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By F. G. Caballero, J. L. Gonzalez-Carrasco, S. Barrius, H. Carreon, M. Lieblich

"The grit blasting is a low-cost technique successfully used to enhance mechanical fixation of the implants through increasing their roughness. As a result of the severe plastic surface deformation, it produces subsurface effects such as grain refinement, hardening and compressive residual stresses which are generally evaluated with destructive techniques. In this research work, non-contacting and contacting thermoelectric power measurements are performed in blasted 316L VM and Ti-6AI-4V specimens using Ah03 and Zr02 particles which yield a coarse and a fine rough surface, respectively. This study correlates the microstructural changes induced by the grit blasting treatment and the limitations and advantages of each of the nondestructive thermoelectric techniques based on the Seebeck effect used to evaluate these biomaterials.IntroductionIt is well known that surface properties play an important role in metallic materials used in bio-medical applications. Since the biological response is correlated directly with surface properties it is comprehensible the intense activity in superficial modification by physics or chemistry methods in this field. Grit blasting, one of the most popular surface modification of metallic biomaterials, enhances the mechanical fixation of the implant through the increase in roughness [1-3]. Roughening is developed by bombarding the surface with a high-velocity jet of ceramic particles, being the final roughness a function of the processing parameters (pressure, distance, time, ... ) and blasting particles (nature, shape, size). As the plastically deformed surface layer tries to expand relatively to the intact interior of the specimen, residual compressive stress gradients develops perpendicular to the surface at shallow depths with a maximum value at a depth in the range of 5 to 60 µm. This surface treatment also may cause subtle variations in the subsurface material properties, such as increased hardness and grain size refinement, which are consequences of the significant plastic deformation through cold work. Blasted affected zones may extend to a depth of up to about 200 µm. The subsurface hardening and the near-surface compressive stress gradient playa beneficial role by retarding fatigue crack nucleation and further growth, ultimately extending the fatigue life of the metallic part [4]. In this work, two non-destructive thermoelectric techniques (NDTT), the non-contacting and contacting thermoelectric power measurements were used to analyze the subsurface induced changes on blasted Ti-6AI-4V and 316L VM specimens using Al2O3 and Zr02 particles. Detailed information on the microstructural induced effects and subsurface mechanical properties were published elsewhere [5-8]. Here the nondestructive evaluation of the involved microstructural changes is used to assess the global subsurface damage. Advantages of using nondestructive techniques during manufacturing are envisaged."

Jan 1, 2012

By W. Y. Kim, K. H. Song, K. Nakata

"The present study was carried out to evaluate the mechanical properties of friction stir welded Inconel 600/SS 400 lap joints. In this process, friction stir welding (FSW) was performed at a tool rotation speed of 200 rpm and welding speed of 100 mm1min, and argon gas was utilized to prevent surface oxidation during the welding. Application of FSW notably decreases the grain size of Inconel 600 alloy from 20 µm in the base material to 8 ~ in the stir zone. However, the grain size of SS 400 in the weld zone was slightly coarsened, when compared to the base material. Also, the hooking in the advancing side and the intermetal1ic compounds (M7C3) in the weld interface between Incone1 600 and SS 400 were well formed. These intermetallic compounds and hooking were effective to increase in mechanical properties such as tensile and peel strengths.IntroductionFriction stir welding (FSW), applicable welding process at solid state, has several advantages in defect suppression such as blow hole, segregation and cracking which mainly occurs in fusion welding [1, 2]. Notable grain refinement in the stir zone due to FSW can expect the outstanding increase in mechanical properties of the welds. In constructing the chemical and power plants, Ni base superal10ys have been used in many parts, moreover, fusion welding as construct method, such as gas tungsten arc welding, electron beam welding and laser welding, has been mainly used [3-5]. However, fusion welding has a limit in an increase in chemical and mechanical properties in the welds. Lately, Ni base superalloys to which FSW applied have been reported with notable enhancement in mechanical properties, which resulted from refined grains in the welds [6-10]. These researches showed the possibility in applying the FSW, directly."

Jan 1, 2012

By Stella Agatzini

Column leach tests were conducted to evaluate the amenability of poor Greece nickel laterites to heap leaching with dilute sulfuric acid at ambient temperature. The ore tested was a limonitic laterite with less than 1 % nickel and it was subjected to a suitable pretreatment with water prior to it being loaded into the columns, following findings of preliminary research work. The acid solution was recycled after suitable pH adjustment. Factorial designs were used to determine the effects and interactions of the following factors: sulfuric acid concentration, ore column height, ore grain size and ratio of leach solution volume to the ore quantity. The response which were investigated included nickel and cobalt recoveries, codissolution of iron, calcium, magnesium, aluminum, chromium and silica and also sulfuric acid consumption. Experimental error was also detennined. The tests showed that a nickel recovery of 88% could be achieved in 60 days.

Jan 1, 1993

By V. Bredykhin

The efficiency of scrap processing depends firstly on reliability of information about its chemical composition. The paper presents the results of the investigation and development regarding solid copper alloy scrap in the range of lump size 40÷300 mm. Nowadays the sorting of lump scrap is done by two methods: 1. Sorting according to metals and alloys is done at places of scrap generation, and further till metallurgical processing each lot has its "certificate"; 2. Hand sorting of scrap is done according to the marks on solid items in special shops using proximate analyzers or manually by experienced workers. This sorting process is labor - consuming low efficient and involves mistakes. The informational method is a promising trend in the copper scrap sorting. The method is direct, i.e. as a result of sorting the chemical composition of each scrap lump or main elements is determined, and assured data of qualitative and quantitative composition are received.

Jan 1, 2006

By Yu. A. Grinin, Yu. A. Sannikov, M. A. Lyamina, V. A. Shumskij, L. V. Slobodkin, N. N. Ushakov

This manuscript describes the Kivcet treatment of lead-bearing materials having high contents of copper and zinc. The tests were carried out on bulk concentrates from the Zyrianovsk Mining and Concentrating complex, "Kazzinc" JSC (Kazakhstan) with the following composition: Pb 37.6%, Cu 10.4% and Zn 6.8%. Two properties of the concentrate were under investigation: their calorific value and their desulphurization rate. By adding flux, the charge properties were brought close to the properties of high-grade lead sulphide concentrate. The charge was melted with high productivity. To ensure high copper recovery, Waelz residue was added to the charge. The residue contained more than 20% carbon and about 30% iron metal. The residue was partially replaced by coke that facilitates high copper recovery into the matte. The smelting achieved a production rate of 20 t/h with one burner. Lead recovery into the lead bullion was 88.8%; copper recovery into matte was 92.3%; zinc recovery into slag was 75.5%; and zinc recovery into the fume was 5.1%.

Jan 1, 2000

By J. R. Wynnyckyj, R. Marr

Continuous measurement based on radiation pyrometry has often met with difficulties whose causes have been obscure. In this paper the experience gained with on-line pyrometry in utility and Kraft recovery boilers in the range 800-l400oC will be reported. It is shown that the inherent problems are best resolved by using a spectral pyrometer not sensitive to gas radiation. The radiation from the suspended particles thus provides the signal. It is further shown that the principle cause of difficulties is signal calibration drift caused by heat fluxes originating from surrounding surfaces and reflected by the particles to the pyrometer. Several examples are given how such problems may be resolved using process information and/or additional measurements, fed to and processed by and on-line microcomputer.

Jan 1, 1989

By Adelana Adetunji

Ilmenite ore samples obtained from Dankoli in Zamfara, North Western Nigeria has been characterized using Energy Dispersive X-ray fluorescence (EDXRF) technique, X-ray diffraction (XRD) technique and the Neutron Activation Analysis (NAA) technique. The major constituents in the ore were quantitatively found to be TiO2 and Fe2O3 in concentrations of about 60wt% and 31wt% respectively. These occur in the forms of magnesian ilmenite (Fe, Mg)(Ti, Fe)O3, pure ilmenite (FeTiO3), and barium copper yttrium oxide (Ba2Cu3YO6.56) minerals. Other constituents/impurities in minor or trace quantities include MnO, Ta2O5, Nb2O5, Wo, SnO2, Hf, Zn, V, Zr, Co, Pb, Br, Al, Rb, Y, Th and U.

Jan 1, 2006

By Tim B. Vanderwood

The mineralogy of dusts from several locations in a lead smelting plant, remotely collected dusts and soils near the lead smelter, and dusts from a secondary copper smelter were examined by reflected light microscopy (RLM) to determine their m1neralogy, texture, and origins. Individual grams were further analyzed by microbeam techniques. Detailed petrographic analysis of the dust has been supplemented by automated scanning electron microscopy combined with energy dispersive x-ray spectroscopy (ASEM-EDS). This technique allows the rapid sizing and chemical analysis of thousands of individual particles in a dust sample, producing particle size distributions as well as statistically meaningful breakdown of a sample into chemical types (e.g., proportion of galena vs chalcopyrite).

Jan 1, 1992

By E. M. Alcântara

This paper describes some aspects about the relationship between copper electrorefining addition reagents and the hydrogen in the cathode. The conditions of electrorefining were studied by factorial design methods. The advantages of this technique are reduction in the number of tests, well organized experiments; improvement in productivity and reliability of results. The dosage of the two main addition agents, glue and thiourea, were varied simultaneously and compared with the hydrogen content in the cathode. The influence of these factors, as well their interactions were analyzed by statistical methods denominated ANOVA (Analysis of Variance). The increase of thiourea quantities, within of levels studied, influenced significantly at 95% confidence in the hydrogen content in copper cathode.

Jan 1, 1999

By Jr. Pomykala, B. J. Jody, E. J. Daniels

Each year, about five (5) million ton of shredder residues are landfilled in the United States. ·Similar quantities are landfilled in Europe and the Pacific Rim. Landfilling of these residues results in a cost to the existing recycling industry and also represents a loss of material resources that are otherwise recyclable. In this paper, we outline the resources recoverable from typical shredder residues and describe technology that we have developed to recover these resources.

Jan 1, 2000

By Tian Li

Simple compartmental models of a laboratory batch gibbsite precipitator were used to investigate the influence of the number of compartments, the local shear rate and solids distribution on the crystal size distribution (CSD) under the conditions where aggregation is the dominant mechanism. In the current work, a power law relationship was assumed between the local agglomeration and shear rate. The simulation results showed that both the local shear rate and solids distribution have significant effect on the CSD responses, and the interchanging flows has a lesser impact with its influence strongly depending on the former two factors. Overall, the results reveal that in an aggregation controlled precipitation system, the influence of each of the factors on the CSD depends on the local hydrodynamic conditions in the precipitator, as well as their interactions.

Jan 1, 2003

By Alexandr I. Volkhin

It is practically useful to separate copper from nickel at the fire refining stage of blister copper by transferring nickel in electrochemical inert silicides which are being concentrated further into the tank-house slimes. The treatment of copper melt by silicon-containing reagents is resulted in lowering the interfacial tension of the melt, its deoxidizing, selective siliconizing of in-melt nickel and forming a by-product with fluxing properties. Si-containing reagents have positive influence on results of fire and electrolytic refining, and further pulverizing of copper in plant conditions.

Jan 1, 2006

By Sunil Jayasekera

This paper describes the results of a study carried out to examine the feasibility of electrolytic recovery of silver from cyanide leach liquor generated from a Western Australian silver mine tailings using a novel high mass transfer electrowinning cell. The proposed circuit involves heap leaching and electrowinning in a closed loop. The filter-press-like closed electrode arrangement of the cell allowed much improved mass transfer of metal ions to the cathode surface, making direct electrowinning of metals from dilute solutions feasible. The tests were conducted both in the laboratory and at large scale using a prototype with ~1.0 m2 cathode area. The results showed that the recovery of silver from as low as 250 mg L-1tenor was feasible. The silver deposit produced with the prototype cell was non-adherent and powdery and could be readily removed from the closed cell. A system was developed so that silver powder was discharged continuously during the run.

Jan 1, 2003

By Tian Li

Molecular crystal growth during gibbsite precipitation from caustic aluminate solutions under different flow regimes was investigated in three different laboratory precipitators. The gibbsite precipitation experiments were conducted at the same temperature, initial liquor composition and seed type. The Taylor-Couette precipitator and the stirred tank precipitator were operated, respectively, under the laminar and turbulent flow regimes, while the bottle roller precipitator was operated in a complex flow regime, where fluid flows are generated by the end-over-end rotation of the bottles. Comparison of the growth rate estimates from the different flow regimes showed good agreement, which suggests that the hydrodynamic regime has little or no effect on gibbsite crystal growth under the operating conditions employed in this work. The growth rate estimates from the current precipitation study showed a second order dependency on supersaturation and is consistent with a screw dislocation growth mechanism. The findings of the current work are in agreement with previous gibbsite crystal growth studies published in the literature.

Jan 1, 2003

By Lauri Pajunen

DSA-anodes are widely used in metal electrowinning. In zinc electrowinning the electrolyte solution contains manganese ions, and the deposition of manganese dioxide happens on the anode. This manganese dioxide layer cannot be removed without losing the active coating of the DSA-anode. The same problem can be found with hybrid anodes. In hybrid anodes mixed metal oxide coated titanium mesh is attached to a lead base material. In this study, the effect of dissolved manganese on anode behaviour is studied with three different anodes. These anodes are lead anode with 0.6% silver, hybrid anode and DSA-mesh. Methods of study include polarization, galvanostatic and potential mapping experiments.

Jan 1, 2003

By Julian Szekely

Transport phenomena, that is heat transfer, mass transfer and fluid flow, play a critical part in the operation of metallurgical reactors. In this paper, we shall present a review of our current state of ability to model these systems mathematically, with emphasis on the use of computational codes that are generally accessible to the public and on the comparison of the theoretical predictions with measurements.

Jan 1, 1993

By J. Miernik, D. Krupka, B. Ochab

The electrolytic zinc plant, with a capacity 75,000 tonnes per year, is part of Zaklady Gorniczo-Hutnicze BOLESLAW. It is the biggest zinc producer in Poland. The electrolytic zinc plant started up in 1955 with a capacity 15,000 tonnes per year, and multiplied its production by 5 till nowadays. At the beginning, the plant processed only calcine from zinc oxides (60% Zn, 3-4% Pb, 0,03 % Cd) which were produced from Waeltz fumes by calcination in a rotary kiln. Participation of calcine from zinc sulfide concentrates in the feed grew during the BOLESLAW plant expansion. Currently, only roasted sulphide concentrates, calcine from fluid-bed roasters, is processed. This paper presents a general description of the ZGH BOLESLAW plant and discusses the processes of roasting, leaching, purification and electrolysis. Also shown are the chemical analyses of the various process materials.

Jan 1, 2000

By Anatoly Sudnev, Vladimir Skorohodov, Igor Kudryavtsev, Boris Radionov, Dmitriy Panov

"In cobalt production technology at a stage of solutions purification manganous cake (slime) basically containing hydroxides of the specified metals is formed. The possibility of full cobalt recycling in the basic technology of metal production at slime processing with generation of pure manganous compounds is shown. After slime dissolution in sulfuric acid in the presence of reducers the solutions containing cobalt, manganese, nickel and other nonferrous metals are formed. Optimum conditions of selective precipitation major part of cobalt by sodium hydroxide from the obtained solution are defined, thus more than 95% of manganese are remained in the solution. The cobalt precipitate is directed to the basic technology and the solution is purified by sorption. The most effective sorbents are chosen, optimum modes of its use are found. Examples of manganese recovery from the purified solutions as MnO2, MnCO3, Mn(OH)2 with a ratio manganese : impurities more than 3000 are presented.In the processes of hard alloys manufacture and processing of cobalt-bearing primary raw materials various cobalt-manganous slimes are formed. After leaching by solutions of mineral acids the problem of cobalt and manganese separation becomes an actual. The common way of metals separation in a solution is the Shreyber’ alkaline method allowing rather selectively to precipitate of cobalt hydroxide by sodium hydroxide. However this way does not allow separating completely target metals because of transfer of some manganese in the hydrated precipitate, even at its rather low content.In the given work the results of researches to improvement of a traditional way by inclusion to hydrometallurgical technology of operation of sorption separation of the specified metals are presented. The main goal is definition of conditions to achievement of the complete removing cobalt at hydrolysis with the minimum sedimentation of manganese and the subsequent additional recovery of cobalt by ionites from the obtained solutions."

Jan 1, 2008

By Alexandre Bonan

The paper reports on the results of a kinetic study on the oxidation reaction of aqueous free cyanide ions with H202, in the presence of Cu(2+) catalyst. The variables and respective ranges studied were the following: (CN) ° = 10 -100 mg/l pH = 10 -11 (H202/CN) mol ratio = 1 -3 (Cu/CN) mol ratio = 0 -0.25 The results lead to the development of a semi-empirical model whish incorporates both the useful oxidation reaction and the parallel alkaline decomposition of H202.

Jan 1, 1992

By T. Taniguchi

The existing Mitsubishi Process line at Naoshima Smelter and Refinery has been operating successfully since 1991, and its present production capacity is 270,000tpy of copper. Furnace relining works have been carried out every two years to coincide with the compulsory bi-yearly boiler inspection, but the next target is to extend the furnace refractory life to four years, while still undergoing the mandatory boiler inspection every two years. Although the damage of hearth bricks beneath lances in the Smelting furnace was a matter of concern, it was reduced by controlling gas velocity and evening solid distribution to each lance. The life of bath level bricks in the Converting furnace was also a concern, but four-years continuous use of the bricks was achieved in the course of the last two campaigns. Several other improvements were also carried out to the cooling systems during the shutdown in 2005 to ensure longer campaign life. This paper summarizes recent improvements implemented to enhance the advantages of the Mitsubishi Process.

Jan 1, 2006