Microstructure and mechanical property of X100 high strength pipeline steel

Effect of controlled cooling on mechanical properties and microstructure of the X100 high strength pipeline steel was studied by using scanning electron microscope(SEM) and tensile test.At the same time,the microstructure and the type and distribution of precipitates in the X100 pipeline steel were also investigated by means of transmission electron microscopy(TEM).The results show that the microstructure and mechanical properties of the X100 pipeline steel are obviously affected by the coiling temperature and the cooling rate.With the coiling temperature decreasing and the cooling rate increasing,strength of the pipeline steel increases,and its total elongation decreases.It is proved that the excellent performance both strength and toughness can be obtained for X100 pipeline steel with the microstructure consisting of granular bainite matrix with a small amount of bainte ferrite and dispersively distributed fine M/A islands.