the grain the higher the fiber rate.