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By John Towers, Paul A. Beck, W. D. Manly

Recent work on grain growth in high purity aluminum and in a solid solution type alloy of aluminum and magnesium1 showed that the isothermal increase of the average grain diameter D with time follows the equation D = K(tg + A)2 Eq 1 Here tg is that portion of the total annealing time 1, which is available for grain growth, that is the annealing time less the time necessary for complete recrystallization. The parameters A and n depend only on the temperature. A has the dimension of time, and is usually of the same order of magnitude as the time for recrystallization: R. In some instances R may be substituted for A in Eq I. This is the case for example at long periods of annealing or at high temperatures, where both A and R become small in comparison with t. In such instances Eq I is simplified to D = K, tn Eq 2 For high purity aluminum the exponent n increases in the ratio of about I to 5 in. the temperature range of 350' to 6w°C. 70-30 brass has been long known to exhibit grain growth of the continuous type, such as occurs in pure metals. For this reason, it was of interest to determine whether grain growth in brass also follows Eq I and 2 as it does in aluminum. Isotherma1 grain growth data for 70-30 brass were published in recent years by R. S. French2 and by H. L. Walker.' Fig I shows a log D vs. log t plot of French's data, together with the 500, 600 and 700°C data by Walker for 42.8 pct reduction by rolling. In such a log D vs. log t plot Eq 2 corresponds to a straight line with a slope of n. As seen in Fig I, the data of French and the 600°C data of Walker can be represented by straight lines. However, the 500 and 7c0°C data of Walker give curved lines and the average slope of his 500°C line is very different from the slope of the line representing French's data for the same temperature. Furthermore the curvature of the 700°C line suggests a tendency for grain growth to stop after 8 hr. If confirmed, this would constitute a definite deviation from Eq 2, not explainable on the basis of the specimen thickness effect found in high purity aluminum.' Walker's specimens were 0.125 in., or 3.18 mm thick, while the deviation occurs at a grain size of approximately 0.4 mm. A further point of divergence arose recently, when J. E. Burke suggested4 on the basis of Walker's data, that, instead of Eq 2, grain growth in 70-30 brass follows the equation D - D, = K . tgn Eq 3 Here D, is the grain size as recrystallized at the temperature in question. Although it was possible to show5 that, for pure aluminum, for which isothermal grain growth has been carefully investigated, Eq 3 is incompatible with the experimental facts, the situation remained somewhat obscure with respect to 70-30 brass. In view of the discrepancies between the published data on brass from different

Jan 1, 1949

By Craig R. Barrett

The influence of the stress dependence of the dislocation density on the overall stress dependence of The steady-state creep rate is discussed. Experimental measurements of dislocation densities and creep rates jor an Fe-3.1 pct Si alloy tested over a wide range of stress are presented which indicate a close correlation between the two quantities. EXPRESSING the stress dependence of high-temperature steady-state creep rates has been the subject of numerous investigations over the past decade. From these investigations have emerged a few general equations which fit most of the available data reasonably well. Garofalo 1 has proposed that for a wide range of stress and temperature the creep rate, i, can be expressed by a relationship of the form: where A, ß, and n are temperature-dependent and is the applied stress. Eq. [I] gives a stress dependence of a at low stresses and exp(nßo) at high stresses, both consistent with experimental observation where n = 5. A number of other investigatorshave proposed a similar expression where: where m and w are in general functions of temperature. Theoretical justification for Eqs. 111 and [2J comes from two different approaches, theories based on dislocation glide3-5 and theories based on the balance between work-hardening and recovery.' Dislocation glide theories predict where p is the mobile dislocation density and V is the activation volume. In order for Eq. [3] to predict a on stress dependence at low stresses with n = 5, it is necessary for p to be a strong function of stress, about proportional to u3 or u4.436 Recovery models of creep start with the general expression:' where r is the recovery rate and h is the work-hardening rate, and then employ a detailed model to determine the stress dependencies of r and h. As example, weertman2 has described a model based on pile-up hardening which results in an expression similar to Eq. [2] with m = 2 and p = 2.5. A recent, seemingly more general approach suggested by McLean is to use Friedels dislocation network growth expression to calculate the stress dependence of r. This model predicts r = p 3,2 and, as h is taken to be a relatively weak function of stress, the stress dependence of i should be about proportional to p3, 2. Once again, it is required that p be a strong function of stress to yield i This recovery model is by no means complete as the stress dependence of network growth is calculated in the absence of an applied stress meaning that r should probably be a stronger function of stress than given by p3, 2 and also some recent work by Mitra and McLean8 suggests that the stress dependence of h may be as large as Because of the importance of the stress dependence of p in determining the overall stress dependence of the strain rate it seems reasonable to examine this relationship in some detail. Measurements made on dislocation densities present during high-temperature steady-state creep generally obey the following relationship a =o0 + aGVWp [5] where uo is usually called a friction stress, a is a numerical constant about equal to unity, G is the shear modulus, and b is the Burgers vector. Depending on the magnitude of uo, data obeying Eq. [5] can give rise to a range of stress dependencies of p. For example, if we assume that the expression where 6 is some constant, adequately represents the stress dependence of p over a range of o, then from Although Eq. [6] obviously breaks down when u 5uo for uo 6 can vary over a wide range of values. In particular, if u > a, > 0 then 6 will be greater than 2. As an example the data of Ishida and McLean are plotted in Fig. 1 showing excellent agreement with dynes per sq cm) and also showing good agreement with a p cc u3 dependence when plotted on a log-log basis. As oo increases 6 tends to increase and correspondingly the stress dependence of the predicted creep rate should also increase,* as-

Jan 1, 1968

By P. P. Gregory

The rate of drilling operations in the West Texas district during 1940 was approximately equal to that of 1939. The total number of wells dillled in the area during the year was 1834, of which 1716 were completed as oil producers, 12 were gas wells and 106 were dry holes. The number of wildcat wells drilled during the year was comparatively small. The drilling of inside locations in proven areas and the drilling of wells for the purpose of extending the productive limits in producing fields constituted the bulk of development during 1940. Gaines County led all other counties in the district in the total number of oil-well completions. The oil production totaled 83,345,381 bbl., the highest figure for any year since proration was begun. The 1940 oil production exceeded the 1939 production by approximately four million barrels. Discoveries While comparatively few new oil-producing areas were discovered during 1940, it appears that the oil production found in simpson lime in the Abell field, pecos County, was an outstanding discovery for the year. This was the second Ordovician discovery in Pecos County. Taubert, McKee & Siemoneit located its discovery well, V. W. Crockett No. 1, set. 4 1/2 H. & T. C. R.R, co, survey in the Imperial area of northwestern Pecos County. The top of pay was encountered at 5270 ft., and the well was bottomed at 5357 ft. in simpson lime, on act. 17, I940. The initial production was 928 bbl. of 43" gravity sweet oil in 11 hr. 23 min., flowing naturally through 2-in. tubing with gas-oil ratio of 783 cu. ft. per barrel. Following the completion of the discovery well, large blocks of land were leased in the area, and several locations were made toward the close of the year. There is every indication that the Abell field will become a major producing field in the West Texas district. There was no pipe-line outlet for the field at the end of the year. Shipley-Silurian field, discovered by the Gulf Oil Corporation, appears to be another major addition to the oil reserves in 1940. The discovery well, Wristen Brothers No. 5, is in sec. 18, block 5, H. & T. C. R.R. Co. survey in Ward County. The well was drilled to a total depth of 9187 ft. and was plugged back to 7075 ft. The Silurian lime section was acidized with 3000 gal., from 6993 to 7075 ft., and on Dec. 5, 1940, the well was completed for initial production of 3040 bbl- of 32.2" gravity oil in 24 hr., flowing through tubing. Todd Deep field, Crockett County, was discovered by the Continental Oil Co. et al. The discovery well, J. S. Todd No. 2, set. 29, block WX1 G.C. & S.F. R.R. Co. survey, was completed on April 3, 1940. The top of pay was encountered at 5623 ft., and the well was bottomed at 5691 ft. for initial production of 1613 bbl. of 40.6' gravity oil flowing naturally through 2-in. tubing. The pay section was found in Strawn lime of Pennsylvanian age. There were six producing wells in the field at the end of the year. This appears to be another major discovery in 1940. There was no pipe-line outlet in the field at the end of the

Jan 1, 1941

By P. P. Gregory

The rate of drilling operations in the West Texas district during 1940 was approximately equal to that of 1939. The total number of wells dillled in the area during the year was 1834, of which 1716 were completed as oil producers, 12 were gas wells and 106 were dry holes. The number of wildcat wells drilled during the year was comparatively small. The drilling of inside locations in proven areas and the drilling of wells for the purpose of extending the productive limits in producing fields constituted the bulk of development during 1940. Gaines County led all other counties in the district in the total number of oil-well completions. The oil production totaled 83,345,381 bbl., the highest figure for any year since proration was begun. The 1940 oil production exceeded the 1939 production by approximately four million barrels. Discoveries While comparatively few new oil-producing areas were discovered during 1940, it appears that the oil production found in simpson lime in the Abell field, pecos County, was an outstanding discovery for the year. This was the second Ordovician discovery in Pecos County. Taubert, McKee & Siemoneit located its discovery well, V. W. Crockett No. 1, set. 4 1/2 H. & T. C. R.R, co, survey in the Imperial area of northwestern Pecos County. The top of pay was encountered at 5270 ft., and the well was bottomed at 5357 ft. in simpson lime, on act. 17, I940. The initial production was 928 bbl. of 43" gravity sweet oil in 11 hr. 23 min., flowing naturally through 2-in. tubing with gas-oil ratio of 783 cu. ft. per barrel. Following the completion of the discovery well, large blocks of land were leased in the area, and several locations were made toward the close of the year. There is every indication that the Abell field will become a major producing field in the West Texas district. There was no pipe-line outlet for the field at the end of the year. Shipley-Silurian field, discovered by the Gulf Oil Corporation, appears to be another major addition to the oil reserves in 1940. The discovery well, Wristen Brothers No. 5, is in sec. 18, block 5, H. & T. C. R.R. Co. survey in Ward County. The well was drilled to a total depth of 9187 ft. and was plugged back to 7075 ft. The Silurian lime section was acidized with 3000 gal., from 6993 to 7075 ft., and on Dec. 5, 1940, the well was completed for initial production of 3040 bbl- of 32.2" gravity oil in 24 hr., flowing through tubing. Todd Deep field, Crockett County, was discovered by the Continental Oil Co. et al. The discovery well, J. S. Todd No. 2, set. 29, block WX1 G.C. & S.F. R.R. Co. survey, was completed on April 3, 1940. The top of pay was encountered at 5623 ft., and the well was bottomed at 5691 ft. for initial production of 1613 bbl. of 40.6' gravity oil flowing naturally through 2-in. tubing. The pay section was found in Strawn lime of Pennsylvanian age. There were six producing wells in the field at the end of the year. This appears to be another major discovery in 1940. There was no pipe-line outlet in the field at the end of the

Jan 1, 1941

By Paulo César Lemes de Almeida

No projeto da usina da VSB, em Jeceaba – MG estão contemplados dois altos-fornos de 350 m3 de volume útil e uma máquina de lingotar gusa (MLG) com capacidade de 150 t/h. Um destes altos-fornos já está pronto para o início de operação. Visando realizar os testes a quente da MLG a aciaria da VSB tem produzido aço com alto teor de carbono para testar o equipamento. Realizaram-se 07 etapas de testes que possibilitaram a implantação de algumas melhorias na MLG, coletar dados sobre a logística de movimentação de panelas, estimar perdas térmicas do gusa e treinar o pessoal para a operação. Nesta contribuição técnica descrevem-se os testes realizados e as modificações decorrentes.

Aug 1, 2018

By S. Zhao, S. P. He, M. Y. Zhu, Y. Tao

"The effect of two refining slags (A: 1.0–1.8 CaO/Al2O3 ratio, 11–20 wt% SiO2; and B: 1.0–1.2 CaO/SiO2 ratio, 25–35 wt% Al2O3) on the inclusion morphology of a carbon structural steel (Q235B) was studied by controlling the balance between the steel and the refining slag at 1600ºC in a Si–Mo resistance laboratory furnace. The results showed that most of the inclusions in the molten steel balanced with slag A were formed by a lowmelting CaO–MgO–Al2O3–SiO2 system with a total oxygen content (T[O]) being fixed at 6–13 ppm. The inclusions in liquid steel balanced with the slag B were mostly formed by the CaO–MnO–Al2O3–SiO2 system, with T[O] controlled to 19–26 ppm. The overall size of the inclusions under balance conditions was higher in the steel reacted with the slag B than that reacted with slag A, with the latter showing more inclusions smaller than 3 um. In order to generate a large number of spherical CaO–MgO–Al2O3–SiO2 inclusions smaller than 3 ??m while decreasing the T[O] in the resulting steel, the composition of slag A should be used. This composition allowed improving the cleanliness of the slab, and is also advantageous for the castability of the molten steel. IntroductionThe sample used in this study was a typical carbon steel manufactured by CQ Steel. The galvanized, tinned, and plastic composite steel plates made of the original plates are used extensively for decorative panels, general dust pipes, drums, instrument cases, switchboxes, and train cars, among other uses. The target control composition is shown in Table I. The S and P contents are usually fixed during production below 0.020 and 0.025 wt%, respectively, with the aim of reducing longitudinal cracks on the slab surface."

Jan 1, 2017

By Luiz Henrique Simões dos Reis

Este trabalho estuda o fenômeno da erosão e a validação de um erosímetro. Com este propósito, as taxas de erosão, perda de massa acumulada por unidade de área e o fator de esfericidade foram medidos. Os testes foram realizados com corpos de prova de latão 360 CLA, efetuando quatro testes com durações de 5, 10, 15 e 20 horas, respectivamente. As amostras foram pesadas em uma balança de precisão antes e após os testes. O abrasivo utilizado foi a areia ABNT em uma concentração de 10% em peso. O impacto repetitivo entre as partículas abrasivas causou trincas, lascamentos e, consequentemente, a formação de partículas menores. Também foi constatado o arredondamento das partículas abrasivas. Tais fatos são a causa do decréscimo da taxa de erosão com o aumento do tempo de teste. Micrografias apresentam a degradação da superfície na parte frontal do corpo de prova devido à remoção de material. O erosímetro obteve sucesso nas comparações com outros artigos.

Oct 30, 2017

By Diana Pérez Escobar

O efeito do caminho de solidificação de um aço High Temperature Processing (HTP) API 5L X65 com 0,09 %Nb, 0,039%C e 0,54% Mn (percentagem em massa) na segregação, microestrutura e distribuição dos precipitados de Ti,Nb(C,N) foi estudado por microscopia ótica, eletrônica de varredura (MEV) e simulação computacional (ThermoCalc e DICTRA). Os resultados foram comparados com os de um aço microligado comercial com 0,04 %Nb, 0,09%C e 0,97 %Mn. Foi encontrado que o principal parâmetro que influencia no caminho de solidificação é o teor de C, o que está de acordo com a maior micro e macrossegregação observada no aço microligado comercial, em comparação ao aço HTP.

Oct 30, 2017

A. L. FIELD, Cleveland, Ohio (written discussion*.-)In equation 2, B is used to denote the ratio of bases (lime plus magnesia ) to acids (alumina plus silica) it being stated that this ratio gives more concordant results than the ratio either of bases to silica, or of lime to silica. I find, however, that, by making use of the ratio between true CaO (CaO by analysis minus sulfur calculated to CaS) to acids, equation 2 may he modified to agree with the observed facts within an average error of 0.0041 per cent. sulfur instead of 0.0045 per cent. The revised equation is s = 0.072 + 0.01835 - 0.00061 (t - 1400) - 0.0403B where B is the ratio of true CaO to Al2O3 Plus Si02, and the other symbols have the same significance as before. I would not appear to stress too much this slightly better agreement of the revised equation with the observed sulfur. Yet I believe that the use of this ratio of true CaO to acids is to be preferred, if for no other reason than the fact that it is more in harmony with the previous findings of the Bureau of Mines with regard to the effect of magnesia and other impurities on slag viscosity.1

Jan 12, 1919

By Lucas Gonçalves Generoso, Larissa Rodrigues de Carvalho Rocha, Mauro Vivaldino Fernandes, Gustavo Serrano dos Santos, Gustavo Alexandre da Costa Manso

O Alto-Forno 3 da Usiminas iniciou sua atual campanha em 1999. Projetada para durar 15 anos de operação, previa-se uma produção de 41 Mt de gusa. A partir de 2008, iniciaram as avarias mais significativas no sistema de refrigeração, possibilitando a entrada de água e os consequentes distúrbios operacionais. Buscando estender a atual campanha até 2021, a Usiminas realizou, dentre outras atividades de preservação, duas trocas de staves, em 2015 e 2018. Neste trabalho, são apresentados o planejamento e os principais procedimentos relacionados à parada operacional do alto-forno para a segunda troca de staves, com foco nas atividades operacionais que permitiram a redução do nível da carga até 25,1 metros em relação ao stock line. Destacam-se os cuidados e o êxito no abaixamento de carga até o nível das ventaneiras e a metodologia de troca de staves adotada. Por fim, a previsão de extensão da campanha em 7 anos, possibilitará atingir uma produção acumulada de 53,5 Mt, superando em 12,5 Mt o valor projetado.

Oct 1, 2019

By Breno Totti Maia

O BOF, Basic Oxygen Furnace, ou convertedor LD, é o processo mais utilizado industrialmente para o refino primário do ferro gusa atualmente. Para aumentar a produtividade do BOF deve-se diminuir o tempo de cada ciclo de operação, especialmente o tempo de sopro aumentado a taxa de descarburação. Durante o sopro do convertedor existem três etapas. A segunda etapa do sopro a taxa de descarburação é alta e constante sendo o fator limitante é a disponibilidade do oxigênio no banho e determina o tempo de sopro. Assim para aumentar a descarburação pode-se melhorar a interação do jato de oxigênio com o banho, configurando o convertedor. Estudando o sopro combinado em um modelo fisíco de um convertedor LD de 220t, foi testado diferentes bicos de lança com um sopro de 160Nm3/h de vazão e vazões de 4Nm3/h e 6Nm3/h nas ventaneiras. Através dos testes pode-se observar que aumentando o número de furos no bico o jato teve menor penetração, maior área de agitação e as projeções tiveram menor altitude, já a injeção pelas ventaneiras aumentou a penetração do jato e diminuiu as projeções. Foi calculado também valores para a constante K para cada configuração, assim é possível prever a penetração do jato industrialmente.

Aug 17, 2017

By Quésia de Freitas Silva Fonseca Rodriguesr

Os diamantes obtidos no sistema Ni-Mn-C com adição de teores de ferro de 0% a 5% foram submetidos ao teste de friabilidade para avaliação da resistência mecânica ao impacto. A resistência dos cristais pode ser influenciada por vários fatores como o dispositivo de alta pressão, sistema catalisador/solvente, tempo de síntese, tipo de grafite. No presente estudo os diamantes foram obtidos sob pressão de 4,5GPa e temperatura 1250ºC de, com período de processo de 10 minutos, utilizando o dispositivoi do tipo bigorna concavidade central. Os teste de friabilidade foram realizados no friatester, onde é determinado o índice de quebra em função do teor de ferro adicionado foi avaliada o índice de quebra e os fragmentos ou cristais que resistiram ou não ao impacto. Foi constatada uma significativa influência do teor de ferro sobre a friabilidade dos cristais

Aug 16, 2017

By Y. V. Swamy, B. Bhoi, H. S. Ray

Low-grade manganese ores with low Mn/Fe ratios can he enriched through selective carbon reduction of iron oxide to magnetite followed by magnetic separation o f the magnetite. Thermogravimetric analysis (TGA) was used to assess the preferential isothermal reduction of pure M1702 and Fe2O3 using solid carbon. This was followed by reduction of a synthetic analogue of composition comparable to an actual low-grade ore (i.e., Sandur manganese ore, Sandur, India). The carbothermic reduction of the manganese ore converts the hematite and goethite minerals to magnetite (Fe3O4), with the magnetite then going into the magnetic, fraction. The resultant nonmagnetic ,fraction becomes depleted of iron with an enhanced manganese content. These results show that it is possible to reduce the iron from 22% to 5.85%, thus increasing the Mn/Fe ratio from 1.52 to 6.2 with a manganese recovery of about 50%. The recovery was, further improved by grinding the magnetic fraction to -75 µm.

Jan 1, 1999

By J. Chipman, N. J. Grant, H. L. Bishop

In a recent review1 of the iron-oxide activity of simple open-hearth type slags containing lime, magnesia, silica, and iron oxide, it was established that activity values were lacking in the range of slag composition most interesting to open-hearth operators. That is, laboratory experimental results were not available for simple slag compositions having basicity ratios ranging from about 1.5 to 4.0 and iron-oxide concentrations ranging from about 10 to 30 pct. However, in order to estimate iron-oxide activities for the range of slag compositions of interest to open-hearth operators, activity values were calculated using ionic concepts of slags by following the treatment of Flood and Grjotheim.2 A study of these data indicated that the desired slag compositions were probably not obtained due to the limited solubility of the basic constituents lime and magnesia. Thus, it was decided to make additional heats equilibrating molten carbon-free iron with slags containing MnO, P2O5, and A12O3 in percentages commonly found in open-hearth refining slags, and to examine the liquid slag field over a greater composition range than that of the simple slags studied previously. The ranges of the constituents used in the present study are summarized as follows: Metal Pct 0 0.070-0.201 PctMn 0.005-0.142 Slag Pet CaO 24.45-41.90 Pct MgO 3.23- 9.21 Pct MnO 1.13- 9.62 Pct FeO 20.08-48.7 Pet Fe2o3 2.23-10.14 Pct SiO, 3.51-28.50 Pct P2O5 0.23- 3.65 Pct A12O3 0.43- 3.38 The experimental procedure consisted of equilibrating the slag and metal in an induction furnace provided with a carbon-arc slag heater as described previously by Winkler and chipman.3 The data obtained were used to establish both the iron-oxide activity values and the activity coefficients for FeO and MnO in the open-hearth type slags. RESULTS AND DISCUSSION I) Iron-Oxide Activity of Open-Hearth Type Slags—The iron-oxide activities of various iron-oxide contents of the open-hearth type slags, as calculated from the oxygen content of the metal by the method of Taylor and Chipman, 4 are plotted against the molar ratio of bases to acids in Fig. 1. The data represent slag-metal studies carried out in the temperature range 1530" to 1700°C. For the purpose of this study, the constituents CaO, MgO, and MnO are assumed equal on a molar basis in their effect on the iron-oxide activity; and, PO2,5 is calculated as an equivalent to SiO2 and A12O3 on a molar basis. The total iron content of the slag is calculated to FeO and is represented by the symbol (FeO) The points presented in Fig. 1 represent the results of this investigation for iron-oxide slags containing between 1 and 8 mol pct MnO and less than about 2 mol pct each of A12o3 and PO2,5 The curved lines shown in Fig. 1 represent the results of the summary1 of the iron-oxide activities of simple slags of the system (CaO + MgO) - SiOz - (FeO),. The solid portions of the curved lines represent experimental data, and the broken portions represent iron-oxide activities calculated from ionic concepts of slags. The iron-oxide values of the open-hearth type slags of this study are in good agreement with the values of the simple iron-oxide slag system. Only a slight modification is indicated. The results of this study suggest that the line for 20 mol pct (FeO), should be lowered slightly in the basicity range 1.5 to about 3.

Jan 1, 1959

By Zirlene Alves da Silva Santos

O desgaste abrasivo é o principal responsável por quebras de equipamentos e, como consequência, paradas não programadas para manutenção; pois causa a perda progressiva de material das partes móveis em contato e movimento relativo. O presente estudo analisa o desgaste abrasivo na superfície do rolete de carga dos transportadores de correia. Para a análise foi utilizado o equipamento abrasômetro do tipo roda de borracha conforme norma ASTM G65. Os procedimentos de ensaio contemplaram: o corte de quatro corpos de prova de aço 1020, limpeza, pesagem - utilizando balança de precisão, avaliação superficial com rugosímetro e ensaio de dureza. Dois corpos de prova foram revestidos com a tinta Laranja Munsell 2,5YR6/14m, para simular as condições de campo. Em seguida, foi realizado ensaio no abrasômetro ASTM G65; utilizando o procedimento “A” previsto na norma ASTM G65 - classificado como desgaste severo com carga de 130N. Logo depois, foi calculado o volume de material perdido e a taxa de desgaste. Os resultados obtidos nos ensaios possibilitaram concluir que, o desgaste predominante na superfície dos roletes de carga é o abrasivo por 3 corpos, em função, principalmente, do transbordo de minério do processo. A superfície do corpo de prova, sem revestimento, apresentou uma perda de material que compromete a vida útil do rolete e da correia. Já, na amostra revestida, foi possível observar que o desgaste abrasivo por três corpos ocorre, mas é reduzido consideravelmente; isso pode ser explicado pela diminuição da rugosidade superficial.

Oct 30, 2017

By Leandro Brunholi Ramos

O aço API 5 CT P110 é amplamente utilizado no setor de petróleo e gás no Brasil devido sua elevada resistência mecânica, contudo ele não possui uma boa resistência a corrosão. Com a descoberta do pré-sal, novos desafios surgem neste setor, tornando necessário o desenvolvimento de novas tecnologias resistentes aos ambientes agressivos que os materiais serão expostos. A aspersão térmica por HVOF se destaca pela obtenção de revestimentos contra corrosão e resistentes ao desgaste com baixa porosidade e com um relativo baixo custo em comparação a outros processos. Dentre os materiais que podem ser aplicados como revestimentos por aspersão térmica, o níquel se destaca pela ótima resistência à corrosão por formar um óxido protetor na superfície. Sendo assim, o presente trabalho tem por objetivo obter e caracterizar revestimentos de níquel obtidos por aspersão térmica HVOF, no aço API 5CT P110. Os revestimentos foram caracterizados morfologicamente por microscopia eletrônica de varredura (MEV). Foram obtidas curvas de polarização para avaliar o comportamento frente à corrosão e foram realizados ensaios para determinação do coeficiente de atrito. A camada aspergida de níquel apresentou resultados satisfatórios quanto às análises estudadas.

Aug 8, 2018

By Shoukun Wei, Cong Wang, Lin Cheng, Zhiyu Qiao, Jingkui Liang, Weidong Zhuang

"The subsolidus phase relations in the Sm2O3-CeO2-CuO ternary system sintered at 1000°C in air have been investigated by X-ray powder diffraction. The system can be divided into two ternary phase regions and three binary phase regions. Solid solution Sm2-xCexCuO4-y is the only ternary phase in the system. The maximum solid solubility was confirmed to be x = 0.2. The crystal structure, oxygen content and superconductivity of the solid solution Sm2-xCexCuO4-y have been investigated.I. INTRODUCTIONAfter the first discovery of the superconducting ceramic system La-Ba -Cu-O[l] with Tc = 30 to 40K, other families of cuprate-based ceramics have been synthesized with higher critical temperature. These oxides include the R-Ba-Cu-O (R: rare earth) systems (Tc=90K or so)[2,3], the Pb-Sr-(R,Ca)-Cu-O systems (T c = 50 to 100K), the Bi-Sr-Ca-Cu-O systems (Tc=80 to 105K)[4], the T1-Ba-Ca-Cu-O systems (Tc=85 to 125K)[5], the Hg-Ba-Ca-Cu-O systems (Tc=90 to 150K)[6,7], and some others. The improvement of Tc is very rapid. The measurement of the Hall and Seebeck coefficients shows that they all are p-type superconductors. In 1989, Tokura et al.[8] discovered the superconductors R2_XCexCU04_y(R = Nd, Pr, Sm) with Tc=20 to 24K (onset) and found that the charge carrier is electron in contrast to their hole doped counterparts. This discovery increases the fundamental understanding of the cuprate-based superconductors by comparing their characteristics and mechanisms to those of the p-type superconductors.One of the outstanding features of these n-type superconductors is the difficulty in obtaining samples in good charactors, such as the difficulty in obtaining zero resistivity state in single crystal or bulk samples; the semi-conductivity of bulk samples in ordinary state (opposite to the superconducting state) and a reducing reaction involved before the superconductivity has been found[9]. Therefore, it is necessary to optimize the sample preparation of the n-type superconductors. All the n-type superconductors have been found· considerable solid solubility. The compositional variations play a governing role in the carrier doping of the superconducting phases. Also, it is vital to the ceramic processing of superconductors to identify the compatible phases in the phase diagram. Finally, there is always the possibility of finding additional compounds, both superconducting and non-superconducting, in an unexplored system."

Jan 1, 1996

By Adriana de Oliveira Vilela

A produção de carvão vegetal em Forno Container Rima (FCR) consiste em um processo semi-contínuo composto por fornos cilíndricos metálicos móveis, com exaustão forçada dos gases. Cada ciclo se divide em 4 fases: carregamento, carbonização, resfriamento e descarregamento. Após o carregamento com toletes de madeira, 20% de umidade, o forno é deslocado para plataforma de carbonização, onde permanece por 3 a 4 horas. A entrada de oxigênio no interior do forno é regulada para controle das reações de pirólise. Todos os gases gerados são conduzidos a um sistema de queima para aproveitamento da energia e eliminação do metano. O peso, a temperatura e a pressão no interior do forno, bem como a vazão, composição e energia do fluxo de gás, são monitorados continuamente, em tempo real. A carbonização finaliza quando é atingido o rendimento gravimétrico de 35% em carvão e 60% em gás. O carvão ainda quente é transferido para cilindros de resfriamento, permanecendo por 12 horas. O forno então, é novamente carregado e se inicia um novo ciclo. Cada plataforma de carbonização pode gerar 1MWe de potência elétrica, produzir 20t/mês de alcatrão, 450t/mês de carvão vegetal e eliminar 500t/mês de CO2 equivalente. Cada FCR substitui 60 fornos Rabo Quente, reduzindo em mais de 50% a mão-de-obra braçal dos processos tradicionais, pela valorização, humanização e qualificação deste trabalho. O carvão produzido atende aos quesitos necessários para uso como redutor na metalurgia e na siderurgia.

Aug 16, 2017

By C. E. Van Orstrand

An intrusive body is a mass of igneous rock that has migrated upward, presumably from great depths. Great variations in form, composition and depth of burial occur. It is not proposed in this paper to go into all of the details of the problem. Instead, it mill be assumed here that the intrusive has the form and characteristics represented in Fig. I. According to W. 11. Emmons minerals are not deposited in appreciable quantities below the "dead line." Important amounts of ores of virtually all metals may be found around summit cupolas, but only gold, copper and zinc (in limited quantities) are usually associated with trough cupolas. Most students of ore deposits agree that temperature changes are largely instrumental in precipitating many ores in the "hood" and that the difference in temperature between the intrusive and that of the country rock may be the chief factor in determining the mineralogy of a deposit. A problem then of some interest is to correlate the principal physical features of the intrusive with the phenomena of heat conduction as evidenced by the cooling curves and the isothermal surfaces. Mathematical Theory In order to show the possible application of heat conduction to the interpretation of the processes of metalliferous deposition associated with intrusives, it will be as- sumed that the intrusive is a large par-allelopiped of dimensions, 2l, 2m, 2n. The equation that represents the flow of heat from the parallelopiped into country rock (v = o, 1 = o), which has the same thermal properties as the intrusive, is2,3 l-x v I FT 2 [2 2 — l-x m — y — m — y n — z In this equation, the origin, x = o, y = o, z = o, is at the center of the parallelopiped. v = temperature at point x, y, z, time 1. v, = initial temperature throughout the intrusive, 1 = o. k = coefficient of thermal diffusivity. a, ß, y are variables of integration. Put n = m in Eq. I, and we have v I [2/5 [2I-x 2 — l-x m — y 2 2 2 kt 2 20xt e-a2da ebrdß

Jan 1, 1946

By C. E. Van Orstrand

An intrusive body is a mass of igneous rock that has migrated upward, presumably from great depths. Great variations in form, composition and depth of burial occur. It is not proposed in this paper to go into all of the details of the problem. Instead, it mill be assumed here that the intrusive has the form and characteristics represented in Fig. I. According to W. 11. Emmons minerals are not deposited in appreciable quantities below the "dead line." Important amounts of ores of virtually all metals may be found around summit cupolas, but only gold, copper and zinc (in limited quantities) are usually associated with trough cupolas. Most students of ore deposits agree that temperature changes are largely instrumental in precipitating many ores in the "hood" and that the difference in temperature between the intrusive and that of the country rock may be the chief factor in determining the mineralogy of a deposit. A problem then of some interest is to correlate the principal physical features of the intrusive with the phenomena of heat conduction as evidenced by the cooling curves and the isothermal surfaces. Mathematical Theory In order to show the possible application of heat conduction to the interpretation of the processes of metalliferous deposition associated with intrusives, it will be as- sumed that the intrusive is a large par-allelopiped of dimensions, 2l, 2m, 2n. The equation that represents the flow of heat from the parallelopiped into country rock (v = o, 1 = o), which has the same thermal properties as the intrusive, is2,3 l-x v I FT 2 [2 2 — l-x m — y — m — y n — z In this equation, the origin, x = o, y = o, z = o, is at the center of the parallelopiped. v = temperature at point x, y, z, time 1. v, = initial temperature throughout the intrusive, 1 = o. k = coefficient of thermal diffusivity. a, ß, y are variables of integration. Put n = m in Eq. I, and we have v I [2/5 [2I-x 2 — l-x m — y 2 2 2 kt 2 20xt e-a2da ebrdß

Jan 1, 1946