bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physical and mathematical modelling of flow and residence time distributions in different tundish designs
Authors: Robert Asish , Mazumdar Dipak 
Published: December 2016

A steady state, three‐dimensional, turbulent flow model has been developed in‐house for analysis of melt flow and residence time distribution phenomena in steelmaking tundish system. The governing equations of flow, turbulence and tracer dispersion were derived in terms of the Cartesian co‐ordinate systems and solved numerically with their associated boundary conditions adapting a control volume based finite difference procedure. In the numerical solution scheme, the pressure‐velocity coupling was treated via the popular Simple (semi implicit method for pressure linked equations) algorithm.Prior to carrying out elaborate numerical predictions for tundish geometry, the model was applied to several standard test problems and evaluated against corresponding bench mark results. Thus, several typical test problems such as, flows in a cubic cavity, flows in ducts of rectangular cross‐section, flow over flat plate and so on were simulated numerically to assess the adequacy and appropriateness of the computational procedure developed. Results thus obtained together with the bench mark solutions indicated that the mathematical model is internally consistent and sufficiently robust. Accordingly, the turbulent flow model was applied to simulate flow and Residence Time Distributions (RTD) in four different tundish designs . These included, a single strand and a two strand slab casting tundish systems, a six strand rectangular shaped tundish and a six strand delta shaped billet casting tundish. Various RTD parameters (e.g., minimum break through time, tmin, time at which peak concentration occurs, tpeak and average residence time, tav) were computed numerically in the four tundish systems and these were subsequently compared with corresponding experimental measurements derived from equivalent water model tundish systems. Except for the single strand tundish system, large differences between measurements and prediction (particularly on tmin and tpeak) were noted for the other three tundish geometries. Furthermore, the extent of such discrepancy was found to be relatively more pronounced for the multi‐strand tundish system. The possible reasons for such discrepancy is discussed in the text and it was shown computationally that relatively better agreement between theory and measurement can be achieved if, instead of the high Reynolds number k‐ε turbulence model, a low Reynolds number turbulence model is applied in the computational procedure.
Development of Zn‐Mg alloy coatings by JVD
Authors: Schmitz Bruno 
Published: December 2016

To promote continuous dry coatings for steel strip by PVD, CRM develops its own JVD (jet vapour deposition) simulator and applies an economical integration strategy combining continuous annealing of steel and vapour deposition by JVD.The JVD system is a very compact system, characterised by a high productivity, a very high metal yield, possibility of working at high partial pressure (up to 1 mbar), homogeneous metal distribution and alloy composition and good coating adherence. It was verified that continuous annealing is a very efficient surface pre‐treatment for steel strip in a wide range of industrial dew points. No additional thermal energy is needed for strip heating since this PVD system is introduced in the end section just after continuous annealing. Application to the Zn‐Mg system is described. Influence of annealing parameters, residual gas pressure, coating speed, steel strip temperature and chemistry are discussed.
Inhibiting the reoxidation of directly reduced iron by vapour phase inhibitors
Authors: Zhang Jianqiang , Grabke Hans J. , Müller‐Lorenz Else 
Published: December 2016

The inhibition of the reoxidation of direct reduced iron was investigated by establishing different contents of vapour phase inhibitors in oxidising gas mixture He‐O2 at 150 and 200 °C. The raw materials were iron oxide powder and iron ore pellets which were first pre‐reduced by H2 at 500 °C and then reoxidised. Three stages of oxidation are identified, a rapid initial stage, an intermediate stage in which the rate of reoxidation decreases significantly, and a final stage, in which the rate of oxidation is very low. The length of each stage and the rate of reoxidation are related to temperature and to the status of raw materials.Four inhibitors were tested. Benzylamine, ammonium benzoate, and the commercial VCI cortec 101 exert a good inhibition on the reoxidation of iron. The inhibition by ammonia, however, is not significant. Presence of water vapour enhances the reoxidation. XPS analysis reveals amines on the surface when benzylamine is added in the oxidation gases.The ignition temperature of reduced iron decreases with the addition of inhibitors in the oxidation gas atmosphere. This unwanted effect probably is due to organic deposits on iron surface, initiating the burning of iron. The extent of reoxidation, however, is significantly diminished by the inhibitors, thus heating of the material is suppressed and the danger of ignition is decreased.
Statistical Design and Evaluation of Experiments in Steel Production
Authors: Lundberg Sven‐Erik 
Published: December 2016

Making experiments under industrial production conditions gives many times difficulties in varying the important parameters in a relevant way in order to significantly Influence the process and thus make it possible to measure the result. The common way of varying one parameter at a time, gives rise to many experiments and mostly, large difficulties in the evaluation.The statistical design method, on the other hand, where the parameters are varied systematically and simultaneously, gives possibilities to influence the process in a more efficient way, thus reducing the necessary number of experiments, and at the same time to obtain more reliable results. In spite of the linear approach presented here, it is always possible to evaluate any kind of influence on a process, by choosing the studied parameters in a relevant way. This is simply done by means of a suitable variable transformation before the experimental matrix is set.Analytical evaluation of the experiments often raises a voluminous mathematical treatment of the results. However due to the linearity of the primary functions, the experiments can be evaluated by means of a simplified linear procedure, and even large experimental matrices can easily be evaluated only by means of a simple spread sheet program.By application of the method to industrial problems, a calculation model was developed for the prediction of process parameters for quenching and self tempering of rebar, as a function of requirements and chemical composition of the steel. Alternately the required chemical composition can be predicted when required mechanical properties and quenching parameters are given, or the mechanical properties can be predicted when composition and quenching parameters are given. Another use of the method has been to optimize the finish rolling and coiling temperatures for on line treated high carbon steel wire rod.
Study of the Effect of Hellenic Diasporic Bauxite Addition on Blast Furnace Operations
Authors: Karamoutsos Spyridon , Alexopoulou Irene. E. , Papanastassiou Dimitri , Papamantellos Demetrios C. 
Published: December 2016

The blast furnace (BF) operation, as well as the steel‐shop downstream, can derive benefits from adjusting the slag alumina content with the proper addition of bauxite flux to its burden. Additions of 5‐15 kg of bauxite/t hot metal lead to a raise of the alumina content of the resultant BF‐slag from 10% to the level of about 12%. In Hellas extensive deposits of diasporic bauxite exist which, however, are under‐utilized by the alumina refineries due to their rather low solubility during the Bayer‐process. The above BF application, therefore, as an alternative use of the diasporic bauxite, is of great interest to the bauxite producers of Hellas.The influence of the bauxite additions on the metal/slag reactions under BF‐conditions was simulated in the laboratory by smelting BF‐slag with diasporic bauxite additions in a graphite crucible. It was achieved the production of BF‐slags with higher alumina contents under the condition of constant slag basicity. The results show the beneficial effect of the bauxite addition to the quality of the produced hot metal. In accordance to its desulphurization and desiliconization as well as the increase of BF‐slag sulphur capacity and fluidity, a thermodynamic evaluation of the metal/slag reaction in respect of SiO2 reduction and S‐transfer to the slag in relation to its Al2O3 content was carried out. This evaluation led to simple algebraic functions and graphs easily applicable by the BF operators. The attained metallurgical results were verified in comparison to industrial test heats with bauxite additions in the BF‐burden in USA, Canada and Europe.
Effect of Annealing Conditions on the Texture and Normal Anisotropy of Al‐Killed Steels in Simulated Batch Annealing
Authors: Juntunen Pasi , Karjalainen Pentti , Peltola Ari 
Published: December 2016

Three commercial cold rolled Al‐killed steels were investigated to study the effect of annealing conditions on the crystallographic texture and the resulting plastic anisotropy. The heating rates, maximum temperatures and isothermal holding times were varied in 18 laboratory scale thermal cycles applied to all steels. The annealed and skin‐passed samples were tensile tested to determine mechanical properties and anisotropy parameters. Grain structures and average grain sizes were examined by an optical microscope and the textures were measured by X‐ray diffraction.It was found that the chemical composition of the steel had a significant effect on the texture and normal anisotropy obtained at certain heating rates. The differences between the current steels were discussed in the light of the competition between the kinetics of AIN precipitation and recrystallization. Excess heating rates led to a low normal anisotropy, which was not improved by extending the isothermal time of annealing. Pancake grain structure and the grain size larger than 20 mm were found to be indicators of the properly chosen heating rate and resulting in high normal anisotropy. At the proper heating rate high normal anisotropy was attained at low annealing temperatures and in short isothermal times, but a longer isothermal annealing was required to obtain a low yield strength.
Optimum Temper Rolling Degree: Pre‐Set and Influencing Effects of Bending Deformations
Authors: Stelzer Reiner , Pütz Paul‐Dieter , Diegelmann Volker , Gorgels Frank , Piesack Ditmar 
Published: December 2016

The present article describes a research project concerning the influence of bending deformations on strip mechanical properties imparted by temper rolling and a strategy for mill pre‐set to achieve the selected temper rolling degree in as short a time as possible. Research results show that, during strip temper rolling, rolls involved in the process, for example deflector rolls and anti‐sticking rolls, introduce plastic bending deformations into the strip which can amount to more than 30% of the temper rolling reduction, depending on the effective bending radii.Bending tests involving strips made of low‐carbon steel in a tension roller system with an integrated bending unit demonstrate that bending deformations influence the mechanical properties of the strip in a manner similar to the temper rolling process itself. It appears necessary to take account of the bending effects when selecting the optimum temper rolling degree.The most accurate roll force pre‐calculation possible and its application at the mill stand are of major importance for pre‐setting the required temper rolling degree. Existing analytical methods have been unable to yield the necessary calculation accuracy. Combination of an optimised analytical approach with a data‐based model to create a hybrid model has led to significant improvements. The accuracy achieved in the pre‐calculation of the required roll force has helped to improve mill pre‐set of the investigated temper mill and to reduce strip head‐end scrap on average by around 6 m per strip. Based on the annual outputs stated by the plant operator, this makes it possible to achieve a cost saving of more than 200,000 € per year.
Pulsed‐Magnetic Hot Joining ‐ New Solutions for Modern Lightweight Structures
Authors: Uhlmann Eckart , Hahn Robert , Jurgasch Dirk 
Published: December 2016

To further significantly reduce the car weight, new and innovative production technologies are necessary which allow to join aluminium and – in the future – magnesium profiles. Then it will be possible to connect components made of aluminium or magnesium base alloy with steel parts to one group. Such a new technology is pulsed‐magnetic joining. In order to lower the process forces necessary for pulsed‐magnetic joining of high strength aluminium alloys and in order to establish a technologically useful forming of magnesium alloys, joining at increased temperatures appears to be a viable solution.As part of the research a tool for pulsed‐magnetic hot joining has been developed that combines the processes of heating by induction and pulsed‐magnetic joining. The applicability and the potentials of the tool have been demonstrated with hot joining of aluminium and magnesium profiles. The combination of the techniques allows for the first time to join magnesium profiles with forming by using pulsed‐magnetic forming at high temperatures. Regarding aluminium the combination of the techniques allows a significant reduction of the magnetic pressure that is necessary for the forming process; it thereby increases the operating life of the tools.
Thermodynamics of Cobalt Aluminate Formation in Molten Cobalt
Authors: Soltanieh Mansour , McLean Alexander 
Published: December 2016

The oxygen concentration of liquid cobalt in equilibrium with cobalt aluminate and alumina was measured by suction sampling at temperatures in the range of 1783 to 1873 K. Experiments were made with cobalt of high and low initial oxygen content and with the addition of cobalt aluminate. The Gibbs free energy of the formation of cobalt aluminate in equilibrium with cobalt containing dissolved oxygen and alumina is:Co (l) + (1+x) Al2O3 + [O]1 wt% in Co = CoO·(1+x)Al2O3 with ΔG° = ‐(226400 ± 8730) + (93.04 ± 4.74) T [J/mol].The oxygen partial pressure in equilibrium with the dissolved oxygen in molten cobalt was determined by zirconia stabilized with magnesia oxygen sensors. The Gibbs standard free energy of dissolution of oxygen in molten cobalt in the range of 1783 to 1873 K is:1/2 O2 = [O]1 wt% in Co with ΔG° = ‐76410 – 2.16 T [J/g·atom].
The MIDAS Technique for Detection of Macroscopic Inclusions in CC‐Material: Fundamentals and Practical Applications
Authors: Jacobi Hatto F. 
Published: December 2016

In this paper twelve years of experience with MIDAS (Mannesmann Inclusion Detection by Analysing Surfboards) testing for macroscopic cleanness of continuously cast steel is reviewed. MIDAS has replaced the previous slime extraction method, which was technically competitive, but too time‐consuming and costly. MIDAS is indispensible for operational trials in the steelworks. The results correlate with quality demands of the final product. The main feature of MIDAS is the flat cross‐rolling procedure transverse to the casting direction. The microstructure of the steel is grain refined by recrystallization. The inclusions are rolled flat, which is advantageous for the ultrasonic inspection. The ultrasonic frequency is 10 MHz and the scanning steps are Δx = Δy = 1 mm. A test plate of dimensions 400 mm x 300 mm is thus scanned within 15 min.MIDAS‐test results in combination with metallographic and EDX‐analysis of the macro‐inclusions enabled a deeper understanding of the fundamentals of ladle metallurgy, metal‐slag reactions, emulsification, agglomeration and coagulation, reoxidation, fluid flow pattern, precipitation and separation. On the basis of MIDAS results CC machines have been revamped and ladle metallurgical facilities and processes optimized. Steel grades with high cleanness demands, e.g. mechanical tubing, HIC line pipe, roller bearing steel, as well as automotive sheet can be produced at lower cost and higher yield to the satisfaction of the customers.
Maximum Copper and Tin Contents in LC‐steel Thin Strip ‐ Hot Shortness Model Calculations
Authors: Pötschke Stephan , Büchner Achim R. 
Published: December 2016

For conventional casting processes low copper and tin contents have to be ensured in LC‐steel to avoid hot shortness. It is expected that higher cooling rates, e.g. in thin strip casting, permit higher copper and tin limits. Hot shortness occurs because of selective oxidation of the iron whereby the more noble copper is enriched at the steel‐oxide interface. A liquid metallic copper phase which wets the grain boundaries supports cracking during hot deformation. The enrichment of the liquid copper phase depends on the oxidation temperature: At low temperatures copper is solid, cannot wet the steel surface and is incorporated into the growing oxide layer. At mid temperatures (1083‐1177 °C) the copper phase is liquid, wets the grain boundaries of the steel surface and causes hot shortness. At high temperatures a liquid fayalitic slag is formed in the oxide layer if the steel contains silicon. The fayalitic phase occludes parts of the steel surface and removes copper from the steel surface; then hot shortness is reduced or even avoided. Other mechanisms to remove copper from the steel surface need the presence of Fe3O4 and Fe2O3 in the oxide layer. These iron oxides are not formed for short oxidation times where linear oxidation takes place. Diffusion of copper into the steel is too slow to reduce hot shortness if copper has an elevated concentration in the steel, e.g. 0.5 wt.‐%. Therefore, only the occlusion mechanism is of importance during linear oxidation. A model is established on the basis of these observations in order to predict an upper copper limit in dependence of the steel strip thickness (cooling behaviour) and the oxygen content in the cooling atmosphere (nitrogen‐oxygen mixture). The model is compared to experimental results from KIMAB which are presented in this issue. It is demonstrated that a copper layer thickness of 0.098 μm at the steel‐oxide interface is sufficient to cause cracks of a depth of more than 0.2 mm. For strip thicknesses below 5 mm a simple approximation can be used to predict the maximum copper content in LC‐steel to avoid hot shortness. For example, thin strip of a thickness of 2 mm will have no cracks (above 0.2 mm) even if 0.7 wt.‐% of copper is contained in the LC‐steel. For atmospheres with a reduced oxygen partial pressure even higher copper contents are possible.Tin is with short oxidation times not a problem concerning hot shortness, as shown by the KIMAB results. This may be explained by the much higher diffusivity of tin in iron compared to copper.
Mechanical Properties and Bake Hardening Behaviour of two Cold Rolled Multiphase Sheet Steels subjected to CGL Heat Treatment Simulation
Authors: Krieger Markus , Estrin Yuri , Janeček Miloš , Niemeyer Matthias , Paul Silke 
Published: December 2016

In recent years, multiphase steels have become a material of choice for use in the car manufacturing industry owing to their excellent mechanical properties. It is anticipated that in the years to come these steels will show the highest increase in usage. A particular aspect of their potential is that multiphase steels often show good bake hardening (BH) properties. The main factors that govern the microstructures and the properties of these steels are the chemical composition and the production process parameters.In this work two commercial cold rolled sheet steels with different carbon content were investigated. In order to produce dual phase (DP) steels with a ferrite‐martensite microstructure, the as‐received material was subjected to heat treatment simulating continuous galvanising line (CGL) cycles with an overageing zone before the zinc pot. After a first CGL cycle predominantly ferritic microstructures with small amounts of martensite, pearlite and retained austenite were obtained, which resulted in deviations from typical DP properties, e.g. in the occurrence of discontinuous yielding. A higher line speed led to improved mechanical properties. BH prestrain was varied between 0 and 10%. While only very little bake hardening was observed without prestrain, with increasing prestrain the amount of BH was evolving quickly towards larger values of more than 60 MPa. Generally, the BH values were somewhat larger for higher carbon content. Finally, an optimised CGL cycle was simulated at laboratory scale with changes in the process parameters. Thus, characteristic DP microstructures resulting in desired mechanical properties were obtained. For these optimised conditions, BH2 values in excess of 60 MPa were achieved for both steels investigated.
Cold Simulation of Metalloids Transport in Blast Furnaces
Authors: Mukherjee Kakali , Prakash Swantantra , Sinha Sharda N. , Mehrotra Surya P. 
Published: December 2016

Metalloids normally get transferred at the interface of metal droplets passing through the slag system in the dropping zone and at the slag‐metal interface in the hearth zone in the lower region of a blast furnace. In these high temperature processes, the mass transport being the rate‐controlling factor, the viscosity of the slag system determines the kinetics of the refining reactions accompanied by mass and heat transfer at the metal droplets and slag interface. Slag systems generally possess random network structures comprising internal regions of weak ordering. The presence of these regions may result in non‐Newtonian behaviour of the slag. The rheological characteristics of a fluid relating to its network structure is expressed in terms of the indices consistency (k') and flow behaviour (n').The extent of metalloids presence in hot metal is subjected to their residence time at the slag‐metal interface. The metal droplet descent through a surrounding fluid system has been studied and a co‐relation between drag Reynolds number and modified Reynolds number has been obtained. This correlation has been used to determine the drag velocity of a metal droplet falling through a slag system and the residence time distribution (RTD) of the metalloids at the slag‐metal interface in the lower region of the blast furnace.
Concussion reporting, sex, and conformity to traditional gender norms in young adults
Authors: Kroshus Emily , Baugh Christine M. , Stein Cynthia J. , Austin S. Bryn , Calzo Jerel P. 
Published: December 2016

ABSTRACTThis study assessed whether between‐sex differences in concussion reporting intention and behavior among young adults are explained by the extent to which the individual conforms to traditional masculine norms that often characterize contemporary sport culture. A survey of college athletes in the United States (n = 328) found greater symptom reporting intention among females as compared to males, but no difference in their likelihood continued play while experiencing symptoms of a possible concussion. Greater conformity to the norms of risk‐taking was associated with greater likelihood of continued play while symptomatic among female athletes but not among male athletes. These findings suggest that gendered behavior, rather than biologically determined sex, is an important consideration for concussion safety in this age group. Addressing elements of the contemporary sport ethos that reinforce risk taking in service of athletic achievement may be a relevant direction for interventions aimed at improving injury reporting among all athletes.