Effect of Geometrical Characteristics of Inclusions on Initiation and Propagation of Cracks in X80 Pipeline Steel during Tensile Test

The effect of size and shape of inclusions in X80 pipeline steel on crack initiation and propagation during tensile test was studied by scanning electron microscopy in-situ observation. The results show that the larger the size of an inclusion, the more the number of cracks initiated in the inclusion, and the lower the stress of the first crack initiation. The shape and size of inclusions determined the location of the first crack initiation, and the size and shape of inclusions had not remarkable effect on the tensile strength of X80 pipeline steel.