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By Sugui Tian

By means of the T6 treatment, the measurement of creep curves and microstructure observation, the influence of T6 heat treatment on the microstructure and creep properties of Ti-6Al-4V alloy is investigated. Results show that the microstructure of the forged alloy consists of the banded-like a phase and networks b phase. After sub-temperture T6 treated, the microstructure of alloy consist of the block a phase and ?networks basket? structure. Under the conditions of the applied stress of 575 MPa at 4000C, the forged alloy displays a lower creep lifetimes, after T6 treated the creep lifetimes of the alloy is enhanced to 548 h from 66 h, which is attributed to the formation of the network basket structure in which the needle-like phase are dispersedly distributed. As creep goes on, the denser dislocations in the a phase are concentrated to occur the dynamic recrystallization for refining grain. which is a main reason of the alloy displaying a better creep lifetimes and plasticity. Thereinto, the creep mechanism of the forged alloy is thought to be the slip of the straight <a> and <a+c> dislocation are activated on the prismatic planes and pyramidal planes, while the creep mechanism of T6 treated alloy is that wave-like <a+c> dislocations are activated on the pyramidal planes.

Jan 1, 2009

By Sergio N. Monteiro

Jute fabric obtained from discarded sackcloth is a promising low cost and post-used material being considered as reinforcement of polymeric matrix composites. In particular, the combination of this fabric with a recycled plastic constitutes an environmentally correct composite with both economical and environmental advantages. The present work investigates the toughness of recycled polyethylene composites reinforced with up to 40 wt% of post-used jute fabric extracted from discarded sackcloth. Standard Izod notched specimens were impact tested and the results showed an increase in toughness with the amount of jute fabric. Observation of the composite fracture by SEM revealed that the fabric weave, in spite of damages caused by the previous use of the sackcloth, act as an effective obstacle to crack propagation.

Jan 1, 2009

By Bin Xu, Qian Li, Yong-bin Yang, Xiao-liang Liu, Tao Jiang, Yan Zhang

Some high sulfur and arsenic-bearing gold concentrate has a gold leaching rate less than 80% by oxidation roasting-pickling-cyanidation process. The characteristics and intensification of gold leaching were studied systemically. By combining chemical composition and phase analysis, the low gold leaching rate was found to lie in the capsulation of gold by iron-containing phases including iron oxides, arsenopyrite and pyrite. 96.66% of gold in the industrial leaching residue was capsulated and 95.88% of the capsulated turned out to be in the iron-containing phases. The results of laboratory pickling-cyanidation experiments on the calcine and industrial leaching residue presented further demonstration for the fact that gold capsulated in the iron-containing phases was hard to be leached. However, the gold cyanide leaching rate of calcine could be raised over 95% by a reduction roasting-pickling pretreatment which played such a significant role in exposing the capsulated gold that gold leaching was intensified remarkably.

Jan 1, 2015

By W. Kunda

A laboratory study was carried out on the treatment of sulphidic copper concentrates in aqueous chloride systems under elevated temperatures and oxygen overpressure. Exploratory tests showed that chalcopyriteoxidizes with various chloride salts to form, depending upon the pH of the system, soluble copper chloride or insoluble copper oxychloride salts; the copper can then readily be recovered from the solution or residues respectively. During the leaching, iron was oxidized to iron oxide and remained in the leach residue while the bulk of the sulphide sulphur was oxidized to the elemental form with a minor portion oxidized further to sulphate. The presence of metal chloride salts in the system increased the oxidation rates of chalcopyrite and depressed the solubilization of iron in the system. A systematic oxidation leach study carried out in (1) ammonium chloride and (2) sodium chloride systems showed that the former system required little or no HC1 addition while the latter required 2 mol of HC1 per mol of dissolved copper (plus zinc). The copper was recovered from the cuprous or cupric chloride leach solutions by cementation with iron. Extractions of 99% copper and zinc, 97% silver, and negligible iron were obtained. Sulphur was oxidized to the elemental or sulphate form; the relative proportions of the total sulphur were 60 and 30% for system (1) and 80 and 10% for system (2). A flowsheet for a conceptual process with minimal reagent requirements was proposed.

Jan 1, 1976

By P. G. Comba

Many gold producing states are requiring rinsing of spent heaps to render the leached ore compatible with the environment and are placing restrictions on effluent pa, cyanide, and metals concentrations. Parameters which may affect efficient rinsing of heaps have been investigated by the U.S. Bureau of Mines in laboratory column studies. Rinse profiles for cyanide, metals, and pH as a function of the volume of water passed through the spent ore are presented. Fresh water rinsing of spent ore in columns showed that rinsing of cyanide was not affected by the rinse solution application rate. Interrupted rinsing with a rest period between applications reduced the volume of water required to meet effluent cyanide concentrations. chemical oxidation of the effluent with recycle of the rinse solutions reduced effluent cyanide concentrations and the volume of waste solution generated. Water rinsing was not successful in reducing the alkalinity of the cement agglomerated ore. A dilute acid solution had to be applied after cyanide removal to reduce effluent pa levels to specified limits.

Jan 1, 1992

By J. M. Zhuang

Lignosulfonates, by-products of the sulfite pulping process, have been utilized in a process [1, 2] to treat acidic rock drainage (ARD). This process is referred to as the LignorTM process. In the present study, lignosulfonates were found to protect lime from developing an external surface coating, and hence to favor its dissociation. Further, the addition of lignosulfonates to ARD solutions increased the clotting and settling rate of the formed sludge. The capability of lignosulfonates to form stable metal-lignin complexes makes them very useful in retaining metal ions and thus improving the long term stability of the sludge against leaching. The LignorTM process involves metal chelation with lignosulfonates, ARD neutralization by lime to about pH 7, pH adjustment with caustic soda to 9.4 ? 9.6, air oxidation to lower the pH to a desired level, and addition of a minimum amount of FeCl3 for further removal of dissolved metals. The LignorTM process removes all concerned metals (especially Al and Mn) from the ARD of the Britannia Mine (located at Britannia Beach, British Columbia, Canada) to a level lower than the limits of the BC Regulations. Compared with the high density sludge (HDS) process, the LignorTM process has many advantages, such as considerable savings in lime consumption, greatly reduced sludge volume, and improved sludge stability.

Jan 1, 2003

By Huimin Lu, Zegao Sun, Zhijiang Gao

The traditional Ti6Al4V alloys were obtained by the smelting reduction of V-Ti bearing beach placer by rotary hearth furnace and aluminothermic reaction in laboratory. First, it gets he lp from combined rotary hearth furnace and grinding magnetic separation process to prepare titanium slag containing vanadium. In this study, a neural network model was used. The comparisons between experiment results and neural network simulation results show that genetic algorithm (GA)-based on back propagation (BP) method can predict the degree of reduction and separation of iron and slag with higher prediction accuracy. Then by aluminothermic reaction process, the optimized process parameters for Ti-V-Al alloys were searched. Al can deoxidize metal V and Ti from the metal oxides of artificial rutile containing vanadium. Finally, traditional Ti6Al4V alloy can be obtained by remelt and adjust the constituents.

Jan 1, 2016

By Bemd. E. Langner

At Norddeutsche AfFmerie the CollaMat is an important instrument for controlling the activity of glue in copper electrolyte. Thanks to on-line measuring of the glue activity appropriate action can to taken in the event of sudden changes, such as an intemption in the glue supply, as well as long-term trends, such as continuously decreasing glue activity over days or weeks. Laboratory tests on the dependence of glue degradation on temperature have shown that relatively small increases in temperature of only 3OC cause the half change value of the glue degradation to reduce by 25 %. It is a similar picture with the sulphuric acid concentration in electrolyte. An increase in the acid concentration from 160 g/l to 200 g/l can - depending on the temperature - likewise result in a decrease in the half change value of up to 25 %.

Jan 1, 1995

By T. C. -M. Cheng

Iron removal and disposal in zinc plants has imposed a major environmental challenge to the industry. Among the existing options of precipitating iron as jarosite, goethite, and hematite, the Hematite Process seems to be the best candidate for the future development of a waste-free technology, because of its potential of producing saleable iron oxide residues for feed in iron-steel making industry. Unfortunately, under the current practice of the Hematite Process, it is not possible to produce iron residues clean enough to meet the specifications of the said industry. In this paper, the practice of industrial hematite precipitation and the relevant technical literature are reviewed with the objective to identify the critical processing parameters which are responsible for the contamination of hematite, particularly with sulfur and zinc. The analysis is conducted from a crystallization theory standpoint with emphasis given to the role of supersaturation with respect to the cleanliness of hematite precipitates.

Jan 1, 1997

By R. C. Hubli

A chemical model has been developed to investigate the dissolution of sulphide minerals in brine solutions containing copper and iron chlorides. The model has been employed to study the dissolution .of synthetic NiS using different initial concentrations of Cu(II), Cu(I), Fe(III) and temperature. The speciation of copper with particular reference to the formation of hydroxy-chlorides as a function of total chloride and H+ has been computed. The model predictions are in agreement with experimental results. It has been found that addition of Fe(III) results in the maintenance of a high Cu(II)/Cu(I) ratio leading to enhanced rates of dissolution and suppresses the loss of Cu(II) due to the formation of hydroxyl-complexes.

Jan 1, 1997

By Anja Pfennig, Thomas Böllinghaus, Marcus Wolf

During CCS components are exposed to a corrosive environment and mechanical stress which results in corrosion fatigue and is inevitably followed by the lifetime reduction of these components. The lifetime reduction of the cyclically loaded high alloyed stainless injectionpipe steel AISI 420C (X46Cr13, 1.4034) constantly exposed to highly corrosive CO2- saturated hot thermal water is demonstrated in in-situ-laboratory experiments (T = 60 °C, brine: Stuttgart Aquifer, flow rate: 30 l/h, CO2) in an environment similar to the on-shore CCS-site in the Northern German Bassin. In-situ tension-compression experiments were established simultaneously along with electrochemical measurements using a newly designed corrosion chamber in a resonant testing machine at a frequency as low as 30 – 40 Hz. In addition technical CO2 was introduced into the closed system at a rate close to 9 L/h. S-N plots, micrographic analysis and surface analysis of the fracture surface are demonstrated. X46Cr13 (surface roughness Rz = 4) reached the maximum number of cycles (12.5 x 106) at stress amplitude of 173 MPa producing a low scatter range of 1:3.5. Hydroxide and siderite layers were found on pits and crack surfaces. No typical fatigue limit exists. Pit corrosion prior to crack initiation may be identified as failure cause.

Jan 1, 2016

By K. R. Robilliard

Ausmelt Technology has been developed to process copper concentrates containing significant levels of lead, arsenic and antimony. A process was developed aimed at smelting these concentrate materials to remove the contaminants to fume and produce a clean copper product. The production of clean copper and the potential economic benefits of this process step over the sale of impure concentrates is discussed.

Jan 1, 1995

By S. Eckert, G. Gerbeth, K. Timmel, B. Willers, T. Wondrak, N. Shevchenko, M. Röder

The quality of the produced steel in the continuous casting process is significantly governed by the melt flow in the mold. However, direct flow measurements in liquid metals are still rather scarce. In order to investigate these flow phenomena, three experimental facilities operating with low melting liquid metals were installed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The melt flow in the models is measured by the Ultrasonic Doppler Velocimetry (UDV) or the Contactless Inductive Flow Tomography (CIFT), multi-phase flows can be visualized by X-ray imaging. The obtained measurement results are primarily used for validation of numerical models. In this paper we will investigate the fluid flow in the mold and the behavior of the surface of the liquid metal using flow measurements by UDV and surface profile measurement by a laser scanner, respectively. Strong fluctuations and deviations of the free surface were observed in case of a static magnetic field

Jan 1, 2016

By P. A. Botha

Most sinter producers prefer to use a range of iron ores with the aim to optimize their sinter blends. ISCOR is however limited to the use of ore from two deposits, namely Sishen and Thabazimbi. Only sinter produced from Sishen ore is described in this report. The Sishen iron ore deposit provides high-grade hematite ore with a mean iron content of 65 per cent. Three major ore types are developed: massive, laminated and conglomeratic. The main ore mineral is hematite with minor to trace amounts of quartz, mica, phosphates and, in places, carbonates. A sinter product is characterized by its mineralogical composition and metallurgical properties. The production rate also plays an important role in the economic evaluation of sinter quality. Sinter-pot tests were conducted with varying basicities, given as the ratio of CaO to SiO:< and coke content. The results of these tests were characterized by mineralogical and metallurgical methods. Basicity of a sinter mix directly influences the mineralogical composition and metallurgical properties. The content of calcium ferrite and calcium silicate increases with increasing basicity, thereby increasing the reducibility and cold strength of the sinter product. Experiments performed during this study provided a model for the optimization of the sinter mix with respect to its mineralogical and metallurgical parameters.

Jan 1, 1991

By Ramiro Escudero G.

Since the introduction of column flotation almost forty years ago the column technology has grown into several non-mineral applications such as among others the effluent treatment, soils recovery and de-inking of recycled paper. Recent studies have demonstrated that particular characteristics of the dispersion (bubble size, gas holdup, bubble surface area flux) are needed for a given flotation column duty. In this work, two kind of spargers were tested (i.e., internal and external) using a 4 inch column lab in a two phase system. Results show that the external sparger provides a dispersion with characteristics that include those produced by the two internal spargers.

Jan 1, 2003

By J. W. Matousek

Cobalt behavior in pyrometallurgical processes is traditionally analyzed using slaglmatte distribution coefficients as functions of matte grades or matte iron contents. L(s/m) = (%Co) I [%Co] = f [%CuNi] or f [%Fe] The method is inconvenient to use in predictive mass balance work because of the interdependence of assays and mass quantities. An alternative procedure is proposed based on cobaltliron ratios for slags and mattes: Js = (%Co) / (%Fe), Jm = [%Co] / [%Fe], and J, = b + m [Jm]

Jan 1, 1993

By Shengli Wu, Wei Huang, Xinliang Liu, Kaifa Zhang

The slagging behavior, the phase of primary blast furnace slag and its transformation law of structure for the single furnace burden were studied in this paper. The results showed that the formation of primary slag was controlled by CaO/SiO2, Al2O3 content, MgO content, reducibility, iron content and porosity of the furnace burden. Fayalite (2FeO•SiO2) was easily formed from acid ferrous furnace burden while kirschsteinite (2(Fe,Ca)O•SiO2) was produced from alkaline ferrous furnace burden

Jan 1, 2015

By M. A. Cocquerel

The future economic necessity of mining copper ores with a high impurity content and increased environmental awareness will require closer examination of the distribution of arsenic within copper smelting processes. A generalized approach is developed which can be adapted to specific projects for the determination of an overall process configuration to satisfy all requirements in a cost effective manner.

Jan 1, 1983

By Jesse White, Tyler Salisbury

Research projects contain many stages of development from the conception of an idea to a fullscale commercial operation. The transition from laboratory-scale research to bench-scale roasting can represent a significant increase in complexity and cost, depending on how many variables are being evaluated. Thermogravimetric analysis (TGA) can simulate roasting conditions and produce a small sample for chemical analysis or materials characterization. A simultaneous thermogravimetric and differential scanning calorimetry (TG–DSC) can identify endothermic and exothermic reaction temperatures. Using thermal analysis, some of the process variables can be tested and eliminated such as ore and reagent blends, retention times, operating temperatures, and some atmospheres.

Jan 1, 2015

By K. Adham

For use in many existing and emerging applications, the purification of natural graphite is required to achieve +99.9% carbon content with minimum metallic impurities. Currently, the hydrofluoric acid process is used, which carries certain environmental and workplace health and safety impacts. While thermal purification of graphite at temperatures over 2500 °C is a known alternative, such high-temperature furnaces are expensive to build and operate. Using chlorine at lower temperatures to purify graphite is also known and patented, but is currently limited to treating solid synthetic graphite shapes in small-scale batch furnaces. Chlorine treatment of natural flake graphite resources can be used commercially, if certain drawbacks are addressed through process improvements that can be helped with the use of fluidized bed reactor technology.