水口类型对大方坯结晶器内钢水流动与凝固行为的影响

采用数值计算方法对比研究了直通式、4分径向以及新型4分切向水口对大方坯连铸结晶器内钢水流动与凝固行为的影响.结果表明,当前常用的直通式水口对坯壳无冲击,利于坯壳均匀生长,但钢水冲击深度大,易在弯月面处形成死区,不利于大方坯内部及表面质量的提高;改用4分水口浇铸时,结晶器宽、窄面冲击区附近都会出现不同程度的坯壳厚度零增长...

Flow Pattern and Solidification Behavior of Molten Steel in Bloom Casting Mold Under Different Types of Nozzles

In view of the heat transfer of liquid steel is closely related to molten flow pattern in mold, we set a coupled mathematical model including fluid flow, heat transfer and solidification in bloom mold region by using porosity method for the solidifying mushy zone. Based on this model, the effect of submerge entry nozzles(SEN) with three types of outlets including normal single straight, quad-furcated in radial direction and the present swirling flow inducing quad-furcated on the flow patterns , solidification behavior of molten steel in bloom casting mold area was investigated respectively. With straight single outlet SEN, the solidified shell increases gradually and uniformly along the withdraw direction without flow impingement on shell, but the impact depth of the molten steel is so large which will not be beneficial to improve strand quality. With the other quad-furcated nozzles, the impact depths have been obviously weakened but zero growth shell thickness regions have been observed to some degree near the impingement zones due to the jet from the outlets. While using the quad-furcated SEN with outlets at tangential direction, however, the jet impingement on shell can be weakened and the solidified shell distributes uniformly at the cross-section of the mold. Additionally, the liquid steel temperature is increased by 3.48 to 5.6℃ near the free surface, which will be beneficial to the dissipation of steel superheat and the melting of mould powder. The solidified shell thickness of wide and narrow faces can achieve about 6mm and 6.2mm near the impingement area, and will reach 20..1mm and 20.8mm respectively at the exit of mold, which will leave much allowance for the increase of bloom casting speed.