凝固末端螺旋电磁搅拌对大圆坯裂纹形成的影响  

Effect of final helical electromagnetic stirring on crack formation in large bloom

作　　者：吴红健 许长军[1] 雷冲 王涛 林辉杰 李静[1] WU Hongjian;XU Changjun;LEI Chong;WANG Tao;LIN Huijie;LI Jing(School of Materials and Metallurgy,University of Science and Technology Liaoning,Anshan 114000,Liaoning,China;Henan Zhongyuan Special Steel Equipment Manufacturing Co.,Ltd.,Jiyuan 459000,Henan,China)

机构地区：[1]辽宁科技大学材料与冶金学院,辽宁鞍山114000 [2]河南中原特钢装备制造有限公司,河南济源459000

出　　处：《中国冶金》2023年第11期72-80,共9页China Metallurgy

摘　　要：内部裂纹是特殊钢大圆坯常见缺陷之一。电磁搅拌是提高铸坯组织成分均匀性的常用技术手段,其中单绕组螺旋电磁搅拌器不仅结构简单、安装方便而且搅拌效果明显。为了探究凝固末端单绕组螺旋电磁搅拌(F-HEMS)对大圆坯内部钢液流动、凝固传热和裂纹形成的影响,采用试验和数值模拟方法进行研究,发现液相穴内钢液受电磁力作用,沿拉坯方向在电磁搅拌器高度范围内螺旋流动。F-HEMS使连铸坯内零塑性温度(TZD)至黏滞性温度(TLI)区间的温度梯度增大了31.56%~42.27%,使T_(ZD)-T_(LI)区间宽度减小了6.6 mm。受F-HEMS影响,糊状区内的液相分数降低。连铸坯内的温度、Von-Mises应力与弹性等效应变分布均呈层状分布。在应用F-HEMS后,连铸坯T_(ZD)-T_(LI)区间内的Von-Mises应力平均降低了0.11 MPa,弹性等效应变平均降低了0.02百分点。在数值模拟和试验的基础上,提出了一种开裂指数,以预测内部开裂风险。研究发现,应用F-HEMS时的开裂指数比未应用时的小0.158~0.280,证明F-HEMS有降低连铸坯裂纹形成概率的作用。然而,内部裂纹的形成受多种因素的影响,连铸过程中大圆坯的开裂预测仍需改进模拟方法并通过大量试验数据验证。F-HEMS影响连铸大圆坯内部的钢液流动和凝固传热,可降低内部裂纹的形成概率,本研究为工业生产提供了理论依据。Internal crack is one of the common defects for special steel bloom.Electromagnetic stirring is the common technical means to improve the uniformity of microstructure and composition of the bloom.The helical electromagnetic stirrer is not only simple in structure,convenient in installation,but also has obvious stirring effect.To investigate the effect of final helical electromagnetic stirring(F-HEMS)on the liquid steel flow,heat transfer and crack formation in large bloom,experiments and numerical simulations were carried out.It is found that the liquid steel in the liquid core is spirally flowing along the casting direction under the action of electromagnetic force,and the range is concentrated in the height range of the electromagnetic stirrer.The temperature gradient between zero ductility temperature and liquid impenetrable temperature(T_(ZD)-T_(LI))in continuous casting bloom is increased by 31.56%-42.27%and the T_(ZD)-T_(LI)zone width is decreased by 6.6 mm with F-HEMS.Under the influence of F-HEMS,the liquid fraction in the mushy zone decreases.The distributions of temperature,Von-Mises stress and elastic equivalent strain in continuous casting bloom are all stratified.After the application of F-HEMS,Von-Mises stress and elastic equivalent strain in T_(ZD)-T_(LI)zone of continuous casting bloom decrease by 0.11 MPa on average and 0.02 percent point on average,respectively.Based on numerical simulations and experiments,a cracking index formula is proposed to predict the internal cracking risk.It is found that the crack index when using F-HEMS is 0.158-0.280 smaller than when not using F-HEMS,which proves that F-HEMS can reduce the probability of crack formation in continuous casting bloom.However,the formation of internal cracks is affected by many factors,and the cracking prediction of large bloom in continuous casting process still needs to improve the simulation method and be proved by a large number of experimental data.F-HEMS affects liquid steel flow and heat transfer in continuous casting large bloom

关 键 词：连铸大圆坯 末端螺旋电磁搅拌 钢液流动 凝固传热 裂纹形成 

分 类 号：TF777[冶金工程—钢铁冶金]