According to the causes,the surface defects can be divided into blister containing non-metallic inclusion,blister without non-metallic inclusion and “raindrop”,“gills”,“mountained”.
By means of the Laika automatic analysis software,non-metallic inclusion can be tested accurately and quickly data treatment and measurement by statistical method.
VD and working procedure.Experiments showed that major of the LF step foreign inclusions are aluminium sesquioxide. spotted non-deforming inclusion and sulphuret.
The crack initiates at stress concentration point in the root of weld, where has much more martenite, carbide and inclusion, and the serious hydrogen segregation.
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.