不同组织特征对X80管线钢粗晶区冲击韧性及裂纹萌生行为的影响

Influences of different microstructural features on impact toughness and crack initiation behavior of coarse grain affected zone in X80 pipeline steel

通过对X80管线钢的焊接热模拟试验(Gleeble 3500),获得了不同热输入下的粗晶热影响区(CGHAZ)试样。采用夏比冲击试验和多尺度表征相结合的方法,研究了不同显微组织特征对冲击韧性和裂纹萌生行为的影响。结果表明:随着热输入的增加,M/A组元含量增加,导致韧性下降,硬度增加。同时,更多的M/A组元倾向于聚集在原奥氏体晶界上,M/A的总体尺寸和M/A岛内部板条马氏体亚结构的宽度、体积分数也会增加。这些变化使得M/A组元边界和原始奥氏体边界之间的交叉点成为裂纹萌生的首选位置之一。此外,还发现只有大尺寸的奇形夹杂物才是裂纹萌生的直接诱因。

The coarse grain heat affected zone(CGHAZ)samples of X80 pipeline steel under different heat inputs were obtained by welding thermal simulation experiments with Gleeble 3500.Charpy impact tests and a combination of multiscale characterization were conducted to investigate the influence imposing on impact toughness and crack initiation behavior by various microstructural features.The results proved that as the heat input increases,the amount of M/A components increases and hence lead to the degradation of toughness and the increases of hardness.Meanwhile,more M/A constituents tend to aggregate on the prior austenite grain boundaries(PAGBs)and the overall dimensions of M/A and the width,volume fraction of lath martensite substructure inside M/A islands would increases too.These changes make the intersections between boundary M/As and PAGBs become one of the preferred sites for crack initiation.In addition,it is also founded that only the large-sized grotesque inclusions can be the direct inducement for crack initiation.