The high-grade pipeline steel can not only meet the requirements of long-distance high-pressure large oil and gas transmission,but also greatly save steels,which can well response to the national strategic goal of"carbon peaking"and"carbon neutrality".However,few domestic manufacturers can realize the stable supply of X80M pipeline steel,among which the coiling process as an important link to affect its stable production has attracted much attention.The tensile properties of X80M hot rolled strip were measured under different coiling processes,and the microstructure was characterized.The effects of coiling temperature on the microstructure and tensile properties of X80M hot rolled strip were analyzed.The results show that with the increase of coiling temperature,lath bainite gradually decreases until to disappear,granular bainite increases,and a small amount of acicular ferrite appears.The average grain size increases with the increase of coiling temperature and morphology of M/A constituents change from strip to block,and its area percentage increases.The yield strength and tensile strength decrease with the increase of coiling temperature,while the elongation and impact energy increase gradually.The Hall-Petch rela-tionship between grain size and yield strength is well fitted,and the contribution rate of grain boundary strengthe-ning to yield strength under each coiling process is 57.1％-62.7％,so it can be considered that grain boundary strengthening is the main strengthening method of X80M pipeline steel.With the increase of coiling temperature,the degree of supercooling decreases,dislocation density decreases and grain size increases.The dislocation sliding is easier to carry out and the resistance during the sliding decreases,leading to the increase of elongation.Meanwhile,the proportion of high angle grain boundary increases,which significantly hinders the crack propagation and increases the impact energy.The experimental results provide a reference for the hot-rolling production of X80M pipeline steel.
X80M hot rolled stripcoiling processmicrostructuregrain boundary strengtheningmechanical prop-erty
NETL
NSTL
万方数据
