International Journal of Minerals, Metallurgy and Materials

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High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering

Bing-ji Yan, Jian-liang Zhang, Hong-wei Guo, Ling-kun Chen, Wei Li

2014, 21(8): 741-747. doi: 10.1007/s12613-014-0966-x

中文摘要(238) PDF(11) SpringerLink

摘要:
The high-temperature performance of iron ore fines is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

Utilization of waste polyethylene terephthalate as a reducing agent in the reduction of iron ore composite pellets

Gökhan Polat, Burak Birol, Muhlis Nezihi Sarıdede

2014, 21(8): 748-754. doi: 10.1007/s12613-014-0967-9

中文摘要(226) PDF(8) SpringerLink

摘要:
The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate (PET), because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450°C for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron (iron nuggets) were reduction at 1450°C for 10 min using composite pellets containing 60% PET and 40% coke.

Influence of silicon on the microstructures, mechanical properties and stretch-flangeability of dual phase steels

Le-yu Zhou, Dan Zhang, Ya-zheng Liu

2014, 21(8): 755-765. doi: 10.1007/s12613-014-0968-8

中文摘要(245) PDF(9) SpringerLink

摘要:
Uniaxial tension tests and hole-expansion tests were carried out to determine the influence of silicon on the microstructures, mechanical properties, and stretch-flangeability of conventional dual-phase steels. Compared to 0.03wt% silicon, the addition of 1.08wt% silicon induced the formation of finer ferrite grains (6.8 μm) and a higher carbon content of martensite (C_m ≈ 0.32wt%). As the silicon level increased, the initial strain-hardening rate (n value) and the uniform elongation increased, whereas the yield strength, yield ratio, and stretch-flangeability decreased. The microstructures were observed after hole-expansion tests. The results showed that low carbon content martensite (C_m ≈ 0.19wt%) can easily deform in coordination with ferrite. The relationship between the mechanical properties and stretch-flangeability indicated that the steel with large post-uniform elongation has good stretch-flangeability due to a closer plastic incompatibility of the ferrite and martensite phases, which can effectively delay the production and decohesion of microvoids.

Effects of pre-strain and baking parameters on the microstructure and bake-hardening behavior of dual-phase steel

Chun-fu Kuang, Shen-gen Zhang, Jun Li, Jian Wang, Hua-fei Liu

2014, 21(8): 766-771. doi: 10.1007/s12613-014-0969-7

中文摘要(195) PDF(10) SpringerLink

摘要:
In a typical process, C-Mn steel was annealed at 800°C for 180 s, and then cooled rapidly to obtain the ferrite-martensite microstructure. After pre-straining, the specimens were baked and the corresponding bake-hardening (BH) values were determined as a function of pre-strain, baking temperature, and baking time. The influences of pre-strain, baking temperature and baking time on the microstructure evolution and bake-hardening behavior of the dual-phase steel were investigated systematically. It was found that the BH value apparently increased with an increase in pre-strain in the range from 0 to 1%; however, increasing pre-strain from 1% to 8% led to a decrease in the BH value. Furthermore, an increase in baking temperature favored a gradual improvement in the BH value because of the formation of Cottrell atmosphere and the precipitation of carbides in both the ferrite and martensite phases. The BH value reached a maximum of 110 MPa at a baking temperature of 300°C. Moreover, the BH value enhanced significantly with increasing baking time from 10 to 100 min.

Arc characteristics of submerged arc welding with stainless steel wire

Ke Li, Zhi-sheng Wu, Cui-rong Liu, Feng-hua Chen

2014, 21(8): 772-778. doi: 10.1007/s12613-014-0970-1

中文摘要(250) PDF(11) SpringerLink

摘要:
The arc characteristics of submerged arc welding (SAW) with stainless steel wire were studied by using Analysator Hannover (AH). The tests were carried out under the same preset arc voltage combined with different welding currents. By comparing the probability density distribution (PDD) curves of arc voltage and welding current, the changes were analyzed, the metal transfer mode in SAW was deduced, and the characteristics of a stable arc were summarized. The analysis results show that, with an increase of welding parameters, the short-circuiting peak in the PDD curves of arc voltage decreases gradually until it disappears, and the dominant metal transfer mode changes from flux-wall guided transfer to projected transfer and then to streaming transfer. Moreover, when the PDD curves of arc voltage are both unimodal and generally symmetrical, the greater the peak probability and the smaller the peak span, the more stable the arc becomes.

Effect of annealing on the microstructure and mechanical properties of Mg-2.5Zn-0.5Y alloy

Li Zhang, Zheng Liu, Ping-li Mao

2014, 21(8): 779-784. doi: 10.1007/s12613-014-0971-0

中文摘要(229) PDF(9) SpringerLink

摘要:
The microstructure and mechanical properties of extruded Mg-2.5Zn-0.5Y alloy before and after annealing treatments were investigated. The as-extruded alloy exhibits a yield tensile strength (YTS) of 305.9 MPa and an ultimate tensile strength (UTS) of 354.8 MPa, whereas the elongation is only 4%. After annealing, the YTS and UTS decrease to 150 MPa and 240 MPa, respectively, and the elongation increases to 28%. Interestingly, the annealed alloy maintains an acceptable stress level even after a much higher ductility is achieved. These excellent mechanical properties stem from the combined effects of fine α-Mg dynamic recrystallization (DRX) grains and a homogeneously distributed icosahedral quasicrystalline phase (I-phase) in the α-Mg DRX grains. In particular, the superior ductility originates from the coherent interface of I-phase and α-Mg and from the formation of the secondary twin {1011}–{1012}(38°<1210>) in the tension twin {1012}.

Microstructure and texture evolution in commercial-purity Zr 702 during cold rolling and annealing

Min Ma, Ming-he Li, Yuan-biao Tan, Hui Yuan, Wen-chang Liu

2014, 21(8): 785-795. doi: 10.1007/s12613-014-0972-z

中文摘要(235) PDF(10) SpringerLink

摘要:
Microstructure and texture evolution in commercial-purity Zr 702 during cold rolling and annealing was investigated by optical microscopy, transmission electron microscopy, and X-ray diffraction. The results showed that crystallographic slip was the predominant deformation mechanism in the early stage of deformation. Deformation twins started to form when the rolling reduction was larger than 38.9%; both the dislocation density and the number of twins increased with increasing rolling reduction. The initial texture of the Zr 702 plate consisted of the basal fiber component. During cold rolling the strength of the basal fiber first decreased and then increased with increasing rolling reduction. The cold-rolled sheets were fully recrystallized after being annealed at 550°C. The recrystallization temperature and the size of recrystallized grains decreased with increasing rolling reduction. A larger rolling reduction resulted in a higher grain growth rate when the annealing temperature increased from 550°C to 700°C. The recrystallization texture was characterized by a major basal fiber and a minor {0113}<2110> component. The strength of the recrystallization texture increased with increasing rolling reduction.

Comparison of TiAlN, AlCrN, and AlCrN/TiAlN coatings for cutting-tool applications

T. Sampath Kumar, S. Balasivanandha Prabu, Geetha Manivasagam, K. A. Padmanabhan

2014, 21(8): 796-805. doi: 10.1007/s12613-014-0973-y

中文摘要(389) PDF(23) SpringerLink

摘要:
Monolayer and bilayer coatings of TiAlN, AlCrN, and AlCrN/TiAlN were deposited onto tungsten carbide inserts using the plasma enhanced physical vapor deposition process. The microstructures of the coatings were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM micrographs revealed that the AlCrN and AlCrN/TiAlN coatings were uniform and highly dense and contained only a limited number of microvoids. The TiAlN coating was non-uniform and highly porous and contained more micro droplets. The hardness and scratch resistance of the specimens were measured using a nanoindentation tester and scratch tester, respectively. Different phases formed in the coatings were analyzed by X-ray diffraction (XRD). The AlCrN/TiAlN coating exhibited a higher hardness (32.75 GPa), a higher Young’s modulus (561.97 GPa), and superior scratch resistance (L_CN = 46 N) compared to conventional coatings such as TiAlN, AlCrN, and TiN.

Influences of synthesis methods and modifier addition on the properties of Ni-based catalysts supported on reticulated ceramic foams

Vesna Nikolić, Željko Kamberović, Zoran Anđić, Marija Korać, Miroslav Sokić, Vesna Maksimović

2014, 21(8): 806-812. doi: 10.1007/s12613-014-0974-x

中文摘要(109) PDF(10) SpringerLink

摘要:
A method of synthesizing Ni-based catalysts supported on α-Al₂O₃-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al₂O₃ catalysts, the chloride reduction route enabled the formation of a Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness (533 and 633 K) were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.

A ternary TiO₂/WO₃/graphene nanocomposite adsorbent: facile preparation and efficient removal of Rhodamine B

Yong-qiang Zhang, Xiao-hui Li, Jie Lü, Chong-dian Si, Guang-jun Liu, Hong-tao Gao, Pi-bo Wang

2014, 21(8): 813-819. doi: 10.1007/s12613-014-0975-9

中文摘要(259) PDF(10) SpringerLink

摘要:
Ternary TiO₂/WO₃/graphene (TWG) nanocomposites were prepared by a facile salt-ultrasonic assisted hydrothermal method. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption. Both anatase TiO₂ and orthorhombic WO₃ formed in the nanocomposites, along with a highly disordered overlay of individual graphene nanosheets. Polyhedral and spherical TiO₂ and WO₃ nanoparticles of uniform size 10–30 nm were densely anchored to the graphene sheets. The maximum specific surface area of the products was 144.59 m²·g⁻¹. The products showed clear abilities for the removal of Rhodamine B in the absence of illumination. Furthermore, the adsorption activity of the products exhibited only a slight decrease after three successive cycles. The results demonstrate that the ternary nanocomposites could be used as a high-efficiency adsorbent for the removal of environmental contaminants.

Preparation of zeolite NaA for CO₂ capture from nickel laterite residue

Tao Du, Li-ying Liu, Penny Xiao, Shuai Che, He-ming Wang

2014, 21(8): 820-825. doi: 10.1007/s12613-014-0976-8

中文摘要(206) PDF(9) SpringerLink

摘要:
Zeolite NaA was successfully prepared from nickel laterite residue for the first time via a fusion-hydrothermal procedure. The structure and morphology of the as-synthesized zeolite NaA were characterized with a range of experimental techniques, such as X-ray diffraction, scanning electronic microscopy, and infrared spectroscopy. It was revealed that the structures of the produced zeolites were dependent on the molar ratios of the reactants and hydrothermal reaction conditions, so the synthesis conditions were optimized to obtain pure zeolite NaA. Adsorption of nitrogen and carbon dioxide on the prepared zeolite NaA was also measured and analyzed. The results showed that zeolite NaA could be prepared with reasonable purity, it had physicochemical properties comparable with zeolite NaA made from other methods, and it had excellent gas adsorption properties, thus demonstrating that zeolite NaA could be prepared from nickel laterite residue.

Synthesis of kalsilite from microcline powder by an alkali-hydrothermal process

Shuang-qing Su, Hong-wen Ma, Jing Yang, Pan Zhang, Zheng Luo

2014, 21(8): 826-831. doi: 10.1007/s12613-014-0977-7

中文摘要(218) PDF(10) SpringerLink

摘要:
The properties of aluminosilicate kalsilite have attracted the interest of researchers in chemical synthesis, ceramic industry, biofuels, etc. In this study, kalsilite was hydrothermally synthesized from microcline powder in a KOH solution. The microcline powder, rich in potassium, aluminum, and silicon, was collected from Mountain Changling in Northwestern China. The effects of temperature, time, and KOH concentration on the decomposition of microcline were investigated. The kalsilite and intermediate products were characterized by means of wet chemistry analysis, X-ray Diffraction (XRD), infrared spectrometry (IR), ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR), ²⁷Al MAS NMR, and scanning electron microscope (SEM). With increasing temperature, the microcline powder transforms into a metastable KAlSiO₄ polymorph before transforming further into pure kalsilite. A mixture of both kalsilite and metastable KAlSiO₄ polymorph is obtained when the hydrothermal reaction is carried out within 2 h; but after 2 h, kalsilite is the predominant product. The concentration of KOH, which needs to be larger than 4.3 M, is an important parameter influencing the synthesis of kalsilite.

Production of HfO₂ thin films using different methods: chemical bath deposition, SILAR and sol-gel process

İ. A. Kariper

2014, 21(8): 832-838. doi: 10.1007/s12613-014-0978-6

中文摘要(279) PDF(10) SpringerLink

摘要:
Hafnium oxide thin films (HOTFs) were successfully deposited onto amorphous glasses using chemical bath deposition, successive ionic layer absorption and reaction (SILAR), and sol-gel methods. The same reactive precursors were used for all of the methods, and all of the films were annealed at 300°C in an oven (ambient conditions). After this step, the optical and structural properties of the films produced by using the three different methods were compared. The structures of the films were analyzed by X-ray diffraction (XRD). The optical properties are investigated using the ultraviolet-visible (UV-VIS) spectroscopic technique. The film thickness was measured via atomic force microscopy (AFM) in the tapping mode. The surface properties and elemental ratios of the films were investigated and measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDX). The lowest transmittance and the highest reflectance values were observed for the films produced using the SILAR method. In addition, the most intense characteristic XRD peak was observed in the diffraction pattern of the film produced using the SILAR method, and the greatest thickness and average grain size were calculated for the film produced using the SILAR method. The films produced using SILAR method contained fewer cracks than those produced using the other methods. In conclusion, the SILAR method was observed to be the best method for the production of HOTFs.

Orientation variation along growth direction of millimeter free-standing CVD diamond thinned by mechanical grinding

Xing-kai Wen, Jun-jun Wei, Jin-long Liu, Jian-chao Guo, Liang-xian Chen, Cheng-ming Li

2014, 21(8): 839-844. doi: 10.1007/s12613-014-0979-5

中文摘要(231) PDF(11) SpringerLink

摘要:
A free-standing diamond film with millimeter thickness prepared by DC arc plasma jet was thinned successively by mechanical grinding. The orientation and quality of the diamond films with different thicknesses were characterized by X-ray diffraction and Raman spectroscopy, respectively. The results show a random grain-orientation distribution during the initial growth stage. As the film thickness increases, the preferred orientation of the diamond film changes from (111) to (220), due to the competitive growth mechanism. Twinning generated during the nucleation stage appears to stabilize the preferential growth along the 〈110〉 direction. The interplanar spacing of the (220) plane is enlarged as the film thickness increases, which is caused by the increase of non-diamond-phase carbon and impurities under the cyclic gas. In addition, the quality of the diamond film is barely degraded during the growth process. Furthermore, the peak shift demonstrates a significant inhomogeneity of stress along the film growth direction, which results from competitive growth.

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2014年第21卷第8期