Effect of finish rolling temperature and final cooling temperature on the yield ratio of X65/X70 pipeline plates

By investigating the change in yield ratio and microstructure of X65/X70 pipeline plates at different finish rolling temperatures and final cooling temperatures,it is found that the microstructure has band structure and the amplitude of high yield ratio is greater than that of tensile strength when the finish rolling temperature is below the Ar3 temperature and the plate is rolled in the two-phase zone.Overcooling at the head of the plate is not beneficial to low yield ratio.By optimizing the processing parameters,the yield ratio of X65/X70 pipeline steel reduces obviously and the qualified rate of products increases greatly.