关键词: GH4169, 真空自耗重熔, 熔池, 枝晶间距, 黑斑

Abstract: To investigate the vacuum consumable remelting process of extra large-size GH4169 alloys and improve ingot quality, an optimiza-tion method for the vacuum consumable melting process of large-sized GH4169 ingots with a diameter of Ф1000 mm was devel-oped based on the MeltFlow software, which has been extensively validated in industrial applications. The study explored the evolu-tion of melten pool morphology, solidification characteristics, inclusion distribution, and macro-element distribution during the re-melting process. Additionally, the effects of melting rate, cooling condition, and hot topping process on segregation probability, sec-ondary dendrite arm spacing (SDAS), element distribution, shrinkage cavity formation, and macro-element distribution were ana-lyzed. After 1055 minutes of vacuum consumable remelting, the molten pool gradually stabilized, with a maximum depth and mushy zone width of 316 mm and 37 mm, respectively. The overall molten pool exhibited a "U" morphology. During stable remelting, the simulated cooling rates of the ingot surface and center were 0.39 K/s and 0.025 K/s, respectively. The primary dendrite arm spacings of the ingot surface and center were 205 μm and 512 μm, while the secondary dendrite arm spacings were 60 μm and 174 μm, re-spectively. Overall, elements such as Nb, Mo, Ti, and Al were evenly distributed throughout the ingot. For Φ1000 mm large-scale GH4169 ingot, when the melting rate is controlled within the range of 3-8 kg/min and water cooling or helium cooling is employed, an increase in melting rate and cooling rate will reduce the secondary dendrite arm spacing. Variations in melting rate and cooling conditions may influence the morphology of Ra values, but all Ra values remain below 1, resulting in a relatively low probability of freckle formation. The SDAS decreased with increasing melting rate and cooling speed, while the segregation probability decreased with increasing melting rate and decreasing cooling rate. Among various hot topping processes, a process with equal durations of the rapid current reduction phase, slow feeding phase, and low-current insulation phase reduced the SDAS and segregation probability in the ingot center.

Key words: GH4169, Vacuum consumable remelting, Molten pool, Dendrite arm spacing, Freckle