品种钢连铸生产实践

邢钢引进奥钢联(VAI)技术建成的品种钢连铸机于2002年12投产。该铸机采用了结晶器电磁搅拌、液面自动控制、DYNAFLEX非正弦液压振动、DIAMOLD钻石结晶铜管、连续矫直等先进技术。在试生产阶段成功生产出冷镦钢、钢绞线、焊丝钢，取得了良好的生产和质量指标。     

Electromagnetic torque detecting for optimization of in-mould electromagnetic stirring in the billet and bloom continuous casting

ABSTRACT

In this paper, an electromagnetic torque device based on the theoretical model was established to determine the optimum frequency accurately and conveniently in billet and bloom continuous casting with in-mould electromagnetic stirring (M-EMS). Magnetic characteristics with M-EMS was investigated by numerical simulation and physical experiment with the application of electromagnetic torque device and gauss meter. In addition, the effects of stirring frequency with M-EMS on macro segregation and equiaxed crystal ratio were compared and analysed for 55SiCr with 150?mm?×?150?mm billet caster and BU with 310?×?360?mm bloom caster by a series of plant trials, respectively. The results showed that maximum magnetic flux density and maximum electromagnetic torque occurred with different frequency and same current in M-EMS, and central equiaxed crystal ratio and macro segregation has been significantly improved by optimum frequency with M-EMS.     

Mathematical modelling of inclusion motion and entrapment in billet mould with effect of electromagnetic stirring

ABSTRACT

In-mould electromagnetic stirring (M-EMS) is a widely used technique during continuously casting (CC). To investigate the M-EMS effect on the inclusion motion and entrapment in a billet CC mould, a coupling mathematical model was developed. The result indicates that the M-EMS changes molten steel flow pattern and transient inclusion distributions in the mould. Inclusions have a tendency to move close to the mould centre under M-EMS. When the M-EMS is off, the distributions of inclusions in the solidified shell is relatively uniform. When the M-EMS is applied, many inclusions are entrapped near the stirrer mid-plane. Furthermore, distances of captured inclusions below the billet surface become larger. Additionally, the M-EMS has a significant effect on the overall removal fraction of inclusions. At last, detection of inclusions in samples obtained from a plant has been performed. A similar tendency can be found between the predicted and experimental results.     

枝晶腐蚀低倍检验技术在连铸生产中的应用

简述了枝晶腐蚀低倍检验技术在连铸生产中的应用。结果表明,枝晶腐蚀低倍检验方法不仅能够非常清晰地显示连铸坯中的缺陷和铸坯凝固组织全貌,而且提供了优化工艺和提高钢材质量的有效途径。同时,在此次检验中,采用砂带磨削代替砂轮磨削可大幅度缩短制样的时间并提高制样的质量。     

重轨钢连铸坯内部质量控制技术

针对攀钢大方坯连铸机投产初期重轨钢连铸坯中心疏松、中心偏析等内部缺陷较严重的问题,研究应用了提高重轨钢连铸坯内部质量的控制技术,包括凝固末端动态轻压下、结晶器电磁搅拌、二冷动态控制、连铸拉速与钢水温度优化控制等核心工艺技术.生产实践表明,重轨钢连铸坯综合合格率达到99.97%,铸坯中心疏松≤1.0级,中心偏析≤1.0级,中心缩孔≤1.0级,中心裂纹≤0.5级,中间裂纹≤0.5级,角部内裂≤0.5级,中心碳偏析指数≤1.05,由连铸坯轧成重轨的内部质量和力学性能满足时速350 km高速铁路用钢轨的要求.     

Effect of in-mould electromagnetic stirring on the flow,initial solidification and level fluctuation in a slab mould: a numerical simulation study

In-mould electromagnetic stirring (M-EMS) is a widely used technique during slab continuous casting. To investigate the effect of M-EMS on the flow and initial solidification in a slab mould, a three-dimensional model coupling electromagnetic field, flow and solidification was developed. To track the steel/slag interface, the volume of fraction (VOF) model was coupled in the model. The electromagnetic force presents a centrally symmetrical distribution on the cross-section. The influences of stirring current and stirrer position on flow, initial solidification and level fluctuation have been discussed. M-EMS enhances the transversal flow and shrinks the lower recirculation in mould. The results indicate that both a higher stirring current and a lower stirrer position produce a reduction of the temperature in the mould centre. Furthermore, a higher stirrer position and a lower stirring current are favourable to the solidified shell growth. However, M-EMS aggravates the level fluctuation, which may lead to slag entrainment.     

连铸机电磁搅拌参数的优化

研究了结晶器电磁搅拌强度及扭矩大小对铸坯质量的影响。结果表明,将高碳钢的搅拌扭矩值控制在200 cm.cN、中碳钢控制在150 cm.cN左右,其铸坯的中心碳偏析、疏松及缩孔等缺陷得到明显改善。通过定期测量电磁搅拌扭矩值,及时发现和处理电磁搅拌线圈使用后期电磁力不足问题,避免了因电磁搅拌效果不良造成的产品质量问题,提出了不同钢种、断面的最佳电磁搅拌工艺参数,改善了铸坯质量,降低了电磁搅拌成本。     

结晶器电磁搅拌在方坯的应用

对结晶器电磁搅拌(M-EMS)在邯钢8机8流方坯连铸机使用情况和效果进行了分析和研究,M-EMS能够提高连铸方坯表面质量和内部质量,改善连铸坯中心疏松、缩孔和中心偏析以及减少角裂漏钢;同时对方坯应用M-EMS过程中存在的钢水过热度过高、电磁搅拌线圈漏水和浸入式水口渣线恶化等问题,提出了相应的改进措施。     

结晶器电磁搅拌对矩形坯轧制大规格齿轮钢圆钢碳偏析行为的影响

通过对齿轮钢矩形坯轧制大规格圆钢宏观碳偏析的分析,结合碳含量和低倍组织,研究了不同结晶器电磁搅拌强度时圆钢的碳偏析行为。结果表明,结晶器电磁搅拌扩大连铸坯柱状晶/等轴晶转换界面(CET)框尺寸,提高等轴晶率,但是产生皮下负偏析带,圆钢的偏析变得明显;结晶器电磁搅拌下,齿轮钢矩形坯与圆钢从表面到中心呈现"N"形碳偏析,搅拌强度越大,偏析幅度越大;圆钢同一圆周上,搅拌时3/4 R、1/2 R处极差大,1/4 R处极差小,不搅拌时则相反。连铸坯的CET区域与圆钢方框偏析有严格的对应性,说明连铸坯与圆钢的组织与成分存在传承关系。