Effect of electroslag remelting on oxidation-prone elements of K4002 alloy
For the control of oxidizable elements Hf,Al,and Ti in electroslag remelting process of K4002 alloy,based on the seven-member slag system CaF2-CaO-Al2 O3-MgO-TiO2-HfO2 and combined theoretical and experimen-tal research,the effect of slag components change on oxidizable element content was investigated using thermody-namic model established by molecular and ion coexistence theory(IMCT).At the same time,the validity of the mod-el was verified by slag-metal equilibrium experiments.The results show that the variation of components in slag has no significant effect on the Ti content,but has a large effect on Hf and Al.Adding HfO2 to the slag can inhibit oxi-dative burnout of Hf,but exacerbate the oxidative burnout of Al.Increasing the temperature can inhibit the burnout of Hf,while decreasing the temperature can inhibit the burnout of Al.The ability of slag components to inhibit the oxidation and burning loss of Hf follows the order of HfO2＞SiO2＞TiO2＞MgO.When the mass fraction of CaO is not more than 30％,the ability to exacerbate the oxidation and burning loss of Hf is in the order of CaOAl2O3＞CaF2.However,when the mass fraction of CaO exceeds 30％,the ability to intensify the oxidation and burning loss of Hf shifts to Al2 O3＞CaF2＞CaO.As C/A increases,the equilibrium Hf content of alloy decreases and then in-creases and reaches a minimum at C/A=1.2.The optimal ratio of the main components that can effectively reduce the oxidation and burning loss of Hf,Al,and Ti elements during the electroslag remelting process of K4002 alloy is 10％-12％HfO2,20％-25％Al2O3,and 10％-15％CaO.In addition,the S mass fraction in the alloy is reduced from 22×10-6 to less than 7× 10-6,indicating that the designed slag system has strong S removal capability.Results provide certain theoret-ical basis for oxidation-prone elements and impurity elements control in process of electroslag remelting K4002 allov.
K4002 alloyelectroslag remeltingthermodynamic modelHf and Al element burning lossmolecular and ion coexistence theory
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