bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of liquidus temperature of low and high alloyed iron base melts from their chemical composition by means of the equivalence factors
Authors: Schürmann Eberhard , Djurdjevic Mile , Nedeljkovic Ljubomir 
Published: December 2016

Liquidus temperature of a steel is calculated from its chemical composition according to the so far proposed procedures by simply summing up the iron melting point lowering effects of all in the steel contained elements Xi, as they are given by approximating the iron liquidus curves with the straight lines in the corresponding binary Fe‐Xi systems. The intensification of the iron melting point lowering effect with the increasing concentration of each element contained in the steel has not been at all or only partly taken into account in this approach. This is the reason why the calculated steel liquidus temperatures are not accurate enough.In the here proposed new calculation procedure the iron melting point lowering effect of an alloying element Xi is first translated into an equivalent effect of carbon in the Fe‐C system by converting the concentration of Xi into an equivalent concentration of carbon taken as a reference element. The carbon equivalent iron melting point lowering effect of all elements contained in the steel including carbon is then evaluated by summing up the calculated equivalent carbon concentrations of all elements together with carbon into a fictitious total equivalent carbon concentration. A so calculated total equivalent carbon concentration has made it possible to determine with a good accuracy the steel liquidus temperature along the stable δ/α or γ liquidus lines in the Fe‐C system. The success of a melting point calculation is strongly dependent on the accuracy of the equivalence factor equations for each alloying element. They are derived by relating the iron liquidus line in the binary Fe‐Xi system to that in the Fe‐C phase diagram.
Modelling of oxygen activity in Fe‐Ni‐Cr melts
Authors: Laag Thomas , Ohser Joachim , Janke Dieter 
Published: December 2016

The subject of this study is the thermodynamics of oxygen dissolved in Fe‐Ni‐Cr liquid alloys. The introduced model is based on a power series to express the logarithm of the activity coefficient of oxygen.The activity coefficients have been computed from experimental data found in literature. With the help of the described model it is possible to predict the activity coefficient for an arbitrary composition of the Fe‐Ni‐Cr melt and for temperatures between 1525 and 1625°C. The results are compared with data published in literature. The analytical description of the activity coefficient widely agrees with the available experimental data.
UV/VIS‐spectroscopy of aluminates in liquid and solid oxide slags
Authors: Mausbach Klaus , Nowack Norbert , Schlegelmilch Franz 
Published: December 2016

Structural information of liquid oxide melts including statements concerning their basicity are important not only for the metallurgy of steelmaking but also for the refractory industry, for ceramic productions and for glass manufacturing. After the introduction of infrared emission spectroscopy of liquid melts up to 1600°C it is now possible to receive UV/VIS‐spectra of these melts in different atmospheres. The comparison to already published spectra is possible by recording spectra of quenched samples at room temperature with the same optical system as the high temperature ones.The suitability of the Fe‐ and Cr‐Ions as test‐ions for the indications of the features of liquid aluminate melts is discussed. A new spectroscopical method for the investigation of melts above 1450°C was developed. Octahedral‐coordinated Fe3+ causes intensive charge‐transfer (CT) absorptions in the melts. These CT‐bands shift towards higher wavelengths and get broader and more intensive at higher temperatures; the results are discussed by the use of the Urbach‐approximation. The CT‐bands of Cr(VI) are attached to various chromate species. The properties of liquid silicates will be the subject of a later investigation.
Precipitation of titanium nitride in low‐alloyed steel during solidification
Authors: Kunze Joachim , Mickel Christine , Leonhardt Monika , Oswald Steffen 
Published: December 2016

The microsegregation of titanium and manganese and the precipitation of titanium nitride during dendritic solidification were investigated on an Fe‐0.051%Ti‐0.77%Mn alloy. Carbon and nitrogen were introduced into the liquid sample via the gas phase. The material solidifies as delta ferrite at a carbon mass content of about 0.08% but predominantly as austenite at ≥ 0.3%.At ferritic solidification, an about 3fold enrichment of the titanium in the residual melt between secondary dendrite arms is attained by segregration, whereas in the corners between some dendrites or grains in maximum a 10fold enrichment was detected. TiN particles of 0.5 to 1.0 μm size are formed only in the regions of maximum segregation where the supersaturation is higher than 15fold. An equal supersaturation has been calculated for homogeneous nucleation in the melt. The number of particles is moderate at 0.016% nitrogen but low at 0.008%.At austenitic solidification, the titanium content in the residual melt increases to more than the 30fold of the starting value. Particles formed in the melt grow to diameters in the 2 μm range.
Prediction of the measured temperature after the last finishing stand using artificial neural networks
Authors: Vermeulen Willem , Bodin Andre , van der Zwaag Sybrand 
Published: December 2016

In this report the development of an artificial neural network, capable of predicting the temperature after the last finishing stand of a hot strip mill for a certain class of steels, is described. Three neural networks with different numbers of hidden nodes (3, 5 and 7) were trained. The relative standard deviation in finish temperature as predicted by the best performing neural network model (7 hidden nodes) was just over 25% smaller than that of the linear Hoogovens model. This improved accuracy can be explained by the incorrect assumption in the Hoogovens model of linear dependence of the finishing temperature on some input parameters.With the trained neural network, the influence of the various input parameters on the finishing temperature could be examined. The dependencies predicted by the neural network can be approximated by a linear fit and are a factor 2 lower for all input parameters.It is conceivable that operation of the mill using an artificial neural network for the prediction of the finishing temperature would have resulted in smaller operational fluctuations.
Final solidification, centre segregation and precipitation phenomena in continuously cast round billets
Authors: Jacobi Hatto , Wünnenberg Klaus 
Published: December 2016

Archimedes’ principle was applied to strand lengths of up to 14 m of round 177 mm diameter billets to determine cavity volume V (in cm3/m) for a series of tubemaking steels. Under steady state casting conditions, V depends primarily on the chemical composition and solidification behaviour of the steels. Averages ranged up to in an extreme case (bearing steel; vC = 2.0 m/min). Stopping the strand and abrupt lowering of withdrawal speed made it possible to artificially induce individual shrinkage cavities with peak values of V = 45 cm3/m. In the round mould, subsequent necking of the liquid crater is initiated in this process. Whisker‐like and icicle‐like dendrites can be observed in horizontally formed macroscopic shrinkage cavities.The liquid crater is broken off by periodic bridging (the mini‐lingot model). As permeability decreases, the bridges deflect downward in a U‐shape under the ferrostatic load. The residual inter‐dendritic melt is squeezed out in this plastic deformation process. Some bridges ultimately break. This interpretation is based on comprehensive CMA studies and concentration maps.Cores taken from the centre of a strand of bearing steel were submitted to various heat treatments between 1100 and 1350°C. Homogenization occurs below solidus (T < 1225°C). Carbides dissolve and sulfides become globular. Spatial segregation, on the other hand, increases, above solidus. In the extreme case at 1350°C/30 h, the residual melt at the grain boundaries migrates practically completely from the surface zone to the centre of the cylindrical sample (40 mm diameter). The propellent forces for this macro‐heterogenization are provided by the activity gradient from the cylindrical surface to the centre and minimization of interface energy γ/I.
Circulation rate of liquid steel in RH degassers
Authors: Ahrenhold Frank , Pluschkell Wolfgang 
Published: December 2016

Vacuum‐decarburization with the Ruhrstahl‐Heraeus process is used for the production of ultra‐low carbon steels. One important aspect of the RH process is the circulation of liquid steel between the degassing unit and the transport ladle. Thus, supervisory control of the RH treatment requires precise mathematical modelling of the circulation rate. In this work, a numerical model of the circulation flow is described in detail.This newly developed model as well as a frequently used semi‐empirical equation are compared with measured data. It is shown that the numerical model is in far better accordance with the measured data than the semi‐empirical equation. The numerical model is then applied to data of a conventional RH treatment. Special emphasis is put on the coupling of circulation rate and reaction rate. Both, circulation rate and reaction rate, are calculated as a function of time.
Analysis of the motion of a flat jet in a direct strip casting feeding system
Authors: Holmberg N. Anders , Åkerstedt Hans O. 
Published: December 2016

The motion and shape of a vertically falling flat rectangular jet of liquid metal issuing from an inclined plane is analysed numerically and analytically. The jet is affected by surface tension and gravity. The main interest in this problem originates from the technological application of the direct strip casting process, which is a novel process to cast steel strips in a thickness range from 2 to 15 mm with a minimum or no hot‐rolling. In this process the liquid metal is fed onto a single endless horizontal belt that runs between two rollers. The bottom of the belt is cooled by water. One of the techniques to feed the liquid metal is down an inclined plane. Due to disturbances in the flow, for instance slag in the liquid metal, the jet issuing from the inclined plane may split into two or several jets. The large convergence of the individual jets causes an unfavourable non uniform distribution of the liquid metal over the belt.In the analysis of the present paper it is shown, using an expansion in the inverse Froude number, that the convergence of a single jet depends to zero order on the inverse square root of the Weber number We−1/2 = (γl(ρw02 h0))1/2. Small convergence of the jet is found for large Weber numbers, which can be accomplished with a large initial velocity w0.
Thermoelectric properties of the Fe‐Al and Fe‐Al‐Si alloys for thermoelectric generation utilising low‐temperature heat sources
Authors: Ono Katsutoshi , Kado Masaki , Suzuki Ryosuke O. 
Published: December 2016

The iron is intrinsically a p‐type conductor. When aluminum with three valence electrons is added to the iron, the d‐subbands are occupied by electrons, so alloying with the aluminum transforms the iron to the n‐type conductor, hence the p‐n junction is made possible. Furthermore, when silicon is added to the n‐type Fe‐Al alloy, this alloy returns to the p‐type conductor. Therefore, the thermoelectric p‐n junctions with high thermoelectric power have been recognised (figures in % refer to mass contents):Fe(p) – Fe12%Al(n): α=38μV/K and Fe12%Al12%Si(p) – Fe12%/Al(n): Δα=70μV/K.Thermoelectric generation offers the possibility of a gigantic electric power generation utilising low‐temperature sources of energy below 700 K such as exhaust heat from the central‐station steam‐electric plant, solar heat and terrestrial heat. The immense production of electricity by this principle is made possible exclusively by means of the conversion materials consisiting of the iron and iron‐based alloy because the generator can be manufactured on an efficient mass production basis, and the alloys mentioned above will meet this requirement. In this paper, the thermoelectric properties of these alloys such as Seebeck coefficient, thermal conductivity and electrical resistivity were experimentally determined in the temperature range between 300 and 700 K to provide basic data on the conversion materials with respect to the thermoelectric generation utilising low‐temperature heat sources.
Modelling steel flow in a three‐strand billet tundish using a turbulence inhibitor
Authors: Morales Rodolfo D. , Díaz‐Cruz Manuela , Palfox‐Ramos Jorge , López‐Ramírez Simón , de Jesús Barreto‐Sandoval José 
Published: December 2016

A three‐strand tundish belonging to a billet caster was water modelled and plant trials were performed to compare the performance of a pouring box and a turbulence inhibitor in terms of melt flow parameters and steel cleanliness.A tailor made turbulence inhibitor for this tundish is useful to accomplish with flow control of fluid turbulence and even melt redirection to all strands. The turbulence inhibitor helps to decrease nitrogen pickup during ladle changes and to float out inclusions towards the covering slag. As a consequence, rod operations to take of alumina deposits from nozzle walls are considerably decreased using a turbulence inhibitor.
Thermodynamic and kinetic aspects of the desulphurisation reaction in secondary metallurgy
Authors: Lachmund Helmut , Xie Yongkun , Harste Klaus 
Published: December 2016

The desulphurisation of liquid steels with a refining ladle top slag is one of the most important processes of secondary metallurgy. But the process control is even now based on empirical rules. Deviations from the sulphur contents aimed at can often be observed in practice. An improvement of the process control supported by knowledge of the thermodynamics and kinetics of the desulphurisation reaction is of great importance, especially for the production of steels with very low sulphur contents.To investigate the removal of sulphur, operational trials were carried out in 185 t steel ladles. In the trials the stirring gas flow rate, the pressure on the bath surface and the steel composition were varied as process parameters. The obtained results show that ladle slags saturated with lime have a high sulphide capacity. The desulphurisation rate of steel melts increases if the specific stirring energy is enhanced by increasing the gas flow rate or reducing the pressure on the bath surface. In the case of production of Al/Si‐killed steel melts, a desulphurisation degree above 90 % can be obtained by a vacuum treatment within 10 minutes.
Prediction of the size distribution of precipitates
Authors: Prikhodovsky Andrey 
Published: December 2016

Modelling has proven to be an efficient way of cutting the time and costs associated with the investigation of materials properties. A new mathematical model for the prediction of the particle size distribution of precipitates has been developed. The model allows the description of all stages of the precipitation process: nucleation, growth and Ostwald ripening of particles. The incorporation of existing thermodynamic databases allows the simulation of a formation of dispersed phases in commercial multicomponent alloys.The influence of the model parameters on the final particle size distribution was investigated with the example of NbC formation in austenite. It was shown that the interfacial energy of a particle‐matrix interface has the most significant effect on the final particle arrangement. A pre‐exponential factor, which is the subject of nucleation theories, plays a less significant role in the final particle arrangement.
The properties and production of iron‐coated burnt lime
Authors: Lee Mark , Barr Peter 
Published: December 2016

Ferruginous lime is the name given to burnt lime (CaO) coated with di‐calcium ferrite (2CaO·Fe2O3). Its high degradation strength, its resistance to hydration and its capacity for fast and complete solution of fluxes in the BOF and EAF make it extremely attractive as a steelmaking flux.The objectives of the present work were to assess the feasibility of producing ferruginous lime in a rotary‐kiln‐type reactor and to determine the operating conditions favourable both for the formation of a hydration resistant product and the minimisation of problems such as accretions and agglomerations within the reactor.With respect to processing conditions, the trials suggest that ferruginous lime should be generated using a peak reaction temperature of 1260 °C and allowing 45 min at greater than 1200 °C. The optimal oxide addition is 10 % (referring to mass contents) of the limestone charge to the rotary lime kiln.When subjected to short duration hydrating conditions i.e. 30 min in contact with steam at 100 °C (as per ASTM specification X6) the ferruginous lime product exhibited good resistance to hydration (relative to pure CaO) and moderate physical degradation. Laboratory tests demonstrated the significantly enhanced rate and degree of dissolution of ferruginous lime (cf. uncoated lime) in a steelmaking slag.
A computerised kinetic database system for metallurgy and materials processing
Authors: Zhang Jiayun , Liu Jianhua , Luo Shiyong , Shi Dongpe 
Published: December 2016

An integrated and computerised kinetic database system, intellectualised database management system on kinetics of metallurgy (IDMSKM) is described in this report. IDMSKM has been designed using MS Windows and a Visual C++ and Foxpro hybrid coding technique. It consists of two packages. The ThermoPhysData package has been established for physical property data retrieval and prediction, and presented in a previous publication in steel research. The emphasis in the present paper is placed on the KineticApp package. KineticApp involves G/S, S/S' and G/L' modules for the kinetic prediction, evaluation and analysis of gas/solid, solid/solid and gas/liquid reactions respectively. The key consideration in the module design is to establish the links of the kinetic model and parameters of a reaction system with the system characterisation. Assessed kinetic parameters stored in the database files in KineticApp include the activation energies for some reduction and decomposition reactions, as well as the diffusion in solid oxide systems.Those data are necessary while dealing with the reaction kinetic prediction problems. Several examples regarding the reduction of wustite pellet, the decomposition of CaCO3 and the synthesis of SrTiO3 are illustrated to show the features and functions of G/S and S/S modules.
Structural Superplasticity at High Strain Rates of Super Duplex Stainless Steel Fe‐25Cr‐7Ni‐3Mo‐0.3N
Authors: Frommeyer Georg , Hofmann Harald , Löhr Jens 
Published: December 2016

The fine‐grained super duplex stainless steel Fe‐25Cr‐7Ni‐3Mo‐0.3N consisting of two phases (δ‐ferrite/austenite) exhibits structural super‐plasticity at higher strain rates of έ ≈ 10−2s−1 in the temperature range between 975 and 1100°C. The equiaxed microstructure with an average grain size of was produced by thermomechanical processing. Maximum strain‐rate‐sensitivity exponents of m ≈ 0.5 and elongations to failure of more than 500% were achieved. From thermal activation analysis an activation energy for superplastic flow of Q = 310 ± 20 kJ/mole was derived.The superplastic behaviour at higher strain rates is quantitatively described by a deformation model where grain or interphase boundary sliding is accommodated by sequential steps of dislocation glide and climb. The high strain‐rate‐sensitivity exponent and the observed dislocation density indicate that dislocation climb in the slightly solid solution strengthened austenite is the rate controlling step for superplastic flow. The deformation mechanism reveals that the investigated super duplex stainless steel exhibits superplastic behaviour that is typical for class II solid solution alloys.
Application of the Master Curve Approach for the Irradiation Embrittlement Evaluation of Pressure Vessel Steels
Authors: Viehrig Hans‐Werner , Böhmert Jürgen 
Published: December 2016

The Master Curve (MC) approach and the associated reference temperature, T0, as defined in the test standard ASTM E1921, is rapidly moving from the research laboratory to application in integrity assessment of components and structures. T0 is the index temperature for the universal MC, which considers the toughness behaviour of a specific material. “The Structural Integrity Assessment Procedures for European Industry” (SINTAP) contain a MC extension for analysing the fracture behaviour of inhomogeneous ferritic steels. This paper presents the application of the MC approach to the T0 determination of different types of Russian WWER‐type reactor pressure vessel (RPV) steels. In addition the SINTAP‐MC approach was applied to determine an alternative reference temperature, TR.The influence of different microstructures and compositions within one type of RPV steel and the effect of irradiation with fast neutrons on T0 are experimentally evaluated. In general the MC based T0 is about 72 K below the Charpy V‐notch transition temperature related to an impact energy of 48 J. The paper demonstrates the application of MC based T0 and TR as an alternative reference temperature for neutron embrittled RPV steels used in the RPV integrity assessment.
Semi‐Solid Processing of Metal Alloys
Authors: Aguilar Julio , Fehlbier Martin , Grimmig Tilman , Bramann Horst , Afrath Carsten , Bührig‐Polaczek Andreas 
Published: December 2016

Semi‐solid metal casting is an innovative technology for the production of near‐net‐shape parts with demanding mechanical properties. The paper describes different processing routes and materials for semi‐solid‐metal casting (SSM), which have been investigated and also partially developed at the Foundry‐Institute of Aachen University.The standard thixocasting process for aluminium, highly reactive magnesium alloys and steel alloys with high melting points was investigated under variation of a wide range of process parameters. Specially adapted pre‐material production and reheating methods were developed for different materials and their application and future potential is pointed out. The thixocasting experiments were executed on a modified high pressure die‐casting machine with a specially designed “step‐die” providing wall thicknesses from 0.5 to 25 mm. The mechanical properties were tested in dependence of the wall thickness and the metal velocity. The results of these examination show high tensile strength values in combination with very good elongations.The rheocasting process is a new SSM‐forming method with liquid melt as feed‐stock and a high recycling potential. The research results of RCP‐technology (Rheo‐Container‐Process) invented at the Foundry‐Institute and of the Cooling‐Channel‐Process for aluminium and magnesium alloys are promising and are presented in this paper.Studies on semi‐solid processing of magnesium alloys and mixtures of them were conducted by ThixomoldingTM. To establish the most adequate process parameters, the temperature and the mixture relations were varied. Using a mould for tensile test specimens, the mechanical properties and the microstructure evolution could be evaluated. The chemical composition of the different phases was determined using SEM and EDX technologies. Evaluations of the flowing properties were conducted using a spiral mould with a total length of 2m and a cross section of 20mm x 1.5mm.