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By AIME

NEW YORK'S largest hotel, the Pennsylvania, will be filled with mining and oil men and metallurgists the third week of February when some 3000 AIME members, their wives, and guests will gather for the Institute's 1948 Annual Meeting-its 166th general meeting. Except for the usual Sunday afternoon and evening sessions of the Mineral Industry Education Division at the Columbia University Men's Faculty Club, the big assembly will be under one top and members will not this year have to consult compass and map to find their next session. Possibly enervated by the stupendous effort of the Anniversary Celebration last spring and the plethora of highly successful fall meetings, the various committees have been a trifle slow in arranging their social and technical programs, but in mid December as we go to press there is already much to report indicative of substantial fare and high interest. The definite timetable schedule will appear in the February M&M.

Jan 1, 1948

By John L. Schroder, Woods G. Talman

EXPERIENCE has shown that certain known natural conditions and other indefinite characteristics combine to make a mining area vulnerable to mountain bumps. Some of the known conditions are heavy overburden, an overlying stratum of strong non-elastic rock, a structurally strong coal seam that does not crush easily and yet is the weakest stratum in the series, and a floor stratum of more than ordinary firmness. The indefinite characteristics could include resistance of top or bottom of a coal seam to lateral flow, effect of immediate top and bottom strata, nature of the coal seam, and other factors about which very little is known. It is in this area that exhaustive study is needed to achieve positive control of the dreaded mountain bump hazard.

Jan 8, 1958

By Lon Santis, David Buckwalter, Ken Steinmetz

This paper describes a magazine security system using two readily available cellular telephone-based technologies. The system is comprised of vibration sensors and remote cameras. The system is used at a Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) licensed explosives storage location in Pennsylvania to comply with PA Department of Environmental Protection (PADEP) regulations. The system provides instant notification to the licensee via cellular modems, text messaging, phone call, and e-mail. Likewise, the licensee can control the system remotely over the internet and using text messaging commands. The vibration sensors attach to the door of the metal type I magazines magnetically and detect any movement or vibration. The cameras trigger on movement and thermal radiation changes and can also be triggered manually to check alarms received from the vibration sensors. The previous system was comprised of a base unit and magnetic strips. The magnetic strips were powered by a hard line from the control unit and mounted on the doors and top of magazine creating a bond, that when broken triggered an alarm. Our main issues with the unit were the delay in alert times and tech support. Because of these issues, we decided an upgrade was necessary. Compared to that previous system used at this site, these new systems are highly affordable, carefree and reliable.

Jan 1, 2014

By Alden Greninger

IN a recent study1 of the deformation of metastable beta copper-zinc and beta copper-tin crystals, it was established that the parallel markings that appear on the surface of these crystals after slight deformation represent lattice transformations. Stereographic analysis showed that in beta copper-tin, the poles of these markings deviated one or two degrees from poles of the form { 133 } . In beta copper-zinc the plane delineated by the markings corresponded to no one crystallographic plane of the matrix lattice; the marking poles deviated from 5° to 11° from poles of the form {110}, and were displaced only a few degrees from (110) zones. Inasmuch as the new transition lattices produced as the result of the deformation are different for each alloy, it was thought at first that the habits of the markings might be the result of a cooperation between matrix lattice and transformed lattice. (Both matrix lattices are body-centered cubic.) Such a cooperative effect is thought to obtain in the formation of Widmanstätten figures, for it is well known that the matrix lattice alone does not determine the habit assumed by a segregate phase. On the other hand, it is not inconceivable that the dissimilarity in mark-ing habit might be due to differences in deformation characteristics of beta brass and beta bronze. Barrett and co-workers2 have shown that slip-line habits in pure iron are markedly different from those in high-silicon ferrite; and although it has been repeatedly demonstrated that plates of a segregate phase do not necessarily form on the slip planes of the matrix lattice, deformation characteristics may be more intimately allied with plate formation when a transformation is made to occur as a result of plastic deformation. However, there is the fact that the orienta-tion of markings in metastable beta copper-zinc is the same whether the markings be produced by quenching, deformation, or liquid-air cooling; likewise, quenching and deformation markings in metastable beta copper-tin are oriented in the same way with respect to the beta matrix.

Jan 1, 1938

By Y. Lahaye, O. Martinsson, B. I. Palsson

"Four main and three minor rare-earth-element (REE)-bearing minerals were identified and quantified in the Kiirunavaara apatite iron ore tailings using optical microscopy, an electron probe microanalyzer (EPMA) and a mineral liberation analyzer, and their chemical compositions were analyzed by the EPMA and laser ablation inductively coupled plasmamass spectrometry. REEs are shown to be contained in the minerals apatite, monazite, allanite, titanite, zircon, thorite and synchysite. In zircon, thorite and synchysite, they occurred in only trace amounts and contributed limited amounts to the total REE budget, and these are consequently of minor importance. Monazite occurred as inclusions in apatite and as free particles, 90 percent liberated. Allanite occurred to some degree in mixed grains with magnetite but also as free particles. Monazite mainly reported to the apatite concentrate, while allanite and titanite largely went to the tailings, the latter preferably to those fractions smaller than 38 µm. The amount of titanite in the finest tailings fraction was 2.3 weight percent, containing close to 1 percent REEs, with heavy rare earth elements (HREEs) making up 28 percent of the total REEs. However, a texturally distinct group of titanite grains showed an HREE/REE ratio of up to 67 percent. Furthermore, titanum dioxide analyses indicate that titanite is preferentially released into the tailings from the secondary magnetic separation step in the concentrator. Our data therefore suggest that titanite, occasionally enriched in HREEs, can be extracted from the processing stream and might thus be considered a new source for REEs at Kiirunavaara and similar deposits.IntroductionDeposits of apatite iron ores are the major source for iron in the European Union and are exploited by Luossavaara-Kiirunavaara AB (LKAB) in several mines in the Kiruna-Malmberget area in northern Sweden. Kiirunavaara is the largest of the apatite iron orebodies in Sweden, comprising more than 2 Gt of iron ore with 60 to 68 percent iron (Fe). At the end of 2015, the total accumulated production of crude ore from openpit and underground mining since the start of mining was 1,566 Mt, with ore reserves of 644 Mt grading 46.3 percent Fe (LKAB, 2016). The deposit defines a steeply dipping tabular body, approximately 6 km long and up to 180 m thick, extending at least 1,500 m below the surface. It is situated in the middle part of the Palaeoproterozoic Kiirunavaara Group of volcanic rocks and follows the contact between a thick pile of trachyandesitic lava and overlying pyroclastics (Martinsson, 2004)."

Jan 1, 2017

By Eugene Baker, Joseph Cervik, Albert Sainato

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the United States is limited to a few plow operations in the Pocahontas No. 3 Coalbed. This Bureau of Mines report describes the technology for infusing water in to a longwall panel and reports the results of a recent demonstration in the Lower Sunnyside Coalbed that achieved dust reductions averaging 58 pct. Because water infusion increases moisture content of the coalbed, face air velocities in excess of 500 ft/min (2.5 m/s) are possible, further diluting dust levels before dust entrainment occurs. An economic analysis shows a 23-pct reduction in operating costs when coal production is increased by changing from unidirectional mining to bidirectional mining with water infusion.

Jan 1, 1983

By William Mikulas Lars Thomassen, Clair Upthegrove

Little work has been done in the field of the nickel-tin binary system. The complete diagram has been investigated on two occasions, but the results are in very poor agreement. The structure of a compound NiSn and the solubility of tin in nickel have been determined by X-ray methods. Several investigations have been made of the liquidus curve, and the compositions of the eutectics have been determined. A study of the literature, however, shows that there is no satisfactory agreement between the data presented in the various papers. The present investigation was undertaken in an attempt to determine the equilibrium conditions, and to correlate X-ray with metallographic data. The equilibrium diagram was determined by thermal and metallographic means, and the solubility of tin in nickel further investigated with X-rays. Powder diagrams were made of the intermetallic compounds, and three of the structures were partly determined. NO attempt was made to determine the range of homogeneity of the intermetallic compounds. Review of the Literature Vigorouxl prepared alloys of tin and nickel containing 74 and 92 per cent of tin. By treating these alloys with very dilute nitric acid or with sodium hydroxide he was able to separate residues, both of which analyzed 66.7 per cent tin. This corresponds to the compound NiSn and was reported as such. Guillet2 made the first investigation of the complete binary diagram Fig 1) The maximum point of the liquidus is at 43.5 per cent nickel. Several solid solution areas were found, and the compound NiSn was included on the strength of Vigoroux's work. The investigation was

Jan 1, 1937

By E. R. Helderman, C. Y. Ang, C. C. Nealey

Beryllium-base alloys have been successfully p7.-epared by the liquid-phase sintering technique. Depending orz the composition and amount of the intended liquid please, microstructures either single -phase or duplex in feature with randomly oriented grains have been obtained. Qualitative and semi-qualitative determination of distribution of alloying elements md microsegregations in some experi)uzental alloys haue been made by electron-micro-probe analysis in conjunction with microliardness testing and standard metallography. Tensile tests reoealed that some conzpositions possess attractive elastic properties with Young's mot1uli greater than 40 X 10' psi. In powder metallurgy, liquid-phase sintering is a process or phenomenon that has proven to be of practical value. For example, the heavy metals such as tungsten-copper-nickel, high-strength heavy gyro alloys,' heavy-duty electrical contacts,' and tungsten carbide tool materials are all products of liquid-phase sintering. Mechanisms involved in liquid-phase sintering, however, are not completely understood. Questions regarding the exact roles played by rearrangement of particles, liquid/vapor surface energy, solution and precipitation, and so forth, have not been completely answered. Evidence has been cited3 that at least volume shrinkage in the densification process is diffusion-controlled. It is possible that the predominant mechanisms for the complete densification and grain growth in a liquid-phase sintered system depend primarily on the alloy systems involved, in addition to processing conditions. Despite the lack of sound understanding of the mechanisms of the process, liquid-phase sintering has been and is being used to advantage either to synthesize microstructures for their special properties or to prepare alloys which are difficult to form by fusion process. Liquid-phase sintering of beryllium alloys was first attempted by Jones and Williams.4 They first tried infiltrating beryllium with magnesium, and then succeeded in preparing the alloy by sintering Be-Mg powder compact in molten magnesium bath. This investigation resulted in the identification of some Mg-Be intermediate phases. Crossley et a1.5 also used liquid-phase sintering technique in an attempt to produce ductile beryllium alloys for structural applications. The major liquid-phase components investigated by Crossley et al. were aluminum and silver with minor additives of germanium, calcium, lanthanum, cerium, and yttrium. The lack of wetting and the bleeding out of liquid phase were the difficulties encountered during experimentation. According to Hodge,6 the two compositions investigated by Crossley, which showed some promise based on compression tests, involved large amounts (over 35 wt pct) of silver, thus making them too heavy to be of practical interest to the aerospace industry and military users. The present investigation was prompted by the search for light-weight (density less than aluminum) beryllium alloys exhibiting small anisotropy in physical properties for precision inertial navigation instrument applications. In addition to isotropy, good structural properties such as high elastic modulus or desirable combination of mechanical and physical properties are also objectives of this investigation. The technique of liquid-phase sintering was chosen for its versatility in producing either duplex or homogeneous microstructures. This report is concerned with the use of copper and aluminum, with or without silicon addition, as the intended liquid phase, and the resultant micro-structures and some physical properties of the beryllium alloys. Qualitative and semiquantitative electron-microprobe analyses of some of the alloys are presented to illustrate the usefulness of this microanalytical technique for the identification of microconstituents and their distribution. EXPERIMENTAL PROCEDURES The beryllium powder used was -200 mesh Brush Beryllium Co. QMV NP-50 grade. Typical chemical analysis of the powder is shown in Table I. Commercial high-purity copper, aluminum, and silicon powders all screened to —100 mesh were used as additions. Mixed powder compositions were ball-milled in ceramic jars for 1/2 hr to ensure thorough blending. Milled powder was loaded either in 3/4-in.-diam button die or in Metal Powder Association flat tensile specimen die and compacted under top and bottom pressure. No lubricant or organic binder was used. Sintering was carried out in a quartz tube under a vacuum of 50 to 100 µ pressure. Surface hardness and some microhardness readings were taken on sintered specimens. Sintered density was

Jan 1, 1965

By G. H. Bishop

The kinetics of the inter granular penetration and embrittlement of [100] tilt boundaries in 99.998 pct pure nickel upon exposure to bismuth-rich Ni-Bi liquids have been determined in the temperature range from 700° to 900°C. The kinetics of penetration are parabolic in time at constant temperature over most of the temperature range. In a series of 43-deg bicrystals the rate of penetration is anisotropic with respect to the direction of penetration into the grain boundaries. In lower-angle bicrystals the penetration rate is isotropic. The rate of penetration decreases with tilt angle at 700°C. The activation energy for penetration in the 43-deg bicrystals is 42 kcal per g-atom independent of direction. It is concluded that the intergranular penetration and embrittlement in the presence of the liquid proceeds by a grain boundary diffusion process and not by the intrusion of a liquid film. This was confirmed by a determination that the kinetics of penetration and embrittlement were the same in the 43-deg bicrystals upon exposure to bismuth vapor under conditions such that no bulk liquid phase would be thermodynamically stable. WhEN solid metals are exposed to a corrosive liquid-metal environment, the grain boundaries are sites of preferential attack. Depending on the temperature, the composition of the liquid, and the composition, structure, and state of stress of the solid, a number of modes of attack are possible. This paper reports a study of the kinetics of intergranular penetration and embrittlement of high-purity nickel bicrystals upon exposure to bismuth which, together with an earlier study by Cheney, Hochgraf, and Spencer,&apos; demonstrates that there are at least two modes of intergranular attack possible in the Ni-Bi system. In the study by Cheney et al., columnar-grain specimens of 99.5 pct pure nickel were exposed to liquid bismuth presaturated with nickel in the temperature range 670" to 1050°C. They found that the majority of the boundaries, which were predominantely high-angle boundaries, were penetrated by capillary liquid films, the attack proceeding by a process which will be termed grain boundary wetting. This process occurs in a stress-free solid when twice the liquid-solid surface tension is less than the surface tension of the grain boundary,* i.e., when 2yLs < YGB In this case the penetration of the grain boundary by the liquid occurs at a relatively rapid rate, resulting in the severe embrittlement of a polycrystalline solid. Grain boundary wetting is a common mode of intergranular attack in systems in which the lower melting component is relatively insoluble in the solid, but the solid has an appreciable solubility in the liquid, for example, the Ni-Bi system, Fig. 1. In systems of this type at temperatures above the range of stability of any intermetallic phases, once the liquid is saturated with respect to the solid so that no gross solution occurs, chemical gradients are small, and surface tensions become major driving forces for attack, provided the solid is stress-free. The results of Cheney et al. appear to be typical of those encountered when grain boundary wetting occurs.&apos; Capillary films were observed in the boundaries after quenching from the exposure temperature. The mean depth of penetration increased linearly with time, and the activation energy for the process was found to be 22 kcal per g-atom. In a study of the Cu-Bi system Yukawa and sinott4 found that the depth of penetration of bismuth into high-purity copper bicrystals of orientations from 22 to 63 deg of tilt about (100) at 649°C ranged from 0.05 to 0.25 in. after a 12-hr anneal. This corresponds to a linear rate of 6 to 15 X 10~6 cm per sec. At the same reduced temperature of 0.68 the rate for the Ni-Bi system&apos; was 7 x lo-&apos; cm per sec. In another study of the Cu-Bi system, Scheil and schess15 determined the kinetics of grain boundary wetting in hot-worked commercial rod. While there were several complicating factors present in this study, there is general agreement with the above results. The kinetics of penetration were linear, the activation energy was 20 kcal per g-atom, and at 650°C the rate of wetting was 2 to 5 x 10-6 cm per sec. The rate of wetting in the A1-Ga system6 is somewhat

Jan 1, 1969

By R. N. Dokken, J. F. Elliott

A high-temperature solution calorimeter was used to measure directly the partial molar heat of mixing of nickel in the Cu-Ni system, 0 to 15 at. pct Ni and 1200°C; of silver in the Cu-Ag system, 0 to 50 at. pct Ag and 1100°C; and of cobalt in the Cu-Co system, 0 to 6 at. pct Co and 1200°C. The heats of fusion of copper and silver were also detervnined directly. The results of these investigations are as follows: Cu-Ni: HM = [2.64 + 0.25Xm JXNiXCy kcal/g-U~OI Cu-Ag: HM =[4.00 + 0.31XAglXAgXCu kcal/g-atom Cu-Co: HF~ = [8- 5X~,]X& kcal/g-atotn Cu, AH, = 3290 * 275 cal/g-atom Ag, AH, = 2890 * 250 cal/g-atom The performance of the calorimeter was enhanced by improving the operational and control procedures, particularly the temperature-wieasuren~ent method and the solute-addition practice. The interpretation of the experimental data was improved by developing machine computational techniques that increased the speed, flexibility, and accuracy of the treatment of the data. THIS paper reports further measurements of the heats of solution of liquid metals with the high-tem- perature solution ca1orimeter.l Measurements were made of the partial molar heats of mixing in the following liquid alloys: Cu-Ni, Cu-Ag, and Cu-Co. In addition the heats of fusion of copper and silver were also determined. The apparatus and the experimental procedure were essentially those of Benz and Elliott.2 Several modifications in the experimental method and the means for interpreting the data were incorporated in this study to improve the results. The operation of the calorimeter and its characteristics will be described only briefly here. The

Jan 1, 1965

By G. Sanders

Discussion by G. Sanders The studies reported on in this paper were initiated to draw attention to the severe contamination problem in the Section 30 drilling program at Chimney Creek. The lithologic-subset sampling study reached a different conclusion from that presented in your paper, and I wish to comment on your subsequent analysis of the data and your conclusions. Request for more complete data In the section on subsampling, you mention that the subordinate lithologies were separated and sampled, yet only the dominantlithology gold value is plotted in Fig. 4. In a contamination study, the reader is interested in the assay values for the individual subsets. Please include a table of the subsample assay data in your reply. Also, please indicate which analytical methods were used to arrive at the gold values in the subsampling study. Turning barren rock into low-grade ore Figure 5 is very revealing and typical of all of the cross sections in Section 30. Note the long strings of low-grade mineralization spread out for hundreds of feet below the ore zones. There were some very high gold values found in certain contaminated fractions during the subset sampling. The conclusion, here, was that the distinctive, strongly-mineralized dolomite layer was probably loose and crumbly and continued to disintegrate during drilling. This caused salting of the unmineralized rock samples below. Missing the high-grade part of the ore body In your statistical analysis, you directly compare the reverse circulation assays to the diamond drill assays in Section 30. Two points argue against a direct comparison and suggest the differences are greater than the 3 % that you report. First, any core loss in a gold zone most likely means that the true gold values are greater. The drillers lost significant amounts of the clay-rich, Section-30 gold mineralization. Also, the initiated salt-mud system, an attempt to improve the core recovery, met with little success. Second, the practice of not sampling core geologically, but instead sampling on even 5-foot intervals, adds a deliberate dilution to the core assay values by including a portion of nonmineralized rock in the first and last samples of each high- grade intercept. The result is often a pair of low-grade assay values on either side of a high-grade gold zone. In reality, a high-grade gold zone has a very sharp assay wall that is often bounded by barren rock. This sampling method may make the diamond-drill core assays more like the reverse circulation values and may help explain the statistical similarities you found. However, it does not represent the true gold values in the high-grade parts of the deposit. You cannot deny that, by careful geological sampling of the drill core, higher and sharper assay values will be obtained. The low core recovery and the diamond-drill-core sampling method used act together to lower the diamond-core assay values. The 3% difference you found between the reverse-circulation and diamond-core assay values could be much larger when you consider what the true diamond-drill core values would be with optimum core recovery and a geologic sampling method for the core. Should statistics have been applied here? The statement "... that reverse circulation holes have overestimated the values of some ore zones and underestimated the values of others" (p. 345) is not correct. The subsampling confirmed what the cross sections hinted at in Section 30. Namely, beneath the high-grade zones, the reverse circulation holes created, by contamination, large intercepts of low-grade ore in regions of barren rock. Because the low-grade material was not there to begin with, this is not a process of overestimating low-grade mineralization. The next statement that "the average result is similar to that of the diamond drill holes" may apply to the data set numerically, but it is not true when viewed spatially on cross sections. Adjacent reverse circulation and diamond drill holes are almost impossible to correlate, high-grade zone values vary widely and many low-grade intercepts make no geologic sense. The subset sampling and cross sections presented in the first part of the paper show that the reverse circulation portion of the data set has some serious problems, as highlighted above, and should not have been dealt with statistically at all. Conclusion Each ore body is different, and each drilling method presents unique sampling problems. In this case, the diamond drill is the

Jan 1, 1994

By A. U. Seybolt

The solubility limit of oxygen in columbium has been determined in the range between 775&apos; and 1100°C by means of lattice parameter measurements and microscopic examination. The solubility is a function of temperature and varies, in the range given above, from 0.25 to 1.0 pct O, respectively. BECAUSE of the marked deleterious effect of oxygen upon the mechanical properties of some of the transition metals, it is desirable to know something about the solubility of oxygen in these metals. The brittleness caused by oxygen in solution is particularly marked in the case of the group VA elements, vanadium, columbium, and tantalum. The solubility of oxygen in vanadium has already been reported in an earlier paper,&apos; and Wasilewski2 has given a value (0.9 wt pct) for the solid solubility of oxygen in tantalum at 1050°C. Brauer3 in 1941 investigated the Cb-0 system up to Cb2O5, but made no real effort to investigate the extent of oxygen solubility in the metal. He made the observation, however, that this solubility must be less than 4.76 atom pct (0.86 wt pct) oxygen. This estimate was made from X-ray diffraction results on the alloys CbO, CbO, and CbO; all alloys consisted of the terminal (Cb) solid solution plus CbO, but the last alloy containing 4.76 atom pct 0 showed only three very weak CbO lines. It is surprising that Brauer, by examining only three alloys, arrived at an estimate of the solubility which agrees very well with the results to be reported herein. Experimental Procedure A columbium strip obtained from Fansteel Metallurgical Products was cut into strips, 0.020x1/2x2 in. Two holes, about 3/16 in. in diameter, were made near the ends of the strips in order to hold them against a flat steel block for mounting in a General Electric X-ray spectrometer for lattice parameter measurements. The same holes were used to hang the specimens inside a fused silica vacuum furnace tube which was part of a Sieverts&apos; gas absorption apparatus. The apparatus and method of adding oxygen gas has been previously described.1 According to the supplier, the columbium obtained had the analysis given in Table I. After degreasing the samples, approximately 0.001 in. was etched from each side of the samples in order to remove possible surface impurities from the last rolling operation. For this purpose the following cold acid pickle was found satisfactory: 8 parts HNO3, 2 parts H2O2 and 1 part HF. Various Cb-O compositions were obtained up to 0.75 wt pct O by the gas absorption and diffusion technique. After the sample had absorbed all the oxygen gas added at 1000°C, an additional 24 hr was allowed for homogenization. This treatment appeared to be adequate, as shown by the linearity of the lattice parameter-composition plot. More concentrated alloys were prepared by arc melting mixtures of Cb and Cb2O5 since it was very time-consuming to make Cb-0 alloys in the neighborhood of 1 pct O, or over, by the diffusion method. When the flat strip specimens were used, they were ready for the X-ray spectrometer after cooling from the Sieverts&apos; apparatus. The cooling rate obtained by merely allowing the hot fused silica furnace tube to radiate to the atmosphere (when the furnace was lowered) was sufficiently fast to keep the dissolved oxygen in solution. Arc-melted alloys were reduced to —200 mesh powder in a diamond mortar, wrapped in tantalum foil, sealed off in evacuated fused silica tubes, and then heat treated as indicated in Table 11. The fused silica tubes were quickly immersed in cold water without breaking the tubes after the heat treatments. The tantalum foil prevented reaction between the fused silica and the sample; there was no reaction between the powdered samples and the foil at 1000°C, but some trouble was experienced at 1100°C. At this temperature level a reaction between the sample and the foil was sometimes observed, which resulted in erroneous parameter values. Experimental Results Hardness Tests: Since most of the X-ray samples were in the form of flat strip, it was convenient to obtain Vickers hardness numbers as a function of oxygen content. Compared to the V-O case,&apos; oxygen hardens columbium much more slowly, presumably because of the larger octahedral volume in colum-bium (about 12.0 compared to 9.3Å3 in vanadium), hence, requiring less lattice strain for solution. The plot of VHN vs wt pct O is shown in Fig. 1.

Jan 1, 1955

By Lingzhi Yang, Feng Chen, Yufeng Guo, Tao Jiang, Zeqiang Xie

Zinc ferrite (ZnFe2O4), one of the major forms of zinc in Electric Arc Furnace (EAF) dust and zinc leaching residue, is very difficult to chemically dissolve in either acidic or alkaline solutions. In spite of the zinc resources in the Electric Arc Furnace (EAF) dust and zinc leaching residue are abundant, there is no mature utilization technology. This situation not only causes the waste of resources, but also produces the harm to the environment. In the paper, the basic principle of this process has been established by revealing the phase equilibria in the CaO–Fe2O3–ZnO system, where Ca2Fe2O5 can be in equilibrium with ZnO rather than ZnFe2O4 at higher CaO region. It has also been demonstrated that the formed ZnO can be solved by ammonia-leaching and Ca2Fe2O5 keep in solid residue, which can be used as a flux for steel refining.

Mar 1, 2017

By Xudong Liu, Ganghua Fu, Yufeng Guo, Wei Chen, Yujia Tan, Tao Jiang

Willemite is usually found in high-silicon oxide zinc ore and zinc metallurgical secondary resources but without effective extraction method yet. In this study, zinc was extracted from willemite by sodium salt roasting and ammonia-leaching process based on the idea of zinc phase reconstruction. The effects of Na2CO3 dosage, roasting temperature and roasting time on phase transformation and zinc leaching rate were studied, respectively. The results show that Zn2SiO4 was transformed into ZnO or Na2ZnSiO4 during roasting process. After roasting at 800 °C for 2.5 h at ratio of n(Na2CO3)/n(Zn2SiO4) = 2.5:1, willemite was thoroughly transformed into ZnO. The zinc leaching rate of the roasted sample was 97.62% in NH4Cl–NH3–H2O leaching system, which increased by 91.57% compared with zinc leaching rate of 6.05% when willemite was directly leached in NH4Cl–NH3–H2O system.

Mar 1, 2017

By José Hugo de Carvalho Souza

Em busca do aumento de produtividade e estabilidade operacional de trefilados e ampliados no setor de acabamento da siderúrgica, na produção de CA60, telas e treliças, foi observado através da metodologia DMAIC a instabilidade operacional no indicador de eficiência do OEE dos equipamentos devido a oscilações de velocidade manual e limitação de velocidade por problemas técnicos. Após as análises de estabilidade nos equipamentos e constatado a necessidade de melhoria do processo foi realizado estudos por meio da técnica de modelagem de Rede de Petri, representando o sistema e modificando a lógica de automação que analisa o status da máquina e a partir desse momento o próprio equipamento toma a decisão segura de acelerar ou desacelerar até a velocidade especificada de “set point” por material produzido, sinalizando antecipadamente ao operador com alarmes visuais e sonoro de forma que o mesmo tenha ciência do que está acontecendo e possa intervir caso julgue necessário. Após a implementação foi capturado um aumento de 6,62% de OEE e 5,5% de produtividade total anual no setor, sem custo de aquisição.

Aug 16, 2017

By Pedro Cunha Alves

A cada ano a demanda por aços limpos aumenta, tornando o controle de inclusões cada vez mais importante. Durante o refino secundário de aços, ocorrem a eliminação de impurezas, ajuste da composição química e ajuste da temperatura do aço líquido. A remoção de inclusões não-metálicas geralmente ocorre nessa etapa, sendo realizada pela escória. Neste trabalho, foi definido um planejamento de experimentos para que numa segunda etapa, os conhecimentos obtidos possam ser comparados e transferidos para a prática industrial. Inicialmente, foi feita uma revisão da literatura sobre experimentos realizados em fornos de laboratório com amostras de aços e escórias focados na remoção de inclusões. Depois de analisados diferentes arranjos experimentais propostos, alguns trabalhos selecionados foram analisados com respeito às inclusões e às escórias presentes. Finalmente, no planejamento proposto, definiu-se que os experimentos serão realizados em forno resistivo com passagem de argônio. As amostras serão fundidas em cadinhos de MgO na temperatura de 1600ºC e, após 90 minutos nesta temperatura, as mesmas serão resfriadas em água. Alguns parâmetros que poderão ser estudados são a população de inclusões, viscosidade efetiva da escória, teor de oxigênio total e composição de inclusões ao longo do tempo.

Oct 30, 2017

By Robin O. Williams

Robin 0. Williams (Oak Ridge National Laboratory)— The authors have questioned the degree to which the coherency strains between the iron-rich and chromium-rich phases are isotropic as proposed in Ref. 5 on the basis of the difference between the elastic properties of the two phases. The relative magnitude of the stresses is determined by the moduli as shown by Eqs. [2], [3], and [4] of Ref. 34. However, the moduli of the two phases have no direct bearing on the uniformity of either the stress or strain within either phase. The idea that the strains are isotropic within each phase (but normally of different magnitude and always of different sign) is based entirely upon the experimental observation that X-ray line broadening has not been detected even when the particles become rather large. It has not proven possible to grow the particles sufficiently large that they lose coherency. Based upon this lack of line broadening one can estimate an upper limit for the nonuniformity of the strains within each phase as follows. It is considered possible to detect line broadening if it is as great as 10 pct of the separation of the K, doublet for the (211) line using chromium radiation. The doublet separation would correspond to a total strain of 0.0017 such that the total variation of lattice parameter relative to the average lattice is now k0.05x0.0017 or something less than ± * For the present case the strain in each phase is roughly 0.002 such that the variation of strain within a phase will not exceed 5 pct. It is stated that the expression derived for strengthening for the hydrostatic straining as observed in this system would substantially overestimate the magnitude due to dislocation flexure. This is contrary to the conclusion reached in the original paper34 for the present range of particle sizes. What is the lowest temperature at which a has been observed to form in this alloy? M. J. Marcinkowski, R. M. Fisher, and A. Szirmae (nutlzors&apos; reply)— -Williams&apos; arguments based on X-ray findings for a chromium-rich precipitate and an iron-rich matrix strained to a common lattice parameter are certainly convincing. This being the case, there are no shear components of strain associated with the precipitate-matrix aggregate to interact with the shear components of the dislocation stress fields, contrary to the opinion expressed by the present authors. On the other hand, the present authors, in spite of this error, did not expect the shear interactions to be significant. The chief objection to Williams&apos; model in the present case is that the various segments of the dislocation line are assumed to pass from one potential valley to the next independently of neighboring segments. This is only true for a highly flexible dislocation line, i.e., one whose radius of curvature is something less than the center to center distance between precipitate particles which amounts to about 90A in the present alloy. In order to maintain this curvature, an externally applied shear stress of at least 230,000 lb per sq in. would be required or about four times the observed stress. It is therefore concluded that the dislocation lines move rather rigidly through the lattice. This being the case, the forces on the dislocation resulting from the hydrostatic interaction between the stress fields of the edge-dislocation components and the precipitate particles should average out to zero; that is particles above the below the slip plane produce forces on the dislocation of opposite sign and therefore will cancel when averaged over the entire length of the dislocation. On the other hand, since the dislocation is not perfectly rigid, Williams&apos; model may lead to some strengthening, but far less than that predicted. A second and equally serious objective to using Williams&apos; strengthening model for the present alloys is that profuse wavy slip due to the motion of screw dislocations played a predominant role not only in the unaged alloys but in the fully aged ones as well. Since the screw dislocation has associated with it only shear components of stress the hydrostatic strengthening model no longer applies. In view of these arguments the present authors must reject Williams&apos; model of strengthening as being pertinent to the present alloy system. The present authors have made no detailed study of the lowest temperature at which a forms in the quenched ferritic alloys. None was ever observed n the alloys aged at 500°C so that forma-tion must occur at temperatures higher than this and was therefore not a factor in the present study.

Jan 1, 1965

By Wei Lv, Yang Zhou, Qiang Li, Xuling Chen, Zhiyun Ji, Min Gan, Guojing Wang, Xiaohui Fan

Mineralization during sintering is a process to make part of the raw material melt after serial complex chemical reactions at high temperature. However, high temperature mineralization behavior of the adhesion layer and nucleus particles in the granules during the sintering process has been studied. Research findings reveal that solid-phase reactions between iron ores and fluxes in adhesion layer occurred first, of which the product would induct the generation of the initial liquid phase. By the assimilation of the initial liquid phase, fluxes which served as nucleus particles in granules, such as limestone and dolomite, could dissolve in the liquid phase and extend its amount as increasing temperature, whereas iron ore nuclear particles remained as unfused ores for their insufficient mineralization. Therefore, the mineralization proceeding for sintering was achieved: the iron ores in fine fraction (−0.5 mm) reacted with all fractions of fluxes to form the melt zone, while the coarse iron ores (+0.5 mm) acted as unfused ores, which formed the final sinters together with the melt zone.

Mar 1, 2017

By Leonardo Lúcio de Araújo Gouveia

Este trabalho objetiva o estudo da influência da adição de fibras vegetais de bambu e cana-de-açúcar nas propriedades mecânicas do concreto. Para este trabalho foram confeccionados corpos-de-prova cilíndricos e prismáticos nos quais foram adicionados 2% e 5% em volume das fibras à massa do concreto. Após a cura, conforme NBR 5738 (2003) [1], os mesmos foram testados via ensaios de resistência à compressão conforme NBR 5739 (2007) [2], resistência à tração por compressão diametral, conforme NBR 7222 (2011) [3], resistência à tração na flexão conforme NBR 12142 (2010) [4] e módulo de elasticidade estático, conforme NBR 8522(2008) [5]. Verificou-se após os testes que todos os concretos produzidos atenderam a resistência mínima a compressão de 20 MPa, recomendado pela NBR 6118 (2003) [6] para fins estruturais. Foi observado um aumento da resistência à compressão em relação à mistura padrão. O concreto com adição de fibras de bambu apresentou melhor resistência mecânica em relação ao concreto com adição das fibras de cana-de-açúcar e ao concreto sem adição.

Aug 7, 2018

By S. Rukhaiyar, M. Ramulu, G. Pradeep, P. K. Singh, P. B. Choudhury

The drill and blast method is the most prominent rock excavation method used in mining and civil engineering projects. The ground vibration is the most undesirable effect of the blasting and needs to be controlled. The blasts are designed so that ground vibration at nearby structures must remain under the prescribed limit. Various empirical blast vibration attenuation models have been presented to estimate the ground vibration for designing purposes. These models assume ground vibration as a function of distance and maximum charge per delay. United States Bureau of Mines (USBM) model is most commonly used for the blast design. However, the uncertainty associated with these models is seldom characterized, thus diminishing its reliability. The probabilistic Bayesian approach associated with the Monte Carlo method can easily quantify uncertainties associated with the model and its parameters. Thirty-three blast vibration observation data from a granite quarry in Kerala, India, is used to estimate the probability distribution of model parameters. Markov Chain Monte Carlo (MCMC) approach is used for sampling 12,000 samples for obtaining the posterior distribution of parameters. The uncertainty associated with model parameters is quantified from the posterior distribution, and this is further used to estimate the credible and prediction limits of the model. The point estimate of the most optimum value of the parameter is estimated using maximum-aposteriori or MAP estimate. The model parameters are also obtained using the commonly used least-square error method, which is a maximum likelihood estimation or MLE approach. It has been observed that the accuracy of the model obtained using both MAP and MLE approach is almost equal. However, the MAP estimate as per Bayesian probabilistic analysis has the added advantage that it can estimate the uncertainty of parameters as well as the model, which is not possible using the MLE approach.

Sep 27, 2021