Abstract��The cause of crack occurring during heat treatment for die steel is determined by several experiments, such as fracture surface analysis��macroscopic examination��metallographic analysis and simulated manual fracture surface observation. It is inferred that the large size crack is formed during quenching and is induced to propagate by the white spot defect and super size inclusion that exist in the steel before the heat treatment. The steel with crack and defect is still processed by heat treatment and put outside for a long time that damage the initial fracture surface a lot, which cause some difficult to do the failure analysis. A manual fracture surface have been processed in similar heat treatment system, and then its morphological analysis is compared with steel fracture surface to determine the deferent terms when white spot and large size crack are formed. This experimental method can be applied to some failure analysis for the work-piece whose fracture surface is damaged by high temperature.
2010, Vol. 28 
