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By Daniel Mapa Clemente

Processing of tin slags in reduction furnaces was studied in order to optimize tin recovery and reduce recirculation rates of slags containing thorium and uranium oxides. A theoretical approach considering a mass balance of the process was developed and adjusted by experimental results in order to predict the final slag composition. A metallic phase (FeSnSi) was discovered trapped in the slag due to high apparent viscosity, raising the FeO and SnO2 contents of the slag sample. This FeSnSi alloy is rich in tin and its recovery would help to reduce the slags recirculation. High contents of ZrO2 were found in the slag, restricting it from reaching complete fluid phase. Through an analysis of the slag in the CaO-FeOx-SiO2 and ZrO2-CaO-SiO2 phase systems it can be concluded that final slags should be modeled aiming fluid phase at working conditions and additions should be planned in order to control ZrO2 levels.

Oct 30, 2017

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 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 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 Steven George Jansto

The hot ductility behavior of different microalloyed steel chemical compositions was examined simulating the thermal and strain conditions through the straightening or unbending section of the continuous casting machine. All samples were obtained from industrial slab casters ranging from 200 to 300 mm in slab thickness from steel mills throughout the world including China, Brazil, North America and Europe. The slabs were crack-free and hot rolled into prime quality products. No laboratory heats were tested. Although these microalloyed steels exhibit inherently lower hot ductility behavior, as measured by percent reduction in area at elevated temperature, these steels still exhibit sufficient ductility to satisfactorily meet the unbending stress and strain gradients existing in the straightening section of most casters. The majority of the published hot ductility data, as measured by % reduction in area (%RA), were based on laboratory heats and hence, are inaccurate in accessing the propensity for slab cracking on an industrial caster. This situation then results in invalid conclusions for different chemistries. This research has determined the minimum required %RA for crack-free casting is significantly lower than results based upon previously published laboratory generated data. For example, the literature quotes 40% RA minimum for Nb-bearing steels when in fact as low as 10% minimum RA is more than sufficient to assure crack-free casting based upon the extensive testing and analysis performed in this study. Instead of %RA, the measurement of strain energy has been introduced to evaluate hot ductility behavior. It is concluded that strain energy is a better measure of hot ductility behaviour than %RA. There is considerable value in the evaluation of the hot stress and strain curves, process metallurgy parameters and their relationship to slab quality instead of just basing hot ductility decisions on simple %RA measurements.

Aug 16, 2017

By Luana Lessa Pacheco, Antônio Vitor Magalhães Cota

With the sharp fall in commodity prices, the terms cost reduction and higher productivity have become subjects that are constantly addressed in the daily life of companies, since these factors represent a question of survival of the organizations. To achieve this, the search for continuous improvement of our processes in order to guarantee space in the market is a reality and necessity, so it is important that companies know their processes in detail and have the maturity to make decisions based on data and facts. Thus, this work aims to apply the Six Sigma methodology to investigate which are the variables that most influence the transportation process, carried out by large trucks, increasing their specific consumption of diesel, which is the second largest expense of a company. mining in the city of Mariana MG. The goal of the project was to reduce diesel consumption in the large transport fleet by 7.4%, from 0.32 l / t (average carried out from Feb / 16 to Jan / 17) to 0.30 by February 2018 , with an estimated gain of R $ 4.2 million. The results achieved exceeded the established target, reaching a 10% reduction in specific diesel consumption, totaling a projected real gain of R $ 6.4 Million, in addition to the reduction of 1,710.52 t of CO2 in the atmosphere.

Oct 3, 2019

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 Michel Rodrigo Luiz, Glaudistoni da Silva Félix, Osmar Duarte Junior

This article deals with a project to reduce the preparation time and threading the coils in the input section of a pickling line coupled to the cold strip mill (PLTCM) at ArcelorMittal Vega. The project developed serves for the detection and elimination of bottlenecks in the input section. The project was conceived by the philosophy of the Theory of Constraints (TOC) and Lean Six Sigma (6 sigma), here seen as sequencing serial / parallel in the preparation and threading the coils. In this context, a proposal to modify the automatic sequencing and reduction of interruptions due to failure of the automation / equipment confirmed its effectiveness reducing the total time preparation time and threading the coils in the entry section by 15%. This project was developed without investment costs, bringing gains on the order of US$613,769.00.

Oct 1, 2019

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 Mariana Carla Mendes Rodrigues

The present study deals with the effects of strain rate on the functional behavior of NiTi thin wires. The samples, in the austenitic condition at room temperature, were mechanically cycled 20 times by loading up to 6% strain followed by complete unloading, at 25°C. Four different quasi-static strain rates were assessed: 1x10-4, 1x10-3, 1x10-2 and 5x10-2s-1. The functional properties are described by means of critical stress to induce martensite, stress at maximum strain, energy dissipated per cycle and residual strain. The sensitivity of repeated cyclic deformation to strain rate is also analyzed in terms of phase stability. The results show that the fluctuation in the loading plateau, due to non-homogeneous transformation, increases with increasing strain rate. During cycling, it is observed that higher strain rates result in lower critical stress to induce martensite after the 5th cycle. However, the stress at maximum strain is higher at high strain rates, regardless the number of cycles. The accumulation of residual strain also increases with the strain rate due to the higher applied stress. During unloading, both the elastic deformation of stress-induced martensite and the reverse transformation seem to overlap at high strain rates. The dissipated energy behavior changes between the 1st and 20th cycle. No martensite is stabilized after training, but the intensity of the X-ray diffraction peaks of austenite increases with strain rate, as a result of stress relaxation.

Aug 17, 2017

By Piezanowski Ludivine

With the aim to reduce the hot metal production cost, ArcelorMittal Gent decided to integrate more ores with finer particle size distribution in the raw material mix for the production of blast furnace sinter. As a consequence of such an increase of finer material in the sinter raw mix, the sinter machine productivity and the quality of the sinter are affected. In order to compensate this impact, modern granulation technology can be employed. Within this context, ArcelorMittal Gent has invested in a vertical intensive mixer. The equipment was placed before the existing drums, with a function of “mixer”, whereas the drums are fully optimised for the nodulizing process. The paper presents the results of the industrial operation during the commissioning phase of the new equipment. Gradually increasing the proportion of fine material in the sinter raw mix has made it possible to compare the performances of the old system using drums for mixing and pelletizing with the new system using an intensive mixer combined with a nodulizing.

Aug 1, 2018

By Peter Hodnik, Gabriele Paulon, Herbert Moser, Thierry Gautreau, Loris Busolini

At voestalpine Stahl, Linz a new conventional slab caster has been installed to produce mainly automotive and electrical applications grades, implementing the latest design solutions: tight pitch roll geometry, mould and strand stirring and braking devices, SEN water modelling validation, enhanced roll cooling design to allow dry casting conditions, finely defined slab cooling system layout to control slab surface temperature across the width. To control these design solutions the latest generation of technological packages has been implemented like detailed solidification model based on meshless computational algorithm and a fully dynamic application of soft reduction to achieve sound internal quality results.

Oct 1, 2019

By Enrique Francisco Somolinos Garcia-Morales

In this paper we will discuss the benefits of a very innovative way of introducing MgO in the blast furnace operation through the sinter, using mini lumps of dunite. By changing the traditional way of using an MgO bearing material in fines form (particle smaller than 5 mm), most of the MgO inserted material behaves as inert during the sintering process, with the effect of having the following parameters (among others) improved: productivity at the sintering bed, permeability inside the blast furnace, energy consumption, stability of the operation.

Aug 1, 2018

By Luca Tommasi

Danieli complemented its wide range of production plants for the iron and steel industry with a further step upstream into iron ore pelletizing and beneficiation. Danieli has engineered and constructed a state of the art and fully automated pilot plant facility – pot grate and sinter box – at Altos Hornos de Mexico S.A. (AHMSA) Pelletizing Plant, Monclova, Mexico. Installation and commissioning were completed in October 2009. Key features of the pot grate include the avoidance of the need for operator intervention during the test, automatic system preheat, absence of dead time, heat recuperation system with an air/air heat exchanger, oxygen control in preheating and firing with zirconia oxygen analyzer, possibility to test deep beds up to 625 mm. A series of projects have been accomplished by AHMSA availing of the pot grate facility with the aim to enhance pellet plant productivity and to reduce operating costs. The results obtained by use of Danieli pot grate combined with the experience and skill of plant operators has shown significant technical and economical benefits thus fully justifying the initial investment made by AHMSA and confirming the importance of having an in-house testing facility in order to optimize industrial plant operations.

Aug 16, 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 Edo Engel

Hot Blast Stove Technology has been developed to such an extent that low cost hot metal production for over 30 years without major repairs has become achievable, making the decision for a campaign length between 5 to over 30 years a design choice for the plant owner/operator. Some of the earlier examples of designs capable of such long campaign lengths are currently close to the 50th year of their running campaign. These examples are found especially in Europe and North America. Along the duration of these campaigns, repairs to subsystems such as burners, hot blast outlets etc. may be required. Depending on a plant’s up and down stream production capacities, the repairs may have to take place in the shortest possible time frame to minimize production loss. This article discusses an approach for intermediate repairs, executed while keeping the majority of the system at operating temperature.

Oct 30, 2017

By Bart de Graaff, Victor van Straaten, Edo Engel

The hot blast system is key ancillary plant equipment with respect to safe and stable operations during a long blast furnace campaign. Hot blast stove designs have been optimized to such an extent that in some cases, their lifetimes have surpassed the campaign lengths of the associated blast furnaces by a substantial margin, with the exception of the burner and a few critical areas. This article presents recent developments with respect to designing, building new and operating existing hot blast systems for a long lifetime and at optimized performance. These developments include fundamental improvements such as dome combustion designs as well as increasingly comprehensive packages for inspection, assessment and maintenance techniques. Examples of such techniques are burner replacement with the hot blast system at operating temperature, improved double shell approaches and TOFD measurement applications.

Oct 1, 2019

By Guilherme Corrêa Soares

The effects of temperature and strain rate on the mechanical behavior of a superelastic NiTi wire were investigated by uniaxial tensile testing. A universal testing machine with an attached heating chamber was used for the tensile tests. Temperature influence was studied through straining of samples until rupture at a fixed strain rate and temperatures of 25, 50, 75, 100, 125, 150, 175 and 200 °C. Strain rate effects were investigated by straining samples until rupture at room temperature and strain rates of 10-2, 5 x10-3 , 10-3, 5 x 10-4 and 10-4 s-1. The effects of temperature and strain rate on NiTi mechanical behavior were discussed in terms of critical stress to induce martensite and austenite yield strength, when applicable; upper plateau stress, transformation plateau length and ultimate plateau stress. It was found that increasing test temperature and strain rate shifted the stress-strain curve upwards, albeit temperature displayed a greater influence. Plateau length increased with temperature, but no significant changes were detected as a result of different strain rates.

Aug 17, 2017

By John Anthony Vasquez

During the last years Riva Acciaio Verona has taken the decision to invest in the route of a fully automated meltshop. The aim is to reduce at the minimum the operator's intervention from the bucket preparation till the ladle transfer to the continuous casting bay. The foundation for achieving the goal is the introduction of innovative technological solutions (fully automated cranes for bucket charge in the EAF, robots for sampling, etc. The paper underlines how the different solutions are based on the best practices to improve operator's safety and describes the different steps of the project, the different solutions adopted and the results in terms of production, energy savings, cost reduction and improved safety. Details are presented for: scrap yard management and bucket preparation, EAFs centralized controls and related robots for auxiliary operations (sampling, EBT cleaning, scraper for slag door automation, complete mass & energy balance based on process control), LFs centralized controls and process integration.

Aug 16, 2017