Melting process for reducing element segregation in nickel-base superalloy

Abstract

The invention discloses a melting process for reducing element segregation in nickel-base superalloy. The melting process comprises the following steps: high-melting-point metal W, Re, Ta, Mo, Nb and Ru in raw materials needed by melting the nickel-base superalloy are replaced by intermediate alloy, and the intermediate alloy uses Ni as matrix; the total quantity of the high-melting-point metal is 20-70 percent of the total quantity of the intermediate alloy, he total quantity of impurity elements is less than or equal to 0.5 percent of the total quantity of the intermediate alloy; the rest low-melting-point metal Ni, Co, Cr and Al is added in a form of pure metal with the purity being 99.95 percent; through vacuum induction melting, the materials are distributed in a crucible in order before melting, and part of Ni blocks, all Al blocks, Co blocks and Cr blocks, the rest Ni block, multi-component intermediate alloy cast ingots without W and Ni-W alloy blocks are added in order. The melting process can avoid low-melting-point metal spattering and insufficient melting of the high-melting-point intermediate alloy, reduces the burning loss of low-melting-point metal, ensures the accurate control of chemical components of cast ingots, and effectively reduces the element segregation.

Description

technical field [0001] The invention relates to the technical field of alloy smelting, in particular to a smelting process for reducing element segregation in nickel-based superalloys. Background technique [0002] Nickel-based superalloys are widely used in the manufacture of aero-engine high-pressure turbine blades and ground gas turbine blades due to their high temperature-bearing capacity and good high-temperature performance. [0003] Nickel-based superalloy is a multi-element alloy containing not only high melting point refractory elements such as W, Re, Ta, Mo, Ru, but also low melting point active metals such as Al and Ti. Whether the high-melting-point metal can be evenly distributed and completely dissolved in the alloy matrix and the control of the volatilization and burning loss of the low-melting-point metal are the keys to smelting superalloy master alloys. The smelting process is very difficult and complicated. [0004] At present, when smelting high-temperat...

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Problems solved by technology

This method has the following problems: (1) The melting point of refractory metals (such as W melting point 3430 ° C, Re melting point 3180 ° C, Ta melting point 2996 ° C) is much higher than the melting point of Ni (Ni melting point 1453 ° C), and the vacuum induction melting furnace The maximum operating temperature is 1600~1700°C. Even if the bottom of the crucible is overheated, the melting point of the refractory metal cannot be reached. The refractory elements cannot be completely melted during the smelting process, resulting in metal inclusions; (2) The density of refractory metals is relatively high (Re density 21.04g / cm 3 , W density 19.35g / cm 3 , Ta's density is 16.65g / cm 3 ), during the smelting process, it is easy to sink to the bottom of the crucible, which weakens the effect of electromagnetic stirring; (3) The low melting point metal (Al melting point 660°C) melts prematurely, and the density (Al density 2.70g / cm 3 ) is small, the melting process floats on the surface of the molten metal, and the volatilization and burning loss is serious; (4) In order to fully melt the refractory elements, it is necessary to increase the heating power and prolong the heating time, which will greatly reduce the service life of the crucible, and the crucible is easy to melt at high temperatures. break down, thereby introducing impurities

The above shortcomings will cause problems such as uneven composition of the superalloy base metal, serious inclusions of refractory metals, serious volatilization of low-melting point metals, and large deviations between the actual composition of the alloy and the expected one, which seriously restricts the subsequent use of the alloy.

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