油气输送高频焊管焊接接头组织结构与性能分析

本课题应用ＴＥＭ观察和微型剪切实验技术，研究了两种常用油气输送高频焊管焊接接头和母材组织结构及机械性能的特点。试验结果表明：（１）强度在焊缝熔合区最高，热影响区次之，母材处最低；（２）母材的冲击韧性和断裂韧性高于焊缝熔合区；（３）焊接接头与母材的位错组态有很大差别，前者位错密度远高于后者。最后，本文根据高频焊接工艺特点，从理论上阐述了焊接接头高密度位错产生的原因，以及它对焊接接头机械性能的影响。

Study of the Relationship Among Mechanical Properties and Microstructure and Substructure in HF Welded Jionts Used in Oil and Gas Pipeline

The relationship among the mechanical properties and micro-structure and substructure in welded joints and base metal of HF welded pipe was studied by means of the micro -shearing test and TEM technique.The expriement reveals some new features. (1)The distribution of mechanical properties in HF welded joints and base metal is as follows:The highest strength is located in the fusion zone,then in the HAZ,and the lowest in the base metal ;the distribution microstructure of ductility is just the reverse. (2)Fracture toughness and impact toughness of the base metal is higher than that of the fusion zoned (3)There is a great difference between the welded joitlts and the base metal in the dislocation microstructure,the dislocation density in the welded joints is much higher than that in the base metal.Finally according to the characteristic of HF welding process,it is explained why the high density of dislocation is produced, and how the mechanical properties of HF weld joints are changed.