THE CHARPY NOTCH IMPACT TEST OF XT0 PIPELINE STEEL
X70管线钢冲击韧性实验研究

The effects of thickness, notch orientation and delamination on the impact toughness of X70 pipeline steel were investigated experimentally by use of the Charpy notch impact test at different temperatures. The couple effect of delamination cracks, thickness, notch orientation and temperature is discovered. The mechanical behaviors of X70 pipeline steel vary with the change of orientation. The failure model is different as the notch orientation of sample changes. The reason of delaminating crack is the slice defect of sample. The delamination crack has certain direction character, and its number is related to the temperature. The delamination crack can improve the actual impact toughness of X70 pipeline steel. The effect of delamination cracks and the actual impact toughness can vary when the angle of the sample notch and the direction of thickness are changed. Safe assessment of pipeline by using test data from only one thickness, one notch orientation or one temperature is not reliable. The couple effect of wall thickness, defect orientation and temperature of pipeline must be taken into account.