Distribution behavior of phosphorus in the coal-based reduction of high-phosphorus-content oolitic iron ore

This study focuses on the reduction of phosphorus from high-phosphorus-content oolitic iron ore via coal-based reduction. The distribution behavior of phosphorus (i.e., the phosphorus content and the phosphorus distribution ratio in the metal, slag, and gas phases) during reduction was investigated in detail. Experimental results showed that the distribution behavior of phosphorus was strongly influenced by the reduction temperature, the reduction time, and the C/O molar ratio. A higher temperature and a longer reaction time were more favorable for phosphorus reduction and enrichment in the metal phase. An increase in the C/O ratio improved phosphorus reduction but also hindered the mass transfer of the reduced phosphorus when the C/O ratio exceeded 2.0. According to scanning electron microscopy analysis, the iron ore was transformed from an integral structure to metal and slag fractions during the reduction process. Apatite in the ore was reduced to P, and the reduced P was mainly enriched in the metal phase. These results suggest that the proposed method may enable utilization of high-phosphorus-content oolitic iron ore resources.     

Effect of mold rotation on the bifilar electroslag remelting process

A novel electroslag furnace with a rotating mold was fabricated, and the effects of mold rotational speed on the electroslag remelting process were investigated. The results showed that the chemical element distribution in ingots became uniform and that their compact density increased when the mold rotational speed was increased from 0 to 28 r/min. These results were attributed to a reasonable mold speed, which resulted in a uniform temperature in the slag pool and scattered the metal droplets randomly in the metal pool. However, an excessive rotational speed caused deterioration of the solidification structure. When the mold rotational speeds was increased from 0 to 28 r/min, the size of Al₂O₃ inclusions in the electroslag ingot decreased from 4.4 to 1.9 μm. But the excessive mold rotational speed would decrease the ability of the electroslag remelting to remove the inclusions. The remelting speed gradually increased, which resulted in reduced power consumption with increasing mold rotational speed. This effect was attributed to accelerated heat exchange between the consumable electrode and the molten slag, which resulted from mold rotation. Nevertheless, when the rotational speed reached 28 r/min, the remelting speed did not change because of limitations of metal heat conduction. Mold rotation also improved the surface quality of the ingots by promoting a uniform temperature distribution in the slag pool.     

Arc characteristics of submerged arc welding with stainless steel wire

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.     

Fabrication of directional solidification components of nickel-base superalloys by laser metal forming

Straight plates, hollow columns, ear-like blade tips, twist plates with directional solidification microstructure made of Rene 95 superalloys were successfully fabricated on Nickel-base superalloy and DD3 substrates, respectively. The processing conditions for production of the parts with corresponding shapes were obtained. The fabrication precision was high and the components were compact. The solidification microstructure of the parts was analyzed by optical microscopy. The results show that the solidification microstructure is composed of columnar dendrites, by epitaxial growth onto the directional solidification substrates. The crystallography orientation of the parts was parallel to that of the substrates. The primary arm spacing was about 10 μm, which is in the range of superfine dendrites, and the secondary arm was small or even degenerated. It is concluded that the laser metal forming technique provides a method to manufacture directional solidification components.     

传统加热和微波加热下氧化锰矿的碳热还原行为研究

For the purpose of exploring a potential process to produce FeMn, the effects of microwave heating on the carbothermal reduction characteristics of oxidized Mn ore was investigated. The microwave heating curve of the mixture of oxidized Mn ore and coke was analyzed in association with the characterization of dielectric properties. The comparative experiments were conducted on the carbothermal reductions through conventional and microwave heatings at temperatures ranging from 973 to 1373 K. The thermogravimetric analysis showed that carbothermal reactions under microwave heating proceeded to a greater extent and at a faster pace compared with those under conventional heating. The metal phases were observed in the microstructures only under microwave heating. The carbothermal reduction process under microwave heating was discussed. The electric and magnetic susceptibility differences were introduced into the thermodynamics analysis for the formation of metal Mn. The developed thermodynamics considered that microwave heating could make the reduction of MnO to Mn more accessible and increase the reduction extent.     

Leaching of a copper flotation concentrate with ammonium persulfate in an autoclave system

The leaching behavior of a copper flotation concentrate was investigated using ammonium persulfate (APS) in an autoclave system. The decomposition products of APS, active oxygen, and acidic medium were used to extract metals from the concentrate. Leaching experiments were performed to compare the availability of APS as an oxidizing agent for leaching of the concentrate under atmospheric conditions and in an autoclave system. Leaching temperature and APS concentration were found to be important parameters in both leaching systems. Atmospheric leaching studies showed that the metal extractions increased with the increase in APS concentration and temperature (up to 333 K). A similar tendency was determined in the autoclave studies up to 423 K. It was also determined that the metal extractions decreased at temperatures above 423 K due to the passivation of the particle surface by molten elemental sulfur. The results showed that higher copper extractions could be achieved using an autoclave system.     

A Revised CFB Wall-to-suspension Heat Transfer Model

Based on the Cluster Renewal Model of the particle motion in a CFB riser, a revised heat transfer model is developed, which introduces the latest research results of the hydrodynamics of the suspension flow in CFB. This model divides the heat transfer into two parts, which are due to the transient heat conduction by the covered clusters and the convection between the uncovered wall and the dispersed phase. Radiation at high temperature is regarded as being additive. The fraction of the covered wall by clusters is revised by a new formula, which is a function of the operating condition and the particle properties. The radiation between the dispersed phase and the uncovered wall includes not only the direct radiation to the uncovered wall, but also the radiation to the clusters and then reflected to the uncovered wall. Calculation was carried out for the CFB heat transfer model. The results were compared with the published typical experimental data of other researchers and showed a good agreement between them.     

Applications of optimal mathematic-physical models in metallurgical manufacture scheduling system at Baosteel

The transfer of mass flow between ironmaking and steelmaking process at Baoshan Iron and Steel Co. Ltd. has been analyzed. The mathematic-physical models of transport scheduling for hot metal manufacturing have been researched combined with the practical problem in the metallurgical manufacture procedure. Taking into account these models, the scheduling software has been designed, programmed and tested on-line. The new automation system of production scheduling has been implemented successfully at Baosteel, which produces a great economic benefit.     

赞比亚卢安西亚矿区复杂铜矿孔雀石的机械活化及浸出研究

Mechanical activation(MA) of malachite was carried out by dry planetary grinding(DPG) and wet Isa grinding(WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 μm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG.However, no agglomeration was observed among particles with sizes 0.4–3 μm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared(FT-IR) spectra of activated malachite, the bands associated with –OH, CO_3^2-and metal lattice vibrations of Cu–O and Cu–OH were weakened, and a new H–O–H bending mode and peaks of gaseous CO_2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite.Furthermore, the leaching behavior of copper ore was greatly improved by MA.     

Design of Flexible Electronic Shogging System for High-Speed Warp-Knitting Machine

A flexible electronic shogging system was presented based on rotary type servo motor,which aimed to improve the dynamic response of the shogging drive and decrease the impact of the guide bar during the higher speed running of warp-knitting machine.In this system,the speed control mode,faster response servo motor,no-flat modified trapezoid motion law,and its electronic cam were chosen;the realization standard and method were also introduced in details.The speed response curves of loaded motor indicated that the system could satisfy the technology requirements of high-speed warpknitting machine which run at the speed of 1000 r/min in the experiments,and the vibration curves showed that the guide bar had weaker mechanical impact and higher dynamic response characteristics.The results indicated that the flexible electronic shogging system designed following the previous step was successful,and the design principle of the electronic shogging was testified validly.     

Improvement of microstructure and corrosion properties of friction stir welded AA5754 by adding Zn interlayer

This study investigated the effect of Zn foil layers on the microstructure and corrosion characteristics of friction stir welded aluminum alloy 5754. Samples of various joints were prepared by applying different rotational and welding speeds, and their microstructures were evaluated via a metallographic technique and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy elemental analysis. The anticorrosion behavior of joints in the absence and presence of a Zn interlayer was studied by cyclic potentiodynamic polarization test in 3.5wt% NaCl aqueous solution, and sound welds were obtained in the presence of the Zn interlayer foil. The results revealed that the joint made at a rotational speed of 800 r/min and traveling speed of 15 mm/min achieved a chemical composition identical to that of aluminum alloy 7xxx series, and as such, it showed the best resistance to corrosion.     

氧化石墨烯和还原氧化石墨烯纳米片对药芯电弧焊低碳钢组织和力学性能的影响

The effect of graphene oxide (GO) and reduced graphene oxide (RGO) nanosheets on the microstructure and mechanical properties of welded joints of mild steel was evaluated by flux-cored arc welding. GO was synthesized by the Hummer’s method and was reduced under hydrothermal conditions at a pressure of 1.1 MPa at 180°C for 12 h. 1, 3, and 10 mg/mL paste fillers were used in GO and RGO, and applied to the weld notch. The results clearly showed that by increasing the concentration of RGO up to 10 mg/mL, the tensile strength and hardness of the weld metal were improved by approximately 20.5% and 38.4%, respectively, because the coarse grains were changed into fine domains. The domain of the nanosheets cluster was 19.85 × 10?9 m. Specifically, the RGO nanosheets contributed to modifying the mechanical properties of the welded steel, likely due to dislocation pinning.     

Study on the mechanical activation of malachite and the leaching of complex copper ore in the Luanshya mining area,Zambia

Mechanical activation(MA) of malachite was carried out by dry planetary grinding(DPG) and wet Isa grinding(WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 μm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG.However, no agglomeration was observed among particles with sizes 0.4–3 μm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared(FT-IR) spectra of activated malachite, the bands associated with –OH, CO_3~(2-)and metal lattice vibrations of Cu–O and Cu–OH were weakened, and a new H–O–H bending mode and peaks of gaseous CO_2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite.Furthermore, the leaching behavior of copper ore was greatly improved by MA.     

Effect of graphene oxide and reduced graphene oxide nanosheets on the microstructure and mechanical properties of mild steel jointing by flux-cored arc welding

The effect of graphene oxide(GO) and reduced graphene oxide(RGO) nanosheets on the microstructure and mechanical properties of welded joints of mild steel was evaluated by flux-cored arc welding. GO was synthesized by the Hummer's method and was reduced under hydrothermal conditions at a pressure of 1.1 MPa at 180°C for 12 h. 1, 3, and 10 mg/m L paste fillers were used in GO and RGO, and applied to the weld notch. The results clearly showed that by increasing the concentration of RGO up to 10 mg/m L, the tensile strength and hardness of the weld metal were improved by approximately 20.5% and 38.4%, respectively, because the coarse grains were changed into fine domains.The domain of the nanosheets cluster was 19.85 × 10~(-9)m. Specifically, the RGO nanosheets contributed to modifying the mechanical properties of the welded steel, likely due to dislocation pinning.     

A piezoelectric tracked vehicle with potential application to planetary exploration

A piezoelectric driving method for rover vehicles is proposed in this paper. Employing this method, a tracked vehicle driven by friction forces from a frame mounted with piezoelectric elements was developed. The vehicle is designed with no driver sprocket, no idler-wheel and no supporting bogie wheels, and the vehicle thus requires no lubrication and has potential application in planetary exploration. The frame consists of a pair of piezoelectric transducers. Each transducer comprises four annular parts jointed by beams adhered with piezoelectric ceramics. The tracks are set to the outer surface of the annular parts by means of track tension. Traveling rotating waves are generated by piezoelectric transducers in the annular parts, which generate microscopic elliptical motions at the interface of the tracks. The microscopic elliptical motions from the piezoelectric transducers drive the track vehicle to move. Finite elements analysis was carried out to verify the operation principle using commercial software ANSYS. Piezoelectric transducers were fabricated, assembled and tested to validate the concepts of the proposed rover vehicle and confirm the simulation results. A prototype vehicle with mass of 0.57 kg moves at a speed of 4.3 mm/s at a driving voltage of 250 V and operating frequency of 65.53 kHz.     

Mass transfer of phosphorus in high-phosphorus hot-metal refining

Mass transfer of phosphorus in high-phosphorus hot-metal refining was investigated using CaO-Fe_tO-SiO₂ slags at 1623 K. Based on a two-film theory kinetic model and experimental results, it was found that the overall mass transfer coefficient, which includes the effects of mass transfer in both the slag phase and metal phase, is in the range of 0.0047 to 0.0240 cm/s. With the addition of a small amount of fluxing agents Al₂O₃ or Na₂O into the slag, the overall mass transfer coefficient has an obvious increase. Silicon content in the hot metal also influences the overall mass transfer coefficient. The overall mass transfer coefficient in the lower[Si] heat is much higher than that in the higher[Si] heat. It is concluded that both fluxing agents and lower[Si] hot metal facilitate mass transfer of phosphorus in liquid phases. Furthermore, the addition of Na₂O could also prevent rephosphorization at the end of the experiment.     

Mechanisms of sodium and potassium ions transfer facilitated by dibenzo-15-crown-5 across the water /1,2-dichloroethane interface using micropipettes

The transfer of sodium and potassium ions facilitated by dibenzo-15-crown-5 (DB15C5) has been studied at the micro-water/1,2-dichloroethane (water/DCE) interface supported at the tip of a micropipette. Cyclic voltammetric measurements were performed in two limiting conditions: the bulk concentration of Na+ or K+ in the aqueous phase is much higher than that of DB15C5 in the organic phase (DB15C5 diffusion controlled process) and the reverse condition (metal ion diffusion controlled process). The mechanisms of the facilitated Na+ transfer by DB15C5 are both transfer by interfacial complexation (TIC) with 1∶1 stoichiometry under these two conditions, and the corresponding association constants were determined at log β1 = 8.97 ( 0.05 or log β1 = 8.63 ( 0.03. However, the transfers of K+ facilitated by DB15C5 show different behavior. In the former case it is a TIC process and its stoichiometry is 1∶2, whereas in the latter case two peaks during the forward scan were observed, the first of which was confirmed as the formation of K+(DB15C5)2 at the interface by a TIC mechanism, while the second one may be another TIC process with 1∶1 stoichiometry in the more positive potential. The relevant association constants calculated for the complexed ion, K+(DB15C5)2, in the organic phase in two cases, logβ2, are 13.64 ( 0.03 and 11.34 ( 0.24, respectively.     

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

To understand the migration mechanisms of phosphorus (P) during coal-based reduction, a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions. The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer (FE-EPMA) and using the basic principle of solid phase mass transfer, respectively. Experimental results showed that the P transferred from the slag to the metallic phase during reduction, and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface, the formation of Fe-P compounds at the slag-metal interface and P diffusing from the slag-metal interface to the metallic interior. The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases. The P content of the metallic phase increased with increasing reduction time and temperature, while that of the slag phase gradually decreased. The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed. P diffusion in the metallic phase was the controlling step of the P migration.     

Characterizations of dissimilar S32205/316L welds using austenitic,super-austenitic and super-duplex filler metals

UNS S32205 duplex stainless steel plates were welded to AISI 316L stainless steel using the pulsed gas tungsten arc welding process with three different filler metals: ER2594, ER312, and ER385. The microstructures of the welds were characterized using optical and scanning electron microscopy, and all of the specimens were evaluated by ferrite measurements. The mechanical properties were studied through hardness, tensile, and impact tests. In addition, the pitting resistance equivalent number was calculated and cyclic polarization tests were performed to evaluate the corrosion resistance of the weld metal. The results showed that chromium nitride was formed in the heat-affected zone of the duplex side, whereas no sigma phase was detected in any of the specimens. The ferrite number increased from the root pass to the final pass. The absorbed energies of the impact test decreased with increasing ferrite number, whereas the tensile strength was enhanced. The fully austenitic microstructure of the specimen welded with ER385 exhibited the highest resistance to pitting corrosion at 25°C, and the super-duplex weld metal presented superior corrosion resistance at 50°C.     

Microstructural evolution and mechanical properties of friction stir-welded C71000 copper-nickel alloy and 304 austenitic stainless steel

Dissimilar joints comprised of copper-nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper-nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper-nickel base metal, respectively.