321不锈钢小方坯浸入式水口堵塞研究

通过观测水口结瘤物的结构和成分的变化,对AISI 321不锈钢小方坯浸入式水口的堵塞机理进行了研究。水口的解剖结果表明水口结瘤物主要由TiN、金属相以及渣相组成。通过计算建立了钢液及凝固过程中TiN的热力学模型。研究发现,TiO2过渡层的存在、较高的钛氮浓度积、不佳的钢水洁净度是导致结瘤物形成的主要原因。因此堵塞机理可以表述为,首先浇注过程中钢液中的[ Ti]与耐火材料中的SiO2进行反应,TiO2过渡层会在浸入式水口内壁形成；钛氧化物的良好传热性能造成钢液温度下降进而导致TiN结瘤物的形成,且不佳的钢水洁净度则会进一步恶化钢水的可浇性；随着结瘤物的不断增长,最终导致水口堵塞。

Research on submerged entry nozzles clogging during AISI 321 stainless steel billet casting

The mechanism of submerged entry nozzles ( SEN) clogging with AISI 321 stainless steel billet was investigated by an-alyzing the structure and composition of the SEN deposits. The results of deposits dissection indicate that nozzle clogs consist of TiN, metal and slag. Then the thermodynamic model of TiN in the steel and solidification was established. The results show that the exist-ence of TiO2 transition layer, high concentration product of titanium and nitrogen, and worse cleanness of the liquid steel have roles to play in the formation of deposits. Therefore the mechanism of clogging can be explained as follows. At first, a transition layer of TiO2 forms at the SEN refractory because of the reaction of [ Ti] with the silicates in the SEN refractory during casting. Subsequently the good heat transfer properties of titanium oxide layer can cause a large drop in temperature of molten steel which makes it possible for the formation of the TiN deposits, additionally low cleanness deteriorates the cast-ability of molten steel. In the end, the growth of the deposits leads to the nozzle clogging.