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由直接平衡法研究了1575—1625℃铁液中钇的脱硫氧平衡,固体电解质定氧探头测定了熔池中的氧活度,低温无水电解液电解法测定了溶解状态的钇含量。实验测得钇在铁液中的脱硫氧常数与温度的关系:LgK_(Y_2O_2S)=-(79487)/T+28.03,钇的硫氧化物在铁液中的标准生成自由能与温度的关系:2[Y]+2[O]+[S]+Y_2O_2S(s)△G~0=-363650+128.24T(Cal/mole)=-1521520+536.55T(J/mole)。由热力学分析进一步计算得到:1600℃铁液中[Y]-[S]-[O]平衡立体图、a_O-a_S平衡图及钇的氧化物、硫化物和硫氧化物稳定形成的条件,为理论上预测夹杂物,生成的先后次序及类型提供了依据。并给出了铁液中钇加入量计算公式:[%Y]=(88.9/32)·([%O]+[%S]及控制夹杂物形态的计算公式:[%Y]/[%S]=2.78(1+[%O]/[%S])
The balance of desulfurization oxygen in yttrium from 1575-1625 ℃ was studied by the direct equilibrium method. The oxygen activity of molten bath was measured by solid electrolyte oxygen probe. The dissolved yttrium content was determined by low temperature nonaqueous electrolyte electrolysis method. The relationship between the temperature and the desulfurization oxygen constant of the yttrium in the molten iron is as follows: LgK_ (Y_2O_2S) = - (79487) /T_28.03. The relation between the standard free energy of formation of yttrium in molten iron and temperature: 2 [Y] +2 [O] + [S] + Y_2O_2S (s) ΔG ~ 0 = -363650 + 128.24T (Cal / mole) = -1521520 + 536.55T (J / mole). From the thermodynamic analysis, we further obtain the equilibrium diagrams of [Y] - [S] - [O] in the liquid iron at 1600 ℃, the equilibrium diagram of a_O-a_S and the stable formation of oxides, sulfides and sulfur oxides of yttrium. On the prediction of inclusions, the order and type of generation provided the basis. The calculation formula of the addition amount of yttrium in molten iron is given: [% Y] = (88.9 / 32) · (% O) + [% S] S] = 2.78 (1 + [% O] / [% S])