双金属复合管环焊缝开裂机理研究

发布时间：2018-06-25 18:48

本文选题：双金属复合管 + 环焊缝　；参考：《西安石油大学》2016年硕士论文

【摘要】：双金属复合管作为重要的油、气输送管线钢管,在恶劣的工况下承担重要的输送任务,复合管的开裂甚至断裂都会产生巨大的经济损失。本文所研究的L415QB+316L双金属复合管环焊缝接头包括:根焊层(R316)、封焊层(R309L)、过渡层(R309LMo)、填充层(E5015)和盖面层(E5015);目的是研究环焊缝上的裂纹开裂的原因以及机理。采用X射线对环焊接头无损检测,确定起裂位置在焊接接头的封焊区;并利用光学显微镜观察断口形貌特征,发现封焊区、过渡层为脆性断裂,填充层、盖面层为韧性断裂;采用扫描电镜、EDS分析仪对焊接接头的成分以及组织进行分析,发现封焊区铁素体含量较高;采用显微硬度计对试样进行硬度检测,发现封焊区、过渡层硬度均高于其他区域的硬度值;封焊区与过度层的脆性组织以及硬度分布不均匀是开裂的重要原因。采用有限元分析软件ABAQUS对焊接接头在不同类型载荷作用下的应力分布进行研究。结果显示,在弯曲载荷作用下,弯曲位移为15mm时,封焊区的应力值达到材料抗拉强度520MPa;在工作内压10.48MPa作用下,焊接接头的应力值较小,内压不是驱动开裂的主要原因;在拉伸载荷为85mm时,封焊区应力值达到抗拉强度520MPa;焊接接头在拉-弯复合载荷作用下,复合载荷为13mm弯曲位移+71mm拉伸载荷时,封焊区的应力值达到抗拉强度而产生裂纹。
[Abstract]:As an important oil and gas pipeline pipe, bimetallic composite pipe takes on important transportation tasks under bad working conditions, and the cracking and even fracture of the composite pipe will cause huge economic losses. The girth welds of L415QB316L bimetallic composite pipe are studied in this paper, including root welding layer (R316), seal welding layer (R309L), transition layer (R309LMo), filler layer (E5015) and cover layer (E5015). X-ray nondestructive testing was used to determine the starting position of the welding joint, and the fracture morphology was observed by optical microscope. It was found that the sealing zone was brittle fracture, the filling layer was brittle fracture, and the cover surface layer was ductile fracture. The composition and microstructure of welded joints were analyzed by EDS scanning electron microscope (SEM). It was found that the content of ferrite in the sealing zone was high, the hardness of the samples was detected by microhardness meter, and the sealing zone was found. The hardness of the transition layer is higher than that of other regions, and the brittle structure and the uneven distribution of hardness in the sealing zone and the transition layer are the important reasons for the cracking. The stress distribution of welded joints under different types of loads was studied by finite element analysis software Abaqus. The results show that under bending load and bending displacement of 15mm, the stress value of sealing zone reaches 520MPa of material tensile strength, and the stress value of welded joint is smaller under working internal pressure of 10.48 MPA, and internal pressure is not the main reason of driving cracking. When the tensile load is 85mm, the stress value of the seal welding zone reaches 520MPa, and when the composite load is 13mm bending displacement 71mm tensile load, the stress value of the seal welding zone reaches the tensile strength and cracks occur.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE973

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