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By Bruno Souza Fernandes

Eixos são componentes utilizados para transmissão de movimento e energia em máquinas. Os eixos são sujeitos à fadiga, visto que são submetidos à esforços combinados de flexão e torção cíclica. No presente estudo foi feita a análise de falha de eixo de uma bomba de alimentação de ureia fundida de uma fábrica de fertilizantes. Foram realizadas inspeção visual, fractografia, metalografia. A falha foi associada à concentração de tensões no raio da chaveta e ranhuras de usinagem, o que causou a fadiga.

Aug 16, 2017

By Julián Andrés Ortiz González

This work presents a series of experiments of Fatigue Crack Growth (FCG), which are intended to provide evidence about the main parameter controlling this phenomenon, whereas still no agreement about this, since the Paris´ theory is based on the principle that FCG is controlled by the ?K and the Elber´s theory says that the driving force is ?Keff. For the development of the experiments, some DC(T) specimens were machined with two different thicknesses: 2 and 30 mm to perform FCG tests in plane stress and plane strain state, respectively. Besides this, all FCG tests were carried out with a constant ?K e Kmax, measuring the strain with a Strain-Gage bonded on the back face of the specimen and seven Strain-Gages located on the crack growth path. The data needed to measure the crack opening load, and the ?Keff, were collected through a program developed in Labview. Finally, the data post-processing was carried out based on the ASTM standards and several articles of recognized authors in this field, in order to compare the two positions with the experimental data, and this way conclude which is the most consistent theory with the observed behavior.

Aug 16, 2017

By Jorge Madias

La mayor parte de las máquinas de colada continua de palanquillas que utilizan buzas calibradas y lubricación con aceite se operan con alta velocidad de colada en secuencias largas, obteniendo alta productividad. Muchos de ellos todavía practican la inyección de aluminio en el molde, para desoxidar el acero líquido sin riesgo de obturación de las buzas. También es todavía usual la práctica de “pescar” la nata que se forma en el menisco. Las salpicaduras del chorro de cuchara contribuyen a la formación de chanchos en el repartidor, requiriendo el lanceo con oxígeno. Alternativamente, diversas plantas prefieren utilizar tubo de protección entre cuchara y repartidor y protección con gas inerte del chorro del repartidor al molde en todos los grados de acero colados con buza calibrada. Se hace una comparación entre ambas prácticas desde los puntos de vista de inversión, costo operativo, seguridad, productividad y calidad.

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 Lucas Breder Teixeira

O uso de ferramentas de simulação numérica para análise estrutural vem se expandindo nos últimos anos, sobretudo utilizando o método dos elementos finitos. Nesse trabalho são apresentados dois exemplos de otimização de projetos envolvendo componentes de mecanismos de válvula gaveta, realizados pela Magnesita Refratários S.A. Partindo da geometria inicial até o produto final, é analisado como o campo de tensões é adequado a valores admissíveis, conforme modificações de projeto são realizadas. Por fim, é demonstrada a importância desse tipo de estudo para alcançar maior confiabilidade e segurança em projetos mecânicos.

Aug 16, 2017

By Breno T. Maia, Débora C. O. Silveira, Mariana A. Ribeiro, Daniel A. G. de Carvalho, Roberto P. Tavares, Raissa S. Salgado

Mixing time is an important parameter when considering chemical and thermal homogenization in steelmaking reactors. It can also be relevant in the kinetics of chemical reactions. Different methods have been used to estimate mixing times in physical models of steelmaking reactors. In the present work a new method to estimate mixing times in physical models has been proposed. This method can be used when transparent fluids are used to simulate the liquid steel and the slag. Results of mixing times in a physical model of a BOF obtained with different techniques were compared. It was shown that the new method is more reliable and consistent than the common methods based on electrical conductivity measurements and colorimetric analysis.

Oct 1, 2019

By Zhi Zhang

The ever increasing demand of high performance rolls in the late finishing stands (F5 – F7) for hot strip mills (HSM) requires better product solutions from roll suppliers. Roll development activities never stop at Union Electric Åkers (UEÅ) in order to meet the requirement. The HYBRID STEEL, a new concept of roll materials especially for the late finishing stands in the HSM, is successfully developed in UEÅ. This paper reviewed the development of previous ICDP as well as enhanced ICDP (eICDP) roll materials, and, the novel HYBRID STEEL roll grade. Rolls manufactured by this new grade have been used in several European mills. A significant improvement over the enhanced ICDP rolls has been observed.

Oct 30, 2017

By Jorge Madias

Pin holes as a surface defect, and blow holes as an inner defect, occur in billet / bloom / beam blank casting, particularly for Si-Mn killed steel cast with metering nozzle and oil lubrication. If they are present in abundance or have a large size, they may originate defects in the rolled products. Their characteristics, factors behind their formation, as well as usual processing conditions that promote their occurrence are discussed. Finally, the evolution of these defects during reheating and rolling is analyzed, with industrial examples.

Aug 16, 2017

By Ivan César Lopes Diniz

Stretcher Reducing Mill (SRM) is a mill used in production of tubes. It is composed with a set 24 of stands responsible to define the final outside diameter (OD) of tubes. External appearance is critical in this process even though this requirement has no effect on mechanical properties. For this reason, an investigation of external longitudinal marks mechanism is in progress using 6 Sigma methodology. This paper is a part of the investigation with focus on the rolls and its mechanical properties. Destructive tests were performed in the rolls and compared with the project. After a detailed investigation, it was concluded that rolls were out of hardness specification and the project was poor of information. A new supplier was developed (internal market) based on the new project and all requirements were achieved as demonstrated in this paper. A monopolistic market for this product in VSB (Vallourec Soluções Tubulares do Brasil) was eliminated. Concerning the effect on the external longitudinal marks, the new rolls developed within hardness range minimized the mechanism of wear on rolls surface and consequently on tubes surface. A collateral effect has been faced, but still better than external longitudinal marks on tubes surface. The quenched and tempered rolls are more sensitive for process variation, mainly linked with cooling system and temperature of tubes (mechanical resistance for deformation). Nevertheless, a new material has been aimed focusing on reduction of rolls breakage with good tenacity and affordable cost.

Oct 4, 2019

By Luiz Alberto dos Santos

. In this work, samples of the alloy with composition of 50.9 % at. Ni were machined and were subjected to hot tensile test, after the machining all the samples were solubilized so that all were in the same condition during the hot tensile test. The hot tensile tests were performed between the temperatures 350-650°C and the yield stress were between 800 and 597.1 MPa and area reduction between 17 and 75% with respect to the initial area. The test at 350°C shows a fragile fracture characteristic while the hot tensile test above this temperature showed a predominantly ductile fracture. The fragile fracture is evidenced by the river marks that are characteristic of this type of fracture, because in this condition does not promote much plastic deformation. The higher temperatures present ductile fracture, because present the dimples that also characterize this type of fracture. This work shows the temperature relationship in the mechanical properties, more specifically the hot tensile test, in the NiTi alloy.

Oct 30, 2017

By Rene Grabowski

Optimization of workflows and intelligent stock management; Slab stacking improvement by automated transport orders; and System automatically registers any slab movements even in manual operation. Case story: Steel producer ArcelorMittal Eisenhüttenstadt GmbH in Germany uses Primetals Technologie’s new stock yard logistics system in its finishing department. An exact image of its slab storage at any times is given by the warehouse logistics system to the company. It not only enhances the composition of the stacks of slabs, but also automates recording of manual restacking operations. Therefore the solution improves workflows and simplifies stock control. Cycle times have also been reduced due to the fact that the slabs can be charged to reheating furnaces ahead of the rolling mill due to less restacking operations within the slab storage. The expandable, modular system is based on the Siemens Simatic IT and Primetals Technologies’ IT4METALS Logistics product platform. It provides a large number of organizational and commercial features in the form of sophisticated graphics and tabular evaluations. For example, it can show how many crane movements have been made per shift for any category of slab, so that the time and cost for each operation can be calculated accurately.

Aug 16, 2017

By Anna Carolina Cerqueira Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Aug 16, 2017

By Pedro Antunes Amaral

Currently there is a constant and essential concern of preserving nature. Over the years the concern with the environment is increasing, new environmental laws are emerging and being applied more rigorously and consequently emerge economic needs and mineral processing practices and other materials. In this sense briquetting becomes an alternative to fine particles agglomeration by means of pressure and or temperature, with the aid or not of a binder, which allows to get a product not only compressed, which presents shape, size, and adequate mechanical properties. The reduction in volume of the material in some cases (beyond the technological benefits) also allows fine materials can be transported and stored more economically, safely and effectively. The production of coke is greater as the content of better coking coal is, thus he low capacity coking coal is not much used in coke ovens. This research aims to demonstrate that briquetting of mineral coals with low coking coal capacity is possible, additionally allows increased coke production, obtaining then a better yield of coke. Basically they take advantage of low price of no coking coals without changing the quality of the coke produced. Anyway, briquetting became a smart alternative to aggregate values, economy and care for the environment.

Oct 30, 2017

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

By Lara de Assis Moreira, Vinicius Thiago Lecco Rampinelli

The energy efficiency of reheating furnaces is a continuous challenge, as these equipment consume a representative portion of the total fuel of an integrated steel plant. Therefore, any investigation and implementation which brings improvement in this figure become an important issue for the mill competitiveness. In the case of production delays due to external factors (the condition addressed in this work), whether predicted or unforeseen, the slabs remain inside the furnace with high temperatures in order to avoid production delay during the production restart, elevating the specific consumption and scale formation. This work increased the energy efficiency of the two ArcelorMittal Tubarão’s walking beam reheating furnaces, by reducing the consumption of mixed gas during production delays (either scheduled or not) lasting less than 3 hours. The objectives were achieved through improvements, among them, tuning of Level 2 automation system parameters, automatization of procedures and operational training. The work resulted in a 34.4% fuel gas consumption reduction during the delays.

Oct 1, 2019

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 Thorsten Müller

In order to increase the production of Advanced High Strength Steel (AHSS) as well as to fulfill the growing expectations of various industries served, steelmakers must have wide- ranging know-how in terms of plant technology, operation, processes, quality control and, last but not least, know-how for AHSS including certification procedures. MET/Con is highly focused on the production of coated AHSS with tensile strengths higher than 600 MPa. Common heating and cooling technologies are unable to handle high alloyed steel grades – pre-oxidation and rapid cooling technologies have been developed to face these new challenges. MET/CON and Drever International have the knowledge to produce newest steel grades with these technologies.

Jul 30, 2018

By Claude Gaspard, Stefan Wahlund, Daniel Cavalier

A point of great importance in the cold rolling process for automotive sheet is the cleanliness of the strip, particularly critical in case of batch annealing with no degreasing line or inefficient cleaning before continuous lines. In this specific cases, pollution of the strip surface could be prohibitive when rolling in the early stands of tandem mill with conventional forged work rolls as ground. The strip cleanliness strongly deteriorates during rolling particularly with high roughness rolls: iron fines are generated at the strip surface due to friction and stick on the sheet. It is well known that chrome plating on ground forged rolls in the early stands improve the strip cleanliness. This paper summarizes the results of 3D surface roughness topography studies on forged work rolls, with and without chrome plating, combined with sheet cleanliness measurement during rolling. It shows that a well determined topography has to be obtained on the work rolls used in early stands in order to roll in the mixed lubrication regime, as described by the Stribeck curve, minimizing the friction coefficient and therefore optimizing the cleanliness of the rolled sheet. The main roll roughness parameters to take into account for that purpose are the roughness level Sa, and even more, the Kurtosis parameters Sk, Spk, Svk and Ssk. The ideal surface morphology promotes deep valleys to the detriment of peaks, leading to a roll surface capable of retaining/trapping oil in the valleys, while peaks are minimized, thus reducing the friction in the roll bite and the amount of iron fines produced. To achieve this objective, new grinding wheel technologies are currently developed, in dialogue with wheel manufacturers, to create such ideal morphology of roughness well adapted to HSS forged rolls.

Oct 1, 2019

By Masahiro Shimura, Yoshiki Takahama, Toshiyuki Shiraishi, Daisuke Kasai

When advanced high strength steel (AHSS) is rolled at a high reduction ratio, the forward slip ratio in cold rolling tends to be lower than that of the other softer strips such as low-carbon steels, and the work roll sometimes skids the strip. To identify why forward slip ratio of AHSS at a high reduction ratio becomes smaller than that of low-carbon steel, the relationship between the reduction ratio and forward slip ratio was investigated by a rolling experiment. For this trial, a 4Hi laboratory cold mill was used. AHSS and low-carbon steel coils were rolled by two different rolls that were set to 0.3 and 0.6 μmRa to create two types of friction conditions. Furthermore, the rolling conditions were numerically analyzed to determine the influence of friction coefficient and flow stress on the relationship between forward slip ratio and reduction ratio. The experimental investigation and numerical analysis revealed that the forward slip ratio reduced with increasing rolling reduction ratio in a low friction state; contrarily, it increased with increasing rolling reduction ratio in a high friction state. This feature was clearly visible when harder materials were rolled.

Oct 1, 2019

By Daniel Antonio Kapper Fabricio

A avaliação das propriedades de mecânica da fratura dos materiais é uma necessidade crescente, sobretudo no setor de óleo e gás. Esse cenário exige a garantia da qualidade na execução de ensaios de tenacidade à fratura. Esse trabalho tem como objetivo realizar uma comparação intralaboratorial para o ensaio de tenacidade à fratura KIC variando o executante do ensaio, visando atender ao requisito de garantia da qualidade da norma NBR ISO/IEC 17025. Os resultados foram comparados através de análise de variância. As diferenças entre os operadores não foram significativas frente ao erro residual a um nível de confiança de 95%, sendo tal resultado considerado satisfatório.

Aug 16, 2017