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Journal of Iron and Steel Research(International) 2022年第1期29卷 124-131页

作者： Dong-bin Jiang Li-feng Zhang Ya-dong Wang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China State Key Lab of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao 066004HebeiChina

The effect of mold electromagnetic stirring(M-EMS)on the solidification structure and solute segregation in the continuous casting bloom of U78CrV steel is investigated.The solute distribution in the macroscale is analyzed using a carbon–sulfur analyzer and that in the microscale is measured with an electron probe microanalyzer.The Image-J software is applied to analyze the number density and area ratio of segregation spots.The results show that the segregation spots are mainly located in the columnar to equiaxed transition zone and the equiaxed zone,which are enriched with C,Cr,and Mn elements.With the M-EMS applied,the columnar grain inclines to the upstream side.As the current intensity increases,the deflecting angle of columnar grain rises,especially with the current intensity larger than 300 A.Besides,the center segregation shows a declining trend and the area fraction of the equiaxed zone rises clearly.Moreover,it is found that the area ratio and number density of segregation spots increase with the higher current intensity of M-EMS.

关键词： Solidification structure macrosegregation Mesosegregation Segregation spot Mold electromagnetic stirring

Multi-scale dendritic patterns sequentially superimposed in a primary semi-solid matrix

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Journal of Materials Science & Technology 2022年第12期107卷 26-33页

作者： Xiaoping Ma Dianzhong Li Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesWenhua Road No.72Shenyang 110016PR China

The principle and control for solidification present crucial challenges.Through in situ and real time observation on the solidification of M50 bearing steel,here we discovered that the base of conventional dendritic arms is constituted by a primary semi-solid matrix.Due to the superimposition of temperature fluctuations from the large to the subtle scale,multi-scale dendritic patterns will sequentially emerge and evolve in the primary semi-solid matrix.These findings redefine the essence of multi-scale dendrites as the multi-scale segregation patterns in the primary semi-solid matrix,reconstitute the time and space sequence in the formation of multi-scale dendrites,and reveal the superimposition of temperature fluctuation as the driving principle.These new understandings will fundamentally influence the solidification field.These results also indicate important engineering applications,such as designing multi-scale dendrites,controlling the dendritic segregation and eliminating the detrimental eutectics.

关键词： Solidification Dendrite Microstructures Microsegregation macrosegregation

Effects of correlative factors on the interdendritic melt flow brought by the bulge in continuous casting slabs

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Journal of University of Science and Technology Beijing 2008年第4期15卷 407-411页

作者： Shuying Chen Guowei Chang Jianzhong Wang Chunjing Wu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Materials and Chemical Engineering Liaoning Institute of Technology Jinzhou 121001 China

The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.

关键词： continuous casting two-phase region melt flow macrosegregation

Investigation of the solute transportation coupled with heat transfer and fluid flow during twin-roll strip casting process

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Acta Metallurgica Sinica(English Letters) 2009年第5期22卷 345-352页

作者： Yongsheng WANG Chenxi JI Jiongming ZHANG Xinhua WANG Wanjun WANG School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Shougang Group Beijing 100043 China Jiuquan Iron ＆ Steel （Group） Co. Ltd. Jiayuguan 735100 China

Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined with the formation mechanism of microstruoture in final as cast strip, analysis shows that solute enriched area is in the transitional area between columnar and equiaxed grain zone.

关键词： Twin-roll strip casting Solute field simulation macrosegregation

Rapid solidification and dendrite growth of ternary Fe-Sn-Ge and Cu-Pb-Ge monotectic alloys

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Science China(Physics,Mechanics & Astronomy) 2007年第4期50卷 491-499页

作者： ZHANG XueHua RUAN Ying WANG WeiLi WEI BingBo Department of Applied Physics Northwestern Polytechnical UniversityXi’an 710072China

The phase separation and dendrite growth characteristics of ternary Fe-43.9%Sn- 10%Ge and Cu-35.5%Pb-5%Ge monotectic alloys were studied systematically by the glass fluxing method under substantial undercooling conditions. The maximum undercoolings obtained in this work are 245 and 257 K, respectively, for these two alloys. All of the solidified samples exhibit serious macrosegregation, indicating that the homogenous alloy melt is separated into two liquid phases prior to rapid solidification. The solidification structures consist of four phases including α-Fe, (Sn), FeSn and FeSn2 in Fe-43.9%Sn-10%Ge ternary alloy, whereas only (Cu) and (Pb) solid solution phases in Cu-35.5%Pb-5%Ge alloy under different undercool- ings. In the process of rapid monotectic solidification, α-Fe and (Cu) phases grow in a dendritic mode, and the transition "dendrite→monotectic cell" happens when alloy undercoolings become sufficiently large. The dendrite growth velocities of α-Fe and (Cu) phases are found to increase with undercooling according to an exponential relation.

关键词： phase separation dendrite growth monotectic alloy undercooling macrosegregation

Structure and mechanical properties of AZ31 magnesium alloy billets by different hot-top semi-continuous casting technology

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Rare Metals 2011年第4期30卷 414-418页

作者： ZHANG Zhiqiang LE Qichi CUI Jianzhong The Key Laboratory of Electromagnetic Processing of Materials （Ministry of Education of China） Northeastern University Shenyang 110004 China

AZ31 alloy billets of 200 mm in diameter were produced by three different processes of conventional direct chill （DC） casting, low-frequency electromagnetic casting （LFEC） and low-frequency electromagnetic vibration casting （LFEVC）, respectively. The effect of LFEC and LFEVC on the microstructures, macmsegregation and mechanical properties of AZ31 alloy billets was investigated. In conventional DC casting, the AZ31 alloy billets exhibited coarse grains （about 370 μa） and severe segregation of A1 and Zn. In the presence of a solo low-frequency alternating magnetic field or a low-frequency electromagnetic vibration field applied during DC casting of Ф200 mm AZ31 billets, grains in the AZ31 alloy billets were effectively reffmed （about 210 μa） and the macrosegregation of A1 and Zn in the billets was greatly decreased. Furthermore, the tensile strength, fracture elongation and hardness of the as-cast AZ31 alloy billets were improved by the processes of LFEC and LFEVC relative to that cast by the process of conventional DC casting.

关键词： magnesium alloys electromagnetic field microstructure macrosegregation mechanical properties casting

Columnar to Equiaxed Transition During Solidification of Small Ingot by Using Electric Current Pulse

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Journal of Iron and Steel Research(International) 2009年第6期16卷 7-12页

作者： LI Jie MA Jian-hong SONG Chang-jiang LI Zhi-jun GAO Yu-lai ZHAI Qi-jie Shanghai Key Laboratory of Modern Metallurgy and Materials Processing Shanghai University Shanghai 200072 China

A new approach to applying the electric current pulse （ECP） with parallel electrodes to the promotion of the transition from columnar crystal to equiaxed crystal and the improvement of macrosegregation was introduced. The ECP was applied to different stages of the solidification. The results showed that the application of the ECP in both the initial stage （the thickness of solidified shell reached 2 mm approximately） and the late stage （the thickness of solidified shell reached 14 mm approximately） of solidification can promote the columnar to equiaxed transition （CET）. The analysis showed that during solidification, a large number of nuclei around the upper surface fell off due to ECP, which subsequently showered on the melt and impinged the growth front of the columnar crystal. Therefore, the CEToccurred. In addition, this method was also employed to influence the solidification process of bearing steel, and the results showed that the structure was changed from columnar crystal to equiaxed crystal, indicating that ECP can enhance the homogeneity of structure and composition of bearing steel.

关键词： columnar to equiaxed transition solidification electric current pulse macrosegregation

EFFECT OF LOW-FREQUENCY ELECTROMAGNETIC FIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES OF HDC 2024 ALUMINUM ALLOY

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 205-210页

作者： Q.F. Zhu Z.H. Zhao J.Z. Cui Y.B. Zuo F. Qu Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern Univer- sity Shenyang 110004 China

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm× 200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting processre- spectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could sub- stantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.

关键词： Horizontal direct chill casting Low frequency electromagnetic field 2024 aluminum alloy Microstructures macrosegregation

Solute Distribution in Columnar Crystal Zone and Influences of Correlative Factors for Continuous Casting Slabs

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Journal of Iron and Steel Research(International) 2008年第4期15卷 21-25页

作者： CHEN Shu-ying CHANG Guo-wei YUE Xu-dong WU Chun-jing School of Materials University of Science and Technology Beijing Beijing 100083 China College ofMaterial and Chemical Engineering Liaoning University of Technology Jinzhou 121000 Liaoning China

The expression of the solute distribution in columnar crystal zone was deduced when the solid-liquid interface bended periodically, and the quantitative calculations of macrosegregation were also made in the process of the continuous casting. The solute distribution along the thickness direction of the slabs was obtained, which verified the theoretical calculation. The effect of the bulge size, solidification speed, and solidification shrinkage speed on macrosegregation of the slabs was calculated. It can be concluded that normal segregation and negative segregation alternatively appear as a result of the bulge. The normal segregation exponentially depends on the bulge size, and the negative segregation linearly depends on the bulge size. The extent of the normal segregation is greater than that of the negative segregation when the bulge size is the same. The macrosegregation of the same position along the thickness direction of the slabs changes in a sine wave with increasing the solidification rate, and the amplitude is larger at the casting blank center. The normal segregation linearly decreases with increasing the solidification shrinkage speed, and when the solidification shrinkage speed exceeds a critical value, the segregation appears negatively and increases linearly.

关键词： continuous casting columnar crystal zone solute distribution macrosegregation

A Three-Dimensional Comprehensive Model for the Prediction of macrosegregation in Electroslag Remelting Ingot

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A Three-Dimensional Comprehensive Model for the Prediction o...