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By Márcia Maria da Silva Monteiro Pereira

Durante o lingotamento contínuo de aço, partículas de ZrO2 adicionadas na escória de molde facilitam a nucleação heterogênea de cristais devido à sua limitada solubilidade. A adição de ZrO2 promove a cristalização da fase cuspidina, o que auxilia na redução da transferência horizontal de calor no molde, amenizando desta forma o problema das trincas longitudinais. Outro benefício da adição de ZrO2 em pós fluxantes é reduzir a taxa de desgaste da válvula submersa (SEN) na interface metal/escória; a erosão da SEN é um problema sério. Através de testes de laboratório e de testes industriais concluiu-se que a adição de ZrO2 em pós fluxantes reduz a taxa de transferência de calor horizontal no molde durante o lingotamento contínuo de aço, considerando os dois tipos de pós fluxantes que foram analisados no presente trabalho. Além disso, observou-se que a adição de ZrO2 reduz a taxa de desgaste da válvula submersa na interface metal/escória.

Aug 16, 2017

By Alessandro Marques

Based on a short overview regarding steel defects in the final product, several refractory approaches to maintain or increase steel cleanliness are reviewed in this publication. By applying a ladle to mold approach, one potential to maintain cleanliness is to reduce the probability of air ingress by selection of a suitable slide gate system. Following this path, also the influence of a special configured impact pot is presented to maintain steel quality. Finally, higher productivity as well as cleanliness can be provided by selection of PROIL as a revolutionary product at the casting machine.

Oct 30, 2017

By Martim Hideki Nakayama Kurauchi

One of the main issues regarding the use of charcoal in metallurgical processes is its mechanical strength, which is much lower than coke. There is no defined standard to determine charcoal compression strength, and the methods described in the literature consist in using a prepared specimen and applying compressing load in the same direction of the charcoal fibres. As charcoal is highly anisotropic, it is proposed a procedure that does not use a specimen and with load applied on a specific direction. Instead, it intends to simulate industrial conditions by randomly dumping charcoal inside a tube, without preferential directional arrangement. This is an attempt to determine charcoal mechanical strength and predict the behaviour of bulk charcoal under a static load, as in a blast furnace. Experiments with controlled loads have been carried out on randomly distributed bulk charcoal with controlled initial size and their effect on the size distribution has been analysed. After compression, charcoal is screened and each size is weighed, determining the particle size distribution of the experiment. This method can therefore be used to evaluate charcoal mechanical strength.

Aug 1, 2018

By Milene Muniz Eloy da Costa

Devido à grande aplicação de polímeros no nosso dia a dia sob condições de trabalho reais, ou seja, sob a influência de intempéries, surgiu a necessidade de estudos visando a avaliação de resistências estruturais e mecânicas desses polímeros. O envelhecimento é um processo que envolve mecanismos simultâneos que influenciam diretamente suas propriedades mecânicas, degradando os materiais. Com esse intuito, foi avaliado o envelhecimento por análise de espectroscopia no infravermelho por transformada de Fourier (FTIR) do PEMD de controle (tempo 0) e das amostras ensaiadas sob raios UV por 300, 600 e 900 horas. Os resultados obtidos mostraram o aparecimento e desaparecimento de bandas nos espectros de FTIR, que, relacionados aos resultados de emissão acústica (EA), indicaram a ocorrência de cisão de cadeias, ramificações e reticulações.

Aug 16, 2017

By Amanda de Angelis Vitoi

Neste trabalho foi estudado o efeito da adição de argônio à atmosfera de nitretação sob plasma sobre a resistência à corrosão do aço inoxidável austenítico AISI 316L. As nitretações foram realizadas em reator a plasma pulsado, a 420°C, por 6 h, adicionando-se 0%, 5% e 10% de argônio à mistura gasosa. Os resultados mostraram que a adição de 5% de argônio promove um aumento na espessura da camada de austenita expandida em relação ao material nitretado sem argônio. Com o aumento da concentração de argônio de 5 para 10%, no entanto, verificou-se a formação de camadas de austenita expandida mais finas e de baixa resistência à corrosão devido à presença de nitreto de cromo em sua estrutura.

Aug 8, 2018

By Matteo Tomba

Today’s steel market is characterised by high competitiveness and tight profit margins; therefore, the operational costs of rolling mills must be as low as possible, while ensuring a final product of the highest quality standards. PERT SRL is an engineering company with a long-term experience in the international steel market, specialised in the design and supply of highly innovative and bespoke solutions for siderurgical and environmental plants. Because of its strong commitment to deliver excellent products and services, and its ability to innovate and adapt to the fastchanging market requirements, PERT has studied a new generation of BI-SUPPORT rolling stands, designed to be used in rolling mill plants for the production of rebars, rounds and sections in special quality bars (SBQ) steel grade, wire rod, light and medium section, suitable also for special steel plants. This paper will provide a deep insight into the key technical and economic features that have revolutionised the rolling technology for long products, such as the absence of spindles and piping on board, the considerably reduced number of spare parts required, a ring gap regulation system, and the compact dimensions, which lead to significant savings in investments and production costs; at the same time, the BI-SUPPORT stands guarantee excellent standards to the final product, an increase in plant productivity and a general improvement in the plant management.

Aug 16, 2017

By João Luiz do Vale

In standard wear tests, such as pin on disk (ASTM-G99) or block on ring (ASTM-G77), the apparatus simulates conditions that are often different from a machine element real application. Therefore, for an accurate investigation of a tribological application, it is essential to test the real condition in which there are similarities as: geometry, contact details, force application mode, materials, among others. It emphasizes that for studies involving polymeric materials it becomes extremely relevant. Thus, the Laboratory of Surfaces and Contact (LASC) at UTFPR developed an apparatus for sliding bearing on shaft test. In that equipment, loads are applied by a dead-weight system and the frictional force is measured on a load cell. The apparatus operating ranges for load added to the dead weight system and rotation shaft are from 0.2 to 5.0 kgf and from 260 to 3500 rpm, respectively. This paper presents a detailed evaluation of such apparatus, which includes free-body diagrams analysis and a deduction to obtain an equation for the kinetic friction coefficient. Also, the standard measurement uncertainties of a caliper, an electronic scale, and a cell load were determined. It was verified that the kinetic friction coefficient equation is dependent on the apparatus geometry, the applied load, and the frictional force value. Additionally, through the statistical significance analysis it was concluded that some terms in the equation were not significant. Finally, through the application of the error propagation theory in the kinetic friction coefficient equation, the standard measurement uncertainty of the apparatus which showed a value nearby 0.002 along the operating range of the apparatus was obtained.

Jul 31, 2018

By Marjorie Benegra

This study aims to compare the wear resistance assessed in rubber wheel abrasion test of nickel aluminide coatings deposited by for Plasma Transferred Arc (PTA) and High Velocity Oxigen Fuel (HVOF) manufacturing, using the same raw material. A nickel aluminide powder was atomized and deposited on 316L steel plate substrate. After deposition, some specimens were submitted to a heat treating (1200 °C for 24 h followed by 760°C for 24 h). The coatings deposited using PTA developed different microstructures due to the incorporation of substrate elements, its performance was better than the HVOF coatings, although their Vickers hardness was similar. After heat treating, a significant variation in hardness and wear resistance was observed. For PTA specimens, there were decrease in hardness of 35%, while for HVOF ones this drop was approximately 20%. Nonetheless, the effect of thermal exposure in wear resistance was quite different: an increase of 21% was observed for HVOF coatings, while a reduction of 20% occurred in PTA ones. Microstructures modifications in PTA coatings were significant for their wear resistance. On the other hand, the reduction of porosity and sintering were responsible for a better performance of heat-treated HVOF coatings.

Jul 31, 2018

By Cristiano José Scheuer

The effect of low-temperature plasma carburizing treatment on the micro-abrasive wear resistance of AISI 420 steel was investigated by mean of a CSM Calowear ball-cratering equipment. Carburized samples were treated at temperatures of 350, 400, 450 and 500°C for a fixed time of 12 h, using a gas mixture containing 99.5% (80% H2+20% Ar)+0.5% CH4. Micro-scale abrasive wear tests were conducted with a 25.4 mm AISI 420 steel sphere, using an abrasive suspension of alumina (Al2O3) with particle size of 1 ?m (abrasive concentration of 0.11 g/cm³). The contact normal force, abrasive flow and ball rotation speed were fixed at: 0.5 N, 0,2 drop/s, and 120 rpm. The wear craters were analyzed using a confocal laser microscope, Olympus OLS 3000. The wear analyses were performed for test times of: 30, 60, 90, 120, 180, 360, 540, 720 and 900 s (equivalent sliding distance: 0.84, 1.68, 2.52, 3.36, 5.04, 10.09, 15.14, 20.19 and 25.23 m, respectively). The results indicate that the wear coefficient in the outer layer and in the diffusion layer are different, being lower in the latter. It was also verified that the wear coefficient on the outer layer region decreases with increasing treatment temperature in the range of 350 to 450 °C, and increase again for 500ºC. The diffusion layer wear coefficient is similar for all the carburized samples. Finally, for all studied conditions, the analysis of the wear craters surface indicates the occurrence of grooving and micro-rolling abrasion wear modes.

Aug 8, 2018

By Moisés Paulo Teixeira

The use of tailings for the synthesis of new materials is a worldwide concern today. This paper approaches the utilization of tailings of soapstone (steatite) in order to produce ceramics. The results show that the addition of soapstone in a ratio over 20% in the ceramic mass has enhanced the bending resistance of the ceramic samples when they were fired at temperatures of 900°C or 1000°C.

Oct 30, 2017

By Giuseppe Pintaude

The use of two-dimensional shape parameters to characterize abrasive particles is a possible approach to express their angularity. Nonetheless, in sliding abrasion, especially in pin abrasion testing, coated papers structure plays an important role and even its damage during the wear process should not be neglected. This manuscript discuss the limitations of two-dimensional shape descriptors in distinguishing wear caused by relatively hard particles, indicating that the wear data obtained in sliding abrasion tests are unable to distinguish different types of coated papers used when only the two-dimensional particle projection is considered for shape characterization.

Jul 31, 2018

By Morgana Cristina Arnold

O Pó de aciaria elétrica (PAE) é um resíduo siderúrgico, produzido pela volatilização de metais pesados durante a fusão da sucata no forno elétrico a arco. Os metais volatilizados, entre eles Zn, Pb, Cd, Ni e Cr, são oxidados e subsequentemente solidificados na forma de um pó fino com partículas de dimensão inferior a 10 micrômetros. Este resíduo é classificado como Classe I – perigoso, segundo a norma NBR 10.004/2004, devido às concentrações de chumbo e cádmio acima do limite estabelecido no ensaio de lixiviação. Neste sentido, uma das alternativas para um possível uso deste resíduo seria a tecnologia de Solidificação/Estabilização (S/S) para a imobilização dos metais tóxicos. O PAE atrasa as reações de hidratação do cimento Portland, o que inviabiliza este cimento na tecnologia de S/S. Portanto, este trabalho tem como objetivo avaliar o efeito do PAE nas características mecânicas e ambientais de argamassas à base de cinzas volantes (CV) e cinzas de casca de arroz (CCA) álcali-ativadas. Foram preparadas argamassas com traço de 1:3 (CV+CCA: areia, 4 granulometrias) e adicionados teores de PAE de 0, 10, 15 e 20% em relação à massa de CV+CCA. Ensaios de resistência à compressão foram realizados nas idades de 7 e 28 dias. Para avaliar a periculosidade do material, análises de lixiviação foram realizadas na idade de 7 dias. Os maiores resultados de resistência à compressão, entre as argamassas contendo o resíduo, foram encontrados para o teor de 20% de PAE.

Aug 16, 2017

By Nigel Marx

In order to understand (and ultimately to predict) the friction reduction resulting from the use of polymer solutions, the rheological properties of model polymer solutions have been measured over a wide range of shear rates. Both temporary and permanent shear thinning have been observed. By using base fluids of different viscosities it has been shown that permanent shear thinning depends more closely on the shear stress experienced by the fluid than on the strain rate. Hydrodynamic measurements have been made on the polymer solutions using a compliant ball on flat lubricated contact that operates in isoviscous-elastic conditions. The measured friction values can only be predicted with reasonable accuracy if the measured shear thinning properties of the lubricant are taken into account in the hydrodynamic model.

Jul 31, 2018

By Sandra Goulart-Santos

Os aços galvanizados são amplamente utilizados devido à sua excelente resistência à corrosão. Além disso, esses aços apresentam alta qualidade superficial, o que é um requisito importante para aplicações exigentes como as da indústria automobilística. Dentre os parâmetros de processo importantes para a qualidade dos revestimentos está o teor de alumínio no banho de zinco. Nesse estudo, foi utilizado o simulador do processo de galvanização a quente (HDPS), para investigar a influência do teor de alumínio efetivo do banho na qualidade superficial do revestimento galvannealed (GA), sendo avaliados os teores de 0,09% e 0,14%. Para acompanhar os estágios de formação das fases Fe-Zn foram realizadas interrupções do ciclo de galvanização ao longo das etapas de imersão no banho e de tratamento térmico de galvannealing. Utilizando a técnica GDOES, foi possível acompanhar as variações da concentração de alumínio ao longo do revestimento durante a formação das fases Fe-Zn. Os resultados das simulações mostraram que o alumínio efetivo mais baixo no banho favoreceu a cinética de formação das fases Fe-Zn durante o tratamento térmico e diminuiu a ocorrência de regiões com aspecto brilhante no revestimento, melhorando a qualidade superficial.

Jul 30, 2018

By Pedro Jorge Walburga Keglevich de Buzin

The steel production in mini mills generates several process residues, among them the electric arc furnace dust (EAFD). This residue has as main elements Fe, O, and Zn, being classified as hazardous by the presence of Pb and Cd. In recent years, a rise in the chlorine content of this residue was observed, motivated by the increased use of scrap with impurities bearing this element. In this work, a qualitative assessment of the presence of chlorine in the electric steelmaking process is made. Complementing it, theoretical considerations based on the computational thermodynamics tool FactSage show the effects of the chlorine on the mineral species in EAFD and on gaseous species in the gas phase (HCl and Cl2). For this study, PVC polymer was used as the chlorine carrier substance which contaminates the EAF charge; presence of other minor elements in the system such as K, Na and Pb were also considered.

Aug 7, 2018

By Fábio de Oliveira Braga

A proteção balística contra projéteis de alta energia, como o 7,62 mm, é mais eficientemente realizada por meio de sistemas de blindagem multicamada (SBM). Estes são formados, em geral, por uma camada frontal de cerâmica, uma camada intermediária de tecido sintético ou de compósito, e uma camada posterior de um metal dúctil. Em trabalho recente, Monteiro et al. (2016) estudaram um SBM com camada intermediária formada por compósito reforçado com tecido de rami em substituição a um laminado tecido de aramida. Eles obtiveram resultados satisfatórios com boa redução de custo. No presente trabalho, foram investigadas fibras de rami in-natura como substituição ao tecido de rami na camada intermediária compósita. Os resultados foram comparados ao desempenho de um compósito reforçado com 30% de tecido de aramida, bem como aos resultados anteriores. Observou-se que a utilização dos compósitos reforçados com fibras de rami manteve o bom desempenho do SBM, com um custo cerca de 5 vezes menor que o SBM com aramida, e 60% menor que com tecido de rami.

Oct 30, 2017

By Esteban Ruisanchez Rodriguez

In this paper we will discuss the process of the grain size customization of the EBT filler sand in relationship to the technical characteristics of the furnace and its tap hole. By customizing the grain size distribution, the glassy area formed on the top of the tap hole varies and supports differently the metallurgical pressure of the molten steel providing increased free opening speeds. Taylor made sand improves therefore the free opening rate, reduces the tap to tap time and increases the lifespan of the tap

Aug 16, 2017

By Levi de Oliveira Bueno

Constant stress testing was used for characterization of creep behavior of a 1Cr0.5Mo steel plate in the virgin condition. The tests were performed on creep machines equipped with Andrade-Chalmers type profiles, high sensitivity SLVC transducer extensometry, high stability temperature controllers, and facilities for monitoring the creep curves with an automatic data logging system. Ten creep machines of this type were used in this research, in an experimental work that lasted for one year. Three temperature levels were selected: 538, 565 and 593°C, with stress in the range from 69 to 258 MPa producing rupture times varying from 8 to about 4908 h. The creep curves were all followed with great scrutiny using data logger scanning rates which enabled storing thousands of readings in each case. The experimental analysis involved measurements of minimum creep rate, rupture time and final elongation at rupture. The data were analyzed according to the classical phenomenological / physical relations (Norton, Arrhenius, Zenner-Hollomon, Monkman-Grant) and also considering five traditional parameterization methodologies (Larson-Miller, Orr-Sherby-Dorn, Goldhoff-Sherby, Manson- Haferd and Manson-Succop). Comparisons are presented among the possibilities of data extrapolation from five different methodologies. Comparison is also made with creep results mentioned in literature for the same material in the virgin condition.

Aug 16, 2017

By Delio Amorim

Industry 4.0 concepts is the new biggest challenge on the industry nowadays and every company in every industry in every part of the globe is looking to implement this somehow on their factories and machines. To do that on the newest long rolling mills, that brings already onboard state-of-the-art technologies, is for sure a challenge of machinery builder industry, but how to become the long rolling mills built on 70’s, 80’s or 90’s part of this innovation process and connected to the new trends? This is the main mission here, to show some examples of applications that goes in this direction.

Oct 1, 2019

By Flávio Beneduce Neto

As trincas a quente ou de solidificação em peças micro-fundidas em superligas a base de níquel podem ser um item importante no índice de perdas em componentes específicos. O aparecimento desse defeito está ligado fundamentalmente à quantidade de líquido interdentrítico nos últimos estágios da solidificação e, principalmente, ligado à composição química desse líquido. Há duas ligas amplamente utilizadas na produção de rotores para turbo-compressores ou turbinas para a geração de energia: o Inconel 713C e o Inconel 713LC. A diferença entre estas duas ligas é essencialmente o teor de carbono. Curiosamente, a liga LC tem uma maior tendência ao aparecimento de trincas de solidificação. O presente trabalho procura identificar as diferenças de comportamento na solidificação dessas duas ligas através da termodinâmica computacional e ligar essas diferenças no aparecimento das trincas. Os resultados indicaram que os teores de Zr e Nb do líquido remanescente da solidificação são muito superiores na liga LC causados pelo atraso na precipitação dos carbonetos tipo MC nessa região que deve ser a fase que aumenta a resistência mecânica da área. O correto balanceamento da composição química da liga em relação aos elementos citados permitiu que o índice de perdas por trincas de solidificação caísse para níveis próximos a zero.

Aug 8, 2018