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By Cristiano José Scheuer

The effect of low-temperature plasma carburizing treatment on the micro-abrasive wear resistance of AISI 420 steel was investigated by mean of a CSM Calowear ball-cratering equipment. Carburized samples were treated at temperatures of 350, 400, 450 and 500°C for a fixed time of 12 h, using a gas mixture containing 99.5% (80% H2+20% Ar)+0.5% CH4. Micro-scale abrasive wear tests were conducted with a 25.4 mm AISI 420 steel sphere, using an abrasive suspension of alumina (Al2O3) with particle size of 1 ?m (abrasive concentration of 0.11 g/cm³). The contact normal force, abrasive flow and ball rotation speed were fixed at: 0.5 N, 0,2 drop/s, and 120 rpm. The wear craters were analyzed using a confocal laser microscope, Olympus OLS 3000. The wear analyses were performed for test times of: 30, 60, 90, 120, 180, 360, 540, 720 and 900 s (equivalent sliding distance: 0.84, 1.68, 2.52, 3.36, 5.04, 10.09, 15.14, 20.19 and 25.23 m, respectively). The results indicate that the wear coefficient in the outer layer and in the diffusion layer are different, being lower in the latter. It was also verified that the wear coefficient on the outer layer region decreases with increasing treatment temperature in the range of 350 to 450 °C, and increase again for 500ºC. The diffusion layer wear coefficient is similar for all the carburized samples. Finally, for all studied conditions, the analysis of the wear craters surface indicates the occurrence of grooving and micro-rolling abrasion wear modes.

Aug 8, 2018

By Li Shanqing, Xu Jianghua, Li Hongmei, Huang Peijie

Cold rolled high strength steel are playing a very important role in reducing automobile weight for energy saving and environment protection. In recent year, more and more high strength steel were manufacturing in steel company. But there are some problems in the cold rolling process for high strength steel products. Periodic thickness deviation especially in strip head or tail is an important one in these problems. In this paper, the reason of periodic thickness deviation was analysed and a new AGC algorithm called Property FFC for high strength steel in tandem cold rolling was developed. The application of this new algorithm shows that it can reduce the thickness deviation.

Oct 1, 2019

By Masakazu Iida

In this article, technologies of unburned Al2O3-MgO (UAM) refractories are demonstrated in terms of microstructure evolution. During operation, Mg2+ diffuses from MgO to Al2O3 through the liquid phase to form spinel (MgAl2O4) network. Molten slag tends to penetrate along the voids in the spinel network structure and spinel dissolves in the penetrated slag. Therefore, maintaining a high degree of spinel saturation in the penetrated molten slag is important. In order to achieve the condition described above, suppression of overall mass transfer through penetrated slag is effective. This is achievable by evolution of complicated spinel network structure with small pore diameter, which increases the flow resistance of molten slag. Thus, optimization of refractory composition and fabricating conditions, with the aim of creating on improved spinel network, is essential. The effectiveness of spinel network improvement was validated by commercial applications. According to the investigation of UAM brick after use, further densification due to heating under restrained conditions was recognized. Hence, it was concluded that the evolution of the spinel network structure in UAM refractories is essential technology needed to improve durability.

Oct 30, 2017

By Markus Reifferscheid

Industry 4.0, Digitalization, Internet of Things (IoT) and Cloud Computing are predominant topics in the world economy at the moment. At the ABM week 2017 Dr. Markus Reifferscheid, Head of Research & Development of SMS-group, will talk about the proceeding digitalization in the steel industry with selected examples of SMS-group. He will present advanced concepts and solutions which are currently being developed.

Oct 30, 2017

By Nathanael Wagner Sales Morais

Os aços maraging tem grande importância tecnológica devido sua aplicação nas industrias aeroespacial e nuclear. Uma das aplicações para esse material é a fabricação de cilindros de alta resistência pelo processo de estampagem profunda, logo o conhecimento da textura cristalográfica torna-se fundamental. Este trabalho investigou o efeito da laminação à frio seguida por um recozimento sobre a microestrutura, textura e anisotropia plástica no aço maraging 350. A anisotropia foi medida pelo cálculo dos coeficientes de Lankford e dos coeficientes de anisotropia normal (Rm) e planar (?R). Os resultados mostraram o aumento na deformação a frio gera um aumento na intensidade da fibra acompanhada de um aumento no valor de Rm. As análises metalográficas mostram que maiores reduções induzem à um precipitação intermetálica após o recozimento.

Aug 8, 2018

By Mariano de Córdova

In this paper, the coke oven life prolongation technology is reviewed from different points of view: blend design; battery heating; operational control; refractory maintenance. A summary of major inspections in critical areas, for the evaluation of the battery conservation situation is presented. A discussion on tools for the diagnostics of the degree of damage is carried out.

Aug 16, 2017

By Roberto Balarini Junior

Tribological behavior of Si3N4 balls sliding against Al2O3 discs in water was investigated by studying the influence of parameters such as initial surface roughness and circular axial run-out of the discs. The objective was to relate these parameters with the occurrence of the phenomenon known as ultra-low friction coefficient (ULFC), which is characterized by µ < 0.01, including the correlation with running-in duration. As a general trend, greater initial surface roughness and circular axial run-out resulted in greater running-in duration. In addition, it was verified that a mixed lubrication regime (hydrodynamic and boundary) is required to guarantee the occurrence of ULFC by comparing the calculated minimum film thickness with the composite roughness of the worn surfaces. Also, ICQ-OES analysis of the water after the tests indicated that a silicon concentration greater than 1.3 mg/l should be fundamental for the occurrence of µ < 0.01.

Jul 31, 2018

By Kazuya Nakabo

In this article, influences of restraint and MgO content on densification of alumina-magnesia castable during heating were experimentally studied. High thermal expansion-alumina-magnesia castable specimens were surrounded by low thermal expansion-alumina-silica castables, and heated in an electric furnace. Doing so allows restrained heating of alumina-magnesia castable. According to the results of simple calculations, the restraint stresses were estimated to be between 2 to 20 MPa, so the experimental conditions were considered reasonable. As a result of the experiments, it was verified that restraint densifies alumina-magnesia castable, resulting in an increase in modulus of rupture and modulus of elasticity. The densification effect of restraint became larger as the MgO content increased. The effects are attributable to an in-situ spinel forming reaction, which improves corrosion resistance.Taking the temperature distribution in the castable lining into account, large restraint stress is expected for the hot face while only a little effect is expected for back end. Thus, excessive difference in material property in the thickness direction, which is undesirable in terms of structural spalling, is a concern.Hence, the MgO content of alumina-magnesia castable should be determined carefully, taking not only corrosion resistance but also spalling resistance into consideration.

Oct 30, 2017

By Marjorie Benegra

This study aims to compare the wear resistance assessed in rubber wheel abrasion test of nickel aluminide coatings deposited by for Plasma Transferred Arc (PTA) and High Velocity Oxigen Fuel (HVOF) manufacturing, using the same raw material. A nickel aluminide powder was atomized and deposited on 316L steel plate substrate. After deposition, some specimens were submitted to a heat treating (1200 °C for 24 h followed by 760°C for 24 h). The coatings deposited using PTA developed different microstructures due to the incorporation of substrate elements, its performance was better than the HVOF coatings, although their Vickers hardness was similar. After heat treating, a significant variation in hardness and wear resistance was observed. For PTA specimens, there were decrease in hardness of 35%, while for HVOF ones this drop was approximately 20%. Nonetheless, the effect of thermal exposure in wear resistance was quite different: an increase of 21% was observed for HVOF coatings, while a reduction of 20% occurred in PTA ones. Microstructures modifications in PTA coatings were significant for their wear resistance. On the other hand, the reduction of porosity and sintering were responsible for a better performance of heat-treated HVOF coatings.

Jul 31, 2018

By Milan Terčelj, Matej Drobne, Urška Klančnik, Peter Fajfar

The study of oxidation behavior of High Chromium Steel material used for surface layer of work rolls was carried out. Specimens taken directly from the roll were subjected to thermal fatigue in the temperature range between room temperature and 500 °C up to 700 °C by using thermo-mechanical simulator Gleeble 1500D. Our observation was focused on the impact of oxidation as a principal mechanism of degradation of the roll’s surface layer - mainly on the characteristics of oxidation propagation in relation to the test temperature and microstructure constituents characteristics of the material. Oxidation is considerably accelerated by certain characteristics of eutectic and primary carbides, i.e. their size (area), composition, morphology, orientation regarding to the water-cooled surface, etc. In the presented paper selected cases where emphasized oxidation takes place are investigated, analyzed and explained. Obtained results thus represent a contribution to explanation of conditions which lead to acceleration of oxidation behavior that in turn can lead to chipping or even early spalling of material from the roll surface layer.

Oct 1, 2019

By Leonardo Camilo dos Reis, Edmilson Fernandes Dadomi, Claudio Silva de Paulo

In the hot strip mill production, one of the factors that may affect the productivity is the occurrence of failure due to the geometry of the strip at the exit of the rolling mill, because the tip of the strip can turn-down or turn-up. This study had the objective of evaluating the behavior of the strip when leaving the working rolls, through numerical simulation, aiming to know the influences of the main variables that govern the formation of the turn-down. The methodology consisted in performing the computational simulation of the strip mill and to vary the operational and geometric parameters that could influence the process. The results showed that the rolling of hot strips of HSLA material with final thickness varying between of 3 to 6 mm and a reduction of 6.6% to 11.0% in the last stand of a hot strip mill, tends to bend towards the roll with larger diameter, higher friction coefficient , higher temperature and lower limit of material flow. It was observed that the variation in diameter is the main factor that contributes to the formation of the curvature of the front-end of strip. Based on these results, several measures were implemented in the industrial line, with a significant reduction in the occurrence of turn-down.

Oct 2, 2019

By Mario González Ramírez

The safe transport of sour gas requires steels with enhanced hydrogen induced cracking (HIC) resistance. Centerline segregation bands of high hardness microconstituents and non-metallic inclusions are the heterogeneities usually linked to HIC failures in pipeline steels. Full-scale production heats of a new low Mn, Nb microalloyed steel were produced by different steel mills aiming at the application in sour gas environments. The new alloy design provides both effective strengthening and control of sulphide inclusions. Coil microstructure consisted of fine grained ferrite with a small volume fraction of uniformly dispersed eutectoid aggregates. Most importantly the microstructure was uniform in both the longitudinal and transverse directions and exhibited exceptional consistency. Samples from this steel were submitted to HIC testing according to NACE standards TM0284-2003 without any sign of cracking. The results, so far, confirm that this new alloy design provides the unique opportunity to economically produce a high strength pipe steel grade with improved sour service resistance for the linepipe industry.

Aug 8, 2018

By Karl Berger

Today we are talking about Industry 4.0, as the latest revolution of industrial processes and progress, considering that the steam engine (Industry 1.0), railways and cars, mass production in the 1920th (2.0), Industrial Automation (3.0), and finally integrated manufacturing, integrated communication, and internet (4.0) can be seen as the state-of-the-art situation in industry, nowadays. Similar to the Industry progress, we can approach the rolling process of material, which started about 150 years ago in a very basic way. Steam engine- and belt driven-mills were very operators’ intensive, brutal and risky to operate. Mechanical improvements brought throughput, safety and quantity, as also quality of the products. The rolling of steel, in particular of rails, beams, rebar, strip (focus in this paper) and plate has enabled the large scale transport and travel, the building of bridges and buildings, the manufacturing of ships and cars. From single stands to continuous rolling trains the production and quality of mills increased significantly. From ingots and blooms to slabs, we have to admit a big jump in which has changed the face of the world significantly. Thin Slab Rolling has revolutionized the output and the throughput of rolling mills (Generation 3.0 to 5.0). Finally, Endless Rolling, has boosted the quality and quantity of rolling mill processes and permitted nowadays to enter in market niches which were not thinkable a decade ago. Mastering the automation and applying reliable systems (mechanical and electronically) of drives, actuators and sensors, as also communication and information interchange to all levels of automation are the success factors of such complex mills, we call herein after “Rolling Mills of Generation 6.0”.

Aug 16, 2017

By Foluke Salgado de Assis

Natural fibers are attracting the interest of engineering sectors owing to specific advantages such as lightweight and lower cost as well as for their inherent condition of being renewable, biodegradable, recyclable and environmental correct material with respect to CO2 emission. The banana fiber is nowadays recognized by its mechanical properties. It is known that with the increase of fibers volume fraction the composite significant increases its tensile strength. This was obtained with amounts up to 30% in volume of banana fiber. However no higher volume of fibers was able to be molded in a composite plate until now. Thus the present work aims to study higher volumes of fiber in terms of the influence on the tensile strength of specimens prepared under 5 tons of pressure. The fibers were previously washed and dried in an oven at 60ºC, after that poured together with the epoxy resin and catalyst mixture in the metal molds bone-shaped, and pressured to ensure specimens quality. The tensile strength increased significantly with higher amounts of banana fiber incorporated in the epoxy matrix. This better performance can be directly related to the fracture obstacle imposed by the fibers as well as the type of cracks resulting from the fiber/matrix interaction.

Aug 16, 2017

By J. N. Stevens, M. Tulwin, P. J. Lawlor

All metals producers are on an unending search for a competitive advantage. They need to produce in the most cost effective way. Sometimes a new mill might be considered but in this paper we present examples of how this might not always be necessary. A detailed investigation by an equipment vendor who can consider the mill and or plant as a complete entity: mechanics, automation and process control can often find solutions that are both lower cost and can be implemented in shorter time frames.

Oct 1, 2019

By João Luiz do Vale

In standard wear tests, such as pin on disk (ASTM-G99) or block on ring (ASTM-G77), the apparatus simulates conditions that are often different from a machine element real application. Therefore, for an accurate investigation of a tribological application, it is essential to test the real condition in which there are similarities as: geometry, contact details, force application mode, materials, among others. It emphasizes that for studies involving polymeric materials it becomes extremely relevant. Thus, the Laboratory of Surfaces and Contact (LASC) at UTFPR developed an apparatus for sliding bearing on shaft test. In that equipment, loads are applied by a dead-weight system and the frictional force is measured on a load cell. The apparatus operating ranges for load added to the dead weight system and rotation shaft are from 0.2 to 5.0 kgf and from 260 to 3500 rpm, respectively. This paper presents a detailed evaluation of such apparatus, which includes free-body diagrams analysis and a deduction to obtain an equation for the kinetic friction coefficient. Also, the standard measurement uncertainties of a caliper, an electronic scale, and a cell load were determined. It was verified that the kinetic friction coefficient equation is dependent on the apparatus geometry, the applied load, and the frictional force value. Additionally, through the statistical significance analysis it was concluded that some terms in the equation were not significant. Finally, through the application of the error propagation theory in the kinetic friction coefficient equation, the standard measurement uncertainty of the apparatus which showed a value nearby 0.002 along the operating range of the apparatus was obtained.

Jul 31, 2018

By Delio Amorim

Industry 4.0 concepts is the new biggest challenge on the industry nowadays and every company in every industry in every part of the globe is looking to implement this somehow on their factories and machines. To do that on the newest long rolling mills, that brings already onboard state-of-the-art technologies, is for sure a challenge of machinery builder industry, but how to become the long rolling mills built on 70’s, 80’s or 90’s part of this innovation process and connected to the new trends? This is the main mission here, to show some examples of applications that goes in this direction.

Oct 1, 2019

By Dagoberto Brandão Santos, Kairo de Barros Guimarães, Túlio Magno Füzessy de Melo

The effect of the cooling conditions on the microstructure and hardness of a Dual Phase hot-rolled steel 800 MPa strength was investigated. Simulations of the cooling conditions using a dilatometer were carried out from samples of a hot rolled coil with variations of the intermediary temperature from 620 to 740°C, isothermal holding time between 1 and 10 s and coiling temperature between 50 and 400°C. In addition, two CCT (Continuous Cooling Transformation) diagrams were developed to evaluate the effect of the isothermal holding time on the phase transformations of the remaining austenite. It was observed that the intermediary temperature has a strong influence on the kinetics of the phase transformation, as well as the isothermal holding time influences the amount of ferrite formed and, consequently, the final microstructure and hardness of the material. The coiling temperature did not cause significant changes in the amount and morphology of the ferrite, but a gradual replacement of martensite with bainite was observed, which, in addition to the self-tempering effect, contributed to the hardness reduction.

Oct 1, 2019

By J. Bas A. F. Smeulders

Traditional laboratory lubrication tests, including those for cold rolling lubricants often involve measurement of neat oils. To achieve increased levels of test severity, such tests are often carried out at high temperatures and prolonged durations. However, we found that the levels of lubricant degradation and wear in these tests can be much higher than in the field. Moreover, steel rolling is not done with neat oils, but with emulsions, where the presence of water influences film formation, surface chemistry and oil composition in the roll bite. To better approach the situation in the field, and thus to be able to develop rolling oils with improved lubrication performance, several lubrication tests were developed for emulsions: direct measurement of film formation and measurement of Stribeck curves, in which the emulsions can be assessed in terms of their boundary lubrication and elastohydrodynamic behaviour. The key innovation is that also another test method was developed, which focuses on boundary lubrication and wear, and the role of extreme pressure and anti-wear additives. Realistic levels of test severity are achieved in the tribometer by mimicking frictional power intensities and flash temperatures for typical cold rolling or tinplate mills. Test conditions can be adapted according to the mill stand or pass number and other cold rolling process parameters. The emulsions are kept at normal operational temperature. Clear differences could be observed between emulsions of various concentration and composition. The viability of the method is illustrated by a number of field cases, in which a good correlation is demonstrated between the laboratory tests and the performance in a pilot or production mill.

Jul 30, 2018

By Valeria Collini, Antonello Mestroni, Enrico Plazzogna

The Danieli Group is deeply involved in the technological improvements stimulated by Industry 4.0 concepts widely applied to the metals industry and process automation. The so-called "Intelligent Mill" is the natural evolution of the company’s consolidated know-how and undisputed leadership in the fields of mini-mill and turnkey plants. Complete and structured data collection is the basis for real-time analysis and process optimization in terms of quality, efficiency and easy maintenance. A centralized repository of information is possible thanks to the strong interconnection between process control system architecture and intelligent sensors, together with dedicated software tools leading to an intuitive approach to data analytics.

Oct 1, 2019