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991.
Effects of deoxidizing degree on the pitting corrosion behavior of carbon and manganese steels
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Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell (SOCC) test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and optical microscopy (OM). The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel. 相似文献
992.
Danda Srinivas Rao Tadiparthi Venkata VijayaKumar Sripada Subba Rao Swarna Prabhakar Guntamadugu Bhaskar Raju 《矿物冶金与材料学报》2011,18(5):515-522
The recovery of iron from the screw classifier overflow slimes by direct flotation was studied. The relative effectiveness of sodium silicates with different silica-to-soda mole ratios as depressants for silica and silicate bearing minerals was investigated. Silica-to-soda mole ratio and silicate dosage were found to have significant effect on the separation efficiency. The results show that an increase of Fe content in the concentrate is observed with concomitant reduction in SiO2 and Al2O3 levels when a particular type of sodium silicate at a proper dosage is used. The concentrate of 58.89wt% Fe, 4.68wt% SiO2, and 5.28wt% Al2O3 with the weight recovery of 38.74% and the metal recovery of 41.13% can be obtained from the iron ore slimes with 54.44wt% Fe, 6.72wt% SiO2, and 6.80wt% Al2O3, when Na2SiO3 with a silica-to-soda mole ratio of 2.19 is used as a depressant at a feed rate of 0.2 kg/t. 相似文献
993.
Based on the first-principles plane wave pseudo-potential method, the electronic structure and electrochemical performance of LixSn4Sb4 (x=2, 4, 6, and 8) and LixSn1-xSb4 (x=9, 10, 11, and 12) phases were calculated. A Sn-Sb thin film on a Cu foil was also prepared by radio frequency magnetron sputtering. The surface morphology, composition, and lithium intercalation/extraction behavior of the fabricated film were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). Lithium atoms can easily insert into and extract out of the β-SnSb cell due to the low lithium intercalation formation energy. It is found that lithium atoms first occupy the interstitial sites, and then Sn atoms at the lattice positions are replaced by excessive lithium. The dissociative Sn atoms continue to produce different Li-Sn phases, which will affect the electrode stability and lead to the undesirable effect due to their large volume expansion ratio. The calculated lithium intercalation potential is stable at about 0.7 V, which is consistent with the experimental result. 相似文献
994.
Identification of thermal effects involved in DSC experiment on Al-Cu-Mg-Ag alloys with high Cu:Mg ratio
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Jian-bo Zhang Yong-an Zhang Bao-hong Zhu Feng Wang Zhi-hui Li Xi-wu Li Bai-qing Xiong 《矿物冶金与材料学报》2011,18(6):671-675
Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test, electrical conductivity test, and transmission electron microscope (TEM) examination. It is discovered that thermal effects can be identified through selected area electron diffraction and bright-field images. The reaction peaks around 171, 231, and 276℃ can be attributed to a structural rearrangement of coherent zones, to the precipitation of Ω phases, and to the precipitation of Ω and θ' and possible combination with the transition of θ'→θ, respectively. In addition, the hardness and electrical conductivity of the alloy change proportionately with the progression of reactions during the heating process. This phenomenon can be attributed to the evolution of the microstructure. 相似文献
995.
The corrosion inhibitor is one of the most important technologies to enhance the durability of steel-reinforced concrete. A kind of time-saving method was developed to assess the inhibitor efficiency by using a 32 V electric field to accelerate chloride ion migration in concrete. Potentiodynamic polarization scanning test was used to evaluate the corrosion states. The comprehensive efficiency of an inhibitor should be assessed in two aspects: resistance to chloride ion permeability and inhibiting efficiency. The specimens with different mixing amount of sodium nitrite and migration corrosion inhibitors were used to verify the accuracy and reliability of this method. The results show the differences in inhibiting efficiency of the inhibitors clearly, indicating the reliability of this time-saving method. 相似文献
996.
Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels
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Effects of cold rolling on the microstructure and mechanical properties of Fe-Ni-Mn-Mo-Ti-Cr maraging steels were studied. To investigate the microstructure and mechanical properties, optical microscopy, scanning electron microscopy, X-ray diffraction, tensile test, and hardness test were used. The results show that the solution-annealing treatment in the cold-rolled steel redounds to the formation of submicrocrystalline Fe2(Mo, Ti) Laves phase particles, which are stable at high temperatures. These secondary Laves phase particles prevent from recrystallization at high temperatures and correspond to semi-brittle fracture in the subsequent aging treatment. 相似文献
997.
The precipitation behaviors of X80 acicular ferrite pipeline steel were investigated by using transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results show that dendritic precipitates in the as-cast steel slabs precipitate mainly in grain boundaries, and these dendritic precipitates dissolve and re-precipitate to two kinds of carbonitrides: Ti- and Nb-rich (Ti, Nb)(C, N) carbonitrides during reheating. Four types of precipitates mainly exist in the hot rolled plate: Ti-rich carbonitrides resulted from the dendritic carbonitrides undissolved during the reheating process; Ti-rich carbonitrides re-precipitated along austenite grain boundaries during the reheating process; NbC carbides mainly heterogeneously nucleated on the small pre-existing Nb-rich carbonitrides in the hot rolling process; and NbC carbides precipitated on dislocations during hot rolling. 相似文献
998.
Simulation of the continuous casting process in a mold of free-cutting steel 38MnVS based on a MiLE method
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A new method called mixed Lagrangian and Eulerian (MiLE) method was used to simulate the continuous casting process in a mold of free-cutting steel 38MnVS. The simulation results are basically in agreement with experimental data in the literature, achieving the three-dimensional visualization of temperature distribution, melt flow, shell thickness, and stress distribution of blooms in a mold. It is shown that the flow velocity of steel melt becomes smaller gradually as the casting proceeds. When the flow reaches a certain depth, two types of flow patterns can be observed in the upper zone of the mold. The first flow pattern is to flow downwards, and the second one is to flow upwards to the meniscus. The corner temperature is higher, and the thickness is thinner than those in the mid-face. The effective stress in the corner area is much bigger than that in the mid-face, indicating that the corner area is the dangerous zone of cracking. 相似文献
999.
Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag
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The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag (NS) and blast furnace slag (BFS) with a small amount of quartz sand was investigated. A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process. The results show that the iron-rich system has much lower melting temperature, glass transition temperature (Tg), and glass crystallization temperature (Tc), which can result in a further energy-saving process. The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918℃. The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample. The crystallization process can be completed in a few minutes. A distinct boundary between the crystallized part and the non-crystallized part exists during the process. In the non-crystallized part showing a black colour, some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to Tc. In the crystallized part showing a khaki colour, a compact structure is formed by augite crystals. 相似文献
1000.
Comparative stability analyses of traditional and selective room-and-pillar mining techniques for sub-horizontal tungsten veins
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Vidal Félix Navarro Torres Carlos Dinis da Gama Matilde Costa e Silva Paula Falc?o Neves Qiang Xie 《矿物冶金与材料学报》2011,18(1):1-8
The stability and productivity concerning a modification on the traditional room and pillar for a new selective technique at the Portuguese Panasqueira Mine have been described. The traditional room-and-pillar stoping uses 5.0-m wide rooms with 3.0 m×3.0 m pillars, while the selective room-and-pillar mining technique consists in stoping with rooms of 4.0 m wide and pillars of 4 m×4 m with a subsequent selective cutting of the quartz veins at the mid pillar of approximately 0.5 m high, to obtain a pillar section with an area of 3.0 m×3.0 m. The stability and productivity analyses indicate that the selective technique obtains smaller average pillar safety factor, more rock mass displacement, more extraction and selectivity ratios, and ore grade improvement, compared with the traditional technique. These results show that the selective technique is also more convenient. This proposed selective room-and-pillar mining technique is applicable to any sub-horizontal narrow quartz veins with wolfram, gold, etc. such as the famous La Rinconada gold mine in the Peruvian Andes. 相似文献