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By Bruno Santos Malaquias, Carlos Eduardo Pessoa Gomes, Diego Canez Fernandes, Henriquison Magela Bottrel Reis

A formação de depósito de carbono é inerente ao processo de coqueificação, com tendência a se acumular nas regiões da zona livre do forno (teto, boca de carregamento e paredes) e no tubo de ascensão dos gases. Contudo, o depósito quando em excesso, se não for removido a tempo, pode causar queda na produtividade, além de impactos ambientais e redução da vida útil da coqueria. Neste contexto, foram avaliados os mecanismos de formação de depósito de carbono, bem como os fatores relacionados ao processo de coqueificação e da mistura de carvões. Foi realizada uma análise estatística dos dados da coqueria, para identificar as principais variáveis que influenciam a formação do depósito de carbono. Em paralelo, foram avaliadas amostras coletadas nas regiões da boca de carregamento, no tubo de ascensão dos gases e do MIQ de alcatrão. Verificou-se que as amostras são formadas por partículas de carbono pirolítico (craqueamento do gás) e majoritariamente pelas partículas carreadas, correspondendo a 60%, 54% e 72%, respectivamente para as regiões da boca de carregamento, da base do tubo de ascensão e superior do tubo. Foram identificadas e sugeridas ações visando minimizar a formação de depósito de carbono, tais como: redução da temperatura da zona livre; aumento da densidade da carga; controle da fração superfina (< 0,105 mm); redução do teor de matéria volátil da mistura de carvões e uso de técnicas de descarbonização.

Oct 1, 2019

By Haysler Apolinário Amoroso Lima, Francisco Pereira Netto, Vladnilson Peter de Souza Ramos, Bruno Nery Stoco, Gilvan Nascimento de Souza

Em um mercado dominado por tijolos de Al2O3-MgO-C, o revestimento de trabalho de panela de aço monolítico e CarbonFree se apresenta como uma tecnologia disruptiva para um novo patamar de qualidade do aço e eficiência energética. O presente estudo relata a motivação para a implementação do primeiro fundo de panela de aço com revestimento monolítico concretado in situ no Brasil, e apresenta uma análise preliminar dos resultados e vantagens observadas. Uma panela da Ternium Brasil foi revestida com refratários de Al2O3-MgO, e colocada em operação sem nenhuma necessidade de ajuste na operação da aciaria. A partir dos dados de processo e das medições a laser, calculou-se o desgaste do revestimento, bem como verificou-se a garantia de qualidade nos aços IF (interstitial free) e a maior preservação na temperatura do aço durante o refino secundário.

Oct 1, 2019

By Rob van Opbergen, Edo Engel

The highly dynamic economic climate of recent years has tightened the operating envelope for steel producers world-wide. Steel producers continue to experience immense pressure to respond quickly to changing circumstances and the focus has shifted towards efficiency improvement and maximizing flexibility in operations. The ability to safely stop, restart and ramp-up production facilities has become essential. Establishing this level of flexibility, without sacrificing efficiency, requires sound process control, fit-for-purpose process management practices and solid know-how and experience regarding special situations in blast furnace ironmaking operations. The same business environment that demands this increased flexibility has made it increasingly difficult for steel producers to sustain sufficient knowledge about these situations. While many experienced, senior operational staff have retired, a new generation of ironmaking specialists has acquired its hands-on experience over more recent decades, during which these process situations have been much less frequent than before. Over the past 10-15 years, the requirement in the industry for external operational support during e.g. blast furnace blow–downs, salamander tapping and restarts after planned and especially unplanned stops, has become increasingly frequent. This article presents a number of these cases from a process management perspective as well as with regard to project organization and optimized cooperation between internal and external teams of experts.

Oct 1, 2019

By Robert Horwood, Richard Harvey

The copper stave was a development of the Blast Furnace cooling system intended to utilise the high heat transfer properties of copper within a fully covered shell cooling solution. They were originally conceived as being able to provide a permanent cooling lining for use primarily in the higher heat zones of the Blast Furnace. Despite a large number of campaign successes around the world the everlasting concept has not proven universal, with some plants having suffered issues in two particular areas: stave bending (leading to water leaks at back of the stave) and stave wear (erosion on the hot face). Primetals Technologies have in the past been approached to provide assistance to a number of Blast Furnace operators who were experiencing operational issues with the copper stave furnace cooling systems of others. Through knowledge gained resolving these issues, and with the positive experiences of their own copper stave designs, Primetals Technologies have worked towards developing a new concept in copper stave design capable of providing a more robust solution to cope with the greater productivities of modern ironmaking. This paper will provide an outline to the concepts that have driven the design of this new technology.

Oct 1, 2019

By José Aparecido Pereira

The innovative methodology developed by the author allows the elaboration of an Angle Roll Pass Design based on the practical observations of the rolling process and applies mathematical criteria, using the Ekelund´s formula supported by Advanced Excel tools (Reach Goal, PROCV-PROCH, Macros) and AutoCad. The first step is the definition of the number of stands, roll dimensions, gear boxes reduction, initial stock, average reductions, spread factors, finishing speed and type of grooves. For each pass are calculated: bite angle, spread, section reduction, lost and gain of temperature, separating force, speed, torque and motor power. After these calculations and checking of the parameters, the program calculates the dimensions of the passes transforming the flat passes into shaped ones. With these dimensions it is possible to draw the grooves using AutoCad and check section reductions. This methodology was already used for the development of a new project and also to check the parameters of existing ones, with comparison of the results and has shown to be reliable in real and tested projects. It is an innovative process that is not available in known literature.

Oct 1, 2019

By L. Martins Demuner, D. Burzic, V. Cunha Aranda, F. L. Lourenço, G. Romeu Trindade dos Santos, F. Ramstorfer

For many years, Dynamic Soft Reduction has been regarded as a proper method in improving internal quality of slabs. Even though processes models improved significantly over the past years, the efficiency of Soft Reduction was always limited by the discretization error, which inherently exists if segment rollers cannot be positioned individually. The recently developed SRD segment type allows for an individual roller positioning within the mushy zone by avoiding any discretization deviation from the optimal gap. This paper provides a detailed technological overview of the SRD segments as well as operational results at their very first implementation at Ternium Brazil.

Oct 1, 2019

By Božidar Šarler, Umut Hanoglu

A rolling simulation system has been developed to calculate the macroscopic rate of deformation, stress, strain, and temperature fields by using a novel meshless method. The model is based on two-dimensional traveling slice assumption. The slices are aligned towards the rolling direction. The initial size of the billet, bloom or slab and the geometry of the grooves at each rolling stand, the distances between the rolling stands, and continuous or reverse rolling can be arbitrarily considered. The purpose of this paper is to complement these development by predicting and visualizing also the grain size of steel over the strand cross-section for each position in the rolling mill. The grain size models have been in one-way coupled to the macroscopic calculations. First the critical strain for dynamic recrystallization is being checked. If the calculated strain is higher than that, considering also the time for meta-dynamic recrystallization, dynamic or meta-dynamic grain size calculations are carried out. If the strain is too low then only the static recrystallization is considered together with its required time. Finally, austenite grain size and ferrite grain size are calculated respectively as the steel cools down. The listed physical models are based on collection of empirical relations found in literature. The user of the system is free to choose or create the model he wants with his own parameters. The simulation system has been coded as a user friendly computer application for an industrial use based on C# and .NET framework and runs on regular PCs. The computational time for a rolling simulation is usually less than one hour and can thus be straightforwardly used for optimization of the rolling mill design in a reasonable time.

Oct 1, 2019

By José Fagundes Junior, Cleudson dos Santos Rego, Bruno Bastos da Silva Murad, Vitor Borlot Borba

Since the startup in 2002, the Hot Strip Mill at ArcelorMittal Tubarão has increased gradually the coil output as the customers demand new and more resistant dimensionally challenging (thinner and/or wider) steel grades. As a critical feature for customer applications, improvements have been carried out aiming a higher thickness performance and reduction of internal losses while still meeting the more restrict tolerances booked by the customers. This paper presents the recent thickness performance evolution since 2017 and the main actions deployed to improve it.

Oct 1, 2019

By Thierno FALL

This paper describes the study of the work-roll during the hot rolling process thanks to a 3D model built with the Finite Element Method (FEM). In terms of computational cost, that method needs high resources compared to 1D model which are mostly used. However, the 3D model is built to have a better understanding of the work-roll thermal and mechanical behavior during the hot rolling process. The thermal model shows that the highest temperature reached during rolling are within the range of 500°C and 600°C. The thermal field input used to simulate the mechanical behavior of the work-roll shows a biaxial thermal stress state, in the circumferential and axial planes. However, a peak of radial stress is observed in the backup zone. It did not generate plastic strain but could influence the fatigue behavior of the work-roll.

Oct 1, 2019

By Hongshuang Di, Tianyu Zhang, Huiqiang Huang

A CMnSiAl transformation induced plasticity (TRIP) steel was used to study the effect of retained austenite on room-temperature mechanical properties. The steel plates with retained austenite were obtained by hot rolling, cold rolling and subsequent continuous annealing. The starting and finishing temperature of hot rolling are between Ac1 and Ac3. Reduction ratio of cold rolling is 75%. The continuous annealing is carried out at different intercritical temperatures. The relationship between work hardening exponent and retained austenite was discussed. The results show that, the Ac1 and Ac3 were much high because of the alloy elements, and the temperature range between them was wide. Due to the high hot rolling temperature, the grains was hereditarily refined as a result of dynamic recrystallization. Annealing at intercritical temperature of 930 ºC, retained austenite with relatively high stability reached a maximum volume fraction of 25%, a maximum total elongation of 30.2% and a best ultimate tensile strength × total elongation of 20.1 GPa·%. Instantaneous work hardening exponent reflects strengthening mechanisms at different strain stages. The TRIP effect of retained austenite is the main mechanism during deformation. With retained austenite of sufficient amount and high stability, continuous work hardening was observed in the tensile specimen of 930 ºC.

Oct 1, 2019

By Marcus Weldon

We are at the beginning of an era of profound transformation and human progress — a new industrial revolution. This “Automation of Everything” era will be brought about by digital interfaces, data analysis and control of the physical world through networks employing the Nokia Bell Labs Future X1 architecture — networks to support the digitization and connection of everything and everyone with the goal of automating much of life. The interconnection of robots, machines, drones, sensors, processing platforms and people through Future X networks will provide transformative tools for the automation and optimization of factories and warehouses, ports, electric grids, transportation networks, food, healthcare, construction, logistics and supply chain, emergency response, mining, and other physical industries. To date, the level of automation has been modest at best. Automating these physical industries — industries that account for 70 percent of the US Gross Domestic Product, for example — has the potential to drive significant increases in the world’s economic productivity.2 Realizing the potential of this next industrial revolution will require billions of wirelessly connected endpoints for high fidelity physical-to-digital conversion, millisecond response times to tightly control and coordinate machines and robots, and intelligent analysis to optimize real-time decisions — tasks beyond the reach of current networks. Increased levels of automation are already being achieved through the use of 4G advanced wireless access technologies. The untethering of sensors and actuators in industrial environments through the low-latency, high-bandwidth, high-reliability, and massive scale provided by 5G wireless access will complete this evolution, providing an unprecedented ability to digitize, analyze, comprehend and manipulate the physical world at a scale never previously thought possible. These new capabilities will enable us to create digital models of the physical world with ever higher levels of fidelity, further enhancing our ability to improve operational efficiencies and increase productivity and worker safety. Doing this will require a dramatic evolution in network architecture toward massively distributed cloud control and baseband capacity to achieve the required ultra-low latency and ultra-high bandwidth for industrial and infrastructure automation services — the Future X architecture. In early 2019, Nokia Bell Labs will publish a sequel to “The Future X Network: A Bell Labs Perspective”. “Future X for Industries: A Nokia Bell Labs Perspective” will explore how the Future X architecture will automate many of the world’s physical industries, including chapters devoted to electric power, cities, rail, mining, public safety, manufacturing, ports, logistics and supply chain, and an overarching chapter devoted to securing this highly automated world. To give you a small taste of the feast that’s to come, we’re sharing with you an initial installment — “Future X for Industries: Mining” — the Nokia Bell Labs view of how mining will be transformed through a Future X architecture..

Oct 1, 2019

By Wenting Zhu, Liqing Chen, Junjun Cui, Zhenye Chen

In this presentation, a low carbon high strength steel microalloyed with Nb and Ti was processed by thermo-mechanical controlled process (TMCP) containing two stages of controlled rolling. The austenite with various grain sizes was obtained by austenitizing this hot-rolled steel at different temperatures. And the effect of austenite grain size on bainitic transformation was investigated in a dilatometer to reveal microstructural change. The results showed that the microstructure of the hot-rolled steel was mainly composed of granular bainite, lath-like bainite, and martenite/austenite constituents (M-A constituents). With increasing the austenitizing temperature, or increasing the austenite grain size, the microstructure was changed from granular bainite to lath bainite. When the steel was reheated to a lower temperature of 860 ºC, a relatively higher start temperature (Bs) was measured for bainitic transformation. This was mainly caused by the formation of solute-depleted region in the austenite and the promotion of the granular bainitic nucleation. The highest reaction rate occurred at austenitizing temperature of 1000 ºC with fine grain size, while the coarse austenite grain can lead to a sharp increase in the amount of bainite. An analysis was made on the kinetics of bainite transformation which was controlled by the volume diffusion of C atom.

Oct 1, 2019

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 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 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 Nelson SOUTO, Nicolas LEGRAND, Christian COUNHAYE, Don EARLEY

The work is motivated by the automotive customer requirements for a roughness with high peak density (RPc > 75 peaks/cm) on steel sheet surfaces to maintain a good strip surface finish after painting. For that purpose, a new approach is utilized to compute roughness transfer and predict final roughness on uncoated steel sheets (average roughness, skewness, peak density) as a function of temper rolling conditions. The approach is based on the Monte Carlo method combined with the Abott curves and an auto-correlation function to numerically generate roughness profiles for roll and strip respectively. To compute the roughness transfer due to the interaction between roll and strip surfaces during rolling, a composite Abott curve that combines roll and strip Abott curves is used with an asperity crushing model integrated with a rolling model. This enables simulating two roughness transfer mechanisms in the roll bite: the strip asperity crushing mechanism by roll roughness and the strip asperity ploughing mechanism due to roll-strip interfacial sliding speed. The model shows the importance of considering the two mechanisms to predict roughness transfer correctly when strip elongation is high, typically a few percent, and roll bite friction is low. In these conditions, the forward slip at the exit of the roll bite tends to erode strip roughness significantly and decrease considerably the peak density on the strip. For lower elongation levels (~1%) and high roll bite friction, the ploughing mechanism becomes negligible and roughness transfer is controlled by the crushing mechanism only. With these two mechanisms, the model reasonably predicts the evolution of average roughness and peak density over a wide range of temper rolling conditions (new/worn work rolls, hard/soft grades, various elongations), but skewness is more difficult to predict for some trials.

Oct 1, 2019

By Uazir Bezerra de Oliveira, Günther Staudinger, Michael Skorianz, Edo Engel

Oct 1, 2019

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