EVOLVEMENT MECHANISM OF SURFACE OSCILLA- TION MARKS ON ROUND BILLET DURING SOFT-CONTACT ELECTROMAGNETIC CONTINUOUS CASTING
EVOLVEMENT MECHANISM OF SURFACE OSCILLA- TION MARKS ON ROUND BILLET DURING SOFT-CONTACT ELECTROMAGNETIC CONTINUOUS CASTING
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发表时间：
2009-04
影响因子：
2.3
通讯作者：
Xu Xiu-jie;Yu En-gang
中科院分区：
文献类型：
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作者：
Xu Xiu-jie;Yu En-gang
在钢铁工业中，连铸产品通常是在送入热轧机组前的预制件，这带来了高成本、高污染和低生产率。因此迫切需要一种新的技术来生产无表面缺陷的方坯和板坯。电磁铸造技术在铝铸件中用于改善表面质量的成功启发了冶金研究人员将这一新技术应用到钢的生产中。在实验室的立式连铸机上进行了高频磁场(26 KHz)的试验。碳素结构钢(0.20%C，研究了结晶器内磁场和弯月面形状的分布规律，并用实验结果解释了电磁铸造条件下结晶器初始凝固区出现的现象。结果表明，与无电磁铸造的圆坯相比，电磁铸造可以完全抑制结晶器内的振痕，使圆坯表面变得非常光滑。根据传统的结晶器结晶器内结晶器内磁场分布和弯月面形状的形成机理，采用电磁铸造技术可以使圆坯表面变得非常光滑。保护渣与钢液之间的相对运动在保护渣通道内产生的压力对金属膜的形成起着重要作用。在EMC保护下，由于高频磁场产生的焦耳热，保护渣通道变小，保护渣通道变宽。保护渣压力变小，使铸坯表面质量变好。但当保护渣超过最佳值时，初始凝固起点沿结晶器周长的分布呈波浪形分布。同时，当保护渣超过最佳值时，保护渣通道变宽。当保护渣超过最佳值时，保护渣沿结晶器周长的初始凝固开始点分布呈波浪形分布。同时，当保护渣超过最佳值时，保护渣通道变宽，使保护渣压力变小，使铸坯具有较好的表面质量。钢水自由面的起伏较大，形成了OM，圆坯表面波状OMS的形成是由于切缝中心和分段中心之间磁场的不均匀以及钢液液位的波动造成的。
In the steel industry,the continuous casting product is usually a pre-produt before being fed to hot rolling mill,which brings in high cost and pollution and low productivity.So a new technology is demanded urgently to produce surface defect free billets and slabs.The success of electromagnetic casting(EMC)technology utilized in aluminum casting to improve surface quality enlightens the metallurgical researchers to apply this novel technology into production of steel.An experiment using high frequency magnetic field(26 kHz)was carried out on a vertical type caster with a segmented copper mold in our laboratory.Carbon structural steel(0.20%C,mass fraction) was used as experimental material.A special power was used to provide high frequency current to an induction coil surrounding the segmented mold.Moreover,the distribution of magnetic field and meniscus shape of Sn-Pb-Bi alloy in the mold were investigated and used to explain the phenomena happened in the initial solidification area in the case of EMC.The result shows that oscillations marks(OMs)can be totally suppressed and the surface of round billets with EMC technology becomes extremely smooth compared to the billets without EMC technology when the output power comes to an optimal one.According to the conventional mechanism of OM formation,the pressure generated in the flux channel due to the relative movement between solid flux rim and molten steel pool plays an important role in the formation of OMs.In the case of EMC,the solid flux rim becomes smaller as temperatures of mold and liquid steel in the initial solidification area increase because of Joule heat generated by the high frequency magnetic field,and the flux channel turns wider as Lorentz force is imposed on the liquid steel.As a result,the flux pressure becomes smaller,which makes the billets have better surface quality.However,when the powder exceeds the optimal value,the distribution of initial solidification starting point along the mold perimeter behaves in a wavy pattern.Simultaneously,the free surface of molten steel fluctuates more greatly,resulting in formation of OMs.As a conclusion,the formations of wavy OMs on the round billet surface are resulted from non-homogeneity of magnetic field between slit center and segment center as well as fluctuation of liquid steel level.