The pattern of fracture by impact penetration test and tensile fatigue test of thermite welding with stereoscan was observed,and the component of defect with energy spectrum was analyed.

微观缺陷主要包括微孔和夹,其中微孔由微气孔和微缩孔组成,夹物和尺寸分团簇夹、夹、粒夹、积聚物夹、丝夹和混合夹。