ons decompose in the liquid metal,the filtration efficiency will be limited.If all of the superalloys need to be filtrated is worthy of consideration.Work 7 reported "Fifteen-ton,VIM heats of wrought alloys of the turbine disk type (e. g.In-718)have been filtered.Some cleanliness improvement is observed.Ho- wever,effects on product are somewhat confouaded by secondary melting and conversion".Perhaps,it is related to the decomposition of inclusions.For removing oxide inclusions,especially in production of alloying steels,to adopt a good deoxidation method concerning with a low oxygen content dissoved is signi- ficant. 3.3 The Denitrification of Superalloys during the Spe:ial Melting Process During the primary melting (e.g.VIM)and secondary melting (e.g.VAR and ESR)processes,the nitrides and carbonitrides will rapidly decompose in the liquid metal at the melting temperature.The denitrification of superalloys occurs at the liquid metal/vacuum atmosphere interface relying on the reaction (I)for VIM and VAR processes or at the liquid metal/molten slag interface for ESR precess.No doubt,to increase the refining time at high temperature,select a suitable slag system will be beneficial to the denitrification.As the nitrogen diss)ving in the liquid metal will result in the precipitation of new inclusions during the solidification process,the control of solidification conditions must be significant for improving the superalloy cleanliness. 4 Conclusion The carbides,nitrides and carbonitrides in the original melals,even if the pure TiN powder added rapidly decomposed in the liquid metal at the superalloy melting temperaturc.The nitride type inclusions in the remelted metals are mai- nly precipitated froin s.lution during the solidification process.It is supposed that the control of slidification process is significant for improving cleanliness of superalloys. Based on the experimental results obtained,some comments on the technolo- gies relaled to the bchavior of inclusions during the special melting processes of superalloys can be given.As the inclusions decompose in the liquid metal and the new inclusions precipitate during solidification,the application arca of the EB-button test for the superalloy cleanliness evaluation and the filtration effici- ency of liquid metal will be limited.The removal mechanism of nitrides during the filtration process becomes comslex,if the nitrides can be removed. 508， 爪 一 “ 一 ， 从 ， · · 一 一 、 一 ， 、、 · 以 ， · ， 元 ， ， 。 气妞 卜 之 ， 丁 刀 · · 了 · ， 、 、 · 、 一 。 〔 ， · ， ， 一 · 、、 · 认 ， 一 ‘ 声口 主 ， ， 。 。 蛋 · 手 · 几 。 之 ， 一 〕 、 、 一 。 · 、 ， 。 、 一 于 、 、 一 、 ，少 、 。 一 一 、 〔 ， 一 几 、、 · 、 ， 一 。 、 、 、 一 、 。 〕 ， 一 、 一