Thermodynamic study on effect of TiO2 addition on Al and Ti distribution during electroslag remelting of Incoloy825
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摘要: 为了研究低氟渣电渣重熔过程中电渣锭中元素的变化，以Incoloy825合金为研究对象，渣中添加不同含量的TiO2和脱氧剂，进行了四组电渣重熔试验；并基于离子分子共存理论、热力学理论和质量守恒定律建立Al、Ti含量控制的热力学模型。结果表明，随着渣中TiO2含量的增加，电渣锭中Ti含量增加，Al含量减少，这是由于铝钛的交换反应4Al+3TiO2=3Ti+2Al2O3控制的，Si和Mn元素含量变化不大。当TiO2含量不变时，Al、Ti元素的含量沿着电渣锭高度的方向上有不同程度的增加，Si、Mn元素的含量则均有所下降。当熔渣中
$ \mathrm{l}\mathrm{g}({a}_{{\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3}}^{2}/{a}_{\mathrm{T}\mathrm{i}{\mathrm{O}}_{2}}^{2}) $ 为−3.16时，结合Al脱氧剂的添加，可以得到Al、Ti含量均匀性较好的产品，试验结果很好地验证了热力学模型的准确性。-
关键词:
- Incoloy825合金 /
- 电渣重熔 /
- TiO2 /
- 热力学模型
Abstract: To investigate the variation of elements in ingots produced by electroslag remelting in low-fluorine slag system, based on Incoloy825 different contents of TiO2 and deoxidizer were added into slag to carry out four sets of electroslag remelting experiments. A thermodynamic model was established based on the Ions and Molecule coexistence Theory (IMCT), thermodynamics theory and the mass conservation law to control Al and Ti contents. It is found out that increasing TiO2 addition into the slag brings increasing Ti content and declined Al content in ingots, which is attributed to exchange reaction of 4Al+3TiO2=3Ti+2Al2O3, but slight changes of Si and Mn contents. When the TiO2 content remains constant, the Al and Ti contents increase along the height of ingots, while Si and Mn contents decrease. When the$ \mathrm{l}\mathrm{g}({a}_{{\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3}}^{2}/{a}_{\mathrm{T}\mathrm{i}{\mathrm{O}}_{2}}^{2}) $ in slag is at −3.16 in combination with addition of Al deoxidizer, the obtained product can achieve uniform Al and Ti distribution. The predicted model shows good agreement with experimental results.-
Key words:
- Incoloy825 /
- electroslag remelting /
- TiO2 /
- thermodynamic model
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图 3 电渣锭轴向上Al、Ti的质量分数
注：图中灰色区域表示合格合金成分范围,下同
Figure 3. Variation Al and Ti contents along the height of ingot
图 4 电渣锭轴向上Si、Mn含量的变化
Figure 4. Variation of Si and Mn contents along the height of ingot
图 5 Incoloy825合金中渣钢反应与温度的关系
Figure 5. Relationship between temperature and slag-steel reactions in Incoloy825
表 1 自耗电极主要化学成分
Table 1. Main chemical composition of consumable electrode
% C Mn Si P S Cr Mo Ni Cu Al Ti Fe 0.101 0.107 0.131 0.009 0.009 20.620 3.180 38.880 1.660 0.120 1.000 33.740 
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表 2 预熔渣成分
Table 2. Chemical component of premelting slag
% 编号 CaF2 CaO Al2O3 MgO TiO2 FeO SiO2 MnO S1 18.60 35.59 36.81 1.51 3.47 1.15 2.44 0.43 S2 18.15 33.51 35.85 1.61 7.04 1.16 2.26 0.42 S3 18.09 30.75 33.53 1.47 11.84 1.27 2.65 0.40 注：S4渣是在S3渣系基础上加入50 g的Al脱氧剂。
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表 3 电渣锭轴向上渣含量的变化
Table 3. Variation of slag content along the height of ingot
% 高度/mm Al2O3 TiO2 SiO2 MnO S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4 S1 S2 S3 S4 25 31.57 31.89 29.94 30.45 6.03 8.69 14.03 12.56 0.39 0.49 0.46 0.45 0.011 0.011 0.012 0.013 85 31.26 30.66 29.20 30.56 5.79 8.12 13.79 12.49 0.42 0.43 0.50 0.51 0.013 0.012 0.014 0.012 145 31.00 30.09 29.00 31.02 5.66 8.19 13.56 12.46 0.47 0.45 0.51 0.53 0.014 0.012 0.013 0.012 205 31.09 30.16 29.35 31.12 5.63 8.04 13.34 12.52 0.48 0.46 0.53 0.53 0.02 0.011 0.012 0.013
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表 4 熔渣中可能存在的粒子结构，标准生成吉布斯自由能及作用浓度
Table 4. Possible units in slag and itsstandard Gibbs free energy of formation and action concentration
粒子类型 结构 编号 ${\Delta _r}G_i^\theta /({\text{J} } \cdot {\text{mo} }{ {\text{l} }^{ - 1} })$ Ni与Ki关系 质量作用浓度 简单离子 Ca2++O2− 1 ${N_1} = \dfrac{{2{n_1}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm CaO}}$ Mg2++O2− 2 ${N_2} = \dfrac{{2{n_2}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm MgO}}$ Fe2++O2− 3 ${N_3} = \dfrac{{2{n_3}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm FeO}}$ Mn2++O2− 4 ${N_4} = \dfrac{{2{n_4}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm MnO}}$ Ca2++2F− 5 ${N_5} = \dfrac{{3{n_5}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm Ca{F_2}}}$ 简单分子 SiO2 6 ${N_6} = \dfrac{{{n_6}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm Si{O_2}}}$ Al2O3 7 ${N_7} = \dfrac{{{n_7}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm A{l_2}{O_3}}}$ TiO2 8 ${N_8} = \dfrac{{{n_8}}}{{\displaystyle\sum {{n_i}} }} = {N_{\rm Ti{O_2}}}$ 复杂分子 3CaO·SiO2 c1 −118826−6.694T ${N_{c1}} = K_{c1}^\theta N_1^3{N_6}$ $ {N}_{c1}=\dfrac{{n}_{c1}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm 3CaO·Si{O}_{2}} $ 3CaO·2SiO2 c2 −236814+9.623T ${N_{c2}} = K_{c2}^\theta N_1^3 N_6^2$ $ {N}_{c2}=\dfrac{{n}_{c2}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm 3 CaO·2 Si{O}_{2}} $ 2CaO·SiO2 c3 −102090−24.267T ${N_{c3}} = K_{c3}^\theta N_1^2{N_6}$ $ {N}_{c3}=\dfrac{{n}_{c3}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm 2 CaO·Si{O}_{2}} $ CaO·SiO2 c4 −21757−36.819T ${N_{c4}} = K_{c4}^\theta {N_1}{N_6}$ $ {N}_{c4}=\dfrac{{n}_{c4}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm CaO·Si{O}_{2}} $ … … … … … 11CaO·7Al2O3·CaF2 c39 −228760−155.8T $ {N_{c{\text{39}}}} = K_{c{\text{39}}}^\theta N_{\text{1}}^{{\text{11}}}N_{\text{7}}^{\text{7}}{N_{\text{5}}} $ $ {N}_{c39}=\dfrac{{n}_{c39}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm 11 CaO·7 A{l}_{2}{O}_{3}·Ca{F}_{2}} $ 3CaO·2SiO2·CaF2 c40 −255180−8.20T $ {N_{c{\text{40}}}} = K_{c{\text{40}}}^\theta N_{\text{1}}^{\text{3}}N_{\text{6}}^{\text{2}}{N_{\text{5}}} $ $ {N}_{c40}=\dfrac{{n}_{c40}}{{\displaystyle \sum {n}_{i}}}={N}_{\rm 3 CaO·2 Si{O}_{2}·Ca{F}_{2}} $
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表 5 文中使用的活度相互作用系数
$e_i^j$ Table 5. Activity interaction coefficient
$ {e}_{i}^{j} $ used in this study
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表 6 Al和Ti含量预测值
Table 6. Prediction Al and Ti contents by developed model
% 渣系 Al预测值 Ti预测值 S1 0.50 0.19 S2 0.32 0.38 S3&S4 0.18 0.84
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