浸入式水口对结晶器钢水流动与液面波动的影响

以国内某钢厂220 mm×1800 mm板坯连铸结晶器为原型,根据相似性原理建立相似比为0.6的水模型,利用粒子图像测速技术(PIV)对比不同浸入式水口(SEN)的出口角度、浸入深度及水口底部结构条件下的结晶器内流场流速特征,同时使用波高仪对液面波动振幅进行实时监测,并结合F数分析各SEN条件对结晶器内钢液流动特征.研究发现,在各浸入式水口条件下,位于结晶器液面1/4宽面处附近出现矢量流速向下的剪切流,同时在水口附近发现不规则漩涡.试验结果表明:浸入式水口的出口角度、浸入深度的增加能够强化上回旋区缓冲作用,降低结晶器液面表面流速;尽管凹底结构SEN能减弱钢液湍动能,但其对1/4宽面处剪切流速度的影响不大.另外,液面波动幅度和F数变化规律一致,且当浸入式水口出口角度15°、20°,浸入深度135 mm、145 mm条件下波幅与F数最为合理,从而减小或避免液面卷渣,提高连铸坯质量.

Effect of SEN on fluid flow and surface fluctuation in a continuous casting slab mold

The fluid flow pattern and free surface fluctuation in a mold profoundly influence both molten steel solidification and molten slag thermodynamics behavior in the continuous casting process. In addition, the fluid flow and surface fluctuation behaviors are important factors of inclusions floatation, meniscus hook formation, and shear layer instability that affect the slab quality. In this work, a 0.6-scale water model of slab mold was built according to a 220 mm×1800 mm actual mold from a Chinese steel plant to investigate the fluid field and free surface fluctuation during the continuous casting process. The characters of fluid flow were studied with particle image velocimetry (PIV) in different submerged entry nozzle (SEN) conditions, including SEN outlet angle, SEN bottom structure, and SEN submerged depth. Simultaneously, the fluctuation behaviors of the mold free surface were monitored using wave-amplitude sensors and analyzed using the F value. The findings show that there are shear flow with tilt down velocity vectors appearing near the one-fourth wide face position of the mold free surface, and some irregular vortexes are detected near the SEN position. In addition, the results show that increasing the SEN outlet angle and submerged depth can expend the up-recirculation flow domain and intensify its buffer action; therefore, the velocity of mold liquid surface decreases. However, changing the SEN bottom structure has negligible effect on fluid flow velocity at the position of one-fourth wide face of the mold free surface, although it can reduce the turbulent kinetic energy of the steel jet. Besides, the variation of surface fluctuate amplitude corresponds to the F value well, and the optimal F, which helps to reduce and avoid the possibility of mold slag entrapment can be obtained in the conditions of SEN outlet angles of 15° and 20° and submerged depths of 135 and 145 mm, respectively.