The invention relates to the field of
metallurgy, and discloses a large-size maraging stainless
steel bar and a preparation method thereof, the
diameter of the bar is larger than or equal to 300 mm, and the method comprises a
vacuum induction melting stage, a vacuum consumable remelting stage, a fast
forging cogging stage and a precision
forging forming stage; wherein the vacuum consumable remelting stage comprises an arcing stage, a stable
smelting stage and a filling
smelting stage; in the arc starting stage, a
molten pool is formed by adopting a current of 8-12 kA; in the stable
smelting stage, the smelting speed is 4.2-4.8 kg / min, the molten drop is 3-5 s <-1 >, the molten drop short-circuit time is 0.6-0.8 s, and
inert gas is started to be filled for cooling after smelting is conducted by the preset weight; and in the filling smelting stage,
inert gas filling is stopped, and the current and the melting speed are controlled to descend in a stepped mode. According to the method, the uniformity of components and structures can be improved, so that the
mechanical property of the large-size maraging stainless
steel bar is improved.