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By Kazuyoshi Shimakage, Shinji Hirai, Kenji Wada

"An amorphous zirconium oxide coating was prepared by the sol-gel process using zirconium tetra-n-butoxide on the surface of aluminum to improve the corrosion resistance to salt, acid and alkaline attacks. The coating films formed on the smooth aluminum substrates under UV-irradiation indicated an excellent corrosion resistance for salt, acid and alkaline attack tests. For example, the corroded area of coating film in salt attack test for 3600ks in the order of sol-gel coating· film< chromate film <boehmite film, and the sol-gel coating film had the best corrosion resistance. The coating film prepared on the coarse aluminum substrate by a boiling treatment after heat treatment at 573K also had greater corrosion resistance, and a water-avid surface appeared a contact angle of approximately 3°.IntroductionAs given in a previous paper1; a composite film consisting of a porous layer of anodically grown aluminum oxide filled with amorphous zirconium oxide and an amorphous zirconium oxide coating layer deposited thereon via the sol-gel process utilizing the dip-coating technique, was prepared to improve the alkaline corrosion resistance of aluminum. The alkaline corrosion resistance of these composite films was increased in the range of 24 to 50 times those of conventional anodic oxide films anodized in sulfuric acid. As a result, it was proved that heat treatment at 573K after dip-coating was an important process to .remove organic component from gel film and to accelerate the densification of coating layer. Furthermore, the effect of ultraviolet (UV) irradiation at ambient temperature on the densification of coating layer was also examined to lower the heat-treatment temperature2.Then, a sol-gel film prepared by UV irradiation at ambient temperature indicated that alkaline corrosion resistance of aluminum was superior in the range of 2.4 times to 2. 6 times that of the conventional composite film heated at 573K."

Jan 1, 2000

By Jingyuan Wang, Hengyi Zhang, Peng Lan, Ruitian Zhang, Jiaquan Zhang, Yang Li

"For the determination of mould taper and wall thickness, a 3-D numerical model of ingot-mould-hot top system has been made to evaluate the related ingot solidification process and the final soundness. The effect of mould wall thickness and the taper of its hot faces on the thermal history and the as cast structure of steel ingot has been revealed through the numerical simulation. It is shown that the ingot soundness can be improved remarkably by increasing the mould wall thickness, which is possibly beneficial to the mould life as well owning to an improved mould thermal state. The mould taper is vital to the ingot soundness but much less coherent to the mould temperature profiles. Under given casting situations, a larger mould taper can lead to a less intensity of the shrinkage porosities at the top part of ingot.IntroductionIngot casting is still one of important processes for steel production, which is adopted especially for the supply of large-sized semi-products of high quality special steels. The understanding to the solidification process is vital to both the yield improvement of casting production and the quality control of steel ingots, such as their soundness and homogeneity.The ingot processing and service performance are closely related to its defects, such as porosities and pipes[1,2], which are the most common but serious defects during ingots casting. In the late 1960s, Mahadevan and Murthy et al.[3], Irani and Kondic[4] began to analyze criteria for the prediction of shrinkage porosities in light metal casting. In 1980s, Niyama and Uchida[5], Hansen and Sahm[6,7] et al have successfully presented some related porosities and pipes criteria for steel casting. At the same time, numerical solidification simulation was well developed and applied to ingot quality studies[8-10]. However, due to the quick development of continuous casting, less emphasis has been given to the further study on ingot casting process. There leaves much work to be made for the comprehensive understanding to ingot quality improvement and the mould design by the aid of modern solidification technology[11, 12]. In this paper, the effects of mould taper and wall thickness on its thermal history, ingot solidification and the final soundness are numerically studied through solidification simulation, which has been adopted in mould design and industrial production of both the mould and its steel ingot."

Jan 1, 2012

By S. Yin, A. Bogno, H. Henein, P. Natzke

Impulse Atomization (IA) (a single fluid atomization technique) was used to rapidly solidify Al- 4.5wt%Cu and Al-4.5wt%Cu-0.4wt%Sc under argon atmosphere. In addition to the IA-generated droplets, the same technique was used to produce strips by Spray Deposition (SD) of the same alloys on a copper substrate with and without oil coating. The rapid solidification microstructures were analyzed using Scanning Electron Microscopy (SEM). From the SEM images, the amount of eutectic and the secondary dendrite arm spacing (SDAS) were measured. These SDAS results lead to the estimation of cooling rate. The eutectic fraction coupled with the metastable extension of the solidus and liquidus lines of Al-Cu (Sc) phase diagram lead to the estimation of primary and eutectic undercoolings. A comparison of the solidification path of the droplets and the strips was done as well as the analysis of the effects of scandium.

Jan 1, 2015

By José Sancho, Julia Ayala, Purificación García, Begoña Fernández

"Electrofilter dust, a residue generated in the last stage of the Bayer process in the hydroxide aluminum calcination, was characterized to evaluate the alumina that was potentially extractable with sulfuric acid. The process studied aims to produce aluminum sulfate for water coagulant uses, taking advantage of the residues that accumulate in large quantities in the proximity of plants with difficult recycling for storage. Acid leaching is carried out at different concentrations of sulfuric acid, at different temperatures, pulp densities, and times, to dissolve gibbsite and transition aluminas. The result is an aluminum sulfate solution without iron and with commercial specifications.IntroductionElectrofilter dust is a residue generated in the last stage of the Bayer Process [1] in the hydroxide aluminium calcination. The residue is a mixture of alumina and hydrates which have not completed their calcination process.Electrofilter dust, composed by alpha alumina, gibbsite and transition aluminas [2] can be leached in an acid medium by putting most of the aluminium in solution; the remaining residue should be mainly andisolved alpha alumina. In many hydrometallurgical processes, sulphuric acid has been selected as the cheapest and the most effective leachant [3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]The aim of this study is to determine the effect of temperature, acid concentration and pulp density on the sulphuric acid leaching of electrofilter fines for aluminium dissolution, in order to produce aluminium sulphate for water coagulant uses. This will provide a commercial product and at the same time eliminate the environmental problem created as a result of the storage of large quantities of electrofilter fines in the vicinity of the Bayer plant."

Jan 1, 2008

By Yasuo Kudo, Wu, Hayato Sato, Hiroshi Nakazawa, Shouming

"In order to recover copper from a waste nickel condenser powder, bioleaching experiments were carried out using Thiobacillus ferrooxidans in a shaking flask. The content of nickel and copper in the waste nickel condenser powder in this study were 8.0% and 3.5%. X ray analysis showed the peak of barium titanate. In the preliminary study using metal nickel and copper powders , the dissolutions of nickel and especially copper were accelerated with the addition of ferric iron in the bioleaching of nickel and copper powders while not in the absence of ferric iron. Ferric iron oxidizes both metals, and Thiobacillusferrooxidans oxidizes ferrous iron resulting from the oxidation of metals, whereby the dissolutions of metals proceeds. The dissolution rates of nickel and copper increased with increase in the concentration of ferric iron in the bioleaching of the waste nickel condenser powder.1. IntroductionNickel condensers rejected from manufacturing plants are crushed and landfilled. Waste nickel condensers contain nickel and copper and could be considered as nickel and copper ores. Since the capacity of landfills is diminishing, it is required to recycle metals of waste nickel condensers in order to reduce the amount of wastes landfilled. Conventionally, metals in the waste were recovered by dry metallurgy after the incineration.Nickel has been refined by solvent extraction - electrowinning method (SX-EW method). Recently the amount of copper refined by SX-EW method has increased (Takahashi, et al. 1994). This method is cleaner and consumes less energy than conventional methods. Nickel dissolved well in acid solutions, but copper is not. If copper is leached efficiently from a waste nickel condenser powder, SX-EW method will be applied to recover copper from them"

Jan 1, 2000

By C. Wieckert

Concentrated solar energy can be used as heat source for the production of metals. One of the most promising respective processes, the solar carbothermic production of Zn from ZnO, is investigated within the European research project SOLZINC, a cooperation of institutes and industries from France, Germany, Israel, Sweden and Switzerland. The solar produced Zn can be used as commodity or as an energy carrier for further processing on demand to electricity in Zn-air fuel cells/batteries or to generate hydrogen by reaction with steam. In both cases the Zn is oxidized to form ZnO, which can be recycled back to the solar plant. In these cyclic processes Zn acts as a means to store and eventually transport solar energy. Second product of the solar process step is a CO-rich offgas, which may e.g. drive a gas engine or may be shifted to hydrogen in a conventional reaction with steam. A pilot plant using 300kW concentrated solar power input has been constructed and operated successfully. 86mass-% of ZnO mixed with 14mass-% of charcoal are reacted to produce Zn and CO at a temperature of about 1200°C, yielding about 50 kg gaseous Zn per hour. Zn-dust with 95% purity is recovered from the offgas system that was designed to produce Zn for Zn-air fuel cells. Based on the results and findings from the pilot plant, a two tons Zn/h solar demonstration plant has been designed conceptually. Cost studies have been performed and scenarios for producing electricity or H2 via these ZnO/Zn-cyclic processes are evaluated.

Jan 1, 2006

By Michael E. Stout

M.A. Industries, Inc. has developed and is now offering on a commercially available basis, complete systems to recover and recycle lead from spent SLI batteries. The system begins with the breaking and separation of the component parts of the batteries and subsequent treatment of the effluent water produced by this operation. The recyclable materials recovered from this process are metallic lead, lead paste and polypropylene. The lead paste is introduced into a process to convert it from a lead sulfate to a lead carbonate. The process also regenerates the salt solutions into reusable carbonate. The lead carbonate is then leached into an acid bath where it is later recovered by a proprietary electrolytic process. The metallic lead is recovered in a short rotary furnace producing metal for further refining and alloying. The polypropylene is further washed and then introduced to a reclaim extruder along with the proper modifiers and additives. The resulting resin can then be sold on the open market to injection molding processors. This complete system greatly reduces the amount of waste to be disposed of and completely complies with all applicable EPA guidelines.

Jan 1, 1993

By Garg. D.

Premixed bronze powders are widely used to produce a wide variety of P/M components including bearings and bushings by the powder metal industry. The physical and mechanical properties of sintered bronze components such as dimensions, strength, microstructural characteristics, and sintered density are well known to change with sinlering furnace design, particle size distribution in powders, green density, preheating and sinlering time" and temperature, and protective atmosphere flow rate. " However, not much is known about the effect of protective atmosphere composition on physical and mechanical properties of sintered bronze components; This paper describes effects of protective atmosphere composition and sintering temperature on physical and mechanical properties of sintered bronze components

Jan 1, 1996

By Jinfu Xu, Youqing Cao, Yuting Lv, Hang You, Peng Jiang

"In present work, we reported the fabrication of composites consisted of M42 powder metallurgy high speed steel and 45 steel at one step via spark plasma sintering (SPS) technology. The interface microstructure, compositions and microhardness with the interface forming mechanism were investigated. The results show that the morphology and microhardness within the M42/45 steel interfaces exhibit a gradient distribution. The interfaces possessed a transition layer up to 10.2 ?m with few distortions and microcracks. The formation of M42/45 steel interfaces were driven by both fusion and diffusion processes. The former one was primary at the early sintering process, while the later one becomes dominant over the followed sintering process.IntroductionPowder high-speed steels have been widely used in cutting tools, cold-hot tools and dies, as well as in cut materials and structure parts with wear resistance and high-temperature resistance, due to its high hardness, good wear resistance, desirable cutting toughness and favorable hot hardness [1-2]. For materials of some parts in practical production, not only the favorable toughness is required to resist the impact action, but also the high hardness and exceptional wear resistance are demanded. According to the functional requirements and working conditions, bimetal composite materials are prepared in a certain mode, proportion and distribution, by designing two metals with different chemical and physical properties [3-6]. Considering the composites exhibit different properties in different positions of the parts with a combination of the advantages of two metals, they can obtain enhanced properties that the single one can not achieve."

Jan 1, 2012

By Hsing Kuang Lin

Extraction of zinc from chloride solution with dibutyl butylphosphonate (DBBP) in Escaid 110 has been investigated. The distribution coefficient of zinc was found to be independent of equilibrium pH. This independence indicates that the mechanism of the extraction may be solvation. Slope analysis for the system of dilute zinc chloride solution reveals that two moles of DBBP react with one mole of zinc. A series of tests were conducted to bring DBBP to its full loading capacity and the analysis of the results confirms this stoichiometric factor of 2. Extraction isotherms were established by varying either the AIO ratio or the concentration of zinc in the aqueous feed. Both curves were found to be identical.

Jan 1, 1990

By Katsunori Yamaguchi

Secondary materials, that contain relatively high concentrations of platinum group metals, (PGMs) are treated in copper smelting process. The PGMs lost in the slag is increasing with increasing quantities of scrap treated amount. To determine the portion of the PGMs chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. An experimental study was carried out to determine the distribution of palladium between the FeOx–SiO2 slag and the liquid Cu2S–FeS matte at 1573 K and a fixed partial pressure of SO2 of 0.1 atm. It was found that the distribution ratios are around 10−3 for platinum and palladium. The distribution ratios show a tendency to increase when the grade of matte is increased above 60 mass% Cu. In addition, the solubility of platinum in FeOx–SiO2 slag equilibrated with a pure palladium and the Pd-Cu alloy was determined at 1573 K and the range of oxygen partial pressure from 10−9 to 10−7 atm. The solubility of palladium in the slag tends to increase with increasing oxygen partial pressure and activity of CuO0.5 in the slag.

By Ali P. Gordon, James Williams

Joints gasketed with viscoelastic seals often receive an application of a secondary torque, i.e., retorque, in order to ensure joint tightness and proper sealing. The motivation of this study is to characterize and analytically model the load and deflection re-torque response of a single 25% glass-fiber reinforced polytetrafluorethylene (PTFE) gasket-bolted joint with serrated flange detail. The Burger-type viscoelastic modeling constants of the material are obtained through isolating the gasket from the bolt by performing a gasket creep test via a MTS electromechanical test frame. The re-load creep response is also investigated by re-loading the gasket after a period of initial creep to observe the response. The modeling constants obtained from the creep tests are used with a Burger-type viscoelastic model to predict the re-torque response of a single boltgasket test fixture in order to validate the ability of the model to simulate the re-torque response under various loading conditions and flange detail.

Jan 1, 2015

By Neusa Alonso-Falleiros, Aristeu Braz da Veiga, Marcelo B. Mourão, Adriano Pescarmona, Antonio Alberto Froes Schettino, Cyro Takano, Carlos A. S. Giraldo

"The Caron process of nickel extraction from lateritic ores produces a fair amount of an inert residue, the so-called “black sludge”, that is disposed in a dam according to the required environmental regulations. On the other hand, it represents an opportunity to resource recovery. This work presents the characterization of the residue, discusses some possible ways to recover the valuables, and presents experimental results of pyrometallurgical runs aimed at recover nickel as an iron-nickel alloy. It has been shown that the residue contains large amounts of silicon, iron, aluminum and magnesium, in the form of oxides and silicates, and small quantities of nickel, cooper and cobalt, besides several other elements. It has also been shown that gravimetric or magnetic concentration methods do not present promising results. On the other hand, it is possible to obtain iron-nickel alloys by high-temperature carbothermic reduction of the “black sludge”.IntroductionThe Caron process consists of a combined pyro-hydrometallurgical process to extract nickel from high iron limonitic lateritic ores, recovering also the cobalt present in the ore. The main steps are the reduction roasting of the ore, aiming at a selective reduction of nickel and cobalt to the metallic state, avoiding as much as possible iron reduction, followed by leaching with ammonium carbonate solution and the recovery of metal from the pregnant liquor [1,2]. As a result, significant amount of tailings are generated, that are disposed in appropriate dams. This residue, called “black sludge”, contains significant proportion of silica and iron, and also small amounts of nickel, cobalt, cooper and some other elements. Due to diminishing deposits of nickel ore, high metal prices and a significant amount of “black sludge “ available after several years of operation of the plant, Votorantim Metais, who operates a facility in Brazil that uses the Caron process, decided to explore the possibility of recover nickel from the residue. This paper presents the characterization of the residue, and the results of experimental work aiming recovery of nickel from it."

Jan 1, 2008

By Ryokichi Shimpo

Much amount of sludge is produced from the wastewater treatments in surface finishing industry. There are many problems for the abandonment of the sludge because of the high water content and heavy metals included. It is often observed that hexavalent chromium, which is toxic, is generated in the course of heat treatments of the sludge for reducing its amount by dispersing water. In this study, conditions of the sludge calcinations for reducing water contents have been examined. Maximum hexavalent chromium generation was observed in the temperature range around 773 K, at which most of the crystallization water decomposed from the sludge. When the heating temperature became higher than 1173 K, the amount of the hexavalent chromium extracted from the calcined sludge became as low as 10 mg/kg sludge. When the sludge was heated with iron oxides, FeO or Fe203, iron ferrite has been synthesized which may be used as a magnetic material. The amounts of hexavalent chromium generated in the heat treatment with iron oxides were not much different from those without iron oxides.

Jan 1, 2003

By L. Katgerman, H. J. Brinkman, J. Duszczyk

"The phase formation sequence in the in-situ synthesis ofTiB2 in A1 from elemental A1, Ti and B powders is identified with a combination of DSC and XRD. After the melting of A1, A1B2 and A13 Ti are formed at the contact areas between A1-B and A1-Ti. The influence of variations in starting composition on the reaction kinetics is explained in terms of there effect on the different processes in the formation sequence. Parameters in the starting composition that were investigated are; fraction ofTiB2 forming reactants, non stoichiometric Ti:2B ratio's, and addition of alloying element Cu.It was found that a liquid Al phase is necessary for the in-situ TiB2 forming reaction from the intermediate A1B2 and A13 Ti phases. If all Al is consumed by the formation of A1B2 and A13 Ti the TiB2 formation is halted until the decomposition of A1B2 and A13 Ti .Overstoichiometric amounts of B are needed for complete conversion of the Ti, present in A13Ti, into TiB2 This is explained by the fact that some of the stable A1B12 phase is formed after the decomposition of A1B2•The addition of Cu leads to an increasing reaction rate in the A1-Ti reaction. A possible explanation for this is that the A1-Cu liquid penetrates more easily between the Ti and its surface oxide than the unalloyed A1 liquid."

Jan 1, 1998

By Susumu Okabe

Injection metallurgy is widely adopted in various fields of metallurgical operations to achieve high productivity. The Mitsubishi Continuous Copper Smelting and Converting Process employs the top blown lance technique for the continuous supply of solid charges and reaction gases into the molten bath, where the agitated bath contributes to enhance the heat and mass transfer and the increased gas/liquid interface area accelerates the reaction. However, excessive splashing of the molten materials accompanied by the injection may cause an unexpected wear of the furnace lining. In order to estimate the splashing rate quantitatively, and to optimize the furnace design and the blowing condition, a physical model study of the top blown gas injection onto the liquid bath was carried out. An equation of the splashing rate was obtained as the function of cavity size, gas velocity and bath properties.

Jan 1, 1995

By Felipe Daroch, Maria C. Ruiz, Rafael Padilla

Copper concentrates with high arsenic contents must be pretreated before conventional smelting to prevent environmental pollution with arsenic compounds. In this work, experimental results concerning the selective removal of arsenic and antimony from copper concentrates are presented. The process consists of an alkaline digestion using concentrated NaHS-NaOH solutions to transform the arsenic and antimony sulfides into soluble compounds. A water leaching follows the digestion to dissolve the arsenic and antimony, leaving clean copper sulfide solid residues. The laboratory scale tests were carried out using a copper–arsenic concentrate with 15.05% As and 1.42% Sb. The results showed that the most important digestion variables were temperature and concentrations of NaHS and NaOH. Over 97% of arsenic and 92% of antimony could be removed in 10 min of digestion using 8.9 M NaOH and 100% excess of NaHS at 80 °C. The subsequent water leaching was performed at 80°C for 20 min.

Jan 1, 2015

By M. M. Kim

Zn-27% Al was pressure infiltrated into a column of 20 micron diameter abrasive grade SiC particles to give billets with particle loading of 50 voli.une %. Some billets were heated to a temperature where they became semi-solid and diluted with liquid Zn-27% Al alloy to give billets with particle loadings of 12 and 16 volume %. Some of these billets were then extruded into wire with an area reduction of approximately 98%. Tensile properties of the as-cast billets were always inferior to those of the matrix alloys; however, the extruded composite samples showed at 37% improvement in ultimate tensile strength compared to their extruded conventional counterparts. The fracture surfaces of these samples are described.

Jan 1, 1990

By Shengqin Zhang, Yousef Mohassab, Feng Chen, Hong Yong Sohn, Mohamed Elzohiery, Amr Abdelghany

A novel ironmaking process is under development at the University of Utah aimed at producing iron directly from iron oxide concentrate in a flash reactor. This process will reduce hazardous emissions and save energy. The kinetics of magnetite reduction with hydrogen was previously investigated in our laboratory in the temperature range 1150 to 1400 oC at large temperature increments (~100 oC increments). Due to the significant melting that occurs above 1350 oC, the reduction kinetics was measured and analyzed in two distinct temperature ranges of 1150 to 1350 oC and 1350 to 1600 oC (~50 oC increments). Experiments were performed using magnetite concentrate particles of different sizes under various hydrogen partial pressures and residence times. Reduction degrees of more than 90 % were achieved in a few seconds at temperatures as low as 1250 ºC. Different rate expressions were needed to obtain reliable agreement with experimental data.

Jan 1, 2016

By Jafar Safarian

Bauxite is the main raw material used for the production of alumina (Al2O3) through the well-known commercial Bayer process. This process has significant challenges such as limitation in using low-grade bauxites as they contain significant amounts of impurities such as Fe, Si, Ti. The Bayer process residue, which is known as red mud, is also a global environmental challenge due to huge amount of this low value residue production. An alternative sustainable process with high potential to solve these problems and produce valuable and consumable by-products is a pyrometallurgical-hydrometallurgical process in which the low-grade bauxite ore is treated through a smelting-reduction process, yielding iron alloys and a calcium-aluminate slag. Alumina is then produced from the slag by hydrometallurgical treatment. In the present work, the reduction of pellets produced from different bauxite ores by hydrogen is studied and it is shown that complete iron oxides reduction is possible. Further smelting and smelting-aluminothermic reduction of the reduced pellets show that iron and silicon ferroalloys can be produced, in addition to a proper slag for alumina extraction.