한국주조공학회

Few studies of large blooms over 700 mm thick among those used for the forging of raw materials have been reported. The cooling rate difference between the surface and the center of a large bloom is large, and the degradation of the mechanical properties is likely in cases involving excessively coarse precipitates resulted from the slow cooling rate of a large bloom after casting. Therefore, a schematic investigation of the growth behaviors of precipitates while varying their locations in blooms is necessary. The dissolution behaviors of precipitates were investigated by simulating a reheating process during which the bloom is heated to a high temperature. The segregation behavior of the as-cast large bloom was also investigated. Reheating s specimens were obtained after an isothermal heat treatment at 1150oC with various h holding times to simulate the reheating process, with the samples undergoing a s subsequent water quenching step. The precipitates were extracted using an e electrolytic extractor and a particle size analysis was conducted with the aid of SEM, E EDS, and TEM. In the present work, Al oxide, MnS and Nb carbide were mainly o observed.