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.

观缺陷主要包括夹杂,其由气缩组成,夹杂物按形态尺寸分为团簇状夹杂、锥状夹杂、粒状夹杂、积聚物夹杂、丝状夹杂混合形夹杂。