The Study on the Orderliness of Change of Microstructure and Mechanical Properties in Simulating the Heating Process of Bending of X80 Pipeline Steels

Abstract

As the development of oil gas transportation project for long distance over the world, the pipeline steel are developed to high grade to reduce the construction cost and increase the efficiency of the gas transportation. But the statistics of the built pipeline engineering in the world showed that most of the steels are below the grade of X70, and the used X80 grade steels are less than 5000km. In 2008, the second west-east pipeline project will startup in China, and the whole line will use X80 grade pipeline steels. So the matched bend pipes should be studied. In this paper, the X80 pipeline steels were reheated under selected condition to simulate the heat history of bending process of it. And the deduced microstructure was observed, also the relationship between microstructure and mechanical properties were discussed. The optimum heat treatment technics were gained. This research will be helpful to the field hot bending in the second west-east gas project.