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By Rafael Abreu Fraga, Carlos Noberto Paula da Silva, Emanuelle Garcia Reis, Daniel Bojikian Matsubara

Since 2016 Gerdau Ouro Branco has been producing steel plates of various qualities and grades. However, it was not until 2018 that the first plates produced by accelerated cooling process were made available for external testing, in this case for large diameter UOE pipes manufacturing. Recent line pipe and OCTG specifications are showing that the oil and gas market still consumes regular API grades, such as X60, X65 and X70, however with increasing wall thicknesses, reaching values up to 1.5 inches. These specifications also demand longitudinal and transverse tensile guarantees and drop weight tear tests in temperatures as low as -40°C. Projects with these types of mechanical properties present process requirements as challenging as those necessary for higher API grades in lower thicknesses. This paper shows the steel design concepts and rolling routes for achieving the necessary properties for X70 steel plates in 28.15 mm. The microstructural features were also investigated and associated with the production process and the tensile and toughness results. Finally, challenges such as tensile anisotropy and DWTT abnormal fracture are presented.

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 Rodrigo Fina Ferreira

This paper presents a mineral liberation study on two iron ore samples from the Quadrilátero Ferrífero, in Brazil: compact itabirite of low-grade metamorphism (CI) and friable itabirite of high-grade metamorphism (FI). The quartz liberation spectrum for both samples have been obtained through QEMSCAN analyses, carried out for several comminution degrees, to compare the liberation characteristics and to evaluate the evolution of the quartz’s liberation degree after fragmentation. The results have shown significant differences in liberation spectrum between the itabirite samples studied. The liberation process of FI was easier than of CI, due its high porosity and larger crystal size compared with CI, which has shown more complex mineral assemblages with low porosity and smaller crystals. The quartz liberation spectrum has shown that grinding at P95 of 0.210 mm for the FI sample, and of 0.045 mm for CI sample, should result in satisfactory liberation for subsequent concentration step.

Aug 1, 2018

By Dalila Chaves Sicupira

A pitting corrosion study of welded joints of lean duplex stainless steel (LDSS) UNS S32304 has been performed. LDSS S32304 thick plates were welded by different processes commonly employed in equipment and piping construction: SMAW (Shielded metal arc welding), GMAW (Gas metal arc welding) and FCAW (Flux cored arc welding). The electrochemical behavior of different weldment zones (fusion zone (FZ), base metal (BM) and heat affected zone (HAZ)) was characterized both independently using an electrochemical microcell and together through whole sample analysis. The electrochemical method applied was performed in acidified glycerin, a process fluid of the biodiesel industry. The results were correlated to the microstructural features of the materials. Based on the results, is possible to conclude that the breakdown potential (Eb) of the fusion zone (FZ) was higher than the Eb obtained for the heat affected zone (HAZ). In general, top samples show higher breakdown potential than root samples and also the samples welded using filler metal 2209 has a better anodic behavior than the filler metal 2307. According to the results, GMAW welding process with 2209 as filler metal was revealed as the optimum chosen for application of 2304 duplex stainless steels in this case.

Jan 16, 2018

By Peter Grawenhof

Universal joint shafts and slipper spindles are commonly used in rolling mills to compensate the design- and process-related offset between the motors and work rolls. Although both types of shafts exhibit on the same kinematic principle, there are basic differences regarding the design concepts. These differences become noticeable on many levels and may become very distinct in terms of Life-Cycle-Costs (LCC). In this respect, a critical comparison between universal joint shafts and slipper spindles can be made.

Aug 16, 2017

By Rodrigo Ribeiro de Andrade, Túlio César Nogueira, Ed Juarez Mendes Taiss, Nilton José Lucinda de Oliveira

The objective of this study was to determine the effects of an eventual slab central macro-segregation in microalloyed steels with low Mn content (0.80%) and high Nb content (0.08 to 0.10%) on the kinetics of recrystallization of austenite during its rolling, on its critical temperatures, that is, of non-recrystallization (Tnr), start Ar3 and finish Ar1 of ferrite transformation and its response to a simulated industrial thermomechanical processing. The determination of the austenite recrystallization kinetics was made through isothermal double compression tests using a dilatometer, while the critical temperatures were determined through hot torsion tests in a Gleeble® 3800. It was found that austenite recrystallization kinetics, Ar3 and Ar1 temperatures did not present significant changes for the samples extracted both at ¼ of the thickness and at the core of the plate, indicating that, as expected, the central segregation in this type of steel was not intense to the point of affecting this phenomenon. The Tnr values determined for the samples extracted in the core of the plate were, on average, 30°C lower than those obtained from specimens extracted at ¼ thickness, which suggests that a significant portion of the carbonitrides present in the core of the slab are eutectic and coarse, not having completely dissolved during the reheating of the specimens. This occurred despite the fact that the austenitization temperature adopted in this treatment theoretically leads to the total dissolution of Nb, as seems to have occurred in the case of specimens extracted at ¼ of thickness, where carbonitrides have a finer size.

Oct 1, 2019

By Lesli Peterson

Spraying Systems Co® has continued to develop and evolve descale nozzles through the years. The most recent addition to the descale nozzle line, the DescaleJet® Pro, provides more impact and a more uniform distribution than previous descale nozzles. The improved performance has been achieved through multiple design changes such as a smoother approach, updated vane design and improved carbide orifice. In addition to providing improved spray performance the nozzle also lasts longer than previous versions. The new technology has been thoroughly tested in the lab using impact measurements and accelerated wear testing. In addition to lab testing the nozzle has provided improved performance and longer wear life for those that have made the change to the new technology. The new nozzle technology and the benefits to the rolling mill will be discussed.

Jul 30, 2018

By Álvaro Lúcio

This paper outlines the DPC process as na economic and environment friendly option for the use of cultivated forest as a source of raw material for metallurgical charcoal.The DPC process was specially developed to bring logistic, environmental, technical, economic and global energy efficiency when compared to termal1 the existing biomass carbonization process. The DPC process utilizes the volatile materials (condensable and non condensable) as a source of the energy required by the carbonization process guarantying its complete combustion. As result the DPC process avoids the burning of termal1 the loaded wood, obtaining a higher charcoal to biomass yield, and avoids the emission to the atmosphere of polluting gases. Gases emitted by the carbonizing wood have na energy termal1e enough to dry the wood soon after its harvesting. By avoiding the storage in the field during na average of 150 days, the resulting economy is quite significant. As a termal1e1 the higher charcoal to biomass yield na termal1e1e economy is obtained through the reduction of the cultivated forest term. This paper emphasizes the economic advantages of the DPC process.

Aug 16, 2017

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 Gigliola Salerno

The carbon-epoxy composite has high specific resistance and strength, which means specific applications. However, its behavior under compressive stress could be decreased by delamination, needing more detailed studies. The main purpose of the present work is to verify the mechanical properties in bending process considering two different fiber orientations. The composite materials were made by woven fibers and epoxy resin. Primarily, the carbon fiber fabrics suffered a superficial physical treatment called silanization, in order to developing a better chemical adhesion between fibers and resin. After the superficial treatment, the layers were embedded with epoxy resin. The composite resin’s cure was made in a Fanem heater, model 320, during 1 hour at 120°C at 1.5 bar; subsequently the specimens were cut by water jet. Specimens oriented in 0°/90° and 0°/90°/45 were manufactured and taken to bending tests, accordingly to the ASTM E855 and D790 standards, in an universal testing machine MTS – Material Test System, full capacity of 250 kN. It was concluded that all specimens failed by tension. Specimens with internal void volumes results in lower flexural modulus and those with presence of fracture mechanisms, like delamination, showed lower strength values. Scanning Electronic Microscopy demonstrated the damages involved during bending process.

Oct 30, 2017

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 Giulio Rodrigues Altoé

Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, we investigate the mechanical behavior of epoxy matrix composites reinforced with continuous fique fiber, through bending tensile tests. Specimens containing 0, 10, 20 and 30% in volume of fique fiber were aligned along the entire length of a mold to create plates of these composites, those plates were cut following the ASTM standard to obtained bending tests specimens. The test was conducted in a Instron Machine and the fractured specimens were analyzed by SEM, the results showed the increase in the materials tensile properties with the increase of fiber amount.

Aug 16, 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 Ulrich Sommers

The Intelligent Furnace (I-Furnace) by SMS group is a smart furnace process and production optimization model. The combination of various tools leads to an optimized heat treatment and production process. It combines a mathematical/physical model to control the furnace with EMG’s IMPOC system for online strength measurement and a newly developed annealing microstructure model to predict material properties. This paper reports about the revamping of an existing galvanizing line, where a mathematical/physical control model has been implemented in combination with an online quality measurement system. This way, the process improvement of continuous galvanizing lines and the quality management of a range of steels including AHSS will be demonstrated. Furthermore, it gives information about the development of the annealing microstructure model to predict material characteristics. Eventually, the I-Furnace will be presented according to the current development and reference status.

Oct 30, 2017

By Juliano Braz Possatti, Arnaldo Carneiro Salles, Cleudson dos Santos Rego, Leandro de Lucas Mendes

The increase in customer demand for steels with higher surface requirements, associated with the need to increase ArcelorMittal Tubarão's HSM productivity, it was necessary the development of controls and actions to reduce scale losses within the scenario of high productivity. This article describes the path followed by the hot strip mill team in order to reduce the occurrence and severity of scales.

Oct 10, 2019

By Sebastien Maillard, Stephane Georges, Thomas Vallee, Stanislas Mauuary

Steel strip manufacturing ever reinvents proposing new grades, requiring to tackle technical limitations of production systems. Primetals Technologies breaks through strip welding by expanding the welder LW21L “Asolid” technology used on low gauges for high-end market such as automotive CAL/CGL. Addressing the usual drawbacks in maintenance, operation and safety of current welding system based on mechanical cutting and CO2 laser welding, the newly developped LW21H “Asolid” technology processes thicker strips up to 7 mm with solid-state laser cutting and welding. This new welder is brought to reality through a scale 1:1 pilot developed, manufactured and tested in Primetals Technologies workshop.

Oct 1, 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 Gabriel Oliveira Glória

In the context of changing culture, the society is increasingly looking for environmentally friendly materials, the natural fibers appear as an option to substitute the synthetic. Among these natural fibers, the PALF fiber may be considered an option, but there is limited information about the flexural strength of epoxy composites incorporated with PALF fibers. Therefore, the objective of this work was to investigate the mechanical properties in bending tests of epoxy composites incorporated with up to 30% in volume of PALF fibers. The results showed that the PALF fiber increase the flexural strength of polymer composites.

Aug 16, 2017

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 Paulo Masiero

Sintered titanium carbide has been extensively used since the early 1980s for demanding wear-resistant applications and, in particular, in environments characterized by high temperature and oxidation. Thanks to its physical characteristics, especially its low density, titanium carbide (TiC) has been successfully applied in the manufacture of cassette guide rollers for hot steel rolling. However, the peculiar characteristics of the sintered Ti carbides make it difficult their redressing and hence this has always represented the limit for a more extensive application. Very often iron based alloys are preferred even if, in general, they are less cost effective just because they are easier to be redressed by turning. The availability of a simple, compact, fully automatic and reasonably priced CNC machine; specialized in the grinding of guide rollers and able to operate accurately and efficiently -both in contour and in plunge- can definitively solve TiC’s redressing problems and render its use even more widespread and attractive.

Oct 30, 2017