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Xuwei T.,University of Science and Technology Beijing | Xuwei T.,Beijing Key Laboratory of Special Melting and Preparation of High End Metal Materials | Rong Z.,University of Science and Technology Beijing | Rong Z.,Beijing Key Laboratory of Special Melting and Preparation of High End Metal Materials
Energy Materials 2014, Conference Proceedings | Year: 2014

This paper compares inclusions in high nitrogen steel before and after ESR process, analyzes the influence of slag systems and total oxygen content in consumable ingots. The total oxygen content is reduced apparently during ESR process, which indicates good effects on removal of inclusions. In the experiment, it shows that different slag systems will affect the result of inclusions removal significantly; proper w(CaO/Al2O3) will reduce the level of inclusions and total oxygen content in ESR ingots. In ESR process, the type and chemical composition of inclusions have no difference when oxygen content in consumable ingots is different, which means O content in consumable ingots have no direct relationship with cleanliness of ESR ingots. In typical inclusions, w(MnO)/w(MnO+Al2O3)≈0.23∼0.32. The total oxygen content of ESR ingots keeps between 20∼30ppm when the oxygen contents in consumable ingots are diverse from 40 to 100ppm. Meanwhile, this paper studies desulfurization process of high nitrogen steel in ESR, analyzes the influence of slag systems a nd remelting rates on desulfurization efficiency. The results indicate that the average size and quant ity of sulfide inclusion decrease after ESR process. The typical inclusion after ESR process is MnS+Al2O3. Slag system with proper CaO content has higher sulfur partition ratio, which leads to better desulfurization effect. The desulfurization rate changes greatly with different remelting rates, which indicates the kinetic parameter has more influence in desulfurization. The reason of this phenomenon is that the process of desulfurization can be considered as a non-equilibrium reaction, which differs with thermodynamic equilibrium. In kinetic study, it is founded that the desulfurization efficiency increases with higher remelting area, sulfur partition and lower remelting rate, which is different from experiment. The desulfurization efficiency decreases firstly and then recovers when remelting rate drops. The enrichment of sulfide in slag results in resulfurization in steel, which leads to lower desulfurization efficiency. Source


Zheng L.,University of Science and Technology Beijing | Zheng L.,Beijing Key Laboratory of Special Melting and Preparation of High End Metal Materials | Lejcek P.,ASCR Institute of Physics Prague | Song S.,Harbin Institute of Technology | And 2 more authors.
Journal of Alloys and Compounds | Year: 2015

Grain boundary (GB) segregation of P in 2.25Cr1Mo steel induced by elastic stress shows that the P equilibrium concentration, after reaching the non-equilibrium concentration maximum at critical time, returns to its initial thermal equilibrium level. This finding confirms the interesting phenomenon that the effect of elastic stress on GB segregation of P is significant in kinetics while slight in thermodynamics. Through extending the "pressure" in classical theory of chemical potential to the "elastic stress", the thermodynamic effect of elastic stress on GB segregation is studied, and the relationship between elastic stress and segregation Gibbs energy is formulated. The formulas reveal that the difference in the segregation Gibbs energy between the elastically-stressed and non-stressed states depends on the excess molar volume of GB segregation and the magnitude of elastic stress. Model calculations in segregation Gibbs energy confirm that the effect of elastic stress on the thermodynamics of equilibrium GB segregation is slight, and the theoretical analyses considerably agree with the experimental results. The confirmation indicates that the nature of the thermodynamic effect is well captured. © 2015 Elsevier B.V. All rights reserved. Source


Duan S.C.,University of Science and Technology Beijing | Duan S.C.,Beijing Key Laboratory of Special Melting and Preparation of High End Metal Materials | Guo X.L.,University of Science and Technology Beijing | Guo X.L.,China Steel Corporation | And 4 more authors.
Ironmaking and Steelmaking | Year: 2016

A thermodynamic model for predicting manganese distribution ratio LMn and manganese capacity CMn of CaO–SiO2–FeO–MgO–MnO–Al2O3 slags, i.e. IMCT-LMn and IMCT-CMn models, has been developed by using a thermodynamic model for calculating mass action concentration of ion couples or structural units in the slags based on the ion–molecule coexistence theory (IMCT). The developed IMCT-LMn and IMCT-CMn models have been verified with the experiment results of CaO–SiO2–FeO–MgO–MnO–Al2O3, CaO–SiO2–MgO–FeO–Fe2O3–MnO–P2O5, CaO–SiO2–MgO–FeO–Fe2O3–MnO–Al2O3–P2O5 slags reported by different researchers, a total of 200 industrial measurements with large compositional variations and predicted results by summarised five LMn models and two CMn models. The developed thermodynamic model for calculating manganese distribution ratio can determine quantitatively the respective manganese distribution ratio LMn,i and the respective manganese capacity CMn,i of four demanganisation products as MnO, (Formula presented.), (Formula presented.) and (Formula presented.). A significant difference of demanganisation abilities among FeO, FeO + Al2O3 and FeO + SiO2 can be found as 98, 1.8 and 0.2%. By comparing binary and complex basicity, the optical basicity is recommended to describe the relationship between basicity and manganese distribution ratio. With the aid of the current model, the co-effects of the (Formula presented.) ratio and optical basicity on the LMn and CMn of CaO–SiO2–FeO–MgO–MnO–Al2O3 slags are investigated. © 2016 Institute of Materials, Minerals and Mining Source


Zheng J.,University of Science and Technology Beijing | Hou X.,University of Science and Technology Beijing | Wang X.,University of Science and Technology Beijing | Meng Y.,University of Science and Technology Beijing | And 3 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2016

Oxidation performance of a newly developed Nb-Ti-V-Cr-Al-W-Mo-Hf alloy at 800-1200°C for 5 h in flowing air was investigated via isothermal oxidation testing, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and electron probe microanalysis. The results indicated that the kinetics followed a mixed parabolic-linear law and the oxidation activation energies were obtained. The oxidation region consisted of external oxide layer (EOL) and internal oxidation zone (IOZ). EOLs were composed of TiO2, Nb9VO25 and CrVNbO6 at 800°C, TiO2 and TiNb2O7 at 1100°C, and CrVNbO6 and TiNb2O7 at 1200°C. Ti-, Hf- and Nb-rich internal oxides were observed in IOZ. The theoretical and experimental analysis suggested that the chemical reactions in oxide/alloy interface and diffusion of Ti4 + and O2 - in alloy were the mechanism to understand the oxidation process. © 2015 Elsevier Ltd. All rights reserved. Source


Pan Z.,University of Science and Technology Beijing | Chen J.,University of Science and Technology Beijing | Chen J.,Beijing Key Laboratory of Special Melting and Preparation of High End Metal Materials | Fan L.,University of Science and Technology Beijing | And 4 more authors.
Materials Research Bulletin | Year: 2015

The temperature stability of electromechanical properties is an important issue of major concern for the design of actuators. In this paper, temperature dependence of ferroelectric properties have been investigated in the (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3 (x = 0.30-0.38) solid solutions. Interestingly, the unipolar strain in the composition of x = 0.38 shows a good linear relationship with increasing electric field, and the large-signal d33 is independent with increasing temperature from room temperature to 100 °C. Furthermore, it also exhibits a very high piezoelectric coefficient d33 = 450 pC/N near the morphotropic phase boundary. All above indicates the present system of (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3 may be a kind of potential application for precisely controlling actuators. © 2014 Elsevier Ltd. All rights reserved. Source

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