Relationship of Microstructure and Toughness Index of Reheated High Grade Pipeline Steels

Bend pipes are very important welding elements in long distance pipe line construction.During the serve of pipeline,the stress in bend pipe is more complex than that in main line pipe for its special structure,so the bends are weak taches.In the project of west to east gas pipe line,the CVN index are prescribed clearly that the sharpy impact energy should reach 120J,85%.So the study on CVN index of reheated high grade line pipes are conducted and a comparison with that of mother pipe is made,including microstructure.EBSD results showed that the effective grain size is a precise parameter to determine the CVN.These results are helpful to the second west to east gas pipe line project.