The variation characteristics of inclusions for GH132 and GH36 are similar to those for GH169 and GH220. The results obtained demonstrated that the inclusions in the original metals decomposed during the formation period of liquid metal droplets at the electrode tip during the VAR and ESR processes and those in the remelted ingots were mainly precipitated from solution bearing nitrogen during the solidification pro- cess of the remelted metal pool. 3 Some Comments on the Technologies Related to the Behavior of Inclusions during the Special Melting Processes of Superalloys 3.1 The Superalloy Cleanliness Evaluation by the EB-Button Test In recent years,the EB-button test has been used for the quantitative eva- luation of the inclusions of superalloys in a number of US corporationsts.This test is considered as an effective method to evaluate the superalloy cleanliness. As well known,the EB-button test is based on the floatation of inclusions from within the melt to the melt surface (form a raft.In this case,the inclusions should not decompose in the melt and keep a certain shape and size during the EB-button test process.However,the experimental results mentioned above indicaled that the inclusions including carbides,nitrides and carbonitrides in superalloys were formed during the solidification prccess.The size of inclu- sions results from the solidification rate of metals. During the EB-button test process,the inclusions in superallcys will deco- mpose in the melt,then precipitate to form new inclusions.The newly forming inclusions during the solidification process cannot completly floate to the melt surface.The solidification rate of the raft is different from that of the metal tested.Thus,the content and size of inclusions in the floating raft cannot be expressive of the real content and size of inclusions in the metal tested. Based on this point of riew,perhaps we can explain why the oxide content in the Rene'95 raft is so low (much less than 1 ppmt61)and the oxygen content and nitrogen content in the button are less than those in the samplet51. 3.2 The Liquid Metal Filtration The liquid metal filtration has been publicized recently for removing inclu- sions from the melt.The mechanism of inclusion removal is the adsorption of inclusion particles on the filter surface.The key problem is that the inclusions must be solid particles at the filtration temperature.As the nitride type inclusi- 507， 」时 、 、 。 卜 丫 丫 卜 一 ， 一 、 ’ · · ， 一 ， 一 · ， ， 从 · · 。 呈 一 ， 。 ， 。 。 。 ， ， ， 〔 。 、 一