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By Nicolás Ariel Zabala

During the make-up and break-out of the connections, threaded joints are exposed to intense mechanical and tribological solicitations. The connection performance is influenced by its geometry, material properties, surface treatments and thread compound. The aim of this work is to evaluate and characterize the tribological behavior of different thread compounds applied on manganese phosphated carbon steel under low speed and high pressure sliding contact. Four thread compounds were evaluated: one containing lead, zinc and graphite; other lead-free, containing copper and finally, the last two lead-free and containing non-metallic solids. The tribological behavior was analyzed by a block-on-ring tribotest. During the test, load varied linearly between 250 N and 7000 N; loading and unloading lasted 14 sec and were performed in opposite directions of rotation to simulate the make-up and break-out operations. Friction force and load as a function of time were registered. Upon completion of the test, wear surfaces were analyzed by SEM, optical microscopy and energy dispersive spectroscopy. The obtained results show that the lead and zinc containing thread compound displayed the best behavior, showing a wear reduction of approximately 20%. These results are in line with previously known oilfield experience. Average COF values around 0.15 were measured and no significant differences between dopes were observed; indicating that the wear behavior was influenced by the additive package.

Jul 31, 2018

By Jorge Maldonado Villa

Se desarrollaron materiales compuestos de matriz polimérica para toberas en cohetes; con dos zonas: una térmica para soportar elevadas temperaturas de combustión y una estructural que resista los esfuerzos generados. La zona térmica se elaboró con materiales de comportamiento ablativo, probados a temperaturas de hasta 2950°C durante dos minutos, los cuales fueron reforzados con polvo cerámico y/o subproducto de la industria siderúrgica (cerámico 2). Con base en los resultados obtenidos del comportamiento de térmico y de conductividad térmica del material ablativo, se construyó la zona estructural en materiales compuestos fibroreforzados (vidrio y carbono) con matriz polimérica. Los moldes se diseñaron en SolidWorks y se fabricaron por prototipado en ABS rápido y se elaboraron machos disgregables en poliuretano. En la zona térmica se usó un procedimiento de vaciado con vibración con diferentes tipos de matrices (poliéster, vinilester, caucho silicona) y de laminación para la zona estructural. Se evaluó el desempeño mediante simulación de las condiciones reales de operación mediante llama de oxicorte y quemador de ACPM, observando el efecto en la pérdida de peso, espesor, diferencial de temperatura, cambio de propiedades mecánicas, etc.; encontrándose un positivo comportamiento del sistema con matriz de resina vinilester reforzado con polvo cerámico 1 y buenos resultados con cerámico 2, así como una estabilidad en la zona estructural construida con fibras de vidrio y carbono. Substituir todo o texto de orientação deste Template pelo conteúdo de seu trabalho. Inserir o texto com no máximo 1.500 caracteres (200 palavras), sem uso de parágrafos. Deve conter, de maneira concisa, o objetivo, a metodologia, os resultados e as conclusões do trabalho.

Aug 17, 2017

By Antonio Fabiano de Oliveira

The aim of the present research work is to study the influence of hard chrome covered skin pass cold rolling rolls using 2D/3D surface topography, i.e. roughness characterization. The common stochastic structure Shot Blast Texturing (SBT) does not meet all requirements related to the production line regards to the finished product. The Hard Chrome layer, applied on these SBT rolls, can improve the sheet surface quality and is of fundamental interest mainly for those steel mills that do not have another alternative to new surface structures such as those that may be provided by the EDT, LT, EBT, etc. methods. The function of the generated surfaces, obtained by these different methods is going to influence the tribological properties during the subsequent forming processes. On the other hand, they can increase the product final cost or require large investments to obtain such surfaces. The results here presented are in accordance with other recently published research work, showing that there is a relationship between these parameters, and that further detailed studies are needed.

Aug 17, 2017

By Guilherme Filipe de França Vieira

Os aços inoxidáveis ferríticos apresentam menor custo que os austeníticos, pois praticamente não possuem níquel em sua composição, e seu custo está diretamente ligado ao preço do níquel que possui alta volatilidade. Devido a sua capacidade de resistência à corrosão, estruturas são construídas a partir deste material e descartam a necessidade de revestimento contra corrosão. O trabalho tem como objetivo caracterizar o comportamento mecânico da liga de aço inoxidável ferrítico, UNS S43932. Metalografia e dureza foram realizadas para caracterizar o material e sua microestrutura. Por meio de ensaios mecânicos de tração, no equipamento MTS 250 kN, analisando sete corpos de prova, obtiveram-se propriedades como: módulo de elasticidade, tensão de escoamento, tensão limite de resistência à tração, tensão de ruptura, alongamento, redução de área, coeficiente de resistência e expoente de encruamento, através da curva monotônica. Pode-se observar que as propriedades mecânicas identificadas estão coerentes com aquelas fornecidas pelo fabricante, o que validou os ensaios e possibilitou a adicional obtenção de propriedades mecânicas referentes ao comportamento da parcela plástica.

Aug 16, 2017

By Carolina Sartori Marzullo

Apresenta-se a metodologia e sistemática para gestão da capacitação como ferramenta para aumento da competitividade e ganho de resultados do negócio num contexto crítico para o segmento.

Aug 16, 2017

By Angelo dos Reis Magalhães

Brazilian companies have adopted in recent years new management practices to remain competitive. Specialized consulting in asset management progressively creates or adapts new techniques in order to increase availability and reduce manufacturing costs, maximizing profits. New engineering concepts were acquired and implemented by executives in all business segments. Techniques, such as FMEA, RCM, LCC, Pas 55, Reliability studies by Monte Carlo simulations, among others, have become increasingly recognized as important tools to enhance managerial performance. Besides these techniques, this study suggests the importance of adequate structuring of a lubrication program, as a critical success factor for the reliability of any asset. Through a case study developed with a company in the mining sector, this work proposes the development of a master plan for lubrication based on three pillars: People, Equipment and Management system. Practices and care with lubricants, hydraulic fluids and coolant, until its point of application, shall be evaluated to ensure a correct contamination control and a high level of assets availability. This discussion sheds light onto other benefits of this process, including occupational health and safety; ergonomics; environment and sustainability.

Jul 31, 2018

By Santiago Faucher

Molten slag from pyrometallurgical furnaces is tapped at high temperature, carrying a large amount of thermal energy. But the common slag dumping and water granulation methods used for slag treatment do not permit energy recovery. Furthermore, water is present in these processes and while operations are designed to minimize risks of steam explosions, from the contact of slag with water, these common slag handling practices have never been inherently safe. Common handling practices do permit some slags to be sold, but often in low volumes at low prices. Dry granulation offers advantages over these common slag handling practices, including the production of by-products, the recovery of thermal energy, and the eliminated consumption and safety hazards of water. For these reasons, there have been various studies in dry granulation and heat recovery, but most have never been brought to commercial scale due to scalability and cost challenges. Ecomaister- Hatch has developed and brought to commercial scale a reliable and simple dry granulation and heat recovery technology. Here we review common slag handling practices, the developments in dry slag granulation over the last three decades, introduce the Ecomaister-Hatch dry slag granulation process, and elaborate on future applications of the technology in the processing of argon oxygen decarburization and blast furnace slags.

Aug 17, 2017

By Juvenil Nunes Oliveira Júnior

O tubo de papelão é um material bastante versátil e pode ser utilizado de diversas maneiras, possibilitando sistemas construtivos variados que, muitas vezes, geram obras arquitetônicas arrojadas [1]. Um abrigo emergencial deve possuir as seguintes características: rápido fornecimento, baixo custo, flexibilidade de adaptação ao terreno, fácil montagem/desmontagem que permita a participação do utilizador do abrigo. Outro ponto é possuir princípios sustentáveis e funcionais, aliando eficiência e diretrizes lógicas para o design do produto. Este trabalho tem como objetivo a caracterização mecânica de tubetes de papelão para a utilização em abrigos emergenciais.

Aug 16, 2017

By Daniel Augusto Godinho de Carvalho

Since the beginning of BOF process, slag formation has been subjected to extensive development. During the initial stages of the blow, fast slag formation is primordial for the process performance. This is mainly to allow oxidizing reactions, and also to protect the refractory. A modeling of BOF process for the purpose of process optimization requires precise knowledge concerning the dissolution of CaO and MgO based materials. Using this knowledge, the optimal process conditions can be ensured by a controlling of the slag formation during the converter steelmaking process. Taking into account an application of large amount of different raw materials, as well as location-specific process conditions, the characterization of the dissolution behavior of different additives is an important key to improve the technological process. Thereby, in the frames of this project, an appropriate model for slag formation is established and compared to operational results for a 330t BOF, operating at ThyssenKrupp CSA, Santa Cruz, Brazil.

Aug 16, 2017

By Claudio Fabbro

The increasing demand of wire rod high carbon grades for both small and large sizes are challenging the wire rod producers to enhance new technologies by combining high plant productivity and efficiency of superior quality finished products with extreme process flexibility. The possibility to change process route according to the final application of the rolled steel grade and to simplify production planning is one of the most important keys to success that distinguishes the mill plants developed by Danieli. This paper will focus on the most important metallurgical and process targets and on the in-line heat treatment technologies representing the core of Danieli know-how on high carbon grades production.

Jul 30, 2018

By Francisco de Paula Pinheiro

Estudo das fontes de variação do processo de vazamento contínuo de chapas de alumínio, através da aplicação de uma metodologia prática e rápida para solução de problema. Após identificação das variáveis críticas à qualidade, ações foram tomadas de modo a minimizar as perdas do processo, o que contribuiu para a redução nos custos de produção das chapas.

Aug 16, 2017

By Daniele Tolazzi

Electric Arc Furnaces keep evolving into highly powerful melting units, shrinking taptotap times by increasing the effectiveness of the energy sources and the material fluxes used in the process. Steelmakers are targeting to increase the efficiency of their injection package in order to reduce the overall conversion costs, seeking for technologies specifically designed to promote the metallurgical reactions in a predictable and reproducible process automatically controlled at the correct timing. Many technological enhancements have focused in the gas management, improving the burner design and the penetration capacity of oxygen injectors, dedicated to decarburization and the other exothermic reactions. Instead, lower evolution efforts have been addressed to engineered solutions for managing the addition of solid materials required in slag forming, although they are playing a key role in EAF process optimization, as well. The paper describes the latest solutions designed to manage efficiently the injection of fuel, oxygen and powdered materials in several EAFs and presents the operational results achieved. Accurate control of reliable additions of coal, lime and magnesia proved crucial for the control of the slag FeO and viscosity, generating stable foamy slag and producing cleaner steel.

Aug 17, 2017

By Samuel Filgueiras Rodrigues

An austenitic stainless steel ISO 5832-9 was deformed in a torsion test machine over the temperature range of 1,000°C – 1,200°C and strain rates of 0.05, 0.1, 1.0 and 5.0s-1. The Steel plastic behavior was studied by analyzing the flow curves shapes and using the constitutive equations under the conditions of thermomechanical treatment. The curves initially presented an increase in stress characterized by hardening work, followed by a drop in stress to an intermediate level that reached or not, for certain conditions, the steady state softening. The plastic flow curves of ISO 5832-9 steel displayed in three different ways: (i) Curves with continuous softening presenting plastic instability for low temperatures and high strain rates; (ii) curves type flat, here after the peak there is little variation of stress with strain presenting softening mechanism by higher contribution of dynamic recovery at low temperatures and low and intermediate strain rates; (iii) curves with softening after the critical deformation favored by high temperatures and low strain rates. These behaviors indicate the influence of the stacking fault energy (SFE) and precipitated particles on the softening kinetics of this steel.

Aug 8, 2018

By Caroline Gomes de Oliveira

As fibras lignocelulósicas representam vantagens econômicas, técnicas e ambientais em comparação com as fibras sintéticas, como fibra de vidro por exemplo, quando se considera as alternativas de reforço aos compósitos. A fibra natural usada no presente trabalho é a fibra de eucalipto, que é largamente cultivada em território brasileiro. Este trabalho tem como objetivo avaliar uma análise estatística da correlação entre o diâmetro e a densidade da fibra de eucalipto. Para isso, foi aplicado o método de Weibull. O diâmetro foi obtido por meio de medições em projetor de perfil, enquanto a densidade utilizou determinações precisas da massa e do volume de fibras. Os resultados revelaram uma dependência inversa entre o diâmetro da fibra de eucalipto e sua densidade

Aug 17, 2017

By Charles David

This work aimed at evaluating the effect of pre-strain of Lean Duplex UNS S32304 on anodic dissolution and hydrogen evolution reaction rates in acidic chloride media. Interrupted tensile testing was employed in order to generate different deformation levels. Potentiodynamic experiments allowed to detect a decrease on the cathodic and anodic reaction rates as a consequence of plastic deformation. A non-linear evolution of corrosion rates was observed, probably as a consequence of the evolution of specific dislocation structures in the material. Strain also caused a slight ennoblement of the ferritic phase, while austenite became a little less noble. These behaviors are analyzed in terms of residual stresses, characterized by X-ray diffraction.

Aug 17, 2017

By Thokozani Lehae Hanes Malinga

O complexo Minas-Rio da Anglo American iniciou suas operações em agosto de 2014. A usina de tratamento produziu, em 2016, cerca de 15,5 milhões de toneladas secas de concentrado. O minério, explorado no município de Conceição do Mato Dentro (MG), passa pelas etapas de cominuição, classificação, concentração e separação sólido-líquido antes de ser bombeado por 529 km até o município de São João da Barra (RJ), onde é filtrado, estocado e embarcado para exportação. A lama e o rejeito da flotação são enviados para um espessador de 90 metros de diâmetro. Testes de sedimentação em bancada mostraram o efeito positivo da sedimentação dessa mistura de lamas e rejeito. A lama, composta predominantemente por partículas finas de hematita e argilo minerais, se adere a ao quartzo do rejeito, que possui maior diâmetro. Apesar dessa mistura aumentar a velocidade de sedimentação, ela propicia a formação de uma espuma com elevada estabilidade, devido a presença de finos da deslamagem e espumante da flotação. Foram feitos testes de bancada objetivando-se avaliar o efeito da retirada do rejeito da alimentação do espessador. A partir dos resultados foram traçados cenários com diferentes participações desse material e suas implicações no processo de sedimentação foram estimados.

Oct 30, 2017

By Adriana Amaro Diacenco

Neste trabalho, os procedimentos para modelagem de estruturas de compósitos do tipo sanduíche que incorporam materiais viscoelásticos são apresentados. A análise numérica foi desenvolvida utilizando a Teoria de Deformação Cisalhante de Primeira Ordem (FSDT), que é implementada em um elemento Serendipity retangular contendo oito nós e cinco graus de liberdade. A incorporação do amortecimento para os modelos de elementos finitos em compósitos de placas laminadas é feita usando a abordagem de módulo complexo e a resolução numérica das equações resultantes do movimento são aspectos particularmente relevantes dos procedimentos de modelagem. Após as discussões de vários aspectos teóricos, as funções de resposta em frequências (FRF's) são calculadas para placas laminadas de compósitos com camada viscoelástica.

Aug 17, 2017

By Maurilio Pereira Gomes

The aim of this work was to heat treat and characterize sintered valve seat inserts (VSI). The powder metallurgy route was the only way found to substitute cobalt and lead, used in the VSI original alloy, due to their high cost and toxicological effect, respectively. The studied VSI was obtained with AISI M2 high-speed steel powder mixed with iron powder and other additives such as manganese sulphide, graphite, zinc stearate, carbides and copper, which was added by metallic infiltration. All the VSI were air quenched and double tempered, for one hour each, at seven different equidistantly temperatures, ranging from 100 °C up to 700 °C. The physical and mechanical properties were evaluated by means of the VSI apparent density, apparent hardness and crush radial strength. The chemical composition was determined through gas analysis, for the light elements such as carbon and sulfur, and energy dispersive X-ray fluorescence spectrometry for other elements. Microstructural characterization was performed with the support of scanning electron microscopy and energy dispersive spectroscopy. Regarding the VSI final application, the best results were achieved with the inserts air quenched and double tempered at 600 °C.

Oct 30, 2017

By Kenneth Williams

Economic drives dictate the exploitation of formerly less attractive ore bodies located close to or even beneath the water table. These ores can cause handling problems and expensive downtime of processing equipment due to their increased adhesive characteristics and are colloquially termed as “wet and sticky” ores. In order to gain a better understanding of the causes of poor handleability, experimental test methods for wall and inter-particle adhesion within bulk solids samples were developed and validated. The results confirmed that adhesion of bulk solid to equipment surfaces is mainly governed by capillary pressure. It can therefore be described using the Young-Laplace equation, which implies that adhesion is primarily dependent on the interfacial water between bulk material and the adhesion partner. Accordingly, the governing material parameters of adhesion are its capillarity and permeability, as these two characterize water transport to or from the interface of the adhesion partners. Furthermore a threshold for the classification of a material as wet and sticky based on the measurements of adhesion has been proposed.

Aug 17, 2017

By Gabriel Oliveira Glória

Como uma boa alternativa a outros materiais, o número de materiais ecológicos está aumentando. As fibras naturais estão substituindo fibras sintéticas, por exemplo, a fibra de vidro. Além dos aspectos ambiental, as fibras naturais são mais baratas do que os sintéticos. A caracterização do FTIR é um indicativo sobre a possibilidade de integração de fibras com as matrizes de polímeros e compósitos ambientais. Portanto, o presente estudo analisou a fibra de PALF por meio de espectroscopia FTIR. O espectro mostrou principais bandas de absorção típicas de interacções moleculares específicas de fibras PALF. A análise FTIR do permitiu a identificação de grupos funcionais moleculares de fibras PALF e as suas características de vibração.

Aug 17, 2017