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Wang D.,Northeastern University China | Jiang M.,Northeastern University China | Liu C.,Northeastern University China | Min Y.,Northeastern University China | And 3 more authors.
Steel Research International | Year: 2012

Steel slag normally contains a large amount of iron and its oxides. Therefore, it is a potential renewable resource in case of inadequate iron ore supply. To recover the metals from steel slag, two types of BOF slags were remelted at 1873K. The liquid slags were cooled using four types of cooling conditions, namely, water granulation, splashing, air cooling, and furnace cooling, to investigate the influence of cooling rate on mineral components, especially the enrichment behavior of Fe-containing minerals. Subsequently, wet magnetic separation was conducted to examine the relations between iron recovery ratio and cooling conditions. The results show that the slags under the four cooling conditions mainly contained dicalcium silicate, RO phase, Fe tO, 2CaO(Fe,Al) 2O 3, and calcium ferrite. However, tricalcium silicate, 12CaO·7Al 2O 3, M-A spinel, and free CaO and MgO were occasionally observed. The amount of glass matrix decreased, the Fe-containing minerals increased, and the minerals more fully crystallized when the cooling rate of the liquid slag was decreased. From granulation to furnace cooling of the slags, the iron content in the recovered concentrate and the iron recovery ratio both increased. This result is in agreement with the findings on phase transformation through SEM analysis. BOF slags under four types of cooling conditions, namely, water granulation, splashing, air cooling, and furnace cooling contained dicalcium silicate, RO phase, Fe tO, 2CaO(Fe,Al) 2O 3, and calcium ferrite. The amount of glass matrix decreased and Fe-containing minerals increased. From granulation to furnace cooling of the slags, the iron content in the recovered concentrate and the iron recovery ratio both increased. Copyright © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu D.,Northeastern University China | Zhu M.-Y.,Northeastern University China | Tang Z.-Y.,Northeastern University China | Liu Z.-M.,Xingtai Iron and Steel Co.
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2013

The continuous cooling transformation (CCT) curves of SCM435 steels were determined and analyzed using a thermal simulation testing machine. The results showed that SCM435 steels were very sensitive to the cooling rates. Ferrite, pearlite and small amount of bainite were observed when the cooling rate was 0.05°C/s. When the cooling rate increased to 1°C/s, ferrite began to end its phase transformation, and a little amount of martensite began to appear. In the actual production, the cooling rates were controlled by combining with the modeling predict so that the production of massive ferrite primary-precipitated was suppressed, the appearance of a large amoun of martensite was avoided and the desirable microstructure for good cold heading property and the spheroidization effect was obtained.

Huang Y.S.,University of Science and Technology Beijing | Huang Y.S.,Control Iron and Steel Research Institute, China | Yang M.S.,Control Iron and Steel Research Institute, China | Li J.S.,University of Science and Technology Beijing | Bai L.G.,Xingtai Iron and Steel Co.
Materials Science Forum | Year: 2015

Utilizing Pro-cast software, the whole vacuum arc remelting process of high-alloy bearing steel ingot (the diameter was 160 mm and the high was 600 mm) was simulated. And moving face quality and moving boundary conditions were added to the simulation. Purposes of the simulation were to explore the influence of smelting powers on the temperature field, pool shape and solidification microstructure in vacuum arc remelting process. The depth of molten bath gradually increased and stabilized finally and the pool shape transferred from flat to funnel. When smelting power increased, the depth of molten pool became deeper and the width of mushy zone slightly reduced; the size of primary dendrite and secondary dendrite spacing increased significantly; the percentage and size of columnar crystals also increased. A reasonable power-time cure was given to guide industrial melting after simulation, the size of molten pool morphology and microstructure were controlled in an ideal range under the reasonable cure. The simulated grain morphology agreed well with the experimental pickling result © (2015) Trans Tech Publications, Switzerland.

Wang D.,Northeastern University China | Li X.,Northeastern University China | Wang H.,Shenyang University of Chemical Technology | Mi Y.,Northeastern University China | And 2 more authors.
Journal of Non-Crystalline Solids | Year: 2012

Four types of slag with different basicity, MgO and Al 2O 3 content were used to simulate the synthetic ladle slag. The dissolution behavior of MgO particles was then investigated using the direct dissolution method. The results show that the dissolution rate of MgO particles strongly depends on the slag composition and temperature. At the initial stage, the dissolution rate shows a good linear relation with time. Once spinel product forms around the MgO core, the dissolution rate decreases remarkably. The formation and function of the inner slag layer between the MgO core and the spinel product were investigated in detail. The inner slag layer is possible to act as a transfer passage for Mg element from the MgO core to the spinel product. The rate-limiting step of MgO dissolution is determined by the diffusion of spinel product toward the bulk slag. © 2012 Elsevier B.V. All rights reserved.

Deng Z.,Northeastern University China | Deng Z.,KTH Royal Institute of Technology | Zhu M.,Northeastern University China | Zhong B.,Xingtai Iron and Steel Co. | Sichen D.,KTH Royal Institute of Technology
ISIJ International | Year: 2014

In the present study, inclusions in calcium-treated steel after RH treatment, in the tundish and in bloom were studied. Only two types of inclusions were detected in all steel samples, namely liquid calcium aluminate inclusions and inclusions of two phases with spinel in the center surrounded by the liquid calcium aluminate. The attachment of the inclusions on the inner surface of SEN was investigated for two types of refractory materials. The results indicated that liquid calcium aluminate inclusions could attach on the wall of SEN, when the refractory had big grain size and big cavities on the surface. On the other hand, tiny grain size and smooth surface of the SEN showed no attachment of the inclusions. The different behaviors of the two types of SEN were well explained using the results of flow calculation in the nozzle. The mechanism of the attachment was also discussed based on the experimental results and the CFD calculation. The tiny nodules formed on the surface of the inner nozzle due to inclusion attachment could be a source of macro inclusions.. © 2014 ISIJ.

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