Fundamental study to develop process for producing ultra clean steel with confocal scanning laser microscope (In-situ observation and analysis of agglomeration and removal of non-metallic inclusions in metal melts)

利用激光共聚焦显微镜结合红外热像炉，对钢水表面各种非金属夹杂物颗粒的行为进行了“原位”研究。Al_2O_3与富Al_2O_3固体夹杂物颗粒之间存在着长距离的强相互吸引，并观察到Al_2O_3团簇在钢水表面的碰撞、团聚和形成的详细顺序。这种引力大于10^~(-16)N，对于大于3微米的氧化铝颗粒，其吸力可达10微米以上，对促进颗粒间的碰撞形成中间集合体、中间集合体之间形成疏松的氧化铝团簇以及致密化疏松的氧化铝团簇起到重要的作用。这一力不受钢液中表面活性剂硫的存在的影响。分析了这种长程强吸引的原因是钢液表面氧化铝颗粒周围的毛细效应所致。CaO-Al_2O_3和CaO-Al_2O_3-SiO_2固体夹杂物颗粒快速团聚形成团簇，更容易致密变形为块状固体夹杂物颗粒。研究还发现，对于不同的颗粒，吸引力也在10^lt；-16；-10^&lt；-13&gt；N的范围内，并延伸到100um的距离。然而，液体CaO-Al_2O_3-SiO_2包裹体颗粒之间没有发现这种毛细吸引。即使两个液体粒子接触，也只是在接触一段时间后才发生合并。对于小于7um的小颗粒，液态CaO-Al_2O_3颗粒的合并更加困难，而对于大于24um的颗粒，则更容易合并。此外，还研究了非金属夹杂物与推进的钢晶熔体/固相界面的相互作用。清晰地观察到了熔体/固体界面对夹杂物的吞噬和推动作用，并针对不同的夹杂物种类确定了夹杂物的吞没判据。

The behavior of various non-metallic inclusion particles on molten steel surface was "in-situ" studied by using a confocal scanning laser microscope combined with an infrared image furnace. A long-range strong attraction between alumina and alumina-rich solid inclusion particles, and detailed sequence of the collision, agglomeration and formation of alumina clusters was observed on molten steel surface. This attraction force was found to be over 10^<-16>N,reach over 10mum for alumina particles larger than 3mum, and play an important role to promote collision between the particles to form intermediate aggregates, the same between the intermediate aggregates to form loose alumina cluster, and to densify the loose clusters into compact ones. This force was not influenced by the existence of surfactant sulfur in the steel melt. The origin of this long-range strong attraction was examined to be caused by capillary effect around alumina particles on molten steel surface. Solid CaO-Al_2O^3 and CaO-Al_2O_3-SiO_2 inclusion particles were subjected to quick agglomeration to form clusters which densified and deformed into massive solid inclusion particles much easier. The attraction was also found to be in the range of 10^<-16>-10^<-13>N for different particles and extended to a distance of up to 100mum. However, such capillary attraction was not at all found between liquid CaO-Al_2O_3-SiO_2 inclusion particles. Even when the two liquid particles came in touch, merger took place only after contacting for a while. The merger of liquid CaO-Al_2O_3 particles was even more difficult for small particles of less than 7mum, but easier for particles larger than 24mum. Furthermore, an interaction of non-metallic inclusions with advancing melt/solid interface of steel crystals was investigated. The engulfment and pushing of inclusions by the melt/solid interface were clearly observed, and criteria for the engulfment were determined for different inclusion species.