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By Luiz Henrique Accorsi Gans

First, this works carries an experimental evaluation for austempered ductile iron (ADI) as a gear material. And second, in order to provide a better understanding of the microstructural effect on the stress state of subsurface regions, a finite element method approach was considered using the submodeling tool in ANSYS 11.0. For this, ADI gears were produced from continuous cast iron bars, heat and thermochemical treated and tested in FZG test rig. The results were compared to those of carburized steel AISI 8620 and induction hardened steel AISI 4140 gears. The wear experiments were performed at the temperature of 90ºC with two torque stages: 135 N.m (running-in) and 302 N.m (steady-state). The time for pitting and spalling on the gears surfaces were measured using image analysis. The results showed a very good potential of using ADI for manufacturing gears, replacing induction hardened steels. Also, the ADI gear with smaller nodules showed higher life for pitting. In contact fatigue tests with severe load, the carburized AISI 8620 steel proved more adequate than the austempered ductile iron, showing that the mechanical properties are critical in the resistance to damage in gear contact. The austempered ductile iron with smaller nodule size showed to be very competitive with wear resistance similar to AISI 4140 steel induction hardened. With ANSYS, it was verified that the nodule size affects the gears life independently of the mechanical properties of the matrix. The results showed that the nodules indicate the presence of a concentration stress, but their size doesn’t affect the contact fatigue life as much as the total amount of nodules, regardless of the ductile iron microstructure. The size and number of nodules affects both the nucleation and the propagation stage of cracks. ADIs with higher amount of nodules have a greater wear resistance. Also, compared to the Hertz contact theory (isotropic material), the presence of graphite nodules indicates a non-isotropic material and made the maximum shear stress point moves toward the surface.

Jul 31, 2018

By Gajraj Rathore

With the advent of modern HRM ( Hot rolling mills) with capacities beyond 5 Million tons with corresponding enriched CRM (Cold Rolling Mill) capacities, the throughput per hour exceeds invariably beyond 50 coils per hour making it possible to manage, track, handle, transport, store and dispatch inevitably with an automation system supplemented by corresponding software and hardware. This is true with respect to the production of Cold rolled Annealed, Galvanized, Continuously Annealed, Galvalume, CRGO, CRNGO and Colour coated coils which need total care in handling, tracking and dispatch. Understanding the above needs precisely JSW, Vijayanagar, India, has rightly gone in for a total automatic Yard management system and ASRS wherein the coils are handled as much as possible automatically in cradles without any damage insuring the receipt of coils to the customer as was produced. This CRM 2 has been commissioned and is operating with maximum automation with least manpower and max productivity with assured quality and safety. Pesmel OY Finland had the opportunity to Design, Supply and Commission this system which is first in the country and this technical paper analyses the above project as a case study enlisting the sound technical aspects as well as emphasis on the techno economics with assured ROI (Return on investment) and enhanced efficiency.

Aug 16, 2017

By Marco Antonio Meggiolaro

Most cyclic plasticity models used in multiaxial fatigue life predictions are based on a concept of a yield surface, which divides the elastic and plastic domains. Plastic straining occurs when the stress state reaches the surface and tries to move outward. Subsequent plastic straining causes the stress state to remain on the yield surface, which will translate to prevent the stress point from moving outside it according to a kinematic hardening rule that models the Bauschinger effect. The accurate modeling of the yield surface shape is fundamental to predict stress-strain relations. In this work, the main yield surface equations for isotropic materials are compared. Even though most materials can be modeled using Mises and Tresca surfaces, other need to consider the effect on the yield strength of the hydrostatic stress or the normal stress acting on a critical plane. It is shown that pressure-sensitive models originally devised for concrete can be applied to predict yielding in some materials, and even fatigue life for metallic structures with short cracks.

Aug 8, 2018

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 Julián Andrés Ortiz González

This work presents a series of experiments of Fatigue Crack Growth (FCG), which are intended to provide evidence about the main parameter controlling this phenomenon, whereas still no agreement about this, since the Paris´ theory is based on the principle that FCG is controlled by the ?K and the Elber´s theory says that the driving force is ?Keff. For the development of the experiments, some DC(T) specimens were machined with two different thicknesses: 2 and 30 mm to perform FCG tests in plane stress and plane strain state, respectively. Besides this, all FCG tests were carried out with a constant ?K e Kmax, measuring the strain with a Strain-Gage bonded on the back face of the specimen and seven Strain-Gages located on the crack growth path. The data needed to measure the crack opening load, and the ?Keff, were collected through a program developed in Labview. Finally, the data post-processing was carried out based on the ASTM standards and several articles of recognized authors in this field, in order to compare the two positions with the experimental data, and this way conclude which is the most consistent theory with the observed behavior.

Aug 16, 2017

By Vitor Orlando Ferreira

The efficiency of an apparatus which uses a forced lubrication system, as well as the useful life of its components, is strongly related to the degree of contamination of lubricating oil. The presence of contaminants and the degradation of the oil itself cause it to release substances that fouling of the wall of the pipes. The cleaning and dialysis of the oil pipes, besides prolonging the life of the lubricant reduces wear of the components. There are several methods of cleaning in pipes, the problem is that some have abrasive characteristics, which could damage some types pipes. Among the non-abrasive methods stand the Flushing and Air scouring. Flushing uses the lubricating oil which circulates in temperatures alternating and high speeds, for generating turbulence to perform washing. The Air scouring method uses oil and filtered compressed air, injected into pipe, to generating higher flow, causing the power supply unit with fluid can work with lower power consumption and higher speeds, removing fouling of the pipe. The objective of this research is to evaluate the Reynolds number to correlate with the efficiency of cleaning the pipe. The method applied was the Air scouring and it was verified that the qualitative effects may occur when compared to Flushing. After testing, it was found that the chosen method brings significant changes in flow, and this flow regime varies considerably increasing the Reynolds number.

Jul 31, 2018

By Aloizio Cesar Gonzaga, Leandro de Paula, Ismael de Souza Dias, Gladston Santos

Looking for greater competitiveness, Gerdau started in 2013 the operation of its hot strip mill in Ouro Branco, being a milestone in Gerdau's history, where it definitely entered the flat products business. This mill consists of the reheating furnace, primary scaler, a Duo-reversible Quadrupole Steckel mill, accelerated cooling and final coiling. The Steckel mill works with two backup rolls and two working rolls, the backup rolls being responsible for supporting the rolling forces and the working rolls for shaping and surface quality to the strips, having as main requirement quality of surface finish. These rolls suffer high wear due to the lamination process and are exchanged with high frequency to ensure the quality of the laminated strips, after the exchange are sent to the Work Roll Shop for grinding and are positioned Grinded work rolls for the next planned change. This movement is accomplished through the crane and an exchange device that attaches to the cylinders to be transported from the Rolling Mill to the Work Roll Shop. The target in this article is focused on an improvement in this Device to increase operational safety and reduce stoppage losses downtime at the mill, improving the cost / benefit ratio and increase production.

Oct 1, 2019

By Cleber Caetano Thomazi

Rotary kilns are continuous process equipment used on calcining of nickel ore. The chemical and physical reactions are created by means of heat up the material to predetermined temperatures. Tertiary air fans are attached to the kiln shell to maintain oxidizing/reduction conditions. Special ducts orientate the air flow inside the kiln. In the present work, two types of failure on distinct tertiary ducts mounted on the same kiln are reported. Chemical analysis, hardness test, metallographic and fractographic examinations were carried out. Fabrication related problems and creep were identified as the root causes of damages.

Oct 30, 2017

By Alberto Pesamosca

The present work analyzes the latest results achieved in scrap based EAFs in terms of application of chemical energy, starting from the observation that the general trend is a reduction of oxygen utilization. Consequently a review is needed about criteria for evaluation of melting process efficiency and equipment design. If from one side the maximization of productivity remains one of the major goals, from the other side some aspects of present market situation, included price of raw materials, are requiring the maximization of process yield. Based on achieved performance figures of selected plants and theoretical considerations, the effect of chemical energy input intensity is analyzed focusing on transformation cost, productivity and total energy input. The effect of present practices with lower oxygen utilization is considered also in terms of global CO2 emissions. Finally, the latest Danieli concepts and technological tools for optimization of chemical input are presented.

Aug 17, 2017

By Steven G. Jansto

Nearly one third of the globally produced structural flat and long structural products are in the 0.11 to 0.16% carbon range. By definition, numerous steelmakers globally define this approximate carbon range as peritectic in their melting grade family within their organization. The metallurgical consequence is the result of numerous global structural specifications which allow carbon to wide carbon ranges resulting in quality issues. For example, such specifications as ASTM A588 set no minimum carbon and a 0.15 to 0.19%C maximum depending on the specific grade designated within the specification. This peritectic region is specifically challenging in production compared to less than 0.10%C because of solidification issues and a higher propensity for slab or billet cracking during continuous casting. During hot rolling, rejects and/or deviates are increased as well. The relative steelmaking operational cost of production is compared between peritectic and non-peritectic carbon compositions for a given specification.

Aug 17, 2017

By Shibu John

The COREX® process is beside the FINEX® technology the only industrially realized alternative to the blast furnace route for the production of hot metal. Changes in the raw material sector in respect of decrease in quality, strictly enforced environmental laws and positive operation results of COREX® reference plants make it worth to carefully re-evaluate the COREX® technology in comparison with the traditional blast furnace technology. Integrated Plant concepts based on COREX® offer solutions for future challenges of the iron- and steelmaking industry, which include: economical hot metal production; efficient and highly economic export gas utilization (power generation, DRI production, syngas production for chemical products); lower raw material cost, higher raw material availability; environmental friendly high grade steel production. The economic evaluation of different COREX® gas based plant concepts in comparison with the traditional blast furnace route shows that the COREX® technology is highly competitive in the challenging iron and steel producing environment.

Aug 17, 2017

By Franco de Castro Bubani

Cu-base alloys (Cu-Zn-Al, Cu-Al-Be, Cu-Al-Ni), depending on their composition, have martensitic transformations that can be thermally or mechanically induced between a metastable structure called austenite and one or more metastable structures called martensites. In single crystals, depending on the specific composition of the alloy and the crystallographic orientation of the tensile axis, martensite-martensite transformations can be mechanically induced. The hysteresis associated to these martensite-martensite transitions is usually much greater than the one associated to the austenite-martensite transformation. Thus, martensite-martensite transitions are potential candidates for energy dissipation in a mechanical damper. Possible applications that would benefit from high hysteresis include seismic damping devices, dampers for satellites and the aerospace industry, defense and others. We present pseudoelastic cycling results of alloys submitted to different thermal treatments. Our conclusions highlight the fact that, under certain conditions, Cu-base alloys deliver better damping performance than commercially available SMAs and even the new Fe-base SMAs.

Aug 7, 2018

By Luciana Lezira Pereira de Almeida

With the increasing use of ornamental rocks, mainly in civil construction, sundry problems were identified in relation to rocks cutting, such as efficiency in the cutting process and rock quality lumber. In recent years several composites have been developed to solve these problems. In this context, the study of the binomial matrix metal-diamond interaction is of paramount importance for the development of new composite materials to improve the efficiency of the cutting tool. The diamond impregnated matrix metal often reveals a reaction between the diamond surface and the matrix. Besides the mechanical connection, chemical reactions can sometimes occur. Therefore, this study aims to assess the achievement of diamond composites in the system Fe / Cu / Ni / Sn via powder metallurgy, with added CRB2. Analyzes have been performed to characterize chemical / physical and mechanical. The results have showed that addition of CRB2 promote significant changes in the properties of composites, especially in wear resistance and fracture toughness. Furthermore, the presence of the composite CRB2 causes a significant improvement in thermal stability.

Aug 16, 2017

By Glaydson Simões dos Reisr

Micropore organosilicas (MOs) were synthesized using methyl-phenyl-polysiloxane as precursor. The MOs were characterized using several analytical and functional techniques. The materials were assigned as micropores materials, with specific surface area up to 642 m2 g-1 and yield up to 72.55%. The adsorbents have hydrophobic surfaces and were used for removal of diclofenac from aqueous solutions. The adsorption kinetic and isothermal data were well described by the general order and Sips models, respectively. Diclofenac exhibited a better affinity than NM and the mechanism of adsorption suggested that hydrophobic groups play a key role in the adsorption process.

Aug 17, 2017

By Andreas Rohrhofer

Reliable high end automation and process optimization systems are main factors for excellent product quality, safe operation and maximized plant performance in the steel industry and its designated environmental plants. Primetals Technologies introduces new automation packages for consequent safe and cost efficient production. Many areas within the steelplant interested to be monitored and measured automatically are not implemented in the automation system due to limited access or technical reasons. A wireless, self-organizing network facilitates wide ranging data transmission in previously inaccessible areas and opens up a wide range of new opportunities. With Fluid Guard a system to detect leakages with highest accuracy and reacts properly for all kind of water cooled circuits is available, improving the safety in steelmaking process. Lance Guard can be utilized for all fully automatic and semi-automatic lance appliances, but is especially suitable for the products of Primetals Sublance Standard/2.0 and LiquiRob applications, since these systems make seamless integration particularly simple. Manual lance appliances may also be tested and diagnosed. Environmental plants have become a main part in steelmaking plants. Highest performance in combination with optimized energy consumption is the main target in Primetals Technologies’ innovations in automation optimization packages for dedusting systems. A new approach for preventive maintenance and operator assistance is introduced with the Acoustic Expert System. In combination with the new Ask cloud based system, Primetals enables a 24/7 monitoring and a whole lifetime observation of any equipment within a steelplant. Furthermore it is now enabled to check the condition of the plant at a fingertip at any time.

Aug 17, 2017

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 Franco Gandin

With increasing demands for highly performing and at the same time efficient and running-costs saving vacuum-degassing equipment, dry mechanical pumps have been confirmed a proper choice to completely fulfill the expectations of steel-making companies worldwide. Regarding the production of both special carbon steel and stainless steel grades, the usage of mentioned pumps allowed reaching simultaneous remarkable results from different viewpoints in various Danieli worldwide installations (treating up to 200 t of liquid steel). As a matter of fact, in front of the replacement of a widely spread and renowned technology such as steamejector pumps with the recently developed technology embodied by the dry mechanical pumps, well-established metallurgical performances in terms of carbonhydrogen- nitrogen-sulphur removal have been repeatedly attained while meeting at the same time the client’s expectations concerning, for example, running-costs and push-button availability. Additionally, thanks to the very flexible, modular, redundant and maintenance-friendly equipment design, random problems occurring to the singular mechanical pumps can be easily solved without affecting the VD-VOD plant availability and metallurgical performance. With a particular regard to the VOD process, a very short overall process-time has been repeatedly performed (averagely less than 58min under-vacuum time at ChMP1) while guaranteeing the expected required quality of the final refined stainless steel. Moreover, in several VOD installations (ranging from 6 t up to 110 t of liquid steel) an efficient automatic process control such as dynamic pressure-regulation during oxygen-blowing has been attained thanks to the controllable variable-speed drives with which each mechanical pump is provided.

Aug 17, 2017

By Klaus Pronold

Once installed rolling mills can look forward to a long life. Around 40% of the 140 conventional hot strip mills presently in operation were built between 1960 and 1970. 17 of the 29 CSP®-plants were commissioned before the year 2000 and have automation platforms that are obsolete and/or have outdated rolling technology. Keeping pace with the market requirements is an ongoing challenge for producers of flat steel. It is a real balancing act keeping production facilities performing at necessary levels, safeguarding the investment and keeping outage periods to a minimum. To overcome these demanding factors and strike the right balance allowing for the production of higher grade steel that meets the current market price the installation of mechanical equipment as well as automation platforms and process technology must meet the latest technology standards. Being discussed in this paper are the different motives for modernizations along with their impact on project handling and commissioning philosophies. Experience gained during recent modernization projects in the field of flat steel rolling relating to Steckel / plate mills or current CSP® modernizations will be shared and demonstrate that each modernization has its own individual solution. Specific strategies are explained to help optimize production, increase plant agility and maximize the return on investment.

Aug 17, 2017

By Débora Cardoso de Oliveira Silveira, Jean-Christophe Huber, Hamzeh Hamadeh, Kateryna Pastel, Guillaume Brosse

The dynamic behavior of oxygen gas flow, determined by the lance nozzle and blow pattern, is a key factor for determining jet efficiency in BOF Steelmaking. The present work compares the performances of Laval and parabolic nozzles with the aid of the Computational Fluid Dynamics (CFD). The Method of Characteristics (MOC) was applied to design a minimum length parabolic nozzle. The results show that the parabolic nozzle generates more uniform and stable jet, with 2% longer potential core and supersonic length and less shock waves. For the parabolic nozzle, the pressure nearby the nozzle wall is higher, which can protect this region from reverse flow of converter gases and offer longer life for the lance tip. Likewise, the flow rate variations would affect less this nozzle. In addition, the nozzle wear was investigated, and the parabolic nozzle has proven relatively less sensitivity to the presence of this deformity.

Oct 1, 2019

By Dusan Ilic

Conveyor system wear of belts and transfers attribute to a significant proportion of the maintenance costs and lost productive hours when handling hard abrasive ores at high unit rates typical of the iron ore industry. The recent growth phase has seen a rapid increase in mine and export capacity, with many new and upgraded plants operating at high throughput and utilisation. Subsequently, the industry has progressed to an optimisation phase, seeking to maximise production capacity and reduce maintenance costs with minimal capital spend. To support this, a programme of modifying designs was executed to improve conveyor transfer chute and belt life, which identified a need to challenge the industry practice for specification of designs to improve the functionality of the installed equipment. While acknowledging the importance of selecting the highest wear resistant materials for the intended application, this paper investigates design criteria related to decreasing conveyor transfer and belt wear. Of focus is a shift in the manner in which designs are specified, from specifications primarily governing geometrical constraints, to those meeting technical and functional requirements aimed at producing optimum geometry for a given set of material handling parameters. An assessment of transfer design criteria is presented.

Aug 17, 2017