Effect of pre-strain on impact fracture behavior of X80 pipeline steel
The influence of pre-strain on the impact fracture behavior of X80 pipeline steel was studied.Fracture morphology and inclusions were analyzed by OM,SEM,EDS spectroscopy,and the crystallo-graphic characteristics near the secondary crack on the fracture cross-section were obtained by EBSD.The results show that the pre-strain has no significant effect on the maximum impact load,but pre-strain will increase brittle fracture tendency and notch sensitivity,which leads to decreasing the crack forma-tion energy and crack resistance.In the process of impact fracture,the pre-strain causes the internal dis-locations of the material to become entangled with each other,and dislocation movement is hindered.Therefore,brittle fracture is easy to occur when the material is subjected to external force,and the brittle inclusions inside the material also act as the source of cracks.Due to the misorientation between adja-cent grains,when the crack propagation encounters the grain boundary,the crack propagation path is de-flected when it enters the next grain.In addition,analysis on the crystal orientation of the cross-section near the fracture area indicated that the main cleavage plane of X80 pipeline steel was {100},followed by {211}.
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