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By J. J. Jonas, G. R. Stewart, A. M. Elwazri

Two important parameters for dynamic recrystallization can be derived from the changes in the strain hardening rate: the critical strain for initiation of dynamic recrystallization and the point of maximum softening. In this work, these values are determined from the flow stress-strain data obtained in continuous compression testing in the range 900-1100°C. The resulting strains are used to calculate a kinetic model of dynamic recrystallization for two materials: 304 austenitic stainless steel and a hypereutectoid plain carbon steel. The mechanical parameters used to define the proposed model are confirmed with quantitative metallographic analysis of the recrystallized microstructure.

Jan 1, 2004

By Janaka J. Kumara, Takashi Kurashina, Yoshiaki Kikuchi, Takahiro Yajima

"The inner frictional resistance of open-ended piles depend heavily on the degree of soil plugging. Many factors including pile diameter, relative density and end conditions of the piles influence the degree of soil plugging. In this paper, the effects of inner sleeves attached at the pile base on the inner frictional resistance are discussed. The experiments were conducted on a medium-dense sandy ground using smallscale model piles. The results suggest that the inner frictional resistance is influenced by sleeve height for 50 mm diameter piles although it is independent for 30 mm diameter piles. The results also indicate that soil plug height is influenced by the sleeve height. The results of the incremental filling ratio (IFR) showed that penetration of non-sleeved piles is closer to unplugged state than the sleeved piles. The results of the IFR also reveal that the degree of soil plugging is affected by the sleeve height for 50 mm diameter piles although the variation is very limited in 30 mm diameter piles. The results on the coefficient of lateral earth pressure suggested that it increases from 1.08 – 1.75 when the sleeve height is increased from 10 – 100 mm for 50 mm diameter piles.INTRODUCTIONPrevious studies have shown that the behaviour of open-ended piles is different from closed-ended piles (Szechy, 1961; Randolph et al., 1979; Paikowsky and Whitman, 1990). Open-ended driven piles are widely used for deep foundations, in particular in offshore deep foundations. Generally, it is accepted that a short open-ended pile produces a smaller bearing capacity than a similar closed-ended pile (Nauroy and Tirant, 1983). However, a long open-ended pile can produce a similar bearing capacity as a closed-ended pile due to a large inner frictional resistance mobilised between the inner pile shaft and inner soil (Lehane and Randolph, 2002). The ultimate bearing capacity of an open-ended pile, Qu consists of three components as given in Eq. 1."

Jan 1, 2017

By Khosrow Badiozamani

Operating mines in Wyoming and Montana, which are generally characterized by shallow overburden and thick coal seams, are faced with reclamation problems which are unique to this area. Unlike the eastern or midwestern mines, removal of thick coal seams and lack of sufficient overburden creates overburden deficiencies that require careful evaluation prior to mining to insure compliance with regulatory requirements. Computer models and computer graphics can assist in such evaluation where appropriate alternatives can be selected which satisfies both the regulatory requirements and minimizes cost. This paper presents one such model used in evaluation of backfill requirements for restoration of surface and ground water regimes, restoration of mined-out areas to the approximate original contour, and the blending of the mined-out areas to the surrounding topography.

Jan 1, 1981

By A. Meléndez

El presente trabajo señala el proceso del entrenamiento para Ingenieros de minas en la corporación minera Cerro Verde a través del plan de perfeccionamiento profesional elaborado por la misma empresa privada. El objetivo del plan es darle al profesional egresado, la experiencia práctica adecuada que complemente la formación académica. Asimismo se busca la eficiencia de su profesión, desarrollar la competitividad y el estímulo de superación del egresado dentro de la empresa minera.

Nov 20, 1972

By S. F., French

IN reviewing the design of the ore haulage system for the Morenci project, the reader should bear in mind that the railroad and its equpiment cannot be considered as an independent railroad provided only for the purpose of transporting ore from one point to another, but as an integral part of the operation which begins at the electric shovels loading ore at the mine, and ends where the ore, after having been crushed in the primary crushing plant, is deposited in the bins at the secondary crushing plant. Obviously then, the problem consisted of designing a system that would function to the best possible advantage in complete co-ordination with the other units.

Jan 1, 1942

By José E. Rondoña

El presente trabajo desarrolla un estudio comparativo de la producción de dos tipos de hornos usados en la fundición de cátodos de zinc en la planta de La Oroya, para asi determinar cúal es el equipo más idóneo para futuras expansiones del proyecto. De los puntos comparativos se encontró que el horno SICE desarrolla más productividad de personal en operaciones, así como en el rendimiento de la energía eléctrica. Mientras que respecto de las consecuencias de las filtraciones del metal, se encontró que el horno Ajax es el más adecuado, dado que la producción de barras se afecta solo en la producción que el horno afectado representa en la instalación total. Por ende, es conveniente el uso de dos hornos SICE tamaño mediano dada la capacidad y productividad de esta.

Nov 20, 1967

By Patrick K. Wong, Richard Kelly

"The variability in strength and compressibility of in situ deep soil mixing products can be greater than the variability of the natural soil. However, satisfactory performance can be achieved by careful construction and an appropriate QA/QC program. This paper presents a case study on the use of deep dry soil mixing columns to support several embankments over soft clay along a highway project. Post-construction settlement monitoring indicated that good performance is achieved where the acceptance criteria are met, except in an area with high organic content. Embankments with contrasting performance are compared to the quality control test results which comprised laboratory testing of core samples as well as in situ test results such as pull-out and push-in vanes and conventional cone penetration tests. Drawing on the performance results and quality control testing, discussions and guidelines are given on quality assurance acceptance criteria and construction control testing regime for future projects.INTRODUCTIONBetween 2008 and 2012, the largest deep dry soil mixing (DSM) contract during that time in the southern hemisphere was carried out for the Ballina Bypass project. The project, comprising 12 km upgrade of the Pacific Highway located in northern New South Wales close to the border of Queensland, was commissioned by the Roads and Maritime Services (RMS) of NSW. The ground improvement contractor was Keller Ground Engineering (KGE) Australia. Seven different types of ground improvement techniques were employed for the project, ranging from low embankment strategy with nominal preloading, to surcharge with wick drains, light weight bottom ash fill, DSM, vibro-replacement stone columns, dynamic replacement, and vacuum consolidation (installed by Menard Bachy Pty Ltd). Different techniques were chosen depending on time program, cost, and performance requirements relative to proximity to piled structures (e.g. bridge abutments) and post-construction settlement and differential settlement for either rigid or flexible pavements at different locations.DSM was the most utilized ground improvement technique employed on the project, comprising a total of about 285 km of 0.8 m diameter columns to depths up to 18 m for the purpose of supporting bridge approach embankments and culverts with embankment heights up to 6 m. DSM was chosen due to the very soft nature of the clay soil with moisture content practically at liquid limit, and the relative speed and economy of the system. Dry cement powder at rates of 160 kg/m3 to 200 kg/m3 were pneumatically discharged via the hollow stem of the mixing tool, and mixed with the soil (using multiple horizontally mounted paddles on a single vertical stem) at high speed as the mixing tool is withdrawn."

Jan 1, 2015

By J. Drelich

The flotation limit of fine particles has been re-examined based on the effect of bubble size on contact angle, and a new surface chemistry-limited relationship describing the minimum particle size which can be floated is proposed. In this analysis the critical value of bubble-solid contact radius (re) for which there is no effective attachment between particle and bubble has to be determined. The values of re determined by extrapolation of our experimental data for contact angle versus bubble-solid contact diameter permit the prediction of the flotation limit of methylated quartz particles, with fraction-al coverage of trimethylsilyl groups from 0.07 to 0.51. The limit of fine particle flotation as determined by this theoretical approach agrees well with experimental data reported in the literature.

Jan 1, 1994

By N. E. Maccallum

(Cleveland Meeting, October, 1912.) ALMOST half a century has passed since the Siemens brothers, after tedious and costly experiments, finally began the manufacture of open-hearth steel. The furnace of that time was very small, having a hearth-capacity of from 3 to 4 tons, and we can appreciate the wonderful development that has taken place in those 50 years by the knowledge that to-day furnaces of 50 times the original capacity are in operation. As the new steel process assumed importance, and furnaces began to grow in number and in size, a question arose, to which no satisfactory answer has ever been given, and that was: ?What is the safe and economical limit of the open-hearth furnace?" Various stopping-places have been suggested, and 20, 30, 40, and 50 tons have each been advocated, but all such arbitrary restrictions have been passed, and 60 tons would probably represent the average furnace, although in a few instances from 70 to 80 tons are regularly tapped into one ladle. The furnaces which are the subject of the present paper have gone far beyond even these limits, and since, in my opinion, they mark another step in the progress of open-hearth steel, they will be considered fairly and frankly, in order that those to whom the matter may be of interest may be able to judge and form their own Conclusions. Short accounts of the work of these furnaces have appeared from time to time in various technical journals, of which the following is a brief résumé. These furnaces are the property of the Phoenix Iron Co., of Phoenixville, Pa., and their distinctive and important feature is, that they charge to twice the capacity of one ladle, and tap simultaneously into two ladles, with a device for controlling the flow into either. In this way the capacity of the furnace is not limited, as formerly, but heats of any size within the capacity of two ladles may be charged.

Oct 1, 1912

By C. D. King

A QUARTER century ago this country was producing an extraordinary quantity of iron and steel, with a decisive influence on the outcome of the first World War. Today this country is again demonstrating its industrial capacity with telling results. If this lapse of time has confirmed the opinion that man learns little from experience with respect to human relationships, at least we can derive some consolation from the knowledge that in the same period we have made huge strides industrially, and particularly in the steel industry. The differences represented by 25 years are striking, and have resulted from a multitude of changes that have contributed to the present-day high state of our pig iron and steel manufacture.

Jan 1, 1944

By Zay Jeffries

AN acute current shortage of copper, with the prospect that conditions may become worse, indicated by Office of Production Management information. Present estimates of copper requirement for defense indicate that nearly all the available metal will be required in the future for this purpose. Severe dislocations are, expected, but the objective is to distribute the copper available for civilian use in such a manner as to minimize these dislocations. The advisory committee on metals and minerals has been asked for a suggestions which may be helpful in meeting this situation.\

Jan 1, 1941

By H. A. Pearse

NORMALLY, the Britannia ore mixture contains chalcopyrite and pyrite as the chief sulfide minerals, together with minor amounts of gold and silver and a low zinc content. Reduction is accomplished by jaw crushers underground, followed at the concentrating plant by Symons cone crushers, rolls, and ball mills. The standard flotation practice, evolved during several years of experimentation, provided for bulk flotation of the two sulfides, after primary grinding to only approximately 35 mesh, followed by regrinding of the bulk concentrate, with subsequent separation of the chalcopyrite and pyrite to make a marketable concentrate of each mineral. This so-called standard milling practice has previously been described in detail in U. S. Bureau of Mines Information Circular 6619. A modification will he discussed here. In the face of a constantly increasing world surplus of copper and a steadily falling price during 1930 and 1931, it was obviously undesirable to continue unprofitable production of large quantities of this metal. On the other hand, company officials were

Jan 1, 1934

By Aruna Mangalpady, Sandeep Kumar Jeripotula, Govinda Raj Mandela

Injuries due to work-related musculoskeletal disorders (WMSDs) are not uncommon in heavy industry like mining. Researchers acknowledged that occupational exposure to ergonomic risk factors is the chief causative factor in the development ofWMSDs. The aim of this study was to perform an ergonomic assessment of musculoskeletal disorders among surface mine workers in India. Standardized Nordic Questionnaire was used to collect subjective response from 500 workers. A stratified random sampling method according to surface mining work activity type was used to obtain the sample. Data was collected by means of a structured questionnaire, and the Statistical Package for Social Sciences (SPSS) was used to analyze data using descriptive and inferential statistical methods. A response rate of 85% was obtained out of 500 targeted groups. TheWMSDs prevalence for the 12-month period was estimated to be 44.23%. The mean and standard deviation of workers’ age were 41.31and 8.927, respectively. The study has shown that the operators of dumpers, dozers, and graders along with electricians were found to be the most susceptible to developWMSD problems. Among the most affected body parts, back disorder reported the highest. Further, it was found that working with static posture over the longer duration has a significant association with the lower back disorder (with p = 0.020) and bouncing and jarring has also significantly associated with the lower back disorder (with p = 0.023). Similarly, a significant association was found between repetitive work and neck pain (with p = 0.016). The study depicted a significant association between ergonomic hazards and WMSDs, like working with prolonged static posture, bouncing and jarring, and repetitive work.

Mar 13, 2020

By C. E. Corson

THE experiments of which the results and significance are set forth in this paper do not by any means cover the whole subject of the heat-treatment of the material referred to, yet they constitute a contribution to that general subject, rather than to the special department of annealing. The material here considered is acid open-hearth steel, containing from 0.50 to 0.80 per cent of carbon, with a nearly uniform percentage of other elements. This class of steel is rapidly increasing in commercial importance. It is even rumored that the rail-specifications of some railroads will hereafter require open-hearth steel. Yet this particular grade seems to have received less study and description from the standpoint of the metallographist than many others. The investigation here described was directed to the following points:-Steel containing about 0.50 per cent, of carbon : 1. The structure as related to the temperature, at the same rate of cooling; 3. The structure and physical properties as related to temperature at different rates of cooling; 3. The structure and physical properties as related to different finishing-temperatures and different rates of cooling; 4. The bearing of these observations upon the statement of Prof. Albert Sauveur.1

Sep 1, 1906

By AIME AIME

SECOND only to the February Annual Meeting of the Institute are the Regional and Divisional meetings held in the fall of each year. Six such gatherings are scheduled in the next the months, with something likely to interest every member of the Institute. A brief résumé of the programs follows. Regional Meeting Vancouver T HE regional meeting of the Institute will be held at Vancouver, Sept. 13 to 20, in conjunction with the annual western meeting of the Canadian Institute of Mining and Metallurgy. The pro gram appeared on page 350 of MINING AND METALLURGY for July and-proof of careful preparation-a month later re- quires no correction and little elaboration. On the technical side there are few changes. A new item on the Wednesday morning program is the paper, "Investigation of Residential-type Stokers," by H. F. Yancey, supervising engineer, Northwest Experiment Station. U. S. Bureau of Mines, Seattle. As to entertainment the meeting is taking on some most pleasurable aspects. Two notable excursions have been arranged.

Jan 1, 1937

By Tcharllis João da Cunha Demartini

A produção de uma rocha artificial a partir da aglutinação de resíduos finos de mármore dolomítico pela resina epóxi pode ser uma alternativa viável do ponto de vista técnico, econômico e ecológico. O resíduo utilizado é proveniente do desdobramento de mármore dolomítico em teares de lâminas diamantadas e geralmente é descartado. Esta nova aplicação agrega valor ao resíduo, diminuindo o impacto ambiental gerado. O objetivo deste trabalho foi avaliar as propriedades físicas e mecânicas do mármore artificial produzido pela metodologia de vibro compressão à vácuo. Para isso, foram confeccionadas placas rochosas, em equipamento apropriado, com 85% em peso de partículas de resíduo e 15 % de sistema epoxídico DGEBA/TEPAc. As placas foram produzidas com uma pressão de compactação de 0,5 MPa, à temperatura de 90 °C por um período de 20 minutos. Posteriormente, as placas foram caracterizadas pelos ensaios de densidade, absorção de água, porosidade, resistência à flexão, resistência à compressão e microscopia eletrônica de varredura. Obteve-se um mármore artificial produzido pela técnica de vibro compressão a vácuo com absorção de água inferior a 0,06%, uma resistência à flexão de 33,93MPa e uma compressão uniaxial de 96,49MPa, confirmando uma boa adesão entre as partículas de resíduo e a resina epóxi.

Oct 30, 2017

By H. W. J. P. Neomagus, R. K. K. Mbaya, J. R. Bunt, N. T. Leokaoke, N. W. Makgobelele

Silicon Smelters consumes more than 80000 t/a of wood-derived charcoal as carbonaceous reductant in the production of silicon metal. More than 10% of this material is discarded as fines (<6 mm) generated due to abrasion during processing. Charcoal fine residues (<650 μm) and polyvinyl alcohol (PVA) binder were used in this study to produce mechanically strong charcoal briquettes for metallurgical application as carbonaceous reductant. The PVA binder was added in mass percentages of 1, 3, and 5 wt% to the charcoal fines. The compressive strength, abrasion resistance index (ARI), drop shatter resistance (SRI), and water resistance index (WRI) were measured as functions of curing for up to 7 days under atmospheric conditions, and the results compared with metallurgical grade coarse charcoal. The ash content of the produced briquettes was found to be high (6.6–8.0%) compared with the coarse charcoal (1–3%). The 3 and 5 wt% PVA-bound briquettes were found to be the strongest, with compressive strengths of 40 and 115 kg/cm2 respectively, with WRI values of 75 and 73% respectively. The produced briquettes were found to have lower ARI and SRI values compared to the coarse charcoal. Future work should include beneficiation of the fine charcoal discards prior to briquetting, and an increase in binder addition to above 6 wt% to improve the ARI and SRIn.

May 1, 2021

By Francisco Alberto Marreiros da Rocha Filho

No processo de laminação a quente ocorre ocasionalmente a perda de ductilidade a quente que pode causar o fenômeno denominado como “abertura de cabeça” da barra durante a sequência de passes. Essa perda de ductilidade a quente pode ser severa e causar interrupções no processo produtivo. Esse fenômeno pode estar associado a diversos fatores entre eles: composição química do aço; defeitos presentes no tarugo; condições do processo de laminação; e temperatura do aço durante o processo, principalmente nos passes de desbaste e intermediários de laminação. No processo em estudo, a perda de ductilidade a quente ocorre associada à laminação de vergalhões a partir de tarugos oriundos diretamente do lingotamento contínuo. O presente trabalho tem como objetivo avaliar a influência da temperatura e da microestrutura formada ao longo do processo na perda de ductilidade a quente das barras através de um exame comparativo entre os vergalhões laminados com e sem o uso da etapa de reaquecimento.

Oct 30, 2017

By H. W. J. P. Neomagus, J. R. Bunt, D. L. Botha, N. T. Leokaoke

Coal briquetting traditionally makes use of high-dosage, nonpolymeric binders (such as coal tar pitch or molasses) or polyvinyl alcohol (PVA) at low dosages for the binding of fine and ultrafine coal. Due to constraints associated with the manufacturing and cost of PVA-bound briquettes, a novel polyacrylic binder was developed that could possibly be added in low dosages at room temperature. A set of formulations of two polyacrylic components (components A and B) was developed, from which an optimal binder mixture was determined. This formulation comprises 40wt.% component A and 10wt.% component B with a 0.04wt.% cross-linking additive, and the balance water. The uniaxial briquette compressive strength was used to obtain the optimal binder mixture. The binder mixture was added to the coal powder in dosages from 0.1 to 1.2wt.%. Mechanical tests and thermogravimetric analysis in an oxidized environment at a maximum temperature of 930°C were conducted. Binder-bound briquettes were compared to binderless briquettes and PVA-bound briquettes. Briquettes made from the polyacrylic formulation had uniaxial compressive strengths double that of the binderless briquette yield strength, as well as the minimum recommended compressive strength of 0.375 MPa. The organic binders did not affect the combustion of the briquettes, since the results compared well with the binderless briquettes. The polyacrylic formulation is considered to be a possible substitute for PVA in terms of mechanical and thermal properties and raw material cost.

Mar 1, 2021

By D. Amariei, G. Bartolacci

Preconcentration of precious and base metal ore types is becoming more relevant with the discovery, the development and the operation of many lower grade deposits around the world. Ore preconcentration designates an operation consisting of sorting an ore to reduce the quantity of waste material sent to the concentrator. It can be seen as rejecting waste material as much as possible, without compromising the recovery, or as the recovery of as much valuable metal as possible into an optimum mass yield. Benefits of preconcentration are multiple: grinding energy savings, costs reduction, lower environmental footprint, extension of the reserves, etc. However, all of these benefits do not apply simultaneously and are not applicable to each ore type. Technologies employed for preconcentration are highly dependent on ore properties, especially on the particle size at which the gangue is liberated. Thus, from coarser to finer particle sizes, technologies such as screening, ore sorting, gravity separation (Dense Media Separation (DMS) and jigs) and coarse flotation could be used for the rejection of liberated gangue. The difficulty starts when a benchmark is needed to select a suitable technology, especially for low-grade gold deposits. This paper presents the challenges of comparing lab-scale technologies (DMS versus jig) for gold preconcentration. The experimental data will show to what extent comparing two lab-scale gravity technologies for gold preconcentration can be challenging. An attempt to evaluate the energy savings by assessing the hardness of the tailings after gravity separation will also be presented. Keywords: Challenges in gold preconcentration, gravity separation, jig, dense medium separation

Jan 1, 2020