X70管线钢冲击韧性实验研究

通过不同实验温度下的不同厚度、不同缺口取向含V型缺口试样夏比冲击实验和宏观断口分析，研究X70高韧性管线钢的冲击韧性的厚度、缺口取向和温度与分层裂纹耦合效应。结果表明：X70管线钢具有严重的各向异性现象，其在平行钢板表面方向和沿钢板厚度方向力学性能差异较大。分层裂纹主要是试样中材料固有的片状缺陷所致，有确定的方向性，同时与温度又有密切的关系，但分层裂纹的产生对X70管线钢的冲击韧性都是有益的。当裂纹扩展方向与厚度方向的相对方位改变时，分层裂纹效应亦将改变，实际的冲击韧性也改变。因此，应用单一试样厚度、单一缺口方向和单一的实验温度的表观冲击韧性数据进行管道结构的安全评定可靠性较差，必须考虑管道的温度、管壁厚度和缺陷方向的耦合效应。

THE CHARPY NOTCH IMPACT TEST OF XT0 PIPELINE STEEL

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.