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By Liuyin Shi, Kang Liu, Fengqi Zhao, Yan Song, Zhiping Yang, Xing Fan

Due to the high energy consumption, long technical process, low usage rate of vanadium during the traditional smelting vanadium steel process, a new method for decarburization by CO2 to directly smelt vanadium-containing steel in blast furnace was proposed. In this paper, the thermodynamics of CO2 decarburization in molten iron process was calculated out by FactSage. The thermodynamic calculations indicated that in standard state, the transformation temperature of C and V was 1357 °C; the oxidation order of element was Si, C, V, Mn and S when using CO2 as oxidant. The experiment of blowing CO2 temperature showed that decarburization reaction temperature was 1550 °C, carbon content could be decreased to 0.676%, the decarburization rate was 88%. There was no effect on vanadium content in molten iron during the decarburization process, vanadium content was 0.323%, which meets the request of vanadium mould steel.

Mar 1, 2018

By Satya Ganti, Bryan Turner, Bill Davis, Veeraraghavan Sundar

This work presents a three dimensional microstructural analysis of medium carbon steels, based on serial sectioning using optical microscopy. The microstructural phases considered here are ferrite and pearlite. Typically conventional 2D microscopy is used to analyze these phases (ASTM E112-13 in Standard test methods for determining average grain size. ASTM International, West Conshohocken, PA, 2013), with eddy current (Khan et al. in J Mater Process Technol Freitas et al. in Mater Sci Eng A 527(16):4431–4437, 2010) as alternatives. Medium carbon steel samples were heat treated in a furnace and either slowly cooled in the furnace, or cooled at higher rates. This resulted in different pearlitic microstructures in the samples. The analysis was conducted with Robo-Met.3D®, a fully automated metallography system for serial sectioning. Based on optical microscopy, volume cubes of hundreds of microns on edge were imaged and reconstructed to conduct grain size and phase volume analysis. The system proved capable of collecting image data with high fidelity, and controlled slice thickness in an automated manner. The resultant dataset was useful in visualization and analysis of pearlite and ferrite phases in steel samples.

Mar 1, 2018

By Guihong Han, Duo Zhang, Yanfang Huang

Ni2SiO4 was prepared by chemical precipitation process as a novel anode material for lithium-ion batteries. The structure and morphology of further annealed Ni2SiO4 samples were characterized by XRD and SEM analysis. The electrochemical performance including cyclic voltammetric curves (CV), electrochemical impedance spectra (EIS), charge/discharge curves and cycling performances were also determined. The results demonstrated that the crystal structure of the samples is orthorhombic having space group Pmn21. The morphological structure of materials exhibited cubic particles with sizes in the range of 50–80 nm. The first cycle charge capacity of the pure Ni2SiO4 particles reached to 753 mAh g−1 with the coulombic efficiency of 63.8%. The charge capacity remained 305 mAh g−1 at a current density of 100 mA g−1 even after 50 cycles, which is nearly 208% higher than those of the Ni2SiO4 with SiO2 impurity. Ni2SiO4 can be a promising alternative anode material.

Mar 1, 2018

By Kazutoshi Haga, Atsushi Shibayama, Altansukh Batnasan

This study presents a viable approach for recovery of precious metals such as gold (Au), silver (Ag), palladium (Pd), and base metals, including copper (Cu), nickel (Ni), cobalt (Co), lead (Pb) and zinc (Zn) from waste printed circuit boards (WPCBs) via iodine-iodide leaching and precipitation. The behaviours of dissolution and precipitation of precious and base metals during iodine-iodide leaching and precipitation processes were discussed. Sodium hydroxide (NaOH) was used to remove base metal impurities exist in the pregnant leach solution under alkaline conditions. Precious metals remained in the resulting solution from NaOH precipitation were recovered by reduction using ascorbic acid (L-AA) solution. Results show that under optimum leaching conditions, almost all (> 99%) of Au was dissolved in an iodine-iodide solution when the dissolution efficiencies of other precious metals (Ag, Pd) and base metals, besides calcium (leaching of 25%) were less than 1 and 6%, respectively. The study revealed that more than 95% of Cu, Ni, Pb, Zn, Fe and Mn were initially removed from the pregnant leach solution at pH of 9.3 with addition of 0.1 M NaOH. Then 99.8% Au, 81.7% Ag and 74% Pd were precipitated from the obtained solution after NaOH precipitation while L-AA dose was 0.6 ml/ml at the condition. It can be concluded that the precious and base metals could be recovered selectively and economically from WPCBs via iodine-iodide leaching followed by precipitation using NaOH and L-AA.

Mar 1, 2018

By Min-Min Lin, Bing Xie, Hong-Yi Li, Yang Yang

After precipitation of ammonium vanadates from vanadium-containing leaching liquor, vanadium (V(V)) and chromium (Cr(VI)) exist in the waste water in form of vanadate ions and chromate ions. In order to efficiently extract and recover V(V) and Cr(VI) from waste water, an environment-friendly method based on anion exchange was investigated in batch tests using macroporous weak base resin Dex-V. The adsorption conditions optimizes in detail, including the effect of pH, initial metal concentration, resin volume, contact time and temperature. The ion-exchange adsorption process for both V(V) and Cr(VI) showed maximum capacity at pH 3.0 for an initial concentration of 100 mg L−1, and reached equilibrium after about 40 min of contact at 298 K. The maximum adsorption ratio under the optimum conditions for V(V) and Cr(VI) was 98.98 and 99.87%, respectively. Result shows that the established method is a promising alternative for simultaneous extraction of vanadium and chromium.

Mar 1, 2018

By Long Meng, Kuiyuan Chen, Zhe Wang, Yiwei Zhong, Zhancheng Guo

Printed circuit boards (PCBs) contain plenty of toxic substances as well as valuable metals (e.g. Pb and Sn). In this study, supergravity as a novel technology was used to separate and recover different mass ratios (Pb/Sn) of Pb-Sn alloys from PCBs. In a supergravity field, liquid metal phase can permeate from the solid particles, and based on this, 200, 280 and 400 °C were selected to separate Pb and Sn from PCBs. The results showed that the gravity coefficient only affected the Pb-Sn alloy weight, and did not change the mass ratio of Pb/Sn. With the increase of gravity coefficient, the recovery values of Pb and Sn were increased. In the separation process, under the gravity coefficient of 1000 and separation time of 2 min, the recovery values of Pb were 33.13, 38.86 and 50.48% at the temperature of 200, 280 and 400 °C, respectively, and the recovery values of Sn were 23.31, 32.57, and 40.81%, respectively, and the mass ratios of Pb/Sn in the Pb-Sn alloys were 0.55, 0.40 and 0.64, respectively. This provided a new approach to recycle Pb and Sn from PCBs.

Mar 1, 2018

By Leizhang Gao, Zhengfeng Qu, Pingsheng Lai, Chenguang Bai, Meilong Hu

Since Fray-Farthing-Chen (FFC) Cambridge process was proposed in 2000 for electrochemical extraction of titanium from titanium oxide, a great quantity of research has been carried out to investigate the mechanism of the electro-reduction of the process. Results show that the intermediate products of perovskite phases are inevitable during the electro-deoxidation process. In this paper, a new perspective focus on the anodic behavior was applied. The behavior of the graphite anode with different times has been investigated. Although the main anodic process in the electrolysis is the oxygen evolution by means of the CO2. The interphases of calcium species appeared on the cathode are closely related with chlorine ions in the molten CaCl2. In addition, the released CO2 from the anode is related with the formation of CaCO3 which floated on the surface of the molten salt.

Mar 1, 2018

By Jingtao Wang, Xiaoyu Han, Jun Bao, Wei Hou

Lightweight stainless steel has widely potential applications in many fields, such as automobile, ship, submarine manufacturing and aerospace. The properties of lightweight stainless steel are significantly affected by the precipitating behaviour of second phase particles. In this paper, the precipitating behaviour was investigated by XRD, DSC in the process of heating and thermodynamic calculation combining the Miedema’s and Chou’s model. The XRD results indicate that there are five types of phases in lightweight Fe–Mn–Al–C–N stainless steel: ferrite, FeAl, AlMn, AlN and Mn4N. The DSC results show that the precipitating temperature of FeAl, Mn4N is 1260, 1031 °C, respectively, corresponding to the thermodynamic calculation. Besides, The DSC measurement reflects the precipitating temperature of AlMn and austenite is 934 and 600 °C.

Mar 1, 2018

By Ting Cheng, Guang-sheng Wei, Ze-shi Yang, Ling-zhi Yang, Yu-feng Guo

The application of the bottom-blowing in the steelmaking process of EAF can effectively shorten the mixing time of the molten bath, accelerate the removal of carbon, phosphorus and sulfur, and improve the production efficiency and product quality. Information about the effects of changing molten steel velocity during the smelting process would help to accurately model molten bath dynamics. In this study, numerical simulation software was employed to simulate the EAF steelmaking process under variable eccentric bottom-blowing gas flow situations. Velocity field data were obtained for the different bottom-blowing schemes. When other nozzles’ bottom-blowing gas flow rates were maintained at 133 L/min, the average velocity of molten steel in EBT (Eccentric Bottom Tapping Area) was increased from 2.8 10−3 to 3.4 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min, the average velocity of molten steel in the bath increased from 4.3 10−3 to 4.6 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min.

Mar 1, 2018

By Xiang Zhang, Junjie Liu, Zhibo Tong, Langsha Shao, Guojun Ma

The aqueous mineral carbonation process that leaching alkaline earth metals from industrial residues by ammonium salt and carbonation thereafter is one of the potential technologies for CO2 sequestration. In this paper, the effect of particle size of waste slag on the leaching rate of metals under a microwave field and effect of microwave irradiation on the carbonation process were investigated. It was found that the initial leaching ratio of Ca decline seriously with the particle size of EAF slag increasing, and the Ca leaching ratio is relatively low during 120 min leaching. The lower leaching ratio of Ca with large particle size is due to the existence of a silica product layer produced on the surface of calcium silicates. Moreover, due to the microwave irradiation, the leaching ratio of calcium and the crystallization rate of calcium carbonate increase, though the particle size and distribution range of calcium carbonate reduce.

Mar 1, 2018

By Jianhua Xin, Min Chen, Lei Xu, Haohua Deng, Nan Wang

A mathematical model of converter slagging and steelmaking process by replacing part of lime with limestone is established. The rate equations of oxidation reactions and lime dissolution in converter under the limestone substitution proportion increasing from 25 to 50% can be obtained and the effects of limestone substitution proportion on the variations of the composition of hot metal, slag and converter gas during the steelmaking process are investigated. In the process of converter slagging and steelmaking by replacing part of lime with limestone, increasing the hot metal temperature and the lance height could be favor to increase the content of FeO in the slag and accelerate the limestone decomposition and dissolution. With the limestone substitution proportion increasing from 25 to 50%, the maximum of oxygen supply ratio increases from 10.7 to 19.7% and the temperature drop of converter bath is 8–60 °C.

Mar 1, 2018

By Shadia Ikhmayies

Thermo-Calc software was used to investigate the phase diagram of the calcium silicon (Ca–Si) system for the range of Si mass percent 0–100, and temperature range T = 200–1800 K. The melting points of Ca and Si deduced from the phase diagram are very close to the values obtained experimentally. Three stable intermediate solid phases were found, which are Ca2Si, CaSi, and CaSi2, where the first one appeared in the Ca rich side of the phase diagram, and the third one in the Si rich side. In addition, three eutectic points were found at Si mass percents of 3.95, 33.00, 62, and temperatures T = 1048.7, 1519.14, 1308.5 K respectively. Atomic Si (Diamond structure) is found mixed with CaSi2 intermediate phase for temperatures less than 1305 K, and mixed with a liquid CaSi for higher temperatures. These results are important for thermodynamic and metallurgic studies of these intermediate phases.

Mar 1, 2018

By Shihan Zhang, Qingguo Xue, Jingsong Wang, Yaxing Du, Guang Wang

The rotary hearth furnace iron nugget process is in line with China’s energy and resource condition. It has the advantages of short reaction time and high quality iron nugget. The fundamental study on the novel ironmaking process is meaningful. Based on CaO-SiO2-Al2O3-FeO quaternary slag system, the effects of slag basicity and Al2O3 content on the melting of slag were studied. Using the iron concentrate as raw material, the effects of different slag basicity and Al2O3 content on the reduction and melting separation behaviors of carbon composite pellets, such as the starting temperature of melting separation and the morphology of melting separation were studied. Then, the relationship between the properties of slag and melting separation quality was established, which could provide standard for the selection of iron ore for the rotary hearth furnace iron nugget process.

Mar 1, 2018

By Baozhong Ma, Chengyan Wang, Yongqiang Chen, Peng Xing

This paper introduces an oxygen-enriched flash smelting (OFS) process for lead smelting. Compared with the bath smelting, OFS has many advantages, including wide adaptability, high yield, low energy consumption, little uncontrolled emission, and considerable metals recoveries. Test results showed that increasing CaO could effectively reduce lead content in the slag, and the appropriate mass ratios of FeO-to-SiO2 and CaO-to-SiO2 were 1.15 and 0.6, respectively. The testing and commissioning indicated when OFS was used to treat material containing 30% of lead, the residual lead in slag could decrease to 4–10%. Furthermore, after zinc volatilization using an ore-smelting electric furnace, contents of lead, zinc, silver, gold and copper in the final slag were below 2%, 2%, 6 g/L, 0.1 g/L and 1%, respectively. The total recoveries of lead, zinc, silver, gold, copper and sulfur were above 98, 90, 99.5, 99.5, 85 and 98%, respectively.

Mar 1, 2018

By Carlos Maurício F. Vieira, Gabriel Oliveira Glória, Maycon Sidney Gomes de Camargo, Sergio Neves Monteiro, Fábio da Costa Garcia Filho, Maria Carolina Andrade Teixeira, Frederico M. Margem

The society is increasingly the concern about the ambiental impacts, and demand for eco-friendly materials. The composites reinforced with synthetic fibers are been replaced by composites reinforced with natural fibers because of the environmental advantages. Besides the environmental advantages, those fibers have economical and properties advantages, like the low density and cost. Composites with up to 30%of PALF fibers were tested. The analyzed parameters were the loss modulus, the storage modulus and the delta tangent. The test was conducted in the temperature interval from 25 to 195 °C in a DMA equipment operating at 1 Hz of frequency under a nitrogen flow. The results showed that the incorporation of continuous and aligned PALF fibers tends to increase the viscoelastic stiffness of the epoxy matrix. Contrasting this, minor changes occurred in both the glass transition temperature and the damping capacity of the structure as measured by the tan delta peaks.

Mar 1, 2018

By Lilong Zhu, Shaoda Zhang, Qian Wang, Shengping He

The effects of ZrO2, Y2O3 and Sc2O3, which are transition metal oxides, on the melting temperature, viscosity at 1300 °C, and break temperature of three mold fluxes (two weak-reactive type and one non-reactive type) designed for the high manganese and high aluminum steels, and one another conventional CaO-SiO2 based mold flux is studied. The results indicate that the melting temperature and viscosity increases slightly, and the break temperature increases dramatically with the addition of ZrO2, Y2O3 and Sc2O3 content in the conventional CaO-SiO2 based mold flux system. While, the addition of ZrO2, Y2O3 and Sc2O3 in the weak-reactive or non-reactive mold flux systems has a negligible in fluence on the melting temperature, viscosity and break temperature, suggesting that these transition metal oxides are possible to regulate radiation heat transfer without changing the basic properties of mold fluxes.

Mar 1, 2018

By Rongjin Zhu, Yue Wu, Shuxing Qiu, Qingyun Zhang, Shengfu Zhang

Co-pyrolysis of biomass and coal was investigated as an effective way to reduce the greenhouse gas emission. The effects of poplar on the thermal behavior of fat coal were studied using thermogravimetric analyzer. The blended samples heated to characteristic temperature were subjected to attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to characterize the macromolecular structure. The results indicated that the synergistic effects existed in co-pyrolysis process of blends since lower char yield than calculated values, and the synergistic effects presented positive and negative trend with the increase of temperature, respectively. The carbonyl/carboxyl C=O stretching vibration functional groups and aliphatic side chain from individual fuels were decomposed in advance during co-pyrolysis. Furthermore, the hydrocarbon-generating potential (A-factor) and thermal maturity(C-factor) of the mixtures showed nonadditivity performance.

Mar 1, 2018

By Jie Li, Wenzhou Yu, Xuewei Lv

An efficient enrichment of primary silicon from the Al–Si melt can be beneficial for the Si purification and the cost reduction of the solvent refining process. In this paper, an alternating magnetic field was used to enhance the mass transfer and promote the crystal growth of primary silicon during the directional solidification of hypereutectic Al–Si alloy. The results show that the growth rate and morphologies of Si crystals changed continuously along the directional solidification direction. With the decreasing of Si content in the melt and the weakness of the electromagnetic stirring, the crystal growth rate of primary silicon gradually decreased and the Si morphologies changed from planetocellular ,cellulardendrite, and columnardendrite, respectively. This provides a deeper understanding of the Si crystal growth during the electromagnetic solidification, which will be good for achieving a high-efficiency enrichment of primary silicon in Al–Si melt.

Mar 1, 2018

By Zhong Zheng, Xiaoqiang Gao, Zhaojun Xu, Shipeng Huang, Shenglong Jiang

Steel enterprises in China are trending to improve material and energy conversion effect, because they are facing great challenges including energy saving and emission reduction, quality and efficiency improvement. According to the theory of metallurgical process engineering, with the process data in steel manufacturing, some novel indices are designed for quantifying the conversions in different metallurgical unit processes. By analyzing common technologic characteristics in different units, the main manufacturing units are divided into two categories: metallurgical reaction unit and other manufacturing unit. The novel concepts named as “material dissipation rate of unit process”, “material accumulation rate of unit process”, “enthalpy change of unit process” and “energy dissipation rate of unit process” are proposed for describing the effect and dynamic characteristics of the conversions in manufacturing units. Finally, material dissipation rate and energy dissipation rate in unit processes are calculated and analyzed respectively with the real-world process data from a steel plant in China.

Mar 1, 2018

By Carlos Maurício F. Vieira, Lázaro A. Pizatto, Marcus Paulo Cardoso, Sergio Neves Monteiro, Joao Victor C. Nunes, Gustavo S. R. Matheus, Frederico M. Margem

The interest in composites with natural fibers is due, among other factors, to the growing worldwide concern with the preservation of environment and renewable raw materials. The natural fibers have many particular properties that make them an attractive alternative to traditional synthetic fibers. The advantages of using these fibers are: low cost, renewability, biodegradability, low toxicity, abundance and specific strength. The searching for new suitable, economically viable and technologically advanced materials justifies the accomplishment of this work that aims at comparing the mechanical behavior of polyester matrix composites with epoxy matrix composites reinforced with hemp fibers Izod impact tested. The specimens with dimensions: 10 63 12.7 mm, made in different volume fractions of fiber: 0–30 vol%. The samples were tested at PANTEC pendulum model XC-50 located at LAMAV/UENF. With this research was possible to analyse the mechanical properties of these two new materials.

Mar 1, 2018