中文摘要：

热的不同分区的微结构特征影响了低焊接的地区(HAZ ) 裂缝危险性钢焊接被使用光显微镜学并且扫描与电子 backscattered 衍射装备的电子显微镜学调查系统。并且焦点被放在在微结构特征和焊接的 HAZ 坚韧之间的关联上。结果表明熔化的坚韧衬里地区(FLZ ) 标本比精细的 HAZ (FGHAZ ) 标本的低得多。在焊接金属的粗糙的包括和在粗糙的颗粒的 HAZ (CGHAZ ) 的大马氏体奥氏体成分在 FLZ 的裂缝开始精力上有明显的否定效果。同时，有大有效谷物的粗糙的小粒的 bainite 减少裂缝繁殖精力严重。由对比，在 FGHAZ 的好结晶的谷物在增加坚韧起一个关键作用，特别在改进裂缝繁殖精力。

英文摘要：

Microstructural characteristics of different sub-regions of heat affected zone （HAZ） of low welding crack susceptibility steel weldment were investigated by using optical microscopy and scanning electron microscopy equipped with electron backscattered diffraction system. And the focus was put on the correlation between microstructural characteristics and HAZ toughness of the weldment. The results reveal that the toughness of fusion line zone （FLZ） specimens is much lower than that of fine grained HAZ （FGHAZ） specimens. The coarse inclusions in the weld metal and the large martensite-austenite constituents in the coarse grained HAZ （CGHAZ） have an obvious negative effect on the crack initiation energy of FLZ. Meanwhile, the coarse granular bainite with large effective grain decreases the crack propagation energy seriously. By contrast, fine crystallographic grains in the FGHAZ play a key role in increasing toughness, especially in improving crack propagation energy.