International Journal of Minerals, Metallurgy and Materials

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Generation process of FeS and its inhibition mechanism on iron mineral reduction in selective direct reduction of laterite nickel ore

Zhi-guo Liu, Ti-chang Sun, Xiao-ping Wang, En-xia Gao

2015, 22(9): 901-906. doi: 10.1007/s12613-015-1148-1

中文摘要(341) PDF(10) SpringerLink

摘要:
Numerous studies have demonstrated that Na₂SO₄ can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na₂SO₄ is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that Na₂S formed by the reaction of Na₂SO₄ with CO reacts with SiO₂ at the FeO surface to generate FeS and Na₂Si₂O₅. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.

Effects of particle characteristics on the granulation ability of iron ores during the sintering process

Sheng-li Wu, Juan Zhu, Ji-cheng Bei, Guo-liang Zhang, Xiao-bo Zhai

2015, 22(9): 907-916. doi: 10.1007/s12613-015-1149-0

中文摘要(351) PDF(20) SpringerLink

摘要:
The granulation behavior of iron ores is essential for subsequent parameter optimization and efficient granulation, especially under changing material conditions. In this study, the effects of surface properties and particle size were analyzed using a laboratory granulation method; an estimation of the granulation of sintering blends was subsequently conducted for the base ores. Circularity and porosity were observed to negatively affect the granulation of iron ores, whereas wettability positively affected the granulation and was the most influential factor, indicating that wetting of iron ores is desirable during granulation. When iron ores with complex size distributions were granulated, the equivalent surface area was the main influencing factor for coarse particles larger than 1 mm and the ratio of adhering fines to intermediates was the main factor for fine particles smaller than 1 mm. By combining the granulation of coarse and fine particles with their proportioning, we proposed a calculation method for estimating the granulation ability of sintering blends. Good verification was demonstrated with the designed schemes. The results suggest that the developed method is effective for predicting the granulation of iron ore mixtures.

Sintering behaviors and consolidation mechanism of high-chromium vanadium and titanium magnetite fines

Mi Zhou, Tao Jiang, Song-tao Yang, Xiang-xin Xue

2015, 22(9): 917-925. doi: 10.1007/s12613-015-1150-7

中文摘要(272) PDF(8) SpringerLink

摘要:
To achieve high efficiency utilization of high-chromium vanadium–titanium magnetite (V–Ti–Cr) fines, an investigation of V–Ti–Cr fines was conducted using a sinter pot. The chemical composition, particle parameters, and granulation of V–Ti–Cr mixtures were analyzed, and the effects of sintering parameters on the sintering behaviors were investigated. The results indicated that the optimum quicklime dosage, mixture moisture, wetting time, and granulation time for V–Ti–Cr fines are 5wt%, 7.5wt%, 10 min, and 5–8 min, respectively. Meanwhile, the vertical sintering speed, yield, tumbler strength, and productivity gains were shown to be 21.28 mm/min, 60.50wt%, 58.26wt%, and 1.36 t·m^-2·h^-1, respectively. Furthermore, the consolidation mechanism of V–Ti–Cr fines was clarified, revealing that the consolidation of a V–Ti–Cr sinter requires an approximately 14vol% calcium ferrite liquid-state, an approximately 15vol% silicate liquid-state, a solid-state reaction, and the recrystallization of magnetite. Compared to an ordinary sinter, calcium ferrite content in a V–Ti–Cr sinter is lower, while the perovskite content is higher, possibly resulting in unsatisfactory sinter outcomes.

Reduction–melting behaviors of boron-bearing iron concentrate/carbon composite pellets with addition of CaO

Guang Wang, Qing-guo Xue, Xue-feng She, Jing-song Wang

2015, 22(9): 926-932. doi: 10.1007/s12613-015-1151-6

中文摘要(207) PDF(9) SpringerLink

摘要:
Although the total amount of boron resources in China is high, the grades of these resources are low. The authors have already proposed a new comprehensive utilization process of boron-bearing iron concentrate based on the iron nugget process. The present work describes a further optimization of the conditions used in the previous study. The effects of CaO on the reduction–melting behavior and properties of the boron-rich slag are presented. CaO improved the reduction of boron-bearing iron concentrate/carbon composite pellets when its content was less than 1wt%. Melting separation of the composite pellets became difficult with the CaO content increased. The sulfur content of the iron nugget gradually decreased from 0.16wt% to 0.046wt% as the CaO content of the pellets increased from 1wt% to 5wt%. CaO negatively affected the iron yield and boron extraction efficiency of the boron-rich slag. The mineral phase evolution of the boron-rich slag during the reduction–melting separation of the composite pellets with added CaO was also deduced.

Influence of rapid heating process on the microstructure and tensile properties of high-strength ferrite–martensite dual-phase steel

Pei Li, Jun Li, Qing-ge Meng, Wen-bin Hu, Chun-fu Kuang

2015, 22(9): 933-941. doi: 10.1007/s12613-015-1152-5

中文摘要(357) PDF(12) SpringerLink

摘要:
Three low-carbon dual-phase (DP) steels with almost constant martensite contents of 20vol% were produced by intercritical annealing at different heating rates and soaking temperatures. Microstructures prepared at low temperature (1043 K, FH1) with fast-heating (300 K/s) show banded ferrite/martensite structure, whereas those soaked at high temperature (1103 K, FH2) with fast heating reveal blocky martensite uniformly distributed in the fine-grained ferrite matrix. Their mechanical properties were tested under tensile conditions and compared to a slow-heated (5 K/s) reference material (SH0). The tensile tests indicate that for a given martensite volume fraction, the yield strength and total elongation values are noticeably affected by the refinement of ferrite grains and the martensite morphology. Metallographic observations reveal the formation of microvoids at the ferrite/martensite interface in the SH0 and FH2 samples, whereas microvoids nucleate via the fracture of banded martensite particles in the FH1 specimen. In addition, analyses of the work-hardening behaviors of the DP microstructures using the differential Crussard–Jaoul technique demonstrate two stages of work hardening for all samples.

Acoustic emission detection of 316L stainless steel welded joints during intergranular corrosion

Meng-yu Chai, Quan Duan, Wen-jie Bai, Zao-xiao Zhang, Xu-meng Xie

2015, 22(9): 942-949. doi: 10.1007/s12613-015-1153-4

中文摘要(324) PDF(12) SpringerLink

摘要:
This study analyzes acoustic emission (AE) signals during the intergranular corrosion (IGC) process of 316L stainless steel welded joints under different welding currents in boiling nitric acid. IGC generates several AE signals with high AE activity. The AE technique could hardly distinguish IGC in stainless steel welded joints with different welding heat inputs. However, AE signals can effectively distinguish IGC characteristics in different corrosion stages. The IGC resistance of a heat-affected zone is lower than that of a weld zone. The initiation and rapid corrosion stages can be distinguished using AE results and microstructural analysis. Moreover, energy count rate and amplitude are considered to be ideal parameters for characterizing different IGC processes. Two types of signals are detected in the rapid corrosion stage. It can be concluded that grain boundary corrosion and grain separation are the AE sources of type 1 and type 2, respectively.

Fabrication of plain carbon steel/high chromium white cast iron bimetal by a liquid–solid composite casting process

V. Javaheri, H. Rastegari, M. Naseri

2015, 22(9): 950-955. doi: 10.1007/s12613-015-1154-3

中文摘要(523) PDF(12) SpringerLink

摘要:
High-chromium white cast iron (HCWCI) is one of the most widely used engineering materials in the mining and cement industries. However, in some components, such as the pulverizer plates of ash mills, the poor machinability of HCWCI creates difficulties. The bimetal casting technique is a suitable method for improving the machinability of HCWCI by joining an easily machined layer of plain carbon steel (PCS) to its hard part. In this study, the possibility of PCS/HCWCI bimetal casting was investigated using sand casting. The investigation was conducted by optical and electron microscopy and non-destructive, impact toughness, and tensile tests. The hardness and chemical composition profiles on both sides of the interface were plotted in this study. The results indicated that a conventional and low-cost casting technique could be a reliable method for producing PCS/HCWCI bimetal. The interfacial microstructure comprised two distinct layers: a very fine, partially spheroidized pearlite layer and a coarse full pearlite layer. Moreover, characterization of the microstructure revealed that the interface was free of defects.

A novel diffusion model considering curvature radius at the bonding interface in a titanium/steel explosive clad plate

Hai-tao Jiang, Qiang Kang, Xiao-qian Yan

2015, 22(9): 956-965. doi: 10.1007/s12613-015-1155-2

中文摘要(318) PDF(10) SpringerLink

摘要:
This article introduces an element diffusion behavior model for a titanium/steel explosive clad plate characterized by a typical curved interface during the heat-treatment process. A series of heat-treatment experiments were conducted in the temperature range from 750℃ to 950℃, and the effects of heat-treatment parameters on the microstructural evolution and diffusion behavior were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. Carbon atoms within the steel matrix were observed to diffuse toward the titanium matrix and to aggregate at the bonding interface at 850℃ or lower; in contrast, when the temperature exceeded 850℃, the mutual diffusion of Ti and Fe occurred, along with the diffusion of C atoms, resulting in the formation of Ti–Fe intermetallics (Fe₂Ti/FeTi). The diffusion distances of C, Ti, and Fe atoms increased with increasing heating temperature and/or holding time. On the basis of this diffusion behavior, a novel diffusion model was proposed. This model considers the effects of various factors, including the curvature radius of the curved interface, the diffusion coefficient, the heating temperature, and the holding time. The experimental results show good agreement with the calculated values. The proposed model could clearly provide a general prediction of the elements’ diffusion at both straight and curved interfaces.

Evolution of the texture and mechanical properties of 2060 alloy during bending

Xiao Jin, Bao-qin Fu, Cheng-lu Zhang, Wei Liu

2015, 22(9): 966-971. doi: 10.1007/s12613-015-1156-1

中文摘要(286) PDF(11) SpringerLink

摘要:
In this study, we examined the evolution of the texture and mechanical properties of 2060 (T8) alloy during bending. A pixel rotation method (PRM) was proposed and used to characterize the textural evolution during bending determined by electron backscatter diffraction. The results showed that the textural components changed insignificantly, with the exception of a decrease in the cube texture. The tensile and yielding properties of the alloy were evaluated at three different orientations with respect to the rolling direction. The mechanical strength was found to increase in three directions with decreasing bending radius; thus, it was concluded that the 2060 (T8) alloy sheet satisfies the usage requirement after bending deformation.

Synthesis of aluminum nitride in a coke–calcium reduction bed using nitrogen in air

Ehsan Noorizadeh Dehkordi, H. R. Samim Banihashemi, R. Naghizadeh, H. R. Rezaie, M. Goodarzi

2015, 22(9): 972-976. doi: 10.1007/s12613-015-1157-0

中文摘要(287) PDF(11) SpringerLink

摘要:
An experimental study on the heating of a mixture of aluminum and lithium hydroxide (LiOH) powders in a reductive bed under air atmosphere is reported. The formation of aluminum nitride (AlN) during this process was the focus of this study. The formation of AlN was achieved using LiOH as an additive and heating the sample in a resistance furnace in a specially designed double crucible within a bed of a mixture of coke and filamentous calcium. The temperature range of the reaction was between 700℃ and 1100℃. The optimum temperature of 1100℃ and the optimum LiOH amount (5wt%) required to achieve maximum yield were determined by powder X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) micrographs clearly indicated the transformation of grain structures from rods (700℃) to cauliflower shapes (1100℃).

Low-temperature densification sintering and properties of CaAl₂Si₂O₈ ceramics with MeO·2B₂O₃ (Me = Ca, Sr, Ba)

Song Chen, De-gui Zhu

2015, 22(9): 977-986. doi: 10.1007/s12613-015-1158-z

中文摘要(274) PDF(10) SpringerLink

摘要:
Dense CaAl₂Si₂O₈ ceramics were prepared via a two-step sintering process at temperatures below 1000℃. First, pre-sintered CaAl₂Si₂O₈ powders containing small amounts of other crystal phases were obtained by sintering a mixture of calcium hydroxide and kaolin powders at 950℃ for 6 h. Subsequently, the combination of the pre-sintered ceramic powders with MeO·2B₂O₃ (Me = Ca, Sr, Ba) flux agents enabled the low-temperature densification sintering of the CaAl₂Si₂O₈ ceramics at 950℃. The sintering behavior and phase formation of the CaAl₂Si₂O₈ ceramics were investigated in terms of the addition of the three MeO·2B₂O₃ flux agents. Furthermore, alumina and quartz were introduced into the three flux agents to investigate the sintering behaviors, phase evolvements, microstructures, and physical properties of the resulting CaAl₂Si₂O₈ ceramics. The results showed that, because of their low-melting characteristics, the MeO·2B₂O₃ (Me = Ca, Sr, Ba) flux agents facilitated the formation of the CaAl₂Si₂O₈ ceramics with a dense microstructure via liquid-phase sintering. The addition of alumina and quartz to the flux agents also strongly affected the microstructures, phase formation, and physical properties of the CaAl₂Si₂O₈ ceramics.

Hardness of Mn₂V₂O₇ thin films and its influential factors

İ. Afşin Kariper

2015, 22(9): 987-991. doi: 10.1007/s12613-015-1159-y

中文摘要(337) PDF(13) SpringerLink

摘要:
Mn₂V₂O₇ thin films were deposited onto amorphous glass substrates using a chemical bath deposition method and different deposition time. X-ray diffraction (XRD) analysis was used to define the structure of the films. Their roughness, thickness, and surface properties were evaluated through atomic force microscopy (AFM). The hardness of the films was measured using a nanohardness tester. The film thickness, average grain size, and roughness were positively correlated with each other. These three parameters were observed to increase with the deposition time. The film thickness and average grain size were inversely correlated with the hardness and roughness. In addition, the number of crystallites per unit area and the dislocation density were observed to be positively correlated with the hardness and roughness. This study was designed to elucidate and formalize the underlying reasons for these relationships.

Preparation of activated ceria and its desulfurization performance

Qing-chun Yu, Yong Deng, Fei Wang, Yue-bin Feng, Xiu-min Chen, Bin Yang, Da-chun Liu

2015, 22(9): 992-997. doi: 10.1007/s12613-015-1160-5

中文摘要(225) PDF(11) SpringerLink

摘要:
Activated ceria (CeO₂/γ-Al₂O₃) prepared by impregnation was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and hydrogen temperature-programmed reduction (TPR). The desulfurization of the activated ceria was investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TG). The results showed that ceria could be highly dispersed or crystallized on the surface of γ-alumina. The reduction temperatures of 0.1CeO₂/γ-Al₂O₃, 0.45CeO₂/γ-Al₂O₃, and CeO₂ ranged from 250℃ to 470℃, 330℃ to 550℃, and 350℃ to 550℃, respectively. The reduction peak temperature of 0.45CeO₂/γ-Al₂O₃ was higher than that of 0.1CeO₂/γ-Al₂O₃, which was consistent with the reduction temperature of CeO₂. O₂ participated in the reaction between ceria and sulfur dioxide. The desulfurization product was cerium(Ⅲ) sulfate. The intensity of the hydroxyl band decreased with the formation of sulfate species.

Preparation and characterization of a chitosan-based low-pH-sensitive intelligent corrosion inhibitor

Yu-ning Wang, Chao-fang Dong, Da-wei Zhang, Pan-pan Ren, Li Li, Xiao-gang Li

2015, 22(9): 998-1004. doi: 10.1007/s12613-015-1161-4

中文摘要(343) PDF(10) SpringerLink

摘要:
A chitosan (CS)-based low-pH-sensitive intelligent corrosion inhibitor was prepared by loading a pH-sensitive hydrogel with benzotriazole (BTA); the pH-sensitive hydrogel was synthetized by crosslinking CS with glutaraldehyde (GTA). Analysis by Fourier- transform infrared (FT–IR) spectroscopy showed that Schiff reactions occurred between amino and aldehyde groups. The swelling ability of the hydrogel was investigated using a mass method, and it was observed to swell more in an acidic environment than in an alkaline environment. The hydrogel’s loading capacity of BTA was approximately 0.377 g·g^-1, and its release speed was faster in an acidic environment than in an alkaline environment because of its swelling behavior. The corrosion inhibition ability of the intelligent inhibitor was tested by immersion and electrochemical methods. The results showed that after 4 h of immersion, the polarization resistance (R4) value of copper with the intelligent inhibitor was approximately twice of that of copper with BTA, indicating that the intelligent inhibitor could effectively prevent copper from corroding.

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2015年第22卷第9期