| 摘要 |
PURPOSE:To obtain an ingot and cast product that do not contain eutectic Nb carbide and precipitated crystals by limiting height/diameter ratio of an ingot of alloy steel that contain specified quantity of Nb, Cr and making the size in the direction of height larger than the size of radial direction by forging the ingot. CONSTITUTION:Molten metal of alloy steel containing 0.08-0.25% C, 0.02- 0.15% Nb, 9-12% Cr, 80% <=Fe in wt% is casted in a mold in which H/D is <=1 where H is height excluding the feeder head and D is diameter at the position of height 1/2 H, and solidified. The ingot obtained is forged by applying pressure in radial direction to make the size in the direction of height of the casting larger than the size in radial direction. By this way, a long, large-sized forged product of high mechanical property such as a rotor shaft of a steam turbine can be obtained. |
