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By Carlos Alberto Mourão, Robson Martins, Letícia Madureira Moreira, Hélio Braz Loss, Joilson Moreira Ferreira da Silva, Edilson Simões Cavalieri, Mauricio Ferreira Coelho

O conversor AOD-L é de uso exclusivo para a produção de aços inoxidáveis na Aperam South America. Entre janeiro a julho de 2018, o consumo de FeSi estava acima do orçado, acarretando em perda de gestão para a Aciaria. O aço inoxidável AISI 304 representa 50% da produção da Aciaria na rota duplex (sem uso do VOD), portanto, esse projeto teve como objetivo a redução do consumo da liga de FeSi no AOD-L para o aço AISI 304. Essa redução foi possível através da utilização da metodologia Lean Six Sigma na qual a causa raiz foi identificada e as ações implementadas o que permitiu uma maior estabilidade operacional, além de aumentar a competitividade da Aperam South America frente aos demais produtores mundiais.

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 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 Qingwen Dai

The Marangoni effect is an important phenomenon where a surface tension gradient drives liquid towards high surface tension regions. Temperature gradient, evaporation, disparity of viscosity, and surface roughness and topography are all significant factors that can affect this thermo-capillary migration. The purpose of this study was to investigate the influence of micro-groove patterns on the migration of paraffin oil, and obtain a well-designed texture of micro-grooves to prevent the thermo-capillary migration. Patterns of micro-grooves with differing orientations and geometric parameters were fabricated on the surface of SUS 316 stainless steel substrates. Experiments on the migration behavior with different viscosities of paraffin oils were carried out various temperature gradients. The experimental phenomena indicated that the surface with the micro-grooves perpendicular or parallel to the temperature gradient have a strong impact on the migration performance of paraffin oil. Micro-grooves perpendicular to the temperature gradient exhibited extraordinary slower migration velocity than that of the parallel one. Width and depth of micro-grooves had an obvious influence on the behavior of temperature-driven migration and detail discussions on the effects of these geometric parameters were carried out.

Jul 31, 2018

By Werner Klein

The Production Management solution (Level 3) covers TYASA’s existing steel making plant, billet caster and new Castrip based coil production line in Ixtaczoquitlan, Mexico. It steers the order based production utilizing product routing information and corresponding process instructions for the individual processing units. A seamless material tracking along the entire production route from heat creation in the electric arc furnace down to the final coil product provides TYASA with the genealogy information customers require for flat products. At each important process step the Level 3 compares actual quality related production results with order requirements. In case of deviations from ordered quality the plant staff is guided by rule based dispositions. The highly configurable solution supports customer to operate its production plant as a smart factory in the sense of industry 4.0.

Oct 30, 2017

By Beatriz Pereda, Ana Clara Fonseca da Silva, Tiago Seixas Bittencourt

Reinforcing steel bars are usually specified based on mechanical properties with flexibility in chemical composition and processing. Most developments, in these steels, are normally focused on alloy and process design to reach minimum cost and conformity to specification. Processing routes using quenching and self-tempering (QST) and accelerated cooling are the most common. Microalloying with V and Nb have been used in rebar. When acicular constituents must be avoided, a combination of Nb microalloying with judicious control of cooling is one of the preferred options. Niobium can contribute to improvement in tensile properties through austenitic grain size control during hot working, precipitation hardening due to carbonitrides or clusters, and hardenability increase. In the present work the alloy design and development processes of a Nb microalloyed steel for rebars are presented. The designed steel has fulfilled the required specification and is under regular production. Austenitic grain size refining – when comparing with the “basic composition” normally used was observed, even without any change in the thermomechanical processing cycle. There are indications that precipitation hardening may also occur. Results indicate that Nb is a good alternative as a microalloying element in rebars.

Oct 1, 2019

By Luciana Lezira Pereira de Almeida

With the increasing use of ornamental rocks, mainly in civil construction, sundry problems were identified in relation to rocks cutting, such as efficiency in the cutting process and rock quality lumber. In recent years several composites have been developed to solve these problems. In this context, the study of the binomial matrix metal-diamond interaction is of paramount importance for the development of new composite materials to improve the efficiency of the cutting tool. The diamond impregnated matrix metal often reveals a reaction between the diamond surface and the matrix. Besides the mechanical connection, chemical reactions can sometimes occur. Therefore, this study aims to assess the achievement of diamond composites in the system Fe / Cu / Ni / Sn via powder metallurgy, with added CRB2. Analyzes have been performed to characterize chemical / physical and mechanical. The results have showed that addition of CRB2 promote significant changes in the properties of composites, especially in wear resistance and fracture toughness. Furthermore, the presence of the composite CRB2 causes a significant improvement in thermal stability.

Aug 16, 2017

By André Oliveira

The present paper describes state-of-the-art Pulverized Coal Injection technology with focus to Dynamic Distribution guaranteeing highest accuracy on equal distribution and being thus one of the key factors enabling constantly highest injection rates. As an alternative to the construction of a new plant, existing plants may be modernized and upgraded to latest technology. Two recent examples are presented. As a conclusion, two case studies of return on investment are showing that the PCI technology, both for new facilities as well as for upgrades, is very profitable and mandatory for high blast furnace operation effectiveness.

Aug 17, 2017

By Larissa Agrizzi Ronqueti

The effect of coiling temperature on selective oxidation behaviour of binary and ternary iron-based model alloys containing different contents of Si or Mn were investigated by SEM and SIMS. The experiments were carried out with a temperature ranging from 450 °C to 700 °C, under N2-5%H2 gas flow with a Dew Point of -3.3°C, for different durations. SEM images of binary iron-based model alloys revealed a decrease of grain boundary oxidation depth with increasing Silicon or Manganese content. At 530°C and 600°C SIMS results showed no Silicon diffusion toward surface, contrary to the results analyzed for Fe-x%Mn. Tests results and Wagner’s theory application (specific cases Fe-0.2%Si and Fe-0.5%Si) showed that grain boundary oxygen diffusion coefficient “DoGB” is almost 60 to 70 times faster than oxygen bulk diffusion coefficient. These results helped to broaden knowledge of single-element effects on grain boundary oxidation, in addition, will contribute of the future works in new steels with complex alloy compositions.

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 Márcio Corrêa de Carvalho

Welded deposited chromium carbide overlay’s has been widely used in various branches of welding overlay’s industry related to wear. Characterization techniques are an important tool in the development of chromium carbide overlays resistant to wear, enabling the identification of phases, constituents and defects. In this work one used optical microscopy, scanning electron microscopy and energy dispersive spectroscopy on chromium carbide overlay’s deposited by submerged arc welding process. The characterization techniques identified precisely the elements of the overlay’s enabling point of the main cause of the observed defects such as cracks, porosity and clusters of particles known in the industry as " rice crispy" .

Aug 16, 2017

By Paulo Henrique Vieira Soares

A filtragem vertical no processo de mineração representa a etapa final de beneficiamento do minério de ferro, pois o material proveniente das etapas anteriores chega em forma de polpa até os filtros verticais a vácuo que por sua vez tem a função de retirar a umidade do material, reduzindo a níveis aceitáveis de forma a propiciar a estocagem do produto no pátio de armazenamento. Este trabalho aborda o uso de análise estatística empregado no processo de filtragem da usina de Conceição I para redução da umidade no pellet feed.

Oct 30, 2017

By Daniel Suarez

Over the last few years the mining industry has continuously been facing increases in capital and operating costs for new projects; plant expansions and also significant increases in the operating costs of existing plants. To counteract such trend the industry is seeking technologies such as the Vertimill as an option to lower the operating costs of grinding circuits. The benefits the Vertimill offers in terms of lower energy consumption and lower media consumption are well established and documented; such benefits can significantly improve the viability of a new project, plant expansions or upgrading grinding mills that need to be replaced. The paper briefly describes the operation of the Vertimill, recent regrind applications in processing Iron ores where the impact of lower energy and grinding media consumption is very significant because of the large tonnages involved, and also applications as a tertiary and secondary grinding stages of grinding circuits. The paper also highlight the expected role the Vertimill can play in secondary applications and the expected impact on the overall economics of the project.

Aug 1, 2018

By Alessandra Spaghetti

Rolling small-diameter hot wire rods at high speeds with conventional laying head pipes can wear the pipe out frequently and affect quality and consistency in the final product. Laying head upgrades using Sandvik SAF2507LHP™ (UNS S32750) tubes make possible to achieve optimal metallurgical properties, smooth coil formation and easier coil handling. Operators can also avoid unwelcome shutdowns due to frequent worn pipe changes and turndowns. Sandvik have been developing different customers and understand their process needs. The suitable selection materials that are able to withstand high levels of wear better than low alloy and carbon steel grades that are commonly used in industry is very important to improve the quality and increase productivity. UNS S32750 tubes were demonstrably superior to low alloy and carbon steels when used in Laying Head Pipe system regarding tubes lifetime, reducing replacement, production interruptions and increasing reliability.

Aug 17, 2017

By Andrea Zanon

Recently steel manufacturers have significantly focused their attention on safety and working conditions thanks to new labour laws, comprehensive operators’ knowledge and increased company social responsibility. Even with a reduced budget, investments on safety are now widely approved. Mill constructors aim at developing upgraded solutions to comply with these new requirements. In some cases mill constructors can even anticipate customers’ requests and consequently put into the market innovative solutions. In this text we will analyze some advanced solutions developed by Danieli & C. Officine Meccaniche Spa - the leading company in long-product rolling mills - aimed at improving working conditions on wire-rod block settings. In particular, we will focus on rolling guides installed on fast-finishing blocks and on servo-assisted device for rolling rings changing. In fact, this equipment has shown effective benefits on our test plants and has mainly cut out the tendency of the personnel to be absent due to backache. This paper will first present standard working conditions, will then introduce the newest equipment developed by Danieli & C. Officine Meccaniche Spa, will analyze its operation and finally will describe in detail the benefits that can be reached with its use.

Jul 30, 2018

By Antonio Augusto Gorni, Kenji Camey, José Herbert Dolabela da Silveira

Recently several studies have been developed on the use of microalloyed steels with low Mn content (below 1%) in the controlled rolling of heavy plates for the manufacture of pipes. However, this novel concept of alloy has peculiarities in its thermomechanical processing. Lower Mn contents should lead to the acceleration of NbCN precipitation kinetics during rolling, leading to a reduction in the soluble Nb content in austenite that delays its recrystallization by drag effect. This fact, plus the heavy and fast passes applied under virtually isothermal conditions in a heavy plate rolling mill with high power, increases the risk of partial recrystallization during the finishing stage of the controlled rolling, since strain hardening of austenite becomes significant and the interaction between precipitation and recrystallization is increasingly delayed. The objective of this study was to analyze the evolution of mean flow stress during the finishing stage of controlled rolling in these low Mn, high Nb microalloyed steels, in order to better understand the metallurgical mechanisms acting during this process and identify conditions that allow full compliance with the requirements of this product class.

Oct 1, 2019

By Frenk van den Berg

In the manufacturing of steel strip for the automotive sector, the mechanical properties are largely defined by the process conditions in the hot strip mill. In particular the phase transformation, from austenite to ferrite, which takes place during the forced cooling stages on the run out table (ROT) after the finishing mill, governs the microstructure and hence the mechanical properties.In current practice, metallurgical models are used to predict the phase state at each position in the strip. These model predictions are supported by pyrometer measurements along the ROT. Although reliable in the majority of the situations, both measurements and models sometimes have difficulties in providing robust output. In this paper, we present a new type of inline measurement, which directly measures the amount of phase transformed. The instrument is based on a technique known as impedance spectroscopy. As result of a collaboration of different institutes and companies, the equipment is robustly running during several years exclusively in the Hot Strip Mill of Tata Steel in IJmuiden.

Aug 16, 2017

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 Márcia Maria da Silva Monteiro Pereira

Tundish is the last reactor where significant metallurgical operations can still be done. Calcium aluminate slags are able to positively contribute to metallurgy considering oxide separation, protection against reoxidation and preclusion of resulphurisation. However, these are poor insulators. When using low melting point slags it is necessary to use another covering material. The deviation from saturation can be used as a measure of absorption capacity. By utilizing computerized construction of ternary and quaternary diagrams it is possible to compare different slags and to find proper slag compositions with reasonable capacity to dissolve inclusions. Objective of the present technical contribution is to evaluate tundish slag capacity to absorb inclusions, considering a particular tundish industrial slag and the changes in its chemical composition during continuous casting of steel. It was observed that slag composition changed during the continuous casting process; this variation is possibly related to interaction between the CaO-Al2O3 liquid slag and the rice hull ash layer which is used above it. Computational thermodynamics was used to determine activity of alumina dissolved in liquid slag; it was observed that the variation in slag composition did not change slag capacity to absorb inclusions, since precipitation of Al2O3 solid phases is not predicted.

Aug 17, 2017

By Walter Valery, Kristy Duffy, Alex Jankovic, Peter Holtham

Hatch’s Mine to Process Optimization projects integrate mining and processing strategies, minimizing operating costs and maximizing overall profit. The methodology involves ore characterization, blast audits, plant surveys, analysis of historical data, and integrated modelling and simulation of mining and processing. Blast designs are tailored according to ore type and the downstream process is optimized for the changed feed. This approach has increased throughput and minimized costs for many operations worldwide. The implementation of this methodology at an iron ore operation that faced challenges with increasing mining strip ratio and ore body mineralogy changes is presented in this paper. The larger stripping ratio increased mining costs and constrained the run-of-mine (ROM) delivery to the process plant. Process performance was affected as the ore mineralogy shifted from predominantly hematite to include greater proportions of magnetite. The project objective was to minimize overall cost per ton mined and processed and maximize profit. Tailoring the blast designs according to ore type and process optimization increased the throughput of all process lines. This provided the potential to shut down one of the five processing line, aligning the mine and plant capacity and significantly reducing the processing costs.

Oct 3, 2019