20th International Forgemasters Meeting - IFM 2017

Monoblock LP (Low Pressure) rotor shaft becomes larger with increasing the capacity and the efficiency of nuclear power plants. In addition, the size of ingot is required over 600 ton. With increasing the size of ingot, the high internal quality is very important to minimize the segregation of chemical compositions, non-metallic inclusions, micro porosities and so on. Therefore, to meet these demands, DHI has simulated by using MAGMASOFT® and designed the shape of the ingot mold. The 650 ton large ingot was produced by an optimized mold design and steelmaking processes based on our previous technologies. The steel scrap was melted with five times by using electro arc furnace and finally adjusted the chemical compositions and temperature in ladle refining furnace. The liquid metal was separately poured into the ingot mold under vacuum atmosphere. After solidifying, the ingot was stripped and transferred to forging and heat treatment shop immediately. The 650 ton ingot was forged by using 1,3000 ton press and manufactured the monoblock rotor shaft with a maximum diameter of Ф2,800 mm. After the heat treatment and UT inspection, the samples for the mechanical and metallurgical investigation were taken at the center and the surface at each of the blocks and evaluated. The overall results of the monoblock rotor shaft were obtained with the high quality thoroughly and met the requirements.