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Removal of inclusion through fine bubble and bubble-curtain by imparting swirling flow in immersion nozzle

通过在浸入式喷嘴中施加旋流，通过微细气泡和气泡幕去除夹杂物

基本信息

批准号：
10650737
负责人：
YOKOYA Shinichiro
金额：
$ 1.73万
依托单位：
Nippon Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Both with water model experiment and numerical analysis, following swirling effect in the immersion nozzle are cleared as follows :Uniform velocity distribution can be obtained within a very short distance from the outlet of the nozzle and remarkable stable bulk mold flow can be easily obtained.Therefore, a decrease in the meniscus flow velocity, remarkable decrease in the amplitude of oscillation, disappearance of vortex and suppression of disturbance, i.e., considerably stable meniscus flow could be observed. Those phenomena contribute to prevent powder from being involved into the mold flow. With an increase in the centrifugal force induced by imparting a swirling motion in the liquid, fine bubbles were accelerated to produce, and obtained bubble sizes were from 1.5 to 6 mm in diameter, i.e., critical diameters of the bubbles were in a range of 1.5 to 2.5 mm. The penetrated volume efficiency of the bubbles increases with increasing the tangential velocity and injected air flow rate. The diameter of bubbles decreases with increasing the tangential velocity. Injection pressure for penetration of bubbles in the metal bath is much lower than that of conventional injection process by tuyeres and lances.A bubble curtain (namely, bubble accumulated zone) can be established from the wall to the central area of the submerged entry nozzle by imposing a swirling flow pattern in the nozzle and injecting gas bubbles from all around the wall of the submerged entry nozzle. The trajectory of an inclusion is spiral in shape, but its displacement in the radial direction is very little compared that of Ar bubble. Therefore, it may be sure for the inclusion to penetrate through the bubble curtain (namely, bubble accumulated zone) to be trapped by the bubbles and be removed together with the bubbles from the molten steel.It has been developed a twist-tape-swirling-blade as a cheap, simple and safe swirling generator, from above-mentioned issues.

通过水模实验和数值分析，明确了浸入式水口内的旋流效应：在离水口出口很近的距离内，可以获得均匀的速度分布，容易获得显著稳定的整体结晶器流动，从而降低了弯月面流速，显著减小了振荡幅度，消除了旋涡，抑制了扰动，即，可以观察到相当稳定的弯月面流动。这些现象有助于防止粉末卷入结晶器流动。随着通过在液体中施加涡旋运动而引起的离心力的增加，加速产生微细气泡，并且所获得的气泡尺寸为直径1.5至6 mm，即，气泡的临界直径在1.5 ~ 2.5 mm之间，气泡的穿透体积效率随切向速度和注入空气流量的增加而增加。气泡直径随切向速度的增大而减小。气泡在熔池中穿透的喷射压力远低于传统的风口和喷枪喷射，通过在浸入式水口内施加旋流流型，从水口壁的四周喷射气泡，可在水口壁面至中心区域形成气泡幕（即气泡聚集区）。夹杂物的运动轨迹呈螺旋形，但其径向位移与Ar气泡相比很小。针对上述问题，研制了一种廉价、简单、安全的扭带式旋流叶片。