Example 1: Fracture of a Forging Die Caused by Segregation(Ref 5). A cross-recessed die of D5 tool steel fractured in service. The die face was subjected to shear and tensile stresses as a result of the forging pressures from the material being worked. Figure 7(a) illustrates the fractured die D5 tool steel a oSs 850 oEoaaeEo6 Fracture 750 (a) (b) (c) Fig. 7 A D5 tool steel forging die that failed in service because of segregation.(a)Hardness traverse correlated with the microstructure of the die. (b) Section through one arm of the cross on the recessed die face showing a severely segregated(banded) structure. Etched with 5% nital. (c)Micrograph of the segregated area. Etched with 5% nital 200x Investigation. A longitudinal section was taken through the die to include one arm of the cross on the recessed die face. The specimen was polished and examined in the unetched condition. Examination revealed the presence of numerous slag stringers The polished specimen was then etched with 5% nital. A marked banded structure was evident even macroscopically(Fig. 7b). Microscopic examination revealed that the pattern was due to severe chemical segregation or banding( Fig. 7c)Example 1: Fracture of a Forging Die Caused by Segregation (Ref 5). A cross-recessed die of D5 tool steel fractured in service. The die face was subjected to shear and tensile stresses as a result of the forging pressures from the material being worked. Figure 7(a) illustrates the fractured die. Fig. 7 A D5 tool steel forging die that failed in service because of segregation. (a) Hardness traverse correlated with the microstructure of the die. (b) Section through one arm of the cross on the recessed die face showing a severely segregated (banded) structure. Etched with 5% nital. (c) Micrograph of the segregated area. Etched with 5% nital. 200× Investigation. A longitudinal section was taken through the die to include one arm of the cross on the recessed die face. The specimen was polished and examined in the unetched condition. Examination revealed the presence of numerous slag stringers. The polished specimen was then etched with 5% nital. A marked banded structure was evident even macroscopically (Fig. 7b). Microscopic examination revealed that the pattern was due to severe chemical segregation or banding (Fig. 7c)