International Journal of Minerals, Metallurgy and Materials

姓名
邮箱
手机号码
标题
留言内容
验证码

Structure instability forecasting and analysis of giant rock pillars in steeply dipping thick coal seams

Xing-ping Lai, Huan Sun, Peng-fei Shan, Ming Cai, Jian-tao Cao, Feng Cui

2015, 22(12): 1233-1244. doi: 10.1007/s12613-015-1190-z

中文摘要(180) PDF(14) SpringerLink

摘要:
Structure stability analysis of rock masses is essential for forecasting catastrophic structure failure in coal seam mining. Steeply dipping thick coal seams (SDTCS) are common in the Urumqi coalfield, and some dynamical hazards such as roof collapse and mining- induced seismicity occur frequently in the coal mines. The cause of these events is mainly structure instability in giant rock pillars sandwiched between SDTCS. Developing methods to predict these events is important for safe mining in such a complex environment. This study focuses on understanding the structural mechanics model of a giant rock pillar and presents a viewpoint of the stability of a trend sphenoid fractured beam (TSFB). Some stability index parameters such as failure surface dips were measured, and most dips were observed to be between 46° and 51°. We used a digital panoramic borehole monitoring system to measure the TSFB’s height (ΔH), which varied from 56.37 to 60.50 m. Next, FLAC^3D was used to model the distribution and evolution of vertical displacement in the giant rock pillars; the results confirmed the existence of a TSFB structure. Finally, we investigated the acoustic emission (AE) energy accumulation rate and observed that the rate commonly ranged from 20 to 40 kJ/min. The AE energy accumulation rate could be used to anticipate impeding seismic events related to structure failure. The results presented provide a useful approach for forecasting catastrophic events related to structure instability and for developing hazard prevention technology for mining in SDTCS.

Reductive leaching of low-grade manganese ore with pre-processed cornstalk

Ai-fei Yi, Meng-ni Wu, Peng-wei Liu, Ya-li Feng, Hao-ran Li

2015, 22(12): 1245-1251. doi: 10.1007/s12613-015-1191-y

中文摘要(182) PDF(9) SpringerLink

摘要:
Cornstalk is usually directly used as a reductant in reductive leaching manganese. However, low utilization of cornstalk makes low manganese dissolution ratio. In the research, pretreatment for cornstalk was proposed to improve manganese dissolution ratio. Cornstalk was preprocessed by a heated sulfuric acid solution (1.2 M of sulfuric acid concentration) for 10 min at 80℃. Thereafter, both the pretreated solution and the residue were used as a reductant for manganese leaching. This method not only exhibited superior activity for hydrolyzing cornstalk but also enhanced manganese dissolution. These effects were attributed to an increase in the amount of reductive sugars resulting from lignin hydrolysis. Through acid pretreatment for cornstalk, the manganese dissolution ratio was improved from 50.14% to 83.46%. The present work demonstrates for the first time the effective acid pretreatment of cornstalk to provide a cost-effective reductant for manganese leaching.

Coordinated control of carbon and oxygen for ultra-low-carbon interstitial-free steel in a smelting process

Min Wang, Yan-ping Bao, Quan Yang, Li-hua Zhao, Lu Lin

2015, 22(12): 1252-1259. doi: 10.1007/s12613-015-1192-x

中文摘要(147) PDF(8) SpringerLink

摘要:
Low residual-free-oxygen before final de-oxidation was beneficial to improving the cleanness of ultra-low-carbon steel. For ultra-low-carbon steel production, the coordinated control of carbon and oxygen is a precondition for achieving low residual oxygen during the Ruhrstahl Heraeus (RH) decarburization process. In this work, we studied the coordinated control of carbon and oxygen for ultra-low-carbon steel during the basic oxygen furnace (BOF) endpoint and RH process using data statistics, multiple linear regressions, and thermodynamics computations. The results showed that the aluminum yield decreased linearly with increasing residual oxygen in liquid steel. When the mass ratio of free oxygen and carbon ([O]/[C]) in liquid steel before RH decarburization was maintained between 1.5 and 2.0 and the carbon range was from 0.030wt% to 0.040wt%, the residual oxygen after RH natural decarburization was low and easily controlled. To satisfy the requirement for RH decarburization, the carbon and free oxygen at the BOF endpoint should be controlled to be between 297×10^-6 and 400×10^-6 and between 574×10^-6 and 775×10^-6, respectively, with a temperature of 1695 to 1715℃ and a furnace campaign of 1000 to 5000 heats.

Slag formation path during dephosphorization process in a converter

Jiang Diao, Yong Qiao, Xuan Liu, Xie Zhang, Xin Qiu, Bing Xie

2015, 22(12): 1260-1265. doi: 10.1007/s12613-015-1193-9

中文摘要(197) PDF(9) SpringerLink

摘要:
The slag formation path is important for efficient dephosphorization in steelmaking processes. The phosphorus capacity and the melting properties of the slag are critical parameters for optimizing the slag formation path. Regarding these two factors, the phosphorus partition ratio was calculated using the regular solution model (RSM), whereas the liquidus diagrams of the slag systems were estimated using the FactSage thermodynamic package. A slag formation path that satisfies the different requirements of dephosphorization at different stages of dephosphorization in a converter was thus established through a combination of these two aspects. The composition of the initial slag was considered to be approximately 15wt%CaO–44wt%SiO₂–41wt%FeO. During the dephosphorization process, a slag formation path that follows a high-iron route would facilitate efficient dephosphorization. The composition of the final dephosphorization slag should be approximately 53wt%CaO–25.5wt%SiO₂–21.5wt%FeO. The composition of the final solid slag after dephosphorization is approximately 63.6wt%CaO–30.3wt%SiO₂–6.1wt%FeO.

A coupled model of TiN inclusion growth in GCr15SiMn during solidification in the electroslag remelting process

Liang Yang, Guo-guang Cheng, Shi-jian Li, Min Zhao, Gui-ping Feng, Tao Li

2015, 22(12): 1266-1272. doi: 10.1007/s12613-015-1194-8

中文摘要(190) PDF(9) SpringerLink

摘要:
TiN inclusions observed in an ingot produced by electroslag remelting (ESR) are extremely harmful to GCr15SiMn steel. Therefore, accurate predictions of the growth size of these inclusions during steel solidification are significant for clean ESR ingot production. On the basis of our previous work, a coupled model of solute microsegregation and TiN inclusion growth during solidification has been established. The results demonstrate that compared to a non-coupled model, the coupled model predictions of the size of TiN inclusions are in good agreement with experimental results using scanning electron microscopy with energy disperse spectroscopy (SEM-EDS). Because of high cooling rate, the sizes of TiN inclusions in the edge area of the ingots are relatively small compared to the sizes in the center area. During the ESR process, controlling the content of Ti in the steel is a feasible and effective method of decreasing the sizes of TiN inclusions.

Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

Hang Zhao, Jian-jun Li, Zhi-zhen Zheng, Ai-hua Wang, Qi-wen Huang, Da-wen Zeng

2015, 22(12): 1273-1282. doi: 10.1007/s12613-015-1195-7

中文摘要(236) PDF(10) SpringerLink

摘要:
In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350–400 µm thickness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti–Fe alloy powder. Microhardness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the samples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstructure and to the presence of TiC particles.

Solid-particle erosion behavior of cast alloys used in the mining industry

Ş. Hakan Atapek, Sinan Fidan

2015, 22(12): 1283-1292. doi: 10.1007/s12613-015-1196-6

中文摘要(231) PDF(20) SpringerLink

摘要:
The erosive-wear response of five commercial ferrous-based cast alloys used for crushing was examined in this study. The microstructures of the alloys were modified to elucidate the effect of microstructural features on wear. Erosion tests were conducted using aluminum oxide particles (90–125 μm) at 70 m/s and a normal impact angle (90°). The worn surfaces were characterized by scanning electron microscopy and 3D non-contact laser profilometry. It is found that (i) a pearlitic structure exhibiting a greater plastic deformation than both bainitic and martensitic structures shows the greatest resistance to erosive wear at normal impact and (ii) the fracture characteristics of carbide and graphite particles plays an important role in determining the erosion wear behavior of the cast alloy matrices.

Linking anisotropy with Fe₃C distribution in AISI 1045 steel

Ke-chang Shen, Gui-hua Li, Yi-min Sun, Yong-gang Wang, Ying-jie Li, Guang-hui Cao, Wei-min Wang

2015, 22(12): 1293-1303. doi: 10.1007/s12613-015-1197-5

中文摘要(241) PDF(9) SpringerLink

摘要:
The anisotropy of the microstructure, thermal expansion behavior, corrosion resistance and magnetic properties of AISI 1045 steel was investigated. The distribution of Fe₃C lamellae in the investigation plane parallel to the radial directions of molds was observed to differ from that in the investigation plane perpendicular to the radial directions by transmission electron microscopy. The lattice constants a₀ of α-Fe deduced from the XRD patterns of samples prepared using a sand (S)-mold and cut parallel to the radial direction of the mold (S//) and using a metal (M)-mold and cut parallel to the radial direction (M//), the corrosion resistance measured using an electrochemical workstation, and the magnetic permeability obtained by vibrating sample magnetometry also indicated the existence of anisotropy in the tested samples. The anisotropic change of corrosion potential (E_corr), pitting potential (E_pit) and magnetic permeability (µ) of the samples was observed to depend on the orientation factor F₂₀₀ of α-Fe in the measured samples, which is controlled by the distribution of Fe₃C lamellae in the eutectoid structure.

Effect of initial microstructure on austenite formation kinetics in high-strength experimental microalloyed steels

Edgar López-Martínez, Octavio Vázquez-Gómez, Héctor Javier Vergara-Hernández, Bernardo Campillo

2015, 22(12): 1304-1312. doi: 10.1007/s12613-015-1198-4

中文摘要(328) PDF(14) SpringerLink

摘要:
Austenite formation kinetics in two high-strength experimental microalloyed steels with different initial microstructures comprising bainite–martensite and ferrite–martensite/austenite microconstituents was studied during continuous heating by dilatometric analysis. Austenite formation occurred in two steps: (1) carbide dissolution and precipitation and (2) transformation of residual ferrite to austenite. Dilatometric analysis was used to determine the critical temperatures of austenite formation and continuous heating transformation diagrams for heating rates ranging from 0.03℃·s^-1 to 0.67℃·s^-1. The austenite volume fraction was fitted using the Johnson–Mehl–Avrami–Kolmogorov equation to determine the kinetic parameters k and n as functions of the heating rate. Both n and k parameters increased with increasing heating rate, which suggests an increase in the nucleation and growth rates of austenite. The activation energy of austenite formation was determined by the Kissinger method. Two activation energies were associated with each of the two austenite formation steps. In the first step, the austenite growth rate was controlled by carbon diffusion from carbide dissolution and precipitation; in the second step, it was controlled by the dissolution of residual ferrite to austenite.

Strain localization and damage development in 2060 alloy during bending

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

2015, 22(12): 1313-1321. doi: 10.1007/s12613-015-1199-3

中文摘要(192) PDF(10) SpringerLink

摘要:
The microstructure evolution and damage development of the third-generation Al–Li alloy 2060 (T8) were studied using in situ bending tests. Specimens were loaded with a series of punches of different radii, and the microstructure evolution was studied by scanning electron microscopy, electron backscatter diffraction, and digital image correlation (DIC) methods. The evolution of the microscopic fracture strain distribution and microstructure in 2060 alloy during bending was characterized, where the dispersion distribution of precipitates was recorded by backscattered electron imaging and later inputted into a DIC system for strain calculations. The experimental results showed that strain localization in the free surface of bent specimens induced damage to the microstructure. The region of crack initiation lies on the free surface with maximum strain, and the shear crack propagates along the macro-shear band in the early stages of bending. Crack propagation in the later stages was interpreted on the basis of the conventional mechanism of ductile fracture.

Morphology of α-Si₃N₄ in Fe–Si₃N₄ prepared via flash combustion

Bin Li, Jun-hong Chen, Jin-dong Su, Ming-wei Yan, Jia-lin Sun, Yong Li

2015, 22(12): 1322-1327. doi: 10.1007/s12613-015-1200-1

中文摘要(184) PDF(10) SpringerLink

摘要:
The state and formation mechanism of α-Si₃N₄ in Fe–Si₃N₄ prepared by flash combustion were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that α-Si₃N₄ crystals exist only in the Fe–Si₃N₄ dense areas. When FeSi75 particles react with N₂, which generates substantial heat, a large number of Si solid particles evaporate. The product between Si gas and N₂ is a mixture of α-Si₃N₄ and β-Si₃N₄. At the later stage of the flash combustion process, α-Si₃N₄ crystals dissolve and reprecipitate as β-Si₃N₄ and the β-Si₃N₄ crystals grow outward from the dense areas in the product pool. As the temperature decreases, the α-Si₃N₄ crystals cool before transforming into β-Si₃N₄ crystals in the dense areas of Fe–Si₃N₄. The phase composition of flash-combustion-synthesized Fe–Si₃N₄ is controllable through manipulation of the gas-phase reaction in the early stage and the α→β transformation in the later stage.

Plasma preparation and low-temperature sintering of spherical TiC–Fe composite powder

Jian-jun Wang, Jun-jie Hao, Zhi-meng Guo, Song Wang

2015, 22(12): 1328-1333. doi: 10.1007/s12613-015-1201-0

中文摘要(217) PDF(9) SpringerLink

摘要:
A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced using a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense structure, and the fine sub-micron TiC particles were homogeneously distributed in the α-Fe matrix. A TiC–Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature; the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

Effect of Yb₂O₃ doping on the grain boundary of NiFe₂O₄–10NiO-based cermets after sintering

Han-bing He

2015, 22(12): 1334-1341. doi: 10.1007/s12613-015-1202-z

中文摘要(173) PDF(9) SpringerLink

摘要:
xYb₂O₃–15(20Ni–Cu)/(85 - x)(NiFe₂O₄–10NiO) (x = 0, 0.25, 0.5, 0.75, 1.0, 2.0, and 10.0) cermets for aluminum electrolysis were prepared to investigate the effect of Yb₂O₃ doping on the grain boundary of the cermets after sintering. The results showed that each interface was very clear and that with increasing Yb₂O₃ content, most of the Yb was evenly distributed at the grain boundary. Moreover, according to the phase composition and microstructural analysis by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), and electron probe microanalysis (EPMA), YbFeO₃ was produced along the grain boundary. The YbFeO₃ was concluded to not only have formed from the interaction between the NiFe₂O₄ or Fe₂O₃ component and Yb₂O₃ at the grain boundary of the cermets, but also from the decomposition of NiFe₂O₄ into NiO and Fe₂O₃ and the subsequent reaction of Fe₂O₃ with Yb₂O₃. Thus, the production of YbFeO₃ resulted in a cermet with high relative density, good electrical conductivity, and good corrosion resistance.

Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

Bao-wei Li, Hong-xia Li, Xue-feng Zhang, Xiao-lin Jia, Zhi-chao Sun

2015, 22(12): 1342-1349. doi: 10.1007/s12613-015-1203-y

中文摘要(190) PDF(8) SpringerLink

摘要:
The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods: conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

留言板

2015年第22卷第12期

视频展示更多>

期刊特色

期刊荣誉更多>

友情链接更多>

留言板

2015年 第22卷 第12期

视频展示更多>

期刊特色

期刊荣誉更多>

友情链接更多>

2015年第22卷第12期