Surface Defects Analysis of GCr15 Shaft

The surface cracks of GCr15 axis were fully analyzed by means of metallographic and SEM etc.The results showed that the included angle between the crack and the surface is small,iron oxide or inclusions like protecting slag existed in crack and obvious decarburization occurred in the two sides of crack.The laps caused by inclusion and corner crack resulted in the cracks.Adopting appropriate tundish nozzle,reasonable secondary cooling system and the protecting slag with excellent performance and so on are effective ways of reducing lap defects.