脱氧顺序对铝钛复合夹杂物的影响

 通过扫描电镜-能谱仪检测和分析了不同铝钛脱氧顺序下钢中夹杂物的形貌、成分、尺寸、数量和分布等参数,通过热力学计算分析了脱氧过程中钢液中的化学反应和夹杂物优势区图。结果表明,脱氧剂添加顺序对夹杂物形貌影响很大,先加钛后加铝的脱氧方式下,钢液中形成了较多含有铁相(“空心”)的具有浓度梯度的铝钛复合夹杂物。夹杂物径向长度增加,夹杂物也更容易偏聚。所以先加钛后加铝不利于夹杂物尺寸细小化,不利于夹杂物弥散分布。先加铝后加钛的脱氧方式下,钢中形成氧化铝夹杂,不会被溶解的钛还原,因此夹杂物内部不含有铁相。夹杂物主要为Al-Ti-O(-N)类夹杂。夹杂物尺寸和数量小于先加钛后加铝钢中的夹杂物。通过FactSage计算结果、化学反应分析和试验检测结果,探究了不同铝钛脱氧顺序下夹杂物形成和演变机理,分析了具有浓度梯度的“空心结构”的铝钛复合夹杂物形成机理,讨论了脱氧剂添加顺序对夹杂物尺寸、数量和分布等特征的影响规律。发现先加钛后加铝的脱氧方式下,钛氧化物会与金属铝反应,钛氧化物逐渐转变为“空心”氧化铝壳,同时溶解的铝、钛和氧发生氧化反应,形成了具有浓度梯度的Al₂O₃-TiO_x复合夹杂物,最终钛氧化物完全转变为氧化铝壳而消失。随着铁液的填充,形成了含有铁相的铝钛夹杂物。

Effect of order of deoxidant addition on Al-Ti composite inclusions

Parameters such as morphology, composition, size, quantity and distribution of inclusions in steel with different order of Al-Ti deoxidation addition were detected and analyzed by SEM-EDS. Chemical reactions in liquid steel in the deoxidation process were analyzed and the predominance diagram of inclusion was obtained by thermodynamic calculation. The results indicate the order of deoxidant addition had a great influence on the morphology of inclusions. When Ti was added prior to Al, many Al-Ti composite inclusions containing Fe phase with concentration gradient ("hollow”) formed in the liquid steel. The radial length of inclusions increases, and inclusions are more likely to be partial. So this deoxidation method is not conducive to refining and dispersing inclusions. When Al was added prior to Ti, alumina is formed in the steel, which will not be reduced by dissolved titanium, so the inclusion does not contain iron phase inside. The inclusions are mainly Al-Ti-O (-N) inclusions. The size and quantity of inclusions are less than Ti was added prior to Al.The formation and evolution mechanism of inclusions under different Al-Ti deoxidation order and the formation mechanism of Al-Ti composite inclusions with "hollow structure" with concentration gradient was explored and analyzed based on the results of FactSage calculation, chemical reaction analysis, and experimental detection. The effect of the addition order of deoxidizer on the size, number and distribution of inclusions was discussed. It is found that under the deoxygenation mode of adding titanium first and then aluminum, titanium oxides will react with aluminum metal, titanium oxides will gradually change into "hollow" alumina shell, while dissolved aluminum, titanium and oxygen oxidation reaction, forming a concentration gradient of Al₂O₃-TiO_x complex inclusions, and finally titanium oxide completely converted into alumina shell and disappear. With the filling of iron liquid, an aluminum titanium inclusion containing iron phase is formed.