包晶钢连铸保护渣固渣膜粗糙度影响因素

在包晶钢板坯连铸过程中,保护渣固渣膜结构及其性能对减少铸坯表面纵裂起至关重要的作用。采用改进型水冷铜探头获取不同保护渣熔融温度、不同探头浸入时间下的固渣膜。同时采用接触测试、光学显微镜及SEM观察的方法检测、评价保护渣渣膜表面(与水冷铜壁接触面)的粗糙度,并揭示了该渣系条件下保护渣渣膜粗糙度的形成与渣膜结晶(液渣凝固结晶及固渣膜玻璃层中玻璃转变结晶)的关系。研究结果表明,保护渣渣膜粗糙度随凝固时间增长无明显变化。液渣温度对生成渣膜的粗糙度有较大影响,提高液渣温度能明显提高渣膜粗糙度。并且,渣膜表面粗糙度的形成与渣膜结晶过程无明显因果关系,而与渣膜凝固中于固渣膜表面形成的开放气孔有关。

包晶钢连铸保护渣固渣膜生长及成分偏析试验

保护渣渣膜的形态及性能对提高连铸坯质量及稳定连铸生产起着至关重要的作用。采用改进型水冷铜探头冷凝获取不同探头浸入时间下的包晶钢保护渣固渣膜,通过光学显微镜及SEM观察方法检测及评价保护渣渣膜的内部结构特性,并结合SEM-EDX检测了渣膜不同部位各主要成分的偏析情况,分析了渣膜凝固过程中凝固前沿元素的偏聚规律。研究结果表明,本渣系及试验条件下,保护渣渣膜主要晶体为枪晶石与三斜霞石;枪晶石凝固析晶过程中凝固前沿成分变化促进了三斜霞石等高熔点相在渣膜凝固前沿与枪晶石混合析出,使得固渣膜厚度迅速增加。

包晶钢连铸保护渣固渣膜凝固密度演变研究

连铸保护渣固渣膜凝固结构及演变对保护渣控制传热至关重要。选取生产现场应用的高碱度及超高碱度保护渣,使用小尺寸大宽厚比水冷铜探头获取了不同液渣温度及凝固时间下的渣膜,检测了不同条件下获得固渣膜的密度演变规律,并使用密度演变法评价了渣膜凝固生长的稳定性及渣膜凝固析晶规律。固渣膜密度演变结果与渣膜结构对应较好,使用密度法评价得到的固渣膜凝固稳定性与对应保护渣的现场使用状况符合。

Local corrosion mechanism of SiO2-based refractories caused by slag movement near solid–liquid–gas interface in different slag systems

Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO-SiO2 slag whose surface tension improves with SiO2 concentration, slag film flows up along four edges under axial Marangoni shear force and wettability. Then, it flows down along four lateral faces under gravity. Corrosion rate at edges is larger than that on lateral faces due to different SiO2 solubilities of ascending and descending flow. Prism cross section shape changes from square to round. For FetO-SiO2 slag whose surface tension reduces with the increase of SiO2 concentration, slag film flows up under the inflence of wettability. Then, it flows down under Marangoni shear force and gravity. Compared to four edges, slag is mainly up and down on four lateral faces due to larger surface tension and size. So, prism cross section shape keeps square.