超低碳钢连铸过程中Ti和P对水口结瘤的影响

浇注含Ti超低碳钢时,浸入式水口内产生结瘤,严重影响生产效率,同时对产品质量造成危害。根据企业生产的经验,随着超低碳钢中Ti和P含量的增加,水口结瘤的问题越来越严重。通过深入分析实际生产过程的试样和实验室研究,阐明浇注超低碳钢时Ti和P对水口结瘤的影响。分析了含Ti含P的超低碳钢水口结瘤物的成分,结果表明结瘤物的主要成分是氧化铝(>90%),Ti含量较少(0.58%～3.58%)。采用脉冲分布解析原子发射光谱法(OES-PDA)测得氧化夹杂物的大小随Ti含量的增加而变小。采用液滴法测定了溶质Ti和P对钢液/Al2O3体系的润湿性影响,结果表明Ti和P使体系接触角和钢液表面张力降低,其中Ti能够降低体系的接触角只是在其具有反应湿润性的情况下。研究表明Ti和P对产生结瘤的作用有显著区别:只要形成的表层界面具有润湿性,Ti就可以降低Al2O3夹杂物的大小,而氧化铝夹杂物颗粒越小,越容易结瘤。为了不产生结瘤就必须控制好Al脱氧的时间和Ti的加入时间。P可以增加Fe-Ti-P三元体系的润湿性是因为P可以增加Ti的活度,降低钢液的粘度。与Ti相比,P对产生结瘤的影响较小。

Investigating the influence of Ti and P on the clogging of ULC steels in the continuous casting process

In the casting of Ti-bearing ULC steels,clogging of the submerged entry nozzle(SEN) affects both the productivity of the caster and the quality of cast products.The plant experience shows a negative influence of increasing Ti and P contents on the clogging tendency of ULC steel grades.Analytical investigations on samples from the process and laboratory experiments have been carried out in order to gain a better understanding of the influence of Ti and P on the clogging phenomenon of ULC steel grades.After casting Ti and P alloyed ULC steels,the deposits from clogged SEN have been analysed.The results indicate that the particles consist mainly of alumina(wAl2O3>90%),while the Ti content makes up only a very small portion(0.58 %～3.58 %).An automated inclusion analysis by OES-PDA shows that the size of oxide inclusions decreases with increasing Ti content.The determination of the influence of Ti and P solutes on the wetting in the liquid Fe/Al2O3 system by the sessile drop method indicates that both elements lower the wetting angle and reduce the melt surface tension.Concerning Ti,the decrease of the wetting angle occurs only in the case of reactive wetting.The effects of Ti and P on clogging are found to be significantly different:Ti lowers the size of Al2O3 nclusions only if an interfacial wettable surface layer forms.Small alumina inclusions enhance the clogging proneness.The time between Al deoxidation and Ti addition is thus an essential process variable in order to prevent clogging.As for P,it increases the Ti activity if both solutes are added to the melt.Moreover,it lowers the melt viscosity,thus increasing the wettability in the Fe-Ti-P system.The negative effect of P on clogging is,therefore,less pronounced than that of Ti and presumably harder to influence.