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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 Esteban Ruisanchez Rodriguez

In this paper we will discuss the process of the grain size customization of the EBT filler sand in relationship to the technical characteristics of the furnace and its tap hole. By customizing the grain size distribution, the glassy area formed on the top of the tap hole varies and supports differently the metallurgical pressure of the molten steel providing increased free opening speeds. Taylor made sand improves therefore the free opening rate, reduces the tap to tap time and increases the lifespan of the tap

Aug 16, 2017

By Dagoberto Brandão Santos, Marcus Vinícius Pereira Arruda, Fernando de Souza Costa, Túlio Magno Fuzessy de Melo

The development of advanced high strength steels (AHSS) is motivated by the automotive industry demands for higher strength steels with better formability and stretch-flangeability to avoid fractures during parts forming. In response to this, the new steel grades must have special microstructures in terms of constitution, morphology, distribution and hardness, which are strongly dependent on the chemical composition of the steel sheet and its processing, especially in the continuous annealing stage, in the case of cold rolled sheets. In this study the influence of the annealing heating rate and intercritical temperature (IT) on the microstructural evolution and the final hole expansion ratio of a cold rolled 980 MPa AHSS grade was evaluated. The annealing process was simulated using a Dilatometer and a Gleeble machine, and the microstructures were characterized using scanning electron microscopy, electron backscattered diffraction (EBSD) and nanohardness measurements. The increase of heating rate resulted in an overlap between ferrite recrystallization and austenite formation, changing the austenite morphology from a random to a fibrous distribution, while a higher IT resulted in more homogeneous microstructures and higher hole expansion ratios. This microestructural homogeneity, confirmed by nanohardness measurements, suggested that the difference in hardness between ferrite and the second phase affects the micro-void formation and crack propagation during the hole expansion test.

Oct 1, 2019

By Diego Berti Salvaro

The morphology, dimensions and chemical composition of tribolayers strongly depend on the pressures and temperatures acting on the contact. They are formed by reactions between the surfaces in contact with each other as well as with the atmosphere, lubricants and possible contaminants. In this paper the influence of test time (180, 500, 1000 and 2500 h) into the formation and characteristics of tribolayers in pairs DLC-stainless steel tested under refrigerant gas R134a atmosphere without presence of lubricating oil was analyzed. The characterization was performed using scanning electron microscopy, energy dispersive spectroscopy (SEM-EDS) (morphology and chemical composition) and white light interferometry (dimensions). The tribolayers thicknesses ranged from 100 to 500 nm and they were composed by elements originated from mutual transfers between the tribological pairs as well as oxides, being more pronounced on the stainless steel surface. The results show that the tribolayers are chemically stable (maintained the same composition over time) and the thickness remained stable after a thousand hours of testing.

Jul 31, 2018

By Jefferson Lisboa Lelis, Marcos Roberto Soares da Silva, Maiara Rodrigues Gouveia

Nowadays, due the development of new hot rolled strips at USIMINAS, established the necessity of realizing studies to define new parameters for the welding machine of new pickling line, in order to improve mechanical and metallurgical properties of these materials. The aim of this study was to evaluate the weldability of high strength low-alloy steel with low boron content with tensile strength above 600MPa.The influence of energy input and preheating temperature on the mechanical properties of hot rolled strips were analyzed at three distinct thickness (2, 4 and 6 mm). To perform these evaluations were used tensile test, micro-hardness, metallography (micro and macro examination) and scanning electron microscopy analysis. In resume, a good welding performance was achieved, increasing preheating temperature and the welding energy higher than 60%.

Oct 13, 2019

By Paulo Rodrigues dos Santos Junior, Luciano Passos de Jesus, Vagno Dordenoni Beltrame, Vinicius Antonio Ramos Pin

Faced with an increasingly demanding and selective market, a thorough analysis of each step of the processes is required in order to achieve high levels of performance. In addition to a major factor of importance in the rolling process, due to its high price, the rolls represent one of the main items in the cost of hot coils production. Using the 6 sigma methodology, there were opportunities for improvement in the grinding process, fatigue analysis, improvement in NDT in rolls, as well as means to guarantee operational stability, which allowed the reduction of roll’s consumption and consequently the cost of production.

Oct 11, 2019

By Kelen Juliane Mucelin

In order to better understand the tribological behavior of self-lubricating materials, Fe-Si-C matrix composites containing solid lubricants added during the mixing step were studied. The samples were produced by conventional powder metallurgy route, presenting total contents of 5%, 7.5% and 10% in volume of h-BN and graphite mixtures as solid lubricants. The composites were evaluated in terms of tribological properties, under reciprocating sliding conditions, and mechanical properties by using tensile tests. Additionally, the wear scars were characterized by Raman spectroscopy and scanning electronic microscopy. Higher total contents of solid lubricants greatly increased scuffing resistance however decreased mechanical properties. Furthermore, increasing h-BN contents reduces both properties. These results confirmed the applicability of such sintered composites as self-lubricating parts, reaching values up to 7000 N.m for scuffing resistance combined with ultimate tensile strength of 220 MPa.

Jul 31, 2018

By Jesús A. Carlos Cornelio

Since their discovery in 1991 Carbon nanotubes (CNTs) have attracted much interest due to their remarkable mechanical, thermal, electrical, chemical and optical properties. In connection with their mechanical properties, CNTs have been studied in various forms for tribological applications including their use as lubricant additives for oil and water. In this paper the tribological properties of CNTs (SWCNTs and MWCNTs) when used as lubricant additives are studied under rolling-sliding conditions in a twin-disc testing machine. The tests were performed using 5% of creepage and pressures of 0.8 GPa and 1.1 GPa. Used functionalized nanotubes were modified with carboxylic acid ultrasonically dispersed at different concentrations (0.01, 0.05%). The results indicated that the presence of carbon nanotubes leads to a decrease in both friction coefficient and wear rate for both systems studied (oil and water).

Jul 31, 2018

By Dong Maolin

A great amount of high temperature off-gas, whose maximum temperature is up to 2100?, is generated during the smelting process of electric arc furnace (EAF). The dust content, which is mainly iron oxide, of the off-gas is high and worthy of industrial recovery. The heat carried by the high temperature off-gas with dust is about 11% of the total energy input of EAF, and some even is as high as 20%. The high-temperature off-gas not only takes away a lot of heat but also places a huge burden to de-dusting system of EAF. It not only reduces the iron oxide dust recovery ratio, but also causes serious pollution problems. With the development of the iron and steel industry, the proportion of molten iron for EAF gradually increases, and even more than 30% in some cases. The increase of molten iron causes increases in the amount of EAF off-gas and heat waste. As a result the problem of dust removal is worsening [1-2]. How to sufficiently recover the sensible heat of the high temperature off-gas, create conditions for efficient dust removal, thus reduce operating costs of dust removal system and the production costs is a problem which EAF steel making companies must pay attention to.

Oct 30, 2017

By Alberto Tremea

In this period a great attention is put on roll cost and the differences in roll behavior in very few situations move the existing balances. Among many variables that are taken into account to evaluate the roll there is the consumption which is normally calculated according to the tonnage rolled. In this work there is a review of some approaches that are used to evaluate the roll efficiency together a description of a new method to make this. The main purpose of this calculation method is to help the comparison of roll results used in different mills. There is the need to have a clear and univocal reference when it’s time to think about innovative products. At now there are available roll grades with excellent technological properties but it’s necessary to have the right tools for a careful evaluation of roll behavior to take a good decision.

Jul 30, 2018

By Michaela Böberl

State of the art sinter coolers are working based on the cross flow cooling principle. Thus, only a part of the thermal energy can be used for heat recovery application. The other part of the cooling air is brought unused to the environment. Furthermore, environmental regulation regarding dust emission and intelligent usage of exergy are getting stronger. Therefore, Primetals Technologies developed sinter coolers based on the counter flow principle. The cooling air passes the sinter bed in counter-flow direction enabling a direct heat transfer from the hot sinter to the air. The exhaust gas temperature can be maximized by using the total heat of the hot sinter. Due to the possible usage of the total exhaust gas amount, diffusive dust emission is reduced to zero. Two types of counter flow coolers are in the portfolio of Primetals Technologies. One type is based on a stationary shaft, in which the hot sinter is charged. The flow of the hot sinter is in vertical direction from top to bottom, in counter direction than the cooling air. The second type is a circular hopper cooler. The hot sinter is charged on top of a moving bed. At the bottom of the bed the sinter is discharged. The cooling air flows also from the bottom to the top, following the counter flow principle. Depending on the requirements, one of the two counter flow cooler types can be chosen for optimized and efficient cooling of hot sinter..

Oct 30, 2017

By George Schipper, Peter Gelten, Pepijn Adriaen, Hugo Uijtdebroeks

Tata Steel IJmuiden Hot Strip Mill 2 (HSM2, 5.5 Mtonnes/yr) is currently being upgraded, resulting in an increased rolling force and motor power capacity. With the current conventional work roll spray cooling, a deterioration in work roll & strip surface quality performance is expected as a result of the increased mill capacities. In order to improve strip surface quality, HSM2 decided to do a full-scale production trial with High Turbulence Roll Cooling (HTRC) at stand FM2. HTRC is a novel way of roll cooling using a high turbulent flow regime. HTRC is positioned very close to the roll surface and gap exit, which is beneficial for the roll surface quality. It is operated at a high flow rate but at a low pressure. HTRC not only significantly improves the roll surface quality, in addition, it makes high pressure pumps, needed for the conventional spray cooling, redundant, leading to substantial savings on electricity costs and thus CO2 emissions. HTRC is in trial operation since 7 August 2018. Results show no operational issues, an excellent roll surface quality and an increased cooling efficiency. In summer 2020 stands FM1-FM2-FM3-FM4 of HSM2 will be equipped with HTRC.

Oct 1, 2019

By Andreas Cestonaro

Roll grade evolution in plate mill applications is traditionally following the development in hot strip mills. New grades normally find their way into service only after being successfully implemented in hot strip production. The majority of the plate mills worldwide are using work roll grades that have been invented before the 1980’s. But today the demands in the mills are pushed by sophisticated product mixes and longer rolling campaigns. The result of this development is a higher wear rate on the work rolls and as a consequence roll hardness is increased and advanced roll materials are used. The backup rolls are also affected by this. The wear rate is higher and the mechanical impact in terms of contact pressure and work hardening is increasing. This paper outlines the results of the roll grade development at Gontermann-Peipers and introduces new materials for work and backup rolls for plate mills.

Jul 30, 2018

By Jose M. Rodriguez-Ibabe, Beatriz Pereda, Beatriz Lopez, Felipe Bastos

The modeling of austenite evolution during the hot rolling of steels is covered in the literature for a wide range of chemical compositions, although mainly for carbon contents below 0.20%. In addition, most research on this topic is oriented for processes that are characteristic of flat products. Compared to those processes, the hot rolling of bars for structural applications presents considerable particularities concerning mainly deformation, rolling speed and rolling temperature profile. Those particularities result in considerable changes on process parameters that affect the austenite microstructure evolution, both in the softening and hardening mechanisms if microalloying elements such as Nb is present. The aim of this work was to develop a model to predict the evolution of austenite microstructure that is suitable for the hot rolling of structural reinforcing bars. Different torsion tests simulating industrial schedules particular from those type of processes were performed. The tests showed the need to investigate Nb strain-induced precipitation interaction with softening mechanisms that can occur during the deformation schedule. At the end, the new proposed kinetics and routines were introduced to a program, MicroSim-Bars®, that is able to model austenite evolution under structural bar hot rolling conditions.

Oct 1, 2019

By Jean-Philippe Houde

The Blast Furnace Campaign lifetime is highly depending on the wear progress of the hearth lining. This progress is monitored in general through single and double thermocouples at the cold side of the lining. This type of monitoring becomes ineffective as soon as heat resistance will be formed in the refractory lining. Paul Wurth’s monitoring system, consisting of MTP-Sensor and Heat Flux Probes, is able to identify such heat resistances to give a true hearth lining wear. Since last year Paul Wurth is also able to install safely those MTP-Sensor and Heat Flux Probes on running blast furnace without salamander tapping, thanks to a newly developed cooled core drilling device. Blast Furnaces that are equipped with Paul Wurth’s monitoring system have optimized their campaign lifetime as they received right information upon the true wear lining such as detection of heat flux transfer failure, detection and monitoring of brittle layer or detection of hot spot.

Aug 16, 2017

By Christian Geerkens

Increasing requirements on slab quality initiates SMS group in developing products with a high sophisticated level regarding production and process. These characteristics are represented by SMS group’s HD family. HD stands for High Definition or the improvement of product quality via higher precision of the casting processes. A deep look inside into casting process is realized by the use of fiber optical equipped HD mold. High definition casting process control is assured using the HD spray and HD size. For objective, environmentally friendly and highly informative analyze of the inner quality of the cast products the new HD scan is present.

Aug 16, 2017

By Filippo Verlezza

The 3-roll technology is a recognized process applied to SBQ production. The main aim of this paper is to show the latest developments on this technology including other equipment´s that also contributes for a better performance on SBQ coils production.

Jul 30, 2018

By Alessandro Pigani

Over the last 25 years the thin slab casting and rolling process has been gaining a major market share in the production of hot rolled strip, progressively eroding the areas previously of exclusive domain of conventional mills. This is mainly thanks to the competitiveness of the process over conventional ones, and to the growing ability of this technology to cover the majority of market niches, well beyond the boundaries of the commodity market. After having significantly contributed to the continuous expansion of this production mode and after an extensive campaign of theoretical research and physical testing in reference plants, Danieli has progressively developed over the years a new generation of thin slab casting and rolling layout, marking a new phase in the evolution of this process. The new step-ahead is epitomized by the name QSP-DUE. This configuration belongs to the Quality Strip Production (QSP) family, which is Danieli’s strip-quality-oriented thin slab based plants. The innovative features of the process are embodied in the acronym DUE, which stands for Danieli Universal Endless (Danieli patented technology – US patent n. 8087449, January 3rd, 2012). What makes this new concept different is the ability of “universal” rolling modes thanks to the fact that, now, within one single plant it is possible to perform coil-to-coil, semi-endless and endless rolling modes, making this plant a major technology innovation compared to the previous generation.

Aug 16, 2017

By Rogério Martins Pereira, Charles Pierri de Souza, Lucas Gabriel Correa

The Tandem Cold Mill is composed by stands with rolls positioned so that the rolling force can be transmitted to the strip being processed. Due to the mechanical stresses inherent in the process, the roll bearings are heated and are equipped with lubrication and cooling systems. Nevertheless, there is the challenge of continuously monitoring the temperature of the bearings, which would allow preventive intervention in case of overheating. This paper presents an in-house solution to temperature measuring system applied to the backup roll bearings of a continuous Tandem Cold Mill. The system uses Zigbee technology and is integrated with the main control system, allowing early diagnosis of bearing heating and proper intervention. Results and features of the system are discussed.

Oct 1, 2019

By Francesco Toschi

The Special Bar Quality family comprises a wide range of steel grades, mainly requested by the automotive, energy and engineering sectors, for applications where significant performances are required (eg. stresses, temperatures, working cycles, etc.). To meet these requirements it is necessary to reach a precise control of both the mechanical characteristics and metallurgy structures along the whole production chain. For semi-product with large dimensions, such as equivalent diameters around 300 mm, this is traditionally obtained through a manufacturing route which comprises the casting in ingots followed by reheating, forging and rolling. After 2010, new processes were investigated and technologies developed to replace the ingot route with a continuous casting followed by controlled high-reduction rolling. In these processes a seamless integration of CCM with rolling is implemented so to obtain the precise control of material flow, applied deformation and working temperatures. By using the proper combination of rolling diameter, speed and applied reduction, a very good control of the metallurgy structure across the whole section can be obtained, so to also remove the internal discontinuities ("voids") generated during the continuous casting. These processes, which can be defined "forging-like", are applicable to several grades also with large semi-product dimensions (300 mm and more). Besides, removing the ingot route means increased yield and productivity, which is very beneficial to the economical management of the plant. An example of this "forging-like" process is represented by the high-reduction blooming stand installed by Acciaierie Venete in the Padova-Camin mill. This article describes its main concepts as well as its technology and process features.

Oct 30, 2017