Search Documents

By Lztok Peruš, Goran Kugler, Matevz Fazarinc, Milan Tercel

"Hot deformability of M42 tool steel additionally alloyed with cobalt and molybdenum was investigated. Hot-compression tests were carried out in the temperature range 850 °C -1200 °C, at strain rates range 0.001--6s-l up to strain of0.9. Field-emission scanning electron microscope and optical microscopy were used for characterization of microstructure of deformed samples, which revealed a very complex precipitation of carbides that strongly depends on the soaking temperature, the soaking time, the stress state, the deformation temperature as well as on the strain rate. Gathered data was used to calculate the processing parameters such as process maps, apparent activation energies and strain hardening exponents. For better understanding of thermodynamical properties of the studied steel a simultaneous thermal analysis was conducted. Furthermore the analysis of phase equilibrium was calculated using Thermo-Cale software. On the basis of these studies the optimal soaking temperature and process windows were determined.IntroductionHot workability ofledeburitic tool steels is important economic factor. This means that for each tool steel individuallysafe range of hot working parameters should be revealed. Publications in the literature with regard to the hot workability of tool steels are rare and therefore more information from this research area is desired.The relatively low hot workability of ledeburitic tool steels, i.e. steels in which the solidification is completed by a eutectic transformation of the residual interdendritic liquid to austenite and various alloy carbides (ledeburitic carbides), is usually characterized by the production of surface and internal cracks during the hot deformation."

Jan 1, 2013

By J. K. Brimacombe

Plant trials have been conducted at the Tacoma Smelter of ASARCO to assess the effect on tuyere blockage and refractory erosion at the tuyere line, of increasing the injection pressure of air into a Peirce-Smith con¬verter. Four tuyeres each having an ID of 19.1 mm (3/4 in) were installed toward one end of the tuyere line of the No. 4 Converter. Air and oxygen-enriched air were injected at 414 kPag (60 psig) through these tuyeres and at the usual 83 kPag (12 psig) through the remainder of the tuyeres in an otherwise normal converter campaign. The test campaign consisted of 88 charges and lasted for 89 days. During this period, punching of the high-pressure tuyeres was found to-be unnecessary; and when, as a precaution, the tuyeres were cleaned by hand at the end of a charge, they were always open. Also it was observed that the flow of high-pressure air remained constant. Accretion formation around the tip of the high-pressure tuyeres varied from charge to charge and was influenced by the matte grade and the level of oxygen enrichment.

Jan 1, 1983

By Bohumír Cech, Jirí Hanika, Václav Veselý

"PET bottles are separated and subsequently crushed into flakes. Except for PET, these flakes contain PE, PVC, paper, adhesives, beverages remainders and mineral impurities. PET itself usually is a glycol and terephthalic and isophthalic acid polymer.The suggested method consists in PET flakes crystallization at 255°C. In the meantime, volatile substances evaporate and PVC disintegrates. Formed crystalline PET is crushed into small particles and then is subject to the basic hydrolysis at an atmospheric pressure. In addition to lye solution, glycol is added in the hydrolysis. Water is eliminated by boiling, which gives rise to suspension of sodium salt of terephthalic acid and glycol. The suspension is skimmed and the filtered glycol is vacuum distilled. Pure glycol is then the distillation product.Crystals are dissolved in water and the solution is filtered, which eliminates PE and impurities. Electrodialysis removes pure terephthalic acid salt from the solution. Glycol solution is returned to the hydrolysis. Terephthalic acid is precipitated by a mineral acid. Subsequently, it is washed and dried. The filtrate is separated through electrodialysis to lye and acid. The lye gets back to the hydrolysis and the acid is used for precipitation. Terephthalic acid and glycol are products in a “polymer grade” quality. The waste is a part of washing waters, distillation residues after glycol regeneration and a filter cake after the terephthalate solution filtration."

Jan 1, 2008

By Shi Guan-Yong, Niu Li-Ping, Dou Zhi-He

"In the preset work, the viscosity model (named modified KTH model) proposed by Sichen Du and S. Seetharaman et al and extended by Shu Qi-feng was applied to the ESR slag systems. A correlation to predict the viscosities of CaF 2-(CaO)-Al203 slags using interaction coefficients of different cations in the presence of oz-and viscosity interaction coefficients between oz-and F in the presence of different cations has been developed. The interaction coefficient between oz- and F- in the presence of Al3+ was determined from the experimental data as shown in known literatures. The good agreement between the calculated viscosities and the experimental data in the CaF2-(CaO)-Al203 systems has indicated that this approach can be successfully employed to predict the viscosities of ESR slags.IntroductionReliable viscosities data of high-temperature slag melts are important for the modeling and design of high temperature metallurgical processes. Although a number of experimental measurements have been carried out, the available viscosities data is still scarce compared to the needs of today's technology, especially in the case of complex melts. In process simulations, the needs of viscosity descriptions for complex systems which could enable the extrapolation of the data as functions of temperature and composition is strongly felt today."

Jan 1, 2013

By Hüseyin Aydin

TWIP (Twinning-Induced Plasticity) steels have exceptionally good combinations of strength, ductility and damage tolerance which satisfy the recent requirements of automotive industries. Firstly, TWIP has the most beneficial effect on the work-hardening. It is believed that deformation twins increase the work-hardening rate by acting as obstacles against gliding dislocations. Moreover, TWIP steels have low to intermediate stacking fault energy and hence undergo extensive mechanical twinning during deformation, which in turn leads a good combination of both strength and ductility. To explain the mechanical characteristics and the mechanical behavior of the TWIP steels, we have been made some investigations and experiments that show the effects of microalloying elements and deformation mechanisms. In this study, three different compositions of TWIP steels have been produced. The microstructure and mechanical properties are characterized by using optical, electron microscopy and mechanical tests.

Jan 1, 2009

By C. García

Several modifications to Zaldivar's original design have been made in order to reach the design cathode production. This paper describes the modifications to the crushing, leaching, solvent extraction and electrowinning operations, which in turn have increased the production by 14.8% over the design capacity in 1999. The principal modifications were to (1) incorporate a dry pre- screening plant between the secondary and tertiary crushers to increase the percentage of fines to the piles, (2) increase the retention time of the solutions inside of the piles, and (3) increase the efficiency of the tertiary crushers to reduce the particle size of the product material. The leaching ratio was increased from 2.8 to 5.6 m3/ton. The temperature of the pregnant leach solution (PLS) was increased, the amount of acid used was reduced, and a strain of native bacteria was adapted in highly contaminated solutions. The copper concentration in the PLS was increased by more than 50% and was stabilized at this level by commissioning a process of two-stage leaching. The current density in the tankhouse was increased from an average of 2 16 to 3 17 A/m

Jan 1, 1999

By Jorge Gibson, P. Chris Pistorius, Megha Jampani

"The main reason for the significant carbon intensity of integrated steelmaking (approximately 1.8 tons of CO2 per ton of steel) is the use of carbon-based reductants in blast furnace ironmaking. Several changes to blast furnace ironmaking have been proposed as ways to reduce carbon intensity and cost. A conceptually simple two-zone blast furnace mass and energy balance can be used to quantify the expected impact of such process changes on coke rate, carbon intensity, and productivity. Examples to be discussed include top gas recycling, combining lower blast temperatures with increased coal injection to produce a rich top gas, using prereduced feed, and tuyère injection of natural gas. The use of the operating window – which illustrates how allowable flame temperatures and top-gas temperatures constrain feasible oxygen enrichment levels – is illustrated. Increased use of natural gas would lower the carbon intensity of blast furnace ironmaking.IntroductionBecause of the significant carbon intensity of steelmaking (approximately 1.8 tons of CO2 emitted per ton of steel produced) and the high production rate of steel (more than 1.4 billion tonnes per annum), steelmaking is responsible for a large percentage, approximately 6.7%, of world anthropogenic CO2 emissions [1]. By far the largest input of the carbon into conventional steelmaking is as coke, which is essential to blast furnace ironmaking. A typical fuel rate for blast furnace ironmaking is 450 kg of fuel per tonne of hot metal (THM). (""Fuel"" includes coke and injectants which partially replace coke; pulverized coal and natural gas are typical injectants.) Assuming the fuels to contain 90% carbon on average, and since nearly all of this carbon exits the steel plant as CO2, a fuel rate of 450 kg is equivalent to a CO2 intensity of 1485 kg/THM – by far the largest part of the total CO2 intensity of steelmaking.Blast furnace ironmaking is expected to remain the main source of new iron units; this paper gives some estimates of the extents to which further reductions in carbon intensity from blast furnace ironmaking is possible. A recent European assessment suggested that blast furnace process intensification options such as increased pulverized-coal injection or natural gas injection would yield only modest energy savings [2]. However, if the focus is on CO2 emissions rather than on total energy use, there would be an advantage to using fuels – such as natural gas – which have lower carbon contents relative to energy content."

Jan 1, 2014

By Young-Dae Kim, Dong-Sic Kim, Jong-Jin Pak, Kyung-Hyo Do

"Sulfur is one of the most harmful elements in stainless steel (SIS) products and the specification of sulfur content is getting more severe for high grade SIS. In order to accurately control the desulfurization reaction in high chromium containing SIS melts, it is important to know the thermodynamic interaction between chromium and sulfur in Fe-Cr melts over a wide range of chromium content. In this study, the equilibrium sulfur distribution, Ls, between a Ca0-Alz03 slag and Fe-Cr-C,.,-S melts were measured under CO atmosphere in the temperature range of 1823-1923 K. The specific effect of chromium on the activity coefficient of sulfur in the melts was determined with the consideration of carbon effect on sulfur. A separate experiment was carried to determine. Ls between a slag and FeCr- S melts (Cr: 0-30 mass%) at 1873K to check the validity of the thermodynamic parameter determined in the present study.IntroductionFerritic stainless steels containing chromium (Cr) up to 30 mass% have been developed for a good corrosion resistance and a high formability to replace austenitic SIS. Especially, Sulfur (S) causes a reduction of high-temperature strength and the hydrogen induced cracking (HlC) in stainless steel for line pipes. [l]Many studies on the desulfurization of hot metal and liquid steel have been carried out for several decades and they used HzS-H2 gas equilibrium technique for measuring the effects of many alloying elements on the activity coefficient of S in liquid iron. However, the study on desulfurization of Fe-Cr melts was very scarce.[2] In order to accurately control the desulfurization reaction of high Cr stainless steel, it is essential to know the thermodynamic relation between Cr and S in Fe-Cr melt over a wide range of Cr content and temperature.In the present study, the thermodynamic interaction between Cr and S in liquid iron was determined by measuring the equilibrium distribution ratios of S between Fe-Cr-C,.1-S melts containing a wide range of Cr up to 30 mass% and a 55 mass%Ca0-45 mass%Alz03 slag of which the sulfide capacity was pre-determined using Fe-C,a1-S melts in the temperature range of 1823-1923 K. The validity of thermodynamic parameter determined in the present study was checked by measuring the S distribution between a Ca0-Alz03-Mg0 slag of known sulfide capacity and liquid Fe-Cr-S alloy at 1873 K. Using Wagner's formalism, the results of experiment were thermodynamically considered to determine the effect of a specific concentration of Cr on the activity coefficient of S in liquid iron."

Jan 1, 2014

By Won C. Park

Experiments showed changes in the mineral content of dolomitic oil shale at temperatures and exposure times which bracket conditions encountered during in situ retorting. Laboratory results correlate with cores from a spent in situ retort at Occidental's Logan Wash test site at Garfield County, Colorado. Dolomite, CaMg(CO3)2, decomposes rapidly to form periclase, MgO, calcite, CaCO3, and CO . Both calcite and periclase are intermediate products that can be stabilized by CO atmosphere at lower temperatures, while steam accelerates the formation 2 of silicates. The decarbonation of calcite appears to involve a direct reaction with both quartz and periclase in forming these silicates. Decarbonation preceeds the formation of akermanite, Ca2 MgSi 207, and diopside, CaMgSi 206, within several hours of heating and is followed by the nucleation of forsterite Mg2SiO4, and monticellite, CaMgSiO4. Under in situ retorting conditions, akermanite and diposide are the major minerals above 800°C. Equilibrium is not attained within 200-300 hours. In situ retorting temperatures above 800°C for extended periods of time should reduce potential ground water leaching by the formation of silicate minerals. These silicates are less soluble than free lime, magnesium or alkali oxides. There is a corresponding decrease in the natural pH of these silicates from approximately 12 down to 7.5 to 9:

Jan 1, 1981

By Thomas Gliick, Jianming Lu, David Dreisinger

"The recovery of manganese from the Boleo project of Baja Mining is via an acid oxidation and acid reduction process in seawater. Manganese as manganese dioxide is leached into solution as manganese sulphate with the addition of sulphur dioxide gas as a reductant and then precipitated as a manganese carbonate. The use of the manganese carbonate intermediate to produce electrolytic manganese metal (EMM) has been extensively studied. The manganese carbonate can be used in place of natural (MnC03) or reduced ores (MnO) of manganese as a feed to the EMM plant. Manganese carbonate can be dissolved in spent electrolyte from manganese plating, followed by purification using ammonium sulphide precipitation of minor elements and then electrowinning in a selenium free process. The results of small cell testing of manganese electrowinning are reported.IntroductionThe Boleo Project of Baja Mining is a greenfields development currently under construction approximately 5 km north of the town of Santa Rosalia, Baja California Sur, Mexico. The Boleo property is held by the Mexican company, Minera y Metalurgica del Boleo S.A. de C. V. (MMB). MMB is owned 70% by Baja Mining Corp. and 30% by a consortium of Korean companies consisting of KORES - Korea Resources Corporation, LS Nikko Copper, Hyundai Hysco, SK Networks and lljin Copper.The Boleo deposit has Measured and Indicated resources of264.7 million tonnes grading 1.50% copper equivalent (CuEq) & Inferred resources of 159.9 million tonnes grading 1.15% CuEq. The calculation of copper equivalent is based on a combination of metal prices and predicted metallurgical recoveries (Table I). The metallurgical recoveries have been confined by extensive bench and pilot plant testing. Proven and probable reserves are available at Boleo to provide for more than a 30 year mine life. Initially, 25 years of mine life and 23 years of process plant operation have been scheduled in the February 2010 Technical Report Update (www.sedar.com)"

Jan 1, 2012

By Yuri Bychkov

The Electron Beam Melting is the most efficient technology for metals and alloys refining. For ,secondary metals processing the Electron Beam Skull Melting (EBSM) with the electromagnetic stirnng (EMS) of melt in the crucible was shown to be the most appropriate. The copper produced by EBSM with EMS possesses higher density and electric conductivity in comparison with other refining methods. The details for high power electrical machines were cast of the copper waste refined by EBSM technology.

Jan 1, 1995

By H. Matsuda, T. Iwashita, H. Awata, H. Liwei, D. Hirabayashi, Y. Saito, S. Ozawa, Y. Goto

"The present study is concerned with investigating the effect of chemical treatment on enhancing the HCl absorption capacities of coal burnt ash and slag. It was found that the HCl absorption capacity of coal burnt ash discharged from fluidized bed combustor was improved by hydration with water and 5% polyethylene glycol solution. This phenomenon was based on an increase of the specific surface area of treated coal burnt ash. The HCl absorption capacity of hydrated ash with polyethylene glycol solution was almost equivalent to that of standard CaO and Ca(OH)2. In particular, the specific surface area of hydrated ash with polyethylene glycol solution was found to be 19 m2/g, which was more than over eight times larger than that of raw sample. Hydrated slag treated with lON sodium hydroxide solution also showed high HCl absorption capacity, with highly improved surface area. It was found that the absorption capacity of slag for HCl depended on the treatment time, showing the maximum absorption capacity for 12 hours of hydration treatment.IntroductionA large amount of coal burnt ash, slag and dust are discharged from such industrial processes as coal combustion and metal refinery etc., and it becomes an serious problem to recover and diminish these solid wastes because of the shortage of dump sites and subsequent metal elution to the environment. Figure 1 shows the present situation of reutilization of coal burnt ash and slag in Japan [1,2]. It is shown in this figure that these solid wastes are recycled as materials in the fields of earthwork, agriculture and forestry etc. A part of these solid wastes, however, is still dumped to landfill. To decrease this dumped amount, the development of environmentally friendly reutilization technique for these solid wastes is of great importance."

Jan 1, 2000

By Takahiro Miki

In order to use metallurgical grade silicon (MG-Si) as a starting material for solar cell, phosphorus has to be removed from silicon because phosphorus is a n-type dopant. On the other hand, silicon, ferrosilicon, and silicomanganese are widely used as deoxidizers in steel refining processes. Since most of the phosphorus introduced during the deoxidation process is brought into final products, it is important -to lower the phosphorus content of these alloys. Hence, thermodynamics of phosphorus in such metals is important for the evaluation of dephosphorization processes. In the present study, thermodynamic properties of phosphorus in molten Si-P alloys at 1723- 1848K and those of Si-Fe-P and Si-Mn-P alloys at 1723K have been determined by equilibrating respective metals in a controlled phosphorus partial pressure. The results are expressed as follows.

Jan 1, 1998

By M. J. Bagshaw, J. D. Hunt, R. M. Jordan

"Continuous casting processes, and the roll casting process in particular, offer considerable potential to the Aluminium industry, both meatallurgically and economically.The three major limiting process problems that occur during roll casting are Centre Line Segregation', 'Sticking' where metal adheres to the rolls during casting, and 'Heat Line' formation. 'Heat Lines' are localised semi-continuous longitudinal defects, usually a few cms in width, where the cast metal leaves the roll bite partially molten. These defects occur at relatively low casting speeds when the mean slab exit temperature remains several hundred degrees below the solidus temperature. The objective of the work described here is to develop a better understanding of the roll casting process in general, and in particular, to understand the phenomenon of 'Heat Line' formation.A steady state two dimensional finite difference model has been developed to describe the roll casting process, incorporating a variable heat transfer coefficient through the roll bite. In the model the difference equations are formulated using a control volume method and latent heat is incorporated according to the Scheil equation. A Gauss-Seidel type technique is used to obtain the solution. Because the rate of heat evolution is non-linear the temperature in each box is determined by using a Newton-Raphson method. The solution for a box can be multi valued and therefore lead to instability particularly near the vicinity of the front. A stability 'criterion is presented which shows that to obtain a stable solution it is better to have long narrow boxes rather than boxes with small dimensions in both directions.The model explains why heat lines form in terms of the variable slab/roll heat transfer coefficient.Experimental measurements of slab exit temperatures are also presented. These were obtained on a Hunter twin roll caster for the binary AI-Cu system, at two compositions over as wide a range· of casting speeds as possible. The experimental results are compared with the predicted ones."

Jan 1, 1986

By R. C. Hubli

A panial equilibrium model? to simulate the dissolution of millerite (NiS) in aqueous solutions containing copper(II) chloride as the oxidizing species has been developed. The predominant copper(I) and copper(II) species are CuQ3 and CUO2 respectively. The model computes the initial concentrations of the species present in the aqueous phase under the specified input conditions, prior to the simulation of dissolution. During the dissolution of millerite, nickel enters the leach liquor as NiH and it has been found that the H+ decreases as a function of NiS dissolution. The simulation has been accomplished under conditions prevailing during actual dissolution, with only one mineral undergoing dissolution. The model can be applied for the simulation of co-dissolution of two or more sulfides. Under the given conditions, the precipitation of Cu1(OH»)O is negligible but loss of Cu(1l) could be significant if the initial H+ is lower than 0.03 M. The results of the simulation compare favorably with experimental observations.

Jan 1, 1996

By Z. Zhang, R. G. Reddy

The viscosities of industrial lead slags with various compositions were measured as a function of temperature. It was found that viscosities of lead slags decreased with increasing temperature, and the plots of ln(11) vs. 104tr followed a linear relation over the reported ranges of temperature. Using the data of this study and available other related data from the literature, a viscosity expression was developed as a function of composition and temperature. The calculated results using this viscosity expression are in good agreement with the measured data. The composition dependency of viscosity of lead slags is discussed.

Jan 1, 2000

By Hal dun Kurama

In thus-study, Bigadic upper zone zeolitic tuff, which contains about 87% clinoptilolite was used as an ion exchanger for removal of Pb++, Cu++, Cd++ and Hg++ ions from wastewater. Bench scale experiments with two different glass columns, were carried out continuously under the closed/ open circuit conditions. Before ion exchange tests, zeolite samples were treated with NaCI (6ml/ min. and 42BV). The effects of particle size, bed volume, pH and flow rate on the ion exchange capacity were determined. Under the best operation conditions, the effect of initial influent solution concentration on ion exchange selectivity was tested. As a-result, it was found that the Bigadiç clinoptilolite had the following ion exchange capacities;

Jan 1, 1995

By U B. Pal

Downsizing and decommissioning of nuclear facility operations is increasing the stockpile of various different grades of Radioactive Scrap Iron (RSI). Disposal of this material not only represents significant resource and value lost, but also necessitates long term monitoring for environmental compliance. The latter results in additional recurring expense. It is desirable to be able to decontaminate the RSI to a very low level that can be recycled or used for fabrication of containers for RSI disposal instead of using virgin metal to fabricate the container. Electro-Slag Remelting and Refining (ESR) is often used for decontaminating radioactive contaminated sources of scrap iron such as stainless steel. Non-radioactive oxides of cerium are used to simulate the radioactive oxide contaminants of Uranium and Plutonium. The success of the ESR process is strongly dependent on the capacity of the slag to rapidly incorporate the radioactive contaminant (simulant). In this study we have measured the slag-metal partition coefficient for cerium and investigated the reaction mechanism for the dissolution CeO, in the slag.

Jan 1, 2002

By Yotamu Stephen Rainford Hara, Animesh Jha

The investigation focuses on a low temperature recovery of Cu and Co from a 40 wt% SiO2-(30 wt%Fe,6 wt%Al)2O3-10wt% CaO-7wt%CuO-7wt%CoO slag over a temperature range of 1173K to 1323K. The alloy phases containing Cu-Co and Fe-Co alloy formed via the carbothermic reduction of oxides: MO + C = M + CO(g), where M represents metallic copper, cobalt or iron. In the direct reduction of oxides, the recovery of metallic phase was well below 90% at 1323K, due to the kinetic barrier which was analysed and attributed to oxygen and metal-ion transport in the slag. This barrier was overcome by adding CaSO4 and carbon, which yields a matte (MS) phase via MO + CaSO4 + 4C = MS + CaO + 4CO reaction. Lime thus produced in situ participates in metal oxide/metal sulphide reduction reactions, which are analysed with the help of X-ray powder diffraction, scanning electron microscopy, and thermogravimetric analysis.

Jan 1, 2014

By Russell E. Clemons

Coarse-crystalline granite, quartz syenite, syenite, meladiorite, and anorthosite in the Florida Mountains, southeast of Deming, New Mexico, were originally mapped as Precambrian. They were remapped in 1971 and some of them described as Mesozoic intrusives. Several subsequent papers presented Precambrian and Ordovician ages. Zinc, lead, copper, silver, gold, manganese, fluorite, and barite mineralization in the Florida Mountains invite more extensive exploration. Clarification of ages of rocks and periods of alteration and mineralization are necessary for efficient exploration. Field observations combined with petrographic studies strongly suggest that all the coarse plutonic rocks are Precambrian and most were altered extensively by late Tertiary hydrothermal activity.

Jan 1, 1982