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和,其中微由微气和微成,物按形态和尺寸分团簇状、锥状、粒状、聚物、丝状和混合形。