850级钢熔化焊焊缝的组织特征

Structure Characteristics of Weld Metal for 850MPa Grade Steel

利用金相显微镜、扫描电子显微镜及附带EDS系统和透射电子显微镜研究850 MPa级焊缝金属的微观组织,并通过分析焊缝金属凝固和相变过程,研究组织形成机制。发现原δ铁素体柱状晶晶界附近的锰和镍含量高于其心部含量。原δ铁素体柱状晶晶界附近组织由平行板条马氏体组成,板条宽度约为300 nm,原δ铁素体柱状晶心部组织由"交织状"板条马氏体组成,板条宽度约为400 nm。分析认为造成原δ铁素体柱状晶晶界附近和心部组织差异的重要原因是锰和镍的偏析,而焊缝金属良好的冲击韧性是因为存在30%"交织状"马氏体和一定量残余奥氏体。

The microstructures of 850 MPa grade weld metals were investigated by means of optical microscopy, scanning electron microscopy with EDS and transmission electron microscopy, and it was investigated on formation mechanism of microstructure by analyzing solidification and phase transformation. It is found that the content of Mn and Ni in the prior δ ferrite columnar boundary region （CBR） are more than in the columnar core. The micro- structure of the prior δ ferrite columnar boundary region consists predominantly of parallel lath martensite whose width is about 300 nm, while the microstructure of the prior δ-ferrite columnar core also consists mainly of interlaced lath martensite whose width is about 400 nm. The important reason that the microstructure of the prior δ ferrite columnar boundary region is different with columnar core is of Mn and Ni segregations. The good charpy impact toughness of weld metal is attributed to 30 % interlaced lath martensite and some residual austenite.