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By Eduardo Dominguez Trindade

Lubricant oils are subjected to reciprocating movement in the piston ring/cylinder tribocouple of automotive engines. In this kind of movement, the relative speed oscillates between zero and a maximum, and therefore the lubrication regime goes from boundary to hydrodynamic. Tribotests are widely used in laboratories to hint at the friction developed in these systems. In the present work, a SRV tribometer was used to evaluate the friction behaviour of lubricant oils under reciprocating movement up to 60 Hz. A high acquisition rate allowed the analysis of data inside each reciprocating cycle. Both a pure base oil and a fully formulated lubricant were used. Changes in the contact pressure, viscosity and speed were seen to influence friction, which was correlated to the relative thickness predicted by Hamrock-Dowson equation. While some observed characteristics were typical consequences of the Stribeck curve, other effects were also observed, such as the occurrence of seizure at high reciprocating frequency. A lower boundary coefficient of friction due to additive package in the formulated oil was also observed. The results allow a better understanding of friction in reciprocating cycles and can be used to evaluate the performance of oils and surfaces in laboratory prior to engine testing.

Jul 31, 2018

By Dyego Monteiro de Souza

This study compares the wear resistance of specimens lubricated with biofluids or mineral oil. Tribological studies were performed by ball-cratering test. In these tests were used as lubricants epoxidized soybean oil, castor oil and mineral oil. The specimens used were untreated and nitrided AISI 4140, while a steel ball AISI 52100 was used as a counterbody. In order to analyze the results obtained, the worn volume was calculated and the characterization of the crater, after the test, was made using optical microscopy and SEM. Wettability was also measured for the different surface condition and lubricants. As expected both specimens showed a smaller volume worn when lubricated with mineral oil due to inherent properties of this type of lubricant. Among the vegetable oils studied, the castor oil showed a better performance in the lubrication of the specimens untreated while on the nitrided specimen have shown less wear when lubricated with epoxidized soybean oil, indicating a difference in the efficiency of oils, as lubricants, depending on the surface conditions of the mechanical components.

Jul 31, 2018

By Adriane Lopes Mougo

Super duplex stainless steel presents a biphasic structure composed by ferrite and austenite with different characteristics and properties. In the micromilling process the cutting edge radius has similar dimensions to the grain size. The biphasic structure found in this material could influence on the cutting tool life and the surface integrity of the workpiece. Due to its low machinability, caused by high hardening level and low thermal conductivity, the process can produce built-up edge and high surface roughness (Ra). In this work it is performed an experimental study of the micromilling of super duplex UNS 32750 and the influence of the cutting speed (Vc) and feed per tooth (fz) on the surface integrity and tool wear. The design of experiments considered two levels and three replicates. Results indicate the increase of roughness for bigger feed per tooth, small influence of the cutting parameters on the burr formation. The tool presented flank wear after the experiments.

Aug 8, 2018

By Ramon Augusto Moretti, Henrique da Rocha Severino, Renato Nascimento de Castro, Fernando Cesar Sousa

Rolling stand 12 (LTx) of long steel, installed in the company A, Piracicaba - SP unit, had presented high levels of vibration, which affected its internal components, such as: shaft, gears and bearings, generating downtime. To evaluate this equipment a study was proposed by the following engineering techniques: Conventional Vibration Analysis, Operational Deflection Shape (ODS) and numerical simulation by the Finite Element Method (FEM). In the Conventional Vibration Analysis, high levels of vibration were observed during manufacturing process, especially when the material reaches the equipment. Impacts generate high values in acceleration, on average 80 m/s² peak to peak. In the moment of impact, misalignment of internal components was observed by ODS. Field results were correlated to those obtained by the Finite Element Method, which allowed to calibrate FEM model. Thus, the most effective structural modification already numerically evaluated was implemented in the system. Afterwards, new measurements by vibration and ODS techniques were performed, and attenuation of vibrational levels and operational mode, which overloaded the internal components rolling stand, were verified.

Oct 1, 2019

By Yong Tian, Tian Zhang, Zhao-Dong Wang

To meet the requirements of high-performance steel plates, while reducing manufacturing costs and saving energy, the advanced cooling system for plate mill (ADCOS-PM) with functions of accelerated cooling (ACC), ultra-fast cooling (UFC), and direct quenching (DQ) was researched and developed by the State Key Laboratory of Rolling and Automation (RAL). Since 2003, several sets of ADCOS-PM device were developed and implemented in industrial practice. To fully utilize the ADCOS-PM technology, the combination of various strengthening mechanisms was promoted by NG-TMCP technology and low-cost, high performance plates were produced such as pipeline steels, and high-strength construction machinery steel.

Oct 1, 2019

By Gustavo Borges Tiboni

The erosive wear caused by the impact of solid particles against a surface is a tribological phenomenon present in many segments of the industry, such as transportation, aerospace, mining, power generation, among others. The most usual method to set the wear rate is by measuring the mass loss of the material. In order to apply one technique with potential to determine the rate of erosion wear, this study developed a dedicated equipment and conducted preliminary erosion tests monitored by non-destructive testing known as acoustic emission technique (AE). This can be defined as a technique able to detect mechanical waves generated by the release of elastic energy accumulated in the material. Erosion tests were performed in order to evaluate the ability of equipment to collect data from AE and to correlate these data with the wear of the samples. Samples of low carbon steel eroded by the impact of angular aluminum oxide particles suspended in air at three different velocities: 45, 57 and 67 m/s. The impact angle between the particles and the sample was set at 30 degrees and the test temperature at approximately 20°C. The wear rate has changed with the velocity in accordance with the kinetic energy of the particles and the AE parameter RMS showed sensitivity to the variation of particle impact velocity and to the wear of the sample eroded. The rate of AE signals collected over time correlated with the flow of particles striking the sample, and with the parameters of energy, rise time and duration of the signal.

Jul 31, 2018

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 Michael Windhager, Karl H. Ziehenberger

ULTIMA® are high performance, centrifugal cast, double poured (CC duplex) work rolls. This paper describes the principle of the ULTIMA® roll concept and its wide range of usability. The ULTIMA® concept provides a solution for rod and bar mills to increase performance and output, even under harsh rolling conditions. The main focus is on highly loaded mill stands that require both high wear resistance and resistance against thermal fatigue, like pre-dog bone, dog bone, slitter. Specific case studies of quite different mill configurations and rolled product mix prove the positive impact on production yield, mill and roll shop operations, and profitability in terms of TCO (total cost of ownership).

Oct 1, 2019

By Eric Yoshimitsu Sako

One of the main difficulties in the operation of trough and runners at Arcelor Mittal Tubarão (AMT) Blast-furnace no.02 is the reduced amount of time available for repair procedures. The consequence is that the castable installation must often be performed during hot conditions and the installed castable could easily detach from the base material during the early stage of operation, exposing the previously oxidized base material to molten iron and corrosive slag attack. When events like this happen, emergency repairs must be executed, resulting in increased refractory unit consumption and an unplanned shutdown of unit operation. Considering these targets, Nippon Crucible Co. and Saint-Gobain HPR Brazil have developed a high-performance Al2O3-SiC-C composition based on an entirely novel anti-oxidation technology. Oxidizing reactions could be attenuated by adding an oxidant inhibitor and a water reducing agent. As a result, the open porosity was significantly reduced, resulting in an improvement of campaign life in terms of pig iron throughput when compared with the regular castable. An analysis of this life improvement showed successful results for the material after 250 days of campaign. The main reason for such successful results was that the deterioration caused by the oxidation was significantly less and that this change made on the high cohesive structure of the base material was maintained for a long time. The attained results allowed Arcelor Mittal Tubarão to achieve longer trough campaigns, and avoid any unplanned stoppages with zero breakdown risks.

Oct 30, 2017

By Rogério Felício dos Santos

Nitriding of metallic materials using electric discharges generated during electric discharge machining (EDM) is a recently developed technique. The aim of this paper was to correlate mechanical properties of a nitrided layer produced in AISI 4140 steel by EDM nitriding with the type and amount of nitrides. A conventional die-sinking EDM equipment and electrolytic copper electrodes were used to generate the electric discharges. The electrolyte was a solution of urea in deionized water. Knoop microhardness profiles assessed the variation of hardness along the nitrided layer, whereas the elastic modulus of this layer was measured using nanoindentation tests. Optical microscopy and X-ray diffraction (XRD) were used to characterize the nitrided surface. The results showed the formation of a nitrided layer containing iron nitrides with average thickness of around 25 µm. The amount of nitrides reduced from the surface towards the centre and these results correlated well with microhardness profiles obtained.

Jul 31, 2018

By Satish V. Kailas

For product sustainability “closing the cycle” is the first requirement. If the materials used in making the product is not replenished at the rate at which it is being extracted, the cycle is open and the product would not be sustainable. This includes the materials used in generating the energy used to make the product, the transportation, use and disposal. If the materials used in a product, that includes lubricants, is one that cannot be replenished, it has to be recycled for the product to be sustainable. The other basic condition for sustainability is the eco-friendliness of the product. It is argued that the present lubricants do not fall in this category. Using the example of cutting oil emulsions we have shown that it is possible to meet the conditions of sustainability in terms of both the material extraction-replenishment cycle and eco-toxicity. Cutting oil emulsions made from coconut oil and natural additives are shown to have superior cutting properties and are completely eco-friendly. It is concluded that products made using these conditions are possible and is a necessity for man to lead a sustainable life. Closing the cycle, with respect to the energy used in the cycle will make the product completely eco-friendly.

Jul 31, 2018

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 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 Edgar Ivan Castro Cedeño

En la producción de aceros limpios el control inclusionario es crítico para la obtención de un producto que cumpla con los requerimientos de calidad. El análisis de la distribución de tamaño de inclusión mediante modelos estadísticos permite estimar la incidencia de inclusiones en el producto solidificado a partir de mediciones tomadas en muestras relativamente pequeñas. En seis coladas de acero bajo carbono desoxidado con aluminio se tomaron muestras de acero a lo largo del procesamiento en horno olla y colada continua. Las muestras se prepararon para estimar mediante análisis metalográfico los tamaños de inclusión. Los datos de tamaño de inclusión se analizaron mediante modelos estadísticos de valores extremos, se hace una comparativa entre la distribución Gumbel (que forma parte de la norma ASTM E-2283) y la distribución Generalizada de Valores Extremos (GEV). Mediante una prueba de hipótesis con el estadístico Anderson-Darling, análisis de cuantiles y con la función de supervivencia se demuestra que la población inclusionaria se describe de una mejor manera con la distribución GEV. Finalmente se da un estimado de la incidencia probable de inclusiones en el producto solidificado.

Aug 16, 2017

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 Eric Schaub

Hot Blast Stove Systems are an important equipment of a Blast Furnace plant. During the last years, performance requirements and operation practice for the Hot Blast Systems have changed and have a big influence on the Blast Furnace operation. Therefore it is necessary to keep the Hot Blast System in proper condition in order to maintain the production capacity of the Blast Furnace. It is important for operators to know the condition and relevant constrains of a Hot Blast Stove Plant. Assessing its condition on a regular basis, especially in advance of a Blast Furnace relining is therefore advisable. Considering the individual condition of the Hot Blast Stove Plant, improvements in operation, but also specific and dedicated repairs might be implemented. Design improvements can be implemented as well during such repairs. This paper will describe some of these design improvements, will illustrate their implementation in new hot blast stoves but will also describe repair methods for existing stoves. In addition new developments became popular during the last decade, like the so called Dome Combustion Stoves, which was invented already 30 years ago in Western Europe. Paul Wurth’s development in this regard will be discussed in this paper as well.

Oct 30, 2017

By "Andreas Steinwandter

The demand for increasing energy efficiency and CO2 reduction is one of the global megatrends of our time. Although the steel industry suffers from a volatile economic environment, the steel plants are interested to find opportunities for sustainable cost reduction and put efforts into healthy solutions for the environmental. Integrated steel plants are trying to cut electrical power and energy costs as these are among the biggest cost factors that can be influenced and taking all the advantages they can. For the integrated iron and steel making route the interaction of waste energy utilization along with process energy demand, natural and metallurgical gases, steam and heating systems as well as power generation has to be considered. Potential energy sources, such as sinter plant, basic oxygen furnace (BOF) cooling stack or reheating furnaces are considered in order to elaborate an integrated energy concept. Especially electric power generation is an attractive option for steel plant operators since it can easily be connected to the existing power grid of the steel plant. When direct local use of waste heat is limited, the best option is to convert it to mechanical/electrical power with a Rankine Cycle. A stand-alone system, compact design with minimum operational costs in order to fit into the existing steel plant layout, are the main requirements of such units. The objective of this paper is to demonstrate economic feasible opportunities for energy recovery for sinter cooler and basic oxygen furnace with focus on electric power generation via ORC modules taking at the same time advantages of CO2 reduction by utilizing waste heat from the process. Furthermore typical arrangements and layouts of such solutions as well as basic economic calculations will be presented in the paper.

Oct 30, 2017

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 Marco Antonio Meggiolaro

Notches are preferential sites for fatigue and for environmentally assisted cracking (EAC) initiation. Semi-empirical notch sensitivity factors have been used for a long time to quantify notch effects on fatigue design. Recently, this concept has been mechanically modeled using techniques which properly consider the notch tip stress gradient influence on the fatigue behavior of mechanically short cracks. This model properly calculates such values from the basic fatigue resistances of the material, its fatigue limit and crack growth threshold, considering the characteristics of the notch geometry and of the loading, without the need for any adjustable parameter. Such criteria to estimate notch sensitivity and tolerable short cracks on fatigue have been extended to EAC conditions and verified by proper tests. In its simplest version, the criterion for the maximum tolerable stress under EAC conditions uses the resistances to crack initiation and to large crack propagation and the characteristic short crack size under EAC, considering the crack size and stress intensity factor. Moreover, the tolerance to short cracks under fatigue and under EAC conditions can be unified in an extended Kitagawa-Takahashi diagram, a new and potentially very useful tool for material selection tasks.

Aug 8, 2018

By Alberto Pesamosca

The paper presents the results obtained by the AC EAF supplied by Danieli at Kroman Çelik (Gebze-Turkey) after the planned upgrade to 150 ton. The EAF – 7,4 m diameter, based on the full platform standard design - is able to handle a maximum power of 114 MW and is equipped with the most advanced and reliable technology, including module injection system and the Hireg electrodes regulation system. Excellent results were already obtained with 120 heat size in terms of fast start-up and excellent performance figures. After the upgrade, productivity was increased up to 212 t/h, maintaining high process efficiency (365 kWh/t with 32,1 Nm3/t O2).

Jul 30, 2018