Author(s): Yu Yang, Guan Ju, Liu Wei
Pages: 49-52
Year: 2015 Issue:  2
Journal: Angang Technology
Keyword:  pipeline steel; yield strength; fluctuation; anisotropy;
Abstract: The causes leading to abnormal fluctuation of the yield strength of pipeline steels with heavy wall thickness are identified by analyzing process parameters in producing X70 pipeline steels and by means of high power metallographic examination. It is concluded that the causes leading to abnormal fluctuation include different sizes of precipitated phases and their heterogeneous distribution, anisotropy of steel plates for pipelines and bending deformation of the specimens. For the causes such measures as prolonging the heating time, suitably increasing the heating-up temperature and final rolling temperature, decreasing the coiling temperature and flatting the specimens repeatedly by adding the temper mill before testing were taken, then the existing problems are solved, which can guarantee the smooth production of pipeline steels.