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By J. Bas A. F. Smeulders

Traditional laboratory lubrication tests, including those for cold rolling lubricants often involve measurement of neat oils. To achieve increased levels of test severity, such tests are often carried out at high temperatures and prolonged durations. However, we found that the levels of lubricant degradation and wear in these tests can be much higher than in the field. Moreover, steel rolling is not done with neat oils, but with emulsions, where the presence of water influences film formation, surface chemistry and oil composition in the roll bite. To better approach the situation in the field, and thus to be able to develop rolling oils with improved lubrication performance, several lubrication tests were developed for emulsions: direct measurement of film formation and measurement of Stribeck curves, in which the emulsions can be assessed in terms of their boundary lubrication and elastohydrodynamic behaviour. The key innovation is that also another test method was developed, which focuses on boundary lubrication and wear, and the role of extreme pressure and anti-wear additives. Realistic levels of test severity are achieved in the tribometer by mimicking frictional power intensities and flash temperatures for typical cold rolling or tinplate mills. Test conditions can be adapted according to the mill stand or pass number and other cold rolling process parameters. The emulsions are kept at normal operational temperature. Clear differences could be observed between emulsions of various concentration and composition. The viability of the method is illustrated by a number of field cases, in which a good correlation is demonstrated between the laboratory tests and the performance in a pilot or production mill.

Jul 30, 2018

By Kazuya Nakabo

In this article, influences of restraint and MgO content on densification of alumina-magnesia castable during heating were experimentally studied. High thermal expansion-alumina-magnesia castable specimens were surrounded by low thermal expansion-alumina-silica castables, and heated in an electric furnace. Doing so allows restrained heating of alumina-magnesia castable. According to the results of simple calculations, the restraint stresses were estimated to be between 2 to 20 MPa, so the experimental conditions were considered reasonable. As a result of the experiments, it was verified that restraint densifies alumina-magnesia castable, resulting in an increase in modulus of rupture and modulus of elasticity. The densification effect of restraint became larger as the MgO content increased. The effects are attributable to an in-situ spinel forming reaction, which improves corrosion resistance.Taking the temperature distribution in the castable lining into account, large restraint stress is expected for the hot face while only a little effect is expected for back end. Thus, excessive difference in material property in the thickness direction, which is undesirable in terms of structural spalling, is a concern.Hence, the MgO content of alumina-magnesia castable should be determined carefully, taking not only corrosion resistance but also spalling resistance into consideration.

Oct 30, 2017

By Alberto Pesamosca

The present work analyzes the latest results achieved in scrap based EAFs in terms of application of chemical energy, starting from the observation that the general trend is a reduction of oxygen utilization. Consequently a review is needed about criteria for evaluation of melting process efficiency and equipment design. If from one side the maximization of productivity remains one of the major goals, from the other side some aspects of present market situation, included price of raw materials, are requiring the maximization of process yield. Based on achieved performance figures of selected plants and theoretical considerations, the effect of chemical energy input intensity is analyzed focusing on transformation cost, productivity and total energy input. The effect of present practices with lower oxygen utilization is considered also in terms of global CO2 emissions. Finally, the latest Danieli concepts and technological tools for optimization of chemical input are presented.

Aug 17, 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 Leonardo Camilo dos Reis, Edmilson Fernandes Dadomi, Claudio Silva de Paulo

In the hot strip mill production, one of the factors that may affect the productivity is the occurrence of failure due to the geometry of the strip at the exit of the rolling mill, because the tip of the strip can turn-down or turn-up. This study had the objective of evaluating the behavior of the strip when leaving the working rolls, through numerical simulation, aiming to know the influences of the main variables that govern the formation of the turn-down. The methodology consisted in performing the computational simulation of the strip mill and to vary the operational and geometric parameters that could influence the process. The results showed that the rolling of hot strips of HSLA material with final thickness varying between of 3 to 6 mm and a reduction of 6.6% to 11.0% in the last stand of a hot strip mill, tends to bend towards the roll with larger diameter, higher friction coefficient , higher temperature and lower limit of material flow. It was observed that the variation in diameter is the main factor that contributes to the formation of the curvature of the front-end of strip. Based on these results, several measures were implemented in the industrial line, with a significant reduction in the occurrence of turn-down.

Oct 2, 2019

By J. N. Stevens, M. Tulwin, P. J. Lawlor

All metals producers are on an unending search for a competitive advantage. They need to produce in the most cost effective way. Sometimes a new mill might be considered but in this paper we present examples of how this might not always be necessary. A detailed investigation by an equipment vendor who can consider the mill and or plant as a complete entity: mechanics, automation and process control can often find solutions that are both lower cost and can be implemented in shorter time frames.

Oct 1, 2019

By Pierre Montmitonnet, Yukio Shigaki, Jonatas Mezêncio Silva

A precise roll stack deformation model of a flat rolling mill is crucial for strip profile assessment as it depends strongly on the roll’s deformation. The need for more and more advanced products with stringent both geometrical and mechanical tolerances (e.g., Advanced High Strength Steels – AHSS), with thinner and harder steel strips, demands more advanced simulation models. The present paper addresses assumptions made in Finite Element Method (FEM)-based roll stack models on some important, yet barely discussed features: What is the impact on precision of the simplifications such as symmetry and anti-symmetry? Should roll neck boundary conditions in bearings be considered as fixed or simply supported? In this paper a hybrid model developed by the authors for a general flat rolling mill is used to assess those questions. This model runs much faster (100x in some cases) than a whole-FEM-modeled 6-high rolling mill with the elastoplastic strip deformation, thanks to its simplifications adopted. This model assumes a steady state rolling condition, and the roll stack is modeled with tridimensional finite elements, and the loads are calculated via a slab method adopting a plane strain state for the strip deformation (especially true for thin strips). An industrial 6-high cold rolling mill is modeled and results on the application of symmetries and different boundary conditions on the roll’s necks are presented. It is concluded that the application of symmetries and anti-symmetries for the 6-high rolling mill is possible for thin strips. And the way the necks are modeled does not impact on the final strip shape, though it influences the magnitude of the roll’s displacement. The coupling of the strip with the work roll applied assuming a symmetry plane of the arc of contact has little influence on the strip shape.

Oct 1, 2019

By Carolina Gomes Dias Ribeiro

The modern composite materials, especially those reinforced with synthetic fibers such as glass and carbon, have been used since last century to attend the demands required by most technological fields, from home appliances to aerospace. Natural fibers composites with biodegradable polymer matrices are considered environmentally friendly materials and currently accepted as possible substitutes for synthetic composites. These green composites can be safely discarded or composted at the end of their life without harm to the environment. Another alternative for synthetic composites is to apply natural lignocellulosic fibers as reinforcement of conventional polymer matrices and already used in the automobile industry. In addition to the environmental and societal advantages of the green composites, the lignocellulosic fiber reinforced conventional polymer composite also has economical and technical advantages. In the case of a fiber collected as a waste, the price of the composite can be considerably lower than “fiberglass”. Furthermore, with high strength lignocellulosic fibers such as sisal, ramie and malva the specific strength of a composite may approach that of “fiberglass”. Therefore the objective of the present work is to investigate the mechanical behavior of polymer matrix composites reinforced with high volumes of natural malva fibers subjected to tensile stresses.

Aug 16, 2017

By Franco Gandin

With increasing demands for highly performing and at the same time efficient and running-costs saving vacuum-degassing equipment, dry mechanical pumps have been confirmed a proper choice to completely fulfill the expectations of steel-making companies worldwide. Regarding the production of both special carbon steel and stainless steel grades, the usage of mentioned pumps allowed reaching simultaneous remarkable results from different viewpoints in various Danieli worldwide installations (treating up to 200 t of liquid steel). As a matter of fact, in front of the replacement of a widely spread and renowned technology such as steamejector pumps with the recently developed technology embodied by the dry mechanical pumps, well-established metallurgical performances in terms of carbonhydrogen- nitrogen-sulphur removal have been repeatedly attained while meeting at the same time the client’s expectations concerning, for example, running-costs and push-button availability. Additionally, thanks to the very flexible, modular, redundant and maintenance-friendly equipment design, random problems occurring to the singular mechanical pumps can be easily solved without affecting the VD-VOD plant availability and metallurgical performance. With a particular regard to the VOD process, a very short overall process-time has been repeatedly performed (averagely less than 58min under-vacuum time at ChMP1) while guaranteeing the expected required quality of the final refined stainless steel. Moreover, in several VOD installations (ranging from 6 t up to 110 t of liquid steel) an efficient automatic process control such as dynamic pressure-regulation during oxygen-blowing has been attained thanks to the controllable variable-speed drives with which each mechanical pump is provided.

Aug 17, 2017

By Klaus Pronold

Once installed rolling mills can look forward to a long life. Around 40% of the 140 conventional hot strip mills presently in operation were built between 1960 and 1970. 17 of the 29 CSP®-plants were commissioned before the year 2000 and have automation platforms that are obsolete and/or have outdated rolling technology. Keeping pace with the market requirements is an ongoing challenge for producers of flat steel. It is a real balancing act keeping production facilities performing at necessary levels, safeguarding the investment and keeping outage periods to a minimum. To overcome these demanding factors and strike the right balance allowing for the production of higher grade steel that meets the current market price the installation of mechanical equipment as well as automation platforms and process technology must meet the latest technology standards. Being discussed in this paper are the different motives for modernizations along with their impact on project handling and commissioning philosophies. Experience gained during recent modernization projects in the field of flat steel rolling relating to Steckel / plate mills or current CSP® modernizations will be shared and demonstrate that each modernization has its own individual solution. Specific strategies are explained to help optimize production, increase plant agility and maximize the return on investment.

Aug 17, 2017

By Shibu John

The COREX® process is beside the FINEX® technology the only industrially realized alternative to the blast furnace route for the production of hot metal. Changes in the raw material sector in respect of decrease in quality, strictly enforced environmental laws and positive operation results of COREX® reference plants make it worth to carefully re-evaluate the COREX® technology in comparison with the traditional blast furnace technology. Integrated Plant concepts based on COREX® offer solutions for future challenges of the iron- and steelmaking industry, which include: economical hot metal production; efficient and highly economic export gas utilization (power generation, DRI production, syngas production for chemical products); lower raw material cost, higher raw material availability; environmental friendly high grade steel production. The economic evaluation of different COREX® gas based plant concepts in comparison with the traditional blast furnace route shows that the COREX® technology is highly competitive in the challenging iron and steel producing environment.

Aug 17, 2017

By Gilson Teixeira Cornélio

O presente trabalho tem como objetivo aumentar o desempenho dos cilindros de trabalho utilizados para laminação de tiras a frio. A motivação deste é a busca por competitividade do processo de laminação por meio da redução de seus custos e que neste caso será focado no consumo de cilindros, ferramenta que afeta diretamente no custo final do produto laminado. Para atender a esse objetivo foram conduzidas três atividades no laminador de tiras a frio da CSN, dedicado a produção de material para indústria automobilística, as quais foram: i) investigação detalhada do comportamento do cilindro durante sua aplicação o que consiste em identificar as principais causas de consumo dos cilindros que prejudicam seu desempenho. ii) desenvolver o processo de fabricação dos cilindros Villares Rolls para que possam oferecer as propriedades mecânicas adequadas para as causas de consumo. iii) fabricar cilindros para teste e avaliar seu desempenho no laminador, investigando-os para identificar pontos de melhoria. Os resultados indicam que as mudanças propostas e realizadas nos cilindros atendem às solicitações durante sua utilização no laminador uma vez que seu desempenho tem sido 22% superior quando comparado àquelas praticadas atualmente.

Jul 30, 2018

By Marcelo de Oliveira Lima

O cenário energético brasileiro nas últimas décadas apresenta períodos de escassez na oferta de energia elétrica. Essa realidade impacta o setor industrial por representar um risco operacional e fortalece a necessidade de aumentar a eficiência energética dos processos. Adicionalmente, a eficiência contribui para a melhoria nos resultados financeiros e minimiza impactos ambientais. Nesse contexto, o uso de iluminação LED se destacou nos últimos anos como alternativa às tecnologias tradicionais. No entanto, inicialmente os preços das lâmpadas e luminárias LED eram proibitivos. Esse trabalho apresenta um histórico do custo dessas lâmpadas em diferentes aplicações típicas à uma empresa siderúrgica e demonstra que atualmente o LED pode ser considerado atrativo em algumas delas. São apresentados também casos de sucesso implantados na AcelorMittal Tubarão, garantindo inclusive melhoria nos índices de iluminamento. Por fim, é apresentado de forma sintetizada o Programa de Eficiência Energética da ANELL que disponibiliza recursos das concessionárias de energia para implantação de projetos, sendo ilustrados exemplos de projetos reais e suas economias de energia utilizando iluminação à LED.

Oct 30, 2017

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 Wellington Ribeiro Moreirar, Anderson Willian Henrique Santini, Lívia Mara Cândido, Adriano Raimundo Totour

Rejects generated in mining projects usually do not have associated economic value. Most of the ore beneficiation processes occur by wet process with a higher fraction of water and ultrafine granulometry, which makes it difficult to dispose of these wastes. In 2013, studies with new tailings treatment and filtering technologies were initiated with the objective of eliminating the disposal of the residue generated in the industrial process to wet in dams. In this context, we tried to evaluate an alternative for the dewatering of the sludge and the tailings, aiming at their disposal in piles. Essentially, we sought to consolidate the application of the high-pressure filtration technology for the effluent dewatering, in order to allow its transport and its disposal in a sustainable way. The studies performed in a pilot filter showed good performance and allowed the industrial implantation. The studies and geotechnical indications of composite tailings (flotation and sludge) make it possible to dispose of the tailings in piles due to their better values of humidity, which allows them to be safely stacked.

Oct 3, 2019

By Evandro Moraes da Gama

Os solos de capeamento de minas de minério de ferro, calcário, gnaisse, granito, entre outros, possuem um característica em comum, são solos lateríticos gerados a partir das intempéries e alteração das rochas citadas. Este fato proporciona a formação dos minerais caulinita, goethita, ilita, etc. na composição mineralógica desses estéreis. Em função de suas características químicas e mineralógicas esses estéreis argilosos podem ser utilizados como matéria-prima para produção de ligantes de alta resistência e de múltiplas aplicações. Nesse trabalho é apresentada a tecnologia flash para calcinação de solos de capeamento de minas para produção desses ligantes (PI 0604142-6A). Essa tecnologia permite processamento termoquímico de material pulverulento, ou seja partículas finas, o que não é possível em fornos convencionais de calcinação. No reator flash as partículas de estéreis argilosos são expostas a temperaturas moderadas durante frações de segundo, provocando o fenômeno de desidroxilação dos minerais hidratados contribuindo para a formação de metacaulinita, metagoethita, metailita, etc. Em função das condições cinéticas e termodinâmicas reinantes no processo os constituintes mineralógicos produzidos são amorfos e possuem uma alta superfície de reação, permitindo alcançar valores típicos de área superficial do ligante acima de 90 m2/grama. Os ligantes produzidos a partir desses estéreis apresentam aplicações em diversas áreas tais como indústria cimenteira, construção civil, pavimentação e metalurgia.

Aug 1, 2018

By Leandro Seixas Bicalho, Raphael Alcantara da Costa, Pedro Martins de Almeida Rollo, Eduardo Tres, Anderson D. Thomazini

Usual pelletizing process requires the use of iron ore within a given range of particle size. The pelletizing plants often have comminution circuits composed of ball mills and roller presses to meet the granulometric parameters. Aiming at the partial removal of grinding operations and elimination of wet ore processing, the present study evaluated the pelletizing of two samples of ore with lower surface area: (1) sample with only one passage into the roller press (specific surface area of 997 cm²/g) and (2) “in natura” sample as fed to the pelletizing plant (specific surface area of 450 cm²/g). These experiments were conducted with the use of bentonite and the products E/PE MIN 070/19 and E/PE MIN 090/19, made available by Clariant for this purpose. The results indicated that conventional bentonite is not efficient for coarse particle agglomeration. On the other hand, the products E/PE MIN 070/19 and E/PE MIN 090/19 achieved good performance. Considering a sample with only one passage into the roller press it was possible to form pellets similar to those produced in the conventional process.

Oct 1, 2019

By Kermit Reins

The most recent modernization phase of the wire rod mill at Sterling Steel involved installation of a pre-finishing mill, using a Morgan Vee Mini-Block, a new water box and shear with utility systems and automation. The new mill configuration adds more stands to the mill for better drafting and is designed to improve finished product quality by providing a more uniform entry temperature, better control of the feed section into the No-Twist® mill as well as enhanced surface quality. The new shear improves cut length accuracy as well as decreases the amount of trimming to reduce yield loss. This paper explains the changes made in the mill and the features of the new equipment and automation.

Aug 17, 2017

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 William Lemos Bevilaqua

No presente trabalho foi realizada uma análise para se determinar as possíveis causas da falha catastrófica e anormal de um virabrequim de motor de combustão interna de ciclo Otto de 25 cm³. A região da falha teve a sua composição química, microestrutura e microdureza avaliadas. Os resultados obtidos indicam que a falha ocorreu por fadiga. Múltiplas trincas nuclearam na superfície próxima ao filete do mancal de apoio, devido a uma região de transição de acabamento de superfície. Essa condição reduziu o limite de resistência a fadiga do material.

Aug 16, 2017