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.

观缺陷主要包括杂,其中由气缩,杂物按形态尺寸分为团簇状杂、锥状杂、粒状杂、积聚物杂、丝状杂混合形杂。