注流方式对大方坯连铸结晶器内钢水流动与温度状态影响
Effects of injection modes on the flow pattern and temperature distribution of molten steel in a bloom casting mould
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摘要: 依据改变水口侧孔射流方向来控制结晶器内钢流流动状态的思想,设计了一种大方坯连铸结晶器新型四分切向水口.对不同类型水口(直通式、四分径向以及四分切向水口)浇注条件下大方坯连铸结晶器内钢水流动形态和温度分布状况进行了流体动力学比较研究.结果表明,新型四分切向水口不仅可以使结晶器内钢水形成上、下两个回流,并能够产生较强的水平旋流.该水平旋流能降低钢水的冲击深度,抑制钢液面波动,促进夹杂物上浮,还具有促进钢水过热耗散的效果.与四分径向水口相比,新型四分切向水口能减弱射流对初生坯壳的冲击,均匀横截面坯壳厚度.此外,该旋流状态使热中心上移,自由液面附近钢水的温度可提高2~6℃,改善化渣条件.Abstract: Based on an idea that the flow pattern of molten steel in a mold can be controlled by changing the direction of jet from the outlets of a submerged entry nozzle (SEN),a new type of quad-furcated SEN with outlets in tangential direction was designed for bloom casting.The flow patterns and temperature distributions of molten steel in the mold were computed by hydrodynamic models under the conditions of single straight SENs,quad-furcated SENs with outlets in radial direction,and quad-furcated SENs with outlets in tangential direction.For the latter,a strong horizontal swirling flow has been observed along with the upper and lower back flows in the mold.The horizontal swirling flow pattern in the mold can not only reduce the impingement depth of molten steel,inhibit liquid level fluctuation and accelerate inclusion floatation,but also be beneficial to dissipation of steel superheat.Compared to quad-furcated SENs with outlets in radial direction,the jet impingement on the initial shell can be obviously reduced and the cross-section solidified shell distributes uniformly in the mold.Additionally,the horizontal swirling flow pattern moves the hot spot upward in the mold and leads to a 2 to 6 ℃ temperature rise of molten steel around the free surface,which is beneficial to quick melting of mould powder.