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By Samuel Filgueiras Rodrigues, Clodualdo Aranas Jr., Gedeon Silva Reis, Eden Santos Silva, Fulvio Siciliano

When austenite is deformed above the Ae3 temperature, partial amount of it transforms dynamically into ferrite by a displacive mechanism. After unloading, it retransforms back into the stable austenite by a diffusional process. This influences the rolling load which decreases under isothermal condition or does not increase with decreasing temperature as rapidly as expected under cooling. Plate rolling simulations under isothermal and continuous cooling conditions were carried out on a 0.09 wt.% Nb X-70 steel. Pass strains of 0.2 were employed together with interpass times of 10 s, and 30 s for the cooling conditions and 0.3 with interval of 10 s at 900 °C for the isothermal experiments; strain rate of 1 s-1 was used during the simulations. The mean-flow-stress (MFS`s) behavior of both conditions indicates that dynamic transformation and dynamic recrystallization were taking place during straining. The critical strains for the initiation of dynamic transformation fell around 0.06 while the critical strain for DRX was 0.12. It has been shown that ferrite is formed due to the applied deformation of roughing passes and increases its volume fraction throughout the finishing rolling stage. Under cooling conditions, the ferrite formation is also favored as the temperature approaches the Ae3 line. Such ferrite forms when the driving force for dynamic transformation is higher than the total free energy barrier preventing its formation. This obstacle consists of the free energy difference between austenite and ferrite as well as the lattice dilatation work and shear accommodation work. The addition of Nb retards the retransformation of the ferrite into austenite. Moreover, holding times after rolling increases the amount of austenite available for microstructure control on subsequent stages. The dynamic transformation (DT) mechanism can be used to design improved rolling schedules

Oct 1, 2019

By Michael Breuer, Christian Mengel, Luis Acainas Caballero, Olaf Jepsen

Stability of the hot strip mill rolling process remains a main topic when it comes to processing thin and hard materials. Strip steering especially at the end of rolling and tail out rips are a main source of unscheduled down times in a hot strip mill. Main focus of this paper is the new X-Roll® Guide system to improve mill stability and quality. An overview of SMS group developments in the recent years regarding equipment and control strategies is given. The new side guiding system in the entry area of the finishing mill is introduced and explained with operational examples. The system provides reproducible conditions for the threading process and during rolling. Steering control has a direct benefit on the availability of the mill. New developments of the roll alignment control strategies based on roll force and mill stand entry guide force measurement will be presented. Additionally a camera based measuring system is introduced that generates a direct process feedback of the strip position. It provides together with the roll alignment control the necessary control parameters for adjusting the roll gap and guiding the strip correct centered through the mill. As a summary the SMS group system is explained combining all features.

Oct 1, 2019

By Glaucon Medeiros Silva

Este trabalho técnico tem por finalidade apresentar a evolução dos ensaios de porosidade em pelotas de minério de ferro. Apresentando as diversas formas de realização deste tipo de ensaio a não correlação entre eles, pois cada método possui uma finalidade distinta e como se ocorreu a evolução do método volumétrico (ótico) desde sua realização manual, na década de 1980, início de medições automatizadas na década de noventa e sua total automatização a partir da década de 2010 até o ano de 2019.

Oct 1, 2019

By Alexandre José Ramos Valentim, Valéria da Silva Guandelini, Fausto Kunioshi

Em um mercado cada vez mais competitivo, garantir serviços com qualidade em ambientes mais produtivos e de custos reduzidos são valores fundamentais para aumentar a eficiência das organizações. Baseada no modelo de gestão de centro de serviços compartilhados, a Diretoria de Suprimentos da Companhia Siderúrgica Nacional criou o BackOffice como uma das formas de dar foco ao core business e tornar estes valores sustentáveis. Este artigo tem como objetivo apresentar a metodologia utilizada para o planejamento, implementação e aprimoramento da área e compartilhar os ganhos de qualidade, performance e custos com a reorganização e padronização de processos que estavam fragmentados e sendo executados em diferentes departamentos.

Oct 1, 2019

By Gerhard Richter, Norbert Asamer, Gerwald Decker

At various stages during their manufacturing processes - from casting to finishing before delivery - semi-finished steel and special alloy products must be cut and surface-treated as well. The requirements for the individual conditioning steps, however, can be quite different. For example, the work piece can be hot, warm or cold. At any rate, the product must always be perfectly prepared for the next manufacturing step - reliably, in the shortest-possible time and at the lowest-possible cost. For cutting and grinding, BRAUN has developed innovative technologies and highly flexible, tailor-made solutions which meet these requirements in the most optimal way. In particular, BRAUN’s cutting and grinding technologies can also be used for large-scale products.

Oct 1, 2019

By Mingyu Ma, Lingling Liu, Liqing Chen, Houlong Liu

In this article, a 444-type heat-resistant ferritic stainless steel containing 0.05wt% Ce and 2wt% (Mo+W) was used as an experimental material and a study was carried out on the effect of rolling processes on the microstructures and texture evolution as well as on the mechanical properties and formability. The rolling processes contain hot rolling at different hot rolling finish temperatures, annealing after hot rolling, cold rolling and subsequent annealing. As for the hot rolling process, two hot rolling finish temperatures, 860 C and 770 C, were adopted, and their influence on the microstructures and mechanical properties was comparatively studied. The results showed that the microstructures after hot rolling and subsequent annealing could be refined by lowering the hot rolling finish temperature. The resultant microstructures after cold rolling and annealing were hereditarily refined. Lowering the hot rolling finish temperature can weaken the -fiber texture in hot rolled or cold rolled ferritic stainless steel strip. However, the -fiber texture was homogeneously strengthened by annealing the cold rolled ferritic stainless steel strip. Enhanced mechanical property and formability in terms of strength and average plastic strain ratio could be obtained by lowering the hot rolling finish temperature of ferritic stainless steel.

Oct 1, 2019

By Jose Maria Rodriguez-Ibabe, Ronaldo Antonio Neves Marques Barbosa, Douglas Glenn Stalheim

Major costs in the production of both flat and long commodity grade structural steel products include alloy, labor and energy. Flat and long commodity grade structural steels such as ASTM A36, ASTM A527Gr50, S235, S275, S355 and other equivalent world societal standards represent over 500 million annual tons worldwide. These simple commodity grades consist of a minimum of three base common alloying elements, carbon, manganese, silicon and then can be supplemented with microalloying elements of either vanadium or niobium. Since 2016 raw material costs for two of the five alloying elements in these commodity grade structural steels, FeMn and FeV, have risen significantly and/or have become volatile making it difficult to maintain stability in profitability for these commodity grades. For steel plants producing hundreds of thousands and in some cases over a million tons annually of these common structural steel grades because of the significant alloy cost increase for Mn and V alloy additions has squeezed profitability of these grades. These grades typically represent the base loading for cost controls in most all steel plants and hence a significant cost increase or volatility in two of the five elements used for these grades having a negative effect on overall production costs. However, with a proper strategy for alloy designs working in conjunction with the mills existing processing capabilities to achieve the desired end metallurgy/mechanical properties, alloy costs and operational efficiencies can be realized.

Oct 1, 2019

By Alexandre Gonçalves Andrade, Crisley Dellaqua Pacheco, Gabriel Miranda Teixeira, Aline Maria Santoro Nasaré, Tatiane Ferreira Alvarenga

Diffuse emissions are that directly related to particulate matter suspended from civil structures, materials disposed in conveyor belts carried out by wind, stack e reclaimers operations and that one where dust collectors are not able to act correctly. Vale implemented in the last years a unique system capable to measure this kind of dust, called RAMPs (Dust Monitoring Automatic Network), which creates an analytical net in Tubarao industrial site, located in Vitória, ES. In order to prevent diffuse emissions in Tubarao’s pellets stockyard, it was proposed and developed a predictive model based on operational and climate variables available on the site, using big data and advanced analytics tools. The models developed shows to be adherent to the real emissions rates measured by the RAMPs and proved to be an efficient tool to predict emissions over the internal target with 4 hours of precedence.

Oct 1, 2019

By Priscilla Messias Pereira, Wellington Bonelar dos Santos, Alex Dalapicola Veronez, Maurício do Santos Rocha Junior, Leandro Resinentti Zanon

The pelletizing process allows inputs to be added to the mixture resulting in better control of the physical, chemical and metallurgical characteristics desired by the pellet. Anthracite is incorporated as input of the pellets as an alternative form of fuel, making the burning more homogeneous, "from the inside out", benefiting the physical resistance of the burned pellets and aiming to reduce the cost of natural gas during the stage of hardening. However, the amount of anthracite should not exceed an optimum value, which may cause an adverse effect on the physical quality of the pellets. Hence, it is very important an accurate control of the coal dosage. Based on that, the present study presents the implementation of a control using advanced control system that applies, using linear regression of historical data, the optimum relationship between anthracite and ore (respecting the physical quality of the pellets during processing in pelletizing furnaces). After the implementation of this control, it was possible to adjust the anthracite dosage automatically, measured in percentage of fixed carbon in the mixture, when the process is able, thus reducing the specific consumption of natural gas.

Oct 1, 2019

By Miguel Araújo Vasconcelos Filho, Ulisses Tetti

In order to determine the influence of the number of increments of the sinter sample on the variability of the chemical composition obtained in Sinter Plant production, a variographic study was carried out. It was performed with two series of samples. The first series was composed of 40 samples with a 6-second interval, with the objective of obtaining the so-called minimum practical error, resulting from the extraction processes of the sample of the conveyor belt and preparation and analysis in the laboratory and the second series composed of 60 samples with a range of 4 minutes, which points to the sample selection error. The results obtained showed that the minimization of the sample selection error occurs for increments spaced in 15 minutes, being in agreement with ISO 3082, but with significantly better results than those currently practiced for intervals between 1hour increments. It was then decided on the suitability of the sampler to allow hourly increments to be collected and on a second opportunity to install a sampling tower with primary and secondary samplers to collect increments every 15 minutes including sample size reduction.

Oct 1, 2019

By Olivier Lacroix, Dubé Mathieu, Guylaine Laforest

The reduction behavior of iron ore pellets in gas-based DR shaft processes has been studied at COREM since the late 80s. At that time, a new DR characterization test called COREM R180 was developped in collaboration with ArcelorMittal Mines Canada (former Quebec Cartier Mining) and ArcelorMittal Long Products Canada (former ISPAT Sidbec Inc.). This paper describes COREM’s approach to improve its understanding of the relations between iron ore pellet microstructure and pellet quality. The differences between the DR90 and the R180 tests are discussed. The evolution of the microstructure during reduction of both tests is also described. The reduction steps during the two tests are put forward as an important factor impacting the microstructural changes as well as the test results.

Oct 1, 2019

By Luiz Afonso Andrade, Pablo Amâncio de Freitas, Ana Patrícia Andrade Jaccard, Eduardo Cezar Ribeiro, Ana Christina Pitard Lima, Rodrigo Ribeiro de Souza

A análise dos carvões em mistura é de suma importância para redução dos custos e controle de qualidade de uma coqueria, esse trabalho trata da influência da cominuição comum de carvões de diferentes ranks, assim como suas implicações no processo de amostragem e consequentes desvios nas análises. O processo de produção da mistura de carvões na Ternium Brasil possuía um desvio não rastreado entre matéria volátil resultante da amostragem automática da mistura de carvões e a matéria volátil esperada pelo resultado da média ponderada dos carvões individuais no recebimento, para tal foram estudadas todas as etapas do processo de produção da mistura de carvões desde a variação dos carvões em pilha, escoamento em silos e na etapa anterior e posterior a britagem. Os dados foram comparados e foi feito um plano de ação para redução do desvio.

Oct 1, 2019

By Bi Zongyue, ZhangYongqing, NiuTao, Guo Aimin

Over the past twenty years, significant advances have been made in the field of microalloying steels and associated applications, among which one of the most successful application cases is development and application of heavy-gauge X80 coil with high temperature processing HTP practice used for China's Second West-East pipeline, the longest X80 pipe in the world. During this process, HTP design concept has been sucessfully applied to develop 18.4mm X80 coil with demanding low-temperature fracture toughness requirements. In the meanwhile, China's metallurgical workers have further optimized HTP design concept with the aid of powerful rolling mill and coiling equipment, and made it possible to develop 21.4mm X80 coil used for Russia-China East line. In the paper, we would simply review the development history of high-strength pipeline steels, and then give more priority to the fundamental points for sucessful development of 18.4mm X80 coil and SSAW pipe, which paved the way for subsequent development of 21.4mm X80 coil and SSAW pipe. Finally, we would present the test results of mass production and burst tests, and dispel the suspicion that SSAW pipes made of X80 coil are more qualified to resist ductile fracture.

Oct 1, 2019

By Dimas Henrique Barros Andrade, Roberto Abreu Alencar

O algaraviz é uma parte importante do sistema de sopro de um Alto-Forno, utilizado para direcionar o sopro e combustíveis injetados para a ventaneira, por conseguinte o interior do forno. O algaraviz consiste em uma caraça metálica revestida de material refratário com resistência ao calor e uma camada de isolante térmico entre o refratário e a carcaça. Falhas em serviço de algaravizes costumam a gerar grandes danos materiais, financeiros e com grande risco à vida dos operadores, por isso o controle e inspeção da integridade estrutural e térmica dos algaravizes é de suma importância. A inspeção nos algaravizes é realizada a fim de se detectar precocemente pontos quentes que são indicativos de falhas estruturais no algaraviz. Portanto este artigo foi feito um modelo numérico de transferência de calor, a fim de se averiguar as condições do algaraviz, de forma a verificar se o algaraviz em condições normais de operação mantem as condições térmicas. O modelo revelou resultados satisfatórios de forma que em comparação com resultados de inspeções em peças em operação se obteve um erro de cerca de 8%.

Oct 1, 2019

By Odair José Kirmse, Bruno das Chagas Bernardo, Simony Barboza, Vinícios Andreatta

Neste trabalho buscou-se avaliar o consumo de sucatas com elevador teor de enxofre, em carro torpedo, sem afetar a qualidade final do produto, objetivando a recirculação de um coproduto gerado internamente e aumento do rendimento de gusa distribuído para Aciaria. A sucata em questão é gerada a partir do beneficiamento da escória resultante do processo de raspagem após dessulfuração do ferro gusa em panela (KR) e do procedimento de limpeza dos carros torpedos. Foi avaliada a operacionalidade da adição, riscos envolvidos no processo e redução da geração com reaproveitamento direto no processo. Os resultados mostraram que existe viabilidade técnica e ganhos financeiros significativos

Oct 1, 2019

By Anand Kumar Agrawal, Kinzel Klaus Peter, Lorenzo Micheletti, Cristiano Castagnola, Horst Kappes, Andre Oliveira, Björn Rösner, Philippe Bermes

Blast furnaces are widely employed today for iron production all around the world, with a total production of around 1.2 billion tons per year. Its operating principle, which relies on usage of coke to reduce the ore, to ensure the permeability in the reaction vessel, to maintain its flexibility of operation and acceptability for varying qualities of iron ores. The blast furnace route is widely considered as the most economic and efficient route of iron production, however it is based on fossil energy carriers. The blast furnace route has undergone significant developments in terms of energy efficiency in the last decades, which led to a substantial reduction in the use of fossil reduction materials. Being an energy intensive process, competitiveness and cost saving in the blast furnace plant was always strongly related to the saving of energy and hence reduction of CO2 emissions. In addition to this, EU emissions trading system (EU ETS) as a cornerstone of the EU's policy in response to climate change has set new “challenges” for iron production in Europe. Paul Wurth has always been deeply involved in the development of energy saving technologies for blast furnaces. In the following a review of energy saving achievements developed in the last decades will be presented and the potential of available CO2 saving technologies will be summarized. Additionally, an outlook about the potential of future technologies, concepts and their impact on the blast furnace and the steel plant’s energy balance will be discussed. Finally, the replacement of carbon by hydrogen as reduction agent in the steel plant will be reviewed, with special focus on a comparison of costs and incentives.

Oct 1, 2019

By Danilo Gonçalves de Oliveira, Rogério Martins Pereira

Chatter is a widely studied vibration phenomenon that affects most cold mills around the world and its impact on these lines are tremendous: from productivity and quality losses to mechanical equipment damage. The investigation of its origins and how to minimize the occurrences and their impact on the equipment require special instrumentation and algorithms in order to have a detection of the vibrations as soon as they start. This paper presents three methods of identification of chatter on a Tandem Cold Mill and the actions to leave the vibration frequency range before its amplitude achieve catastrophic values.

Oct 1, 2019

By Thomas Höfler, Michael Auinger, Bernhard Linder

Gas-fired pusher furnaces are commonly used to heat steel slabs before hot rolling. Temperatures well above 1000 °C combined with an oxidizing atmosphere containing H2O, CO2 and O2 result in rapid oxidation of most steel grades. The resulting oxide scale and the chemistry of the metal-scale-interface are major determining factors for the occurrence of hot rolling defects. To better understand these phenomena, lab-scale trials were performed with two different steel grades in an electric tube furnace in the temperature range 1000-1250 °C, using an atmosphere of about 20 % H2O, 7 % CO2 and 3 % O2. Humidification of the gas was achieved by evaporation, using a custom thermostat with standard laboratory glassware. The resulting samples were prepared metallographically, using cold mounting under vacuum with taper section angles, and analyzed using light microscopy and SEM/EDS. The scale structure of the Si alloyed steel was highly dependent on the oxidation temperature due to the formation of eutectic liquid phases of FeO, Fe2SiO4 and FeAl2O4. Below the eutectic temperature, the scale of the Si steel appeared to be made up of three distinct areas: The external scale consisting solely of Fe oxides, the internal scale containing Fe2SiO4 and FeAl2O4, and an internal oxidation zone with SiO2 and Al2O3 in a mostly plain Fe matrix. Comparisons of the experimental results with simulations of the internal oxidation showed good qualitative agreement.

Oct 1, 2019

By Stefan Stein, Jorge Davo, Adrian Villanueva, Abhay Kulkarni, Shane Hoff

Pellet sizing plays a key role in the productivity of the entire pelletization and subsequent induration processes, whereas uneven pellet sizing can increase the circulating load of the balling circuit inducing operational instability leading to production loses. The present work focuses in comparing the agglomeration kinetics, expressed as the number of pellets produced in a determined target size range, of different organic binder-bentonite binder systems. The batch experimental results show that the binder system has a great influence in the resulting pellet sizing, which could lead to advantages in terms of balling circuit efficiency and eventually operational de-bottlenecking.

Oct 1, 2019

By Johan PEERS, François DUMORTIER

Today, solutions to optimize Capital Expenditure (CAPEX) & Operational Expenditure (OPEX) for small capacity Cold Rolling Mills (CRM) as well as for high capacity CRM are available, as extensively described by various Original Equipment Manufacturers (OEMs) & steel makers. A suitable solution for small capacity CRM is to start with a single stand reversing mill (up to 400 ktpy, depending on product mix), which can then be expanded into a twin stand mill (up to 900 ktpy, depending on product mix). The main drawbacks in conventional practice are the off-gauge length in single stand set-up and the long downtime of the mill during the erection of the second stand. For higher productions CRM, it is common practice to directly select a new Pickling Line Tandem Cold Mill (PLTCM), with a high CAPEX. Is there an in-between solution that would allow to start with limited output and CAPEX, without jeopardizing the ultimate expansion goal (1.2 to 2 mtpy), for which PLTCM is the best techno-economical choice? In the absence of a solution, JOHN COCKERILL developed an integrated solution that limits the CAPEX in the first phase of development, without crippling affecting future endeavors through an easy and economically sustainable expansion into a PLTCM, without long production downtime. The solution consists of first installing a twin stand mill, expandable into a tandem mill thanks to a smart design of the line. It is therefore possible to limit the production to 900 ktpy in the first phase of the project and then convert the mill into PLTCM in the second phase to increase the production from 1.2 to 2 mtpy, depending on the market trends and financial capabilities. In summary, JOHN COCKERILL has developed a smart new layout in reversing phase combined with a brand new rolling strategy to optimize productivity and limit off-gauge, compared to conventional solutions (patents pending). In addition the layout enables an easy conversion to tandem mill without high over investments, which is more sustainable financially than the initial purchase of a PLTCM. Long downtimes to allow for capacity extension, detrimental to this phase-by-phase approach, are also avoided. Technical and process description of the new layouts and rolling strategies, together with CAPEX & OPEX descriptions of the phases are detailed in this paper.

Oct 1, 2019