浸入式水口对82B钢方坯渣沟缺陷的影响

Effect of SEN structure on slag-scratch defect of 82B strand surface during continuous casting

为了解决82B钢连铸坯表面出现渣沟的问题,以提高钢渣界面温度、改善保护渣的熔化与润滑效果为出发点,对连铸现场180mm×180mm小方坯结晶器建立三维数学模型,对比施加电磁搅拌工艺不同直通型浸入式水口下结晶器内流场和温度场分布。计算结果表明,当水口内/外径由40/100mm变为30/70mm后,水口两侧流速大于0.15m/s的流场区域扩大,水平截面环流最大流速由0.44m/s降低至0.42m/s,这表明流股对四周壁面的冲刷作用减弱;钢液面最大流速由0.12m/s增大至0.15m/s,高温区域范围扩大。综合效果显示,水口内外径减小对结晶器内的流场影响较小,钢渣界面附近钢液温度提高。现场试验统计表明,水口内外径减小后,保护渣消耗量由吨钢0.189kg提高到0.228kg,钢液面处保护渣的熔化良好,润滑效果得到了改善。配合保护渣优化等措施,铸坯表面渣沟发生率明显下降,由改进前的40%~50%降低到改进后的1%以内。

To solve the problem of slag-scratch defect on the surface of the 82B steel strand,a three-dimensional mathematical model of 180 mm×180 mm billet mold was built in the light of a continuous casting site.The study was based on the thought of increasing the temperature on the steel-slag interface and improving the melting and lubrication of mold slag.Under the use of mold electromagnetic stirring(M-EMS)process,the distribution of flow field and temperature in mold were compared with different straight bore type submerged entry nozzle.The results showed that,as the SEN internal-external diameter changed from 40/100 mm to 30/70 mm,the flow field zone with speed bigger than 0.15 m/s was enlarged near both sides of SEN,the impact of flow on the wall was weakened as the maximum speed on the horizontal section circumfluence decreased from 0.44 m/s to 0.42 m/s,and the maximum speed of molten steel on the mold surface increased from 0.12 m/s to 0.15 m/s,the area with high temperature was expanded.Comprehensive effects indicated that with the decrease of the inner-outer diameter of SEN,the temperature of molten steel near the slag-steel interface increased while the flow field in the mold has a relatively small impact.According to the field measured data,after decreasing the inner-outer diameter of SEN,the consumption of mold slag increased from 0.189 kg/t to 0.228 kg/t and the occurrence of slag-scratch defect on billet surface decreased obviously.It indicated that the slag melting at the molten steel surface was good and the lubrication effect was improved.The mathematical model can provide a good guide for optimizing the production process.