bluuebunny/crossref_metadata_2025 huggingface dataset:
Possible failure of emf oxygen sensor in liquid iron containing dissolved calcium or magnesium
Authors: Turkdogan Ethem Tugrul
Published: December 2016

The solubility products of CaO and MgO in liquid iron, measured using the emf oxygen sensor, are several orders of magnitude greater than those calculated from the thermochemical data. This would imply that the values of Δ and Δ derived from the solubility products are, by a large amount, less negative than those given in the compiled thermochemical tables. As is shown in this paper, the values of Δ derived indirectly from numerous experimental data on various gas‐solid (‐liquid) reactions involving pure CaO, are in general accord with the compiled thermochemical data. It is surmised from these observations that the oxygen activities in liquid iron saturated with CaO or MgO, measured by the emf cell, giving high solubility products of CaO and MgO, may be attributed to the failure of the emf oxygen sensor in liquid iron containing dissolved calcium or magnesium. Two reaction mechanisms are discussed in the paper to account for the malfunction of the oxygen sensor under highly reducing conditions, which will prevail in liquid iron containing even a small amount of dissolved calcium or magnesium. These two mechanisms are (i) redox reaction at the (Y2O3)ThO2 electrolyte/melt interface and (ii) oxygen flux through the electrolyte from the reference electrode Cr–Cr2O3 to the melt/electrolyte interface. Suggestions are made for some experimental work to confirm or refute the argument presented in this communication.
Estimation of partial excess Gibbs energy of solutes in infinitely dilute liquid iron base binary alloys
Authors: Tanaka Toshihiro , Gokcen Nev A. , Neuschütz Dieter , Spencer Philip J. , Morita Zen‐ichiro
Published: December 2016

The partial excess Gibbs energy ΔḠBEx as well as the relationship between the partial enthalpy of mixing ΔH̄B and the partial excess entropy of solution ΔS̄BEx of various solute elements in liquid Fe, Al and Pb binary alloys were evaluated from a new solution model, in which ΔS̄BEx can be calculated from the values of ΔH̄B by Miedema's semi‐empirical method and some relevant physical properties of the components in the alloys. These calculated values of ΔḠBEx were found to be in reasonable agreement with the selected values presented so far. The present model gives the values of ΔḠBEx, for which the experimental data are not yet available.
Entwicklung, Eigenschaften und Anwendung von konventionell erzeugten hochstickstoffhaltigen austenitischen Stählen
Authors: Gillessen Christoph , Heimann Winfried , Ladwein Thomas L.
Published: December 2016

Durch legierungstechnische Maßnahmen lassen sich mit konventionellen Verfahren (Elektrolichtbogenofen, AOD‐/VOD‐Anlage) hochstickstoffhaltige austenitische Stähle erzeugen, die im lösungsgeglühten Zustand beachtliche Eigenschaften aufweisen. Die Wirkungen des Stickstoffs sind eine Erhöhung der Festigkeit durch Mischkristallverfestigung (und Auscheidungshärtung bei Amagnit 3974 (X 3 CrNiMnMoNbN 23 17 5 3)), eine Erhöhung der Austenitstabilität, die Verzögerung von Ausscheidungsvorgängen sowie eine Verbesserung der Loch‐ und Spaltkorrosionsbeständigkeit.

Nach der Entwicklung von hochfesten unmagnetischen Stählen führte die Legierungsoptimierung zu dem Werkstoff Remanit 4565 S (X 2 CrNiMnMoN 24 17 6 4), der bei hoher Festigkeit eine ausgezeichnete Beständigkeit in zahlreichen Medien aufweist. Aufgrund des günstigen Einflusses von Stickstoff weist dieser Stahl mit nur 4,5 % Molybdän eine höhere Wirksumme PRE und eine höhere Beständigkeit gegen Loch‐ und Spaltkorrosion auf als die gängigen 6%‐Mo‐Austenite. Das Schweißen der beschriebenen hochstickstoffhaltigen Stähle ist ohne besondere Vorkehrungen mit allen üblichen Verfahren möglich. Porenbildung tritt nicht auf. Mit dem empfohlenen Schweißzusatz Thermanit NimoC (SG‐NiCr 20 Mo 15) lassen sich mit dem WIG‐ und dem UP‐Schweißen an Remanit 4565 S (X 2 CrNiMnMoN 24 17 6 4) Verbindungen herstellen, die ebenso beständig gegen Loch‐ und Spaltkorrosion sind wie der Grundwerkstoff. Somit steht mit Remanit 4565 S (X 2 CrNiMnMoN 24 17 6 4) eine vielseitige wirtschaftliche Alternative zu 6 %‐Mo‐Stählen und Nickelbasislegierungen zur Verfügung.
Physical properties in the temperature range from –180 to 400°C of nickel alloy steels for low‐temperature applications
Authors: Richter Friedhelm , Hemminger Wolfgang , Hanitzsch Erich
Published: December 2016

Nickel, which is the second neighbour to iron in the periodic table of elements, has a significant effect on most of the physical properties of the steels studied here, with the nickel content of the steels varying between 3 and 9%. Density and coercive force increase as the nickel content in the steel increases. By contrast, thermal expansion, modulus of elasticity and shear modulus decrease with increasing nickel content.

Because of large scatter in the data, it is not possible to notice any significant influence of nickel content on Poisson's ratio and bulk modulus. Specific heat is also found not to vary with the nickel content of the steel. Electrical resistivity and thermal resistivity values increase, as expected, with increasing nickel content. The results of thermal conductivity measurements on 12 Ni 19 and X 8 Ni 9 have led to the development of modified Smith‐Palmer relationships, which allow the calculation of the thermal conductivity values for the present set of steels and other steels with similar compositions.
On the effect of discontinuous decomposition on the structure and properties of high‐nitrogen steels and on methods for suppression thereof
Authors: Bannykh Oleg Alexandrowich , Blinov Victor Michailowich
Published: December 2016

The features of discontinuous decomposition in high‐nitrogen austentitic steels are considered. Structure and formation kinetics of pearlite‐like colonies of “the austenite‐with‐equilibrium‐nitrogen‐content – Cr(M)2N nitride” are discussed. The discontinuous decomposition of nitrogen supersaturated austenite is shown to effect harmfully the mechanical properties of the steels studied. To suppress the harmful effect of the discontinuous decomposition of the austenite the four methods are proposed as follows: use of vanadium as an alloying element, high‐temperature thermomechanical treatment, production of a “microduplex” type structure and granule technology.
Experimental studies on the flow velocity of molten metals in a ladle model at centric gas blowing
Authors: Xie Yongkun , Oeters Franz
Published: December 2016

Experimental measurements of the flow velocity were carried out with liquid Wood's metal in a ladle‐shaped vessel with an inner diameter of 40 cm at centric gas blowing. By means of permanent magnet probes the liquid flow field was measured under various blowing conditions. The results show that a circulating flow field is established in the vessel. In the bubble plume zone an upwardly directed liquid flow is formed. The radial distribution of the flow velocity in this zone follows a Gaussian function. The axial flow velocity increases with growing gas flow rate and is nearly constant in vertical direction. The width of the upward flow becomes larger with increasing distance from the nozzle and its dependence from the gas flow rate is not considerable. At centric gas blowing the liquid in the upper part of the bath streams quickly, whereas in the lower part so‐called “dead zones” with very low flow velocity are present.

Besides the time‐averaged value of the flow velocity, the turbulent behaviours of the liquid flow such as fluctuation velocity, the turbulent kinetic energy and its dissipation rate were investigated on the basis of measured data. It was found that the liquid flow is turbulent particularly in the region of bubble plume and of bath surface. The radial profiles of these parameters can also be described by a Gaussian function. Only a small part of the gas stirring energy is changed into the kinetic energy of the directed liquid flow. Most of the stirring energy is already dissipated in the bubble plume zone.
The effects of triaxial stress on void growth and yield equations of power‐hardening porous materials
Authors: Kong Xianming , Zhao Hualing , Holland Dirk , Dahl Winfried
Published: December 2016

In engineering applications, especially for ductile fracture of materials, nucleation, growth and coalescence of voids have often been observed. Currently there is an increase in interest for the effects of voids on the behaviour of engineering materials. In this paper, by the method of combining micro‐ and macro‐parameters, the effects of triaxial stress on the rates of void growth and yield equations are presented for porous materials with power‐hardening. The relations between triaxial stress and the rates of void growth for different n‐values and yield equations with different n‐values and void volume fractions are discussed. Following results have been obtained: For a porous material with power‐hardening, the yield equation can be approximately expressed by an elliptical equation in equivalent stress and triaxial stress. Both the long half‐axis and the short half‐axis of the elliptical equation are functions of the void volume fraction for a given hardening exponent. The triaxial stress has a strong effect on the growth rates of voids. For linear hardening materials, the relation between the growth rate of voids and the triaxial stress is linear. For elastic/perfectly plastic materials with a small void volume fraction, the growth rate of voids can be described in relation to the triaxial stress with an exponential function. The results from this paper are compared with theoretical results from other researchers for elastic/perfectly plastic materials. A good agreement is shown.
Reanalysis of solidification behaviour from the microstructure in near‐net‐shape casting of steels
Authors: Thiem Steffen , Löser Wolfgang
Published: December 2016

Numerical calculations revealing the relationship between the as‐cast structure and cooling conditions in near‐net‐shape casting of steels are presented. The solidification behaviour of steels of different composition was investigated for different process conditions with a one‐dimensional heat‐flow model. The dependence of the secondary dendrite arm spacing (SDAS) on the distance from the chill surface was determined on the basis of the empirical relationship between local solidification time and SDAS. The numerical results were compared with experimental values of SDAS for a stainless steel, a carbon tool steel and a high‐speed steel, resp. Reasonable agreement of model calculations with the experimentally determined SDAS was obtained utilizing time‐dependent effective heat‐transfer coefficients of the order of 2.5 to 4.5 · 103 W/m2K for typical thin‐slab dimensions and 6.0 · 103 W/m2K for thin‐strip casting.
Formation of pearlitic banded structures in ferritic‐pearlitic steels
Authors: Großterlinden Rolf , Kawalla Rudolf , Lotter Ulrich , Pircher Hans
Published: December 2016

The conditions for ferrite and pearlite banding in strip and plate made of structural steels were investigated. Factors found to influence the formation of banded structures were the cooling rate during the γ/α‐transformation, the former austenite grain size, and the work‐hardened condition of the former austenite. Analyses with the aid of an electron beam microprobe made it possible to demonstrate that the carbon‐rich bands correspond locally with banded manganese enrichments, yet that they do not form before the course of the γ/α‐transformation as a result of secondary segregation. It was possible to explain the mechanism of action of the influencing factors on the basis of this model.
Model study for subsurface trajectory of 75FeSi and SiMn ferroalloys in steel
Authors: Lee Young Eun , Tveit Halvard , Guthrie Roderick Ian Lawrence
Published: December 2016

The present study, using a low temperature model, is aimed at examining the feasibility of subsurface melting of 75FeSi and SiMn alloys added to steel baths. Wooden objects, simulating 75FeSi and SiMn of various sizes and shapes, were prepared so as to have same density ratio of 75FeSi and SiMn to steel, and their subsurface trajectories in water or zinc chloride solution following three meters of free fall through air were analyzed using video images. In general, subsurface retention times were observed to gradually increase with size of object up to a steady value. For those objects simulating 75FeSi, it was found to be dependent on shapes, spherical objects having longer retention times. The effect of shape was less pronounced for objects simulating SiMn. In a gas stirred bath, smaller cuboids for SiMn were entrained. Comparisons with estimated melting times of 75FeSi suggest that regular sized 75FeSi (ex. 20 to 50 mm) will float up and melt at the surface, when dropped to the steel bath in a ladle. A similar situation is expected with SiMn alloys. Subsurface melting may be feasible by reducing the size of 75FeSi addition from 1 to 5 mm dia. and of SiMn down to about 10 mm while simultaneously applying sufficient turbulent mixing of steel bath or providing entraining downflow velocities in the range of 10 to 30 cm/s.
Physical parameters and boundary conditions for the numerical simulation of hot forming processes
Authors: Kopp Reiner , Philipp Franz‐Dieter
Published: December 2016

Exact simulation of hot‐forming processes using the finite element method requires the most precise possible specification of the material parameters and physical boundary conditions prevailing in each case. The report presents a method to supply all the necessary data. New experimental concepts have been developed and applied, particularly for the more complex boundary conditions, which are virtually undocumented in literature. These techniques permit analysis of the real workpiece/interlayer/die combination, supplying reliable data for an FEM simulation.
Development of a reduction process and test results of the reduction equilibria of wustite as a function of oxygen content and temperature
Authors: Schürmann Eberhard , Janhsen Urban , Beppler Erhard
Published: December 2016

A new measurement technique allows the continuous measurement of the oxygen contents of the wustite as a function of temperature without having to pass through the disintegration of the wustite to iron and magnetite and have the accompanying problems during the chemical analysis by cooling the sample. Measurements are carried out in form of isothermal oxygen reduction tests, starting with pure Fe2O3in a thermogravimetric balance with an upstream gas mixer which, operating with CO2/CO gas mixtures, ensures a graduation of the input reduction potential CO'2in steps of 1%. Simultaneous weighing of the test material sample permits, by means of the measured weight loss and relation to the charged amount of Fe2O3, a very accurate measurement of the oxygen concentration within the test material at any point in time during testing. Testing was carried out along these lines in the range between 700 and 1300°C. The results show that, at constant temperatures, the wustite oxygen contents decrease linearly from the right‐ to the left‐hand boundary of the wustite field, with the oxygen pressure of the gas phase (logpCO2/pCOor logpO2). When comparing these results with the findings of Darken and Gurry, a difference becomes apparent in the curves of the logpO2values as a function of the temperature. While our own curves are substantiated by very many measured values, the curves of Darken and Gurry are based on only twenty‐three values at four different temperatures. Based on this result, systems of equations are developed which describe the homogeneous field of the wustite in the Fe‐O‐C reduction system without any gaps. An equivalent system of equations can also be developed from the values of a literature evaluation carried out by Giddings and Gordon. The curves resulting from the two equations do not differ very greatly. But the differences are large enough for corresponding variances to be expected when establishing the wustite boundaries and, thus, the position of the wustite field in the phase diagram.
Study of the oxidation protection of MgO‐C refractories by means of boron carbide
Authors: Rymon‐Lipinski Tadeusz , Fichtner Ralf , Benecke Theodor
Published: December 2016

Boron carbide is used as a highly effective antioxidant in carbon‐containing refractories. The oxidation‐inhibiting action of this additive has not been clearly defined. The work first deals in theory with the stability of boron carbide at high temperatures. The practical section presents the reaction sequence as determined by means of thermogravimetric analysis and X‐ray diffraction analysis. The tests showed that B4C oxidizes during firing at below 1000°C, to give magnesium borate (3 MgO · B2O3), which is stable at high temperatures.
Thermodynamics of nitrogen in CaO‐TiO2‐TiO1.5 slags
Authors: Tanabe Jun , Suito Hideaki
Published: December 2016

The nitride capacities in CaO‐TiO2‐TiO1.5 slags, and nitrogen distribution ratio between these slags and liquid Cu (LN = (mass‐% N)/[mass‐% N]) were measured by a gas‐slag‐metal equilibration technique, using a Mo crucible in the temperature range of 1823 to 1923 K under controlled partial pressures of oxygen and nitrogen . The values for , (mass‐% Ti3+)/(mass‐% Ti4+) ratio, and solubility of TiN in CaO‐TiO2‐TiO1.5 slags were obtained as a function of slag composition (XCaO = 0.24 ∼ 0.39) and temperature. Activity coefficients of TiN were evaluated from the values for activity coefficients of Ti in liquid Cu which were calculated from the results of TiN saturation experiments.
Wetting conditions and microstructural characteristics of a fired B4C‐containing MgO carbon brick
Authors: Rymon‐Lipinski Tadeusz , Fichtner Ralf
Published: December 2016

This investigation is a continuation of the studies of the use of boron carbide as an antioxidant in refractory carbon‐containing materials. The previous studies were concerned with the stability of boron carbide at high temperatures. The present work gives an account of the wetting conditions and microstructural characteristics of a fired MgO‐C brick containing boron carbide additive. The results obtained show that a contribution may be made to the oxidation‐inhibiting protective action of the carbide by the formation of a continuous network of dense bridges of borate melts between periclase grains. A white layer with a high percentage of magnesium borate is produced between the decarbonized and non‐decarbonized material. The nature of this layer is similar to that from secondary MgO in MgO‐C bricks with no additive. The occurrence of this layer is the subject of further research.
Linear contact algorithm for rigid‐plastic finite element simulation
Authors: Tekkaya Ahmet Erman , Şen Abdullah
Published: December 2016

The rigid‐plastic finite element analysis of metal forming processes is known to be much more efficient and stable than the elastic‐plastic one. This efficiency results from the absence of kinematical nonlinearities in the formulation. Contact algorithms used in rigid‐plastic models must agree with this fact, otherwise the efficiency can be damaged seriously.

The aim of this paper is to present a linear contact algorithm designed specially for rigid‐plastic analysis of metal forming problems. The linearization is achieved by dictating constancy of boundary conditions during one increment according to the requirement of the variational principle by Markov. The algorithm consists of two parts: the contact search and the contact control. The procedure has been implemented for two‐dimensional cases. However, the generalization to three dimensions is straightforward.

The efficiency and the stability of the proposed procedure has been validated by means of examples of application such as extrusion and forging. Furthermore, parametric studies of the contact variables have been performed.
Mass transfer in a bottom blowing cold model converter
Authors: Gerlach Friedemann , Frohberg Martin G.
Published: December 2016

In a model converter containing oil and water the volumetric mass transfer of caprylic acid was determined in dependence of the gas flow rate. Several other parameters were varied such as the number and configuration of nozzles, gas velocity, oil viscosity and volume and model size. Partially the results could be described by dimensionless equations. Visual observations of the bath surface with special regard to the wave formation complete the results of the measurements. By knowledge of the drop size spectrum independently determined, the mass transfer coefficient under dispersion conditions could be evaluated. These values were compared with mass transfer coefficients which had been directly measured by the single rising drop technique as well as the bubble stirred interface without dispersion. It seems that turbulence in dispersed systems does not enlarge the mass transfer coefficient.
Hot model experiments of the metal bath spraying effect during the decarburization of Fe‐C melts through oxygen top blowing
Authors: Koch Klaus , Falkus Jan , Bruckhaus Ralf
Published: December 2016

During recent years decarburization has been steadily gaining importance in converter steel metallurgy at the expense of refining reactions for other slag‐forming companion elements. Because decarburization is currently a low‐slag operation, the phase contact between gas and metal is critical. With the decrease in the amount of slag foam, more attention must be paid to the spraying of iron droplets during oxygen blowing.

The experiments were carried out in a hot model reactor with a 50 kg capacity by oxygen top blowing upon Fe‐C melts. The resulting spray of iron droplets was collected with the help of a special droplet sampler in the blowing converter.

In the metal droplets a pronounced enhanced decarburization was found in comparison to the metal bath. The amount of metal spray was determined with respect to the oxygen blowing pressure, nozzle diameter, and distance between the lance and bath. Depending on the reactor contents, a high circulation rate of the droplets could be observed. At low blowing rates, FeO‐slag is formed and sprayed along with the metal.
Mechanisms of dust generation in a stainless steelmaking converter
Authors: Delhaes Carsten , Hauck Alejandro , Neuschütz Dieter
Published: December 2016

The four possible mechanisms of dust formation in converter steelmaking are evaporation of metal, ejection of slag, ejection of metal and entrainment of solids. In order to describe the relation between process operation and dust formation and take appropriate measures to minimize the quantity of dust, more detailed information is needed on the amounts contributed by the different dust generation mechanisms. For their determination, dust samples were taken from the off‐gas during refining of five austenitic heats in a modified 80‐t AOD converter. On the basis of dust, metal and slag analyses and process and product gas flow rates, the contributions of the different dust generation mechanisms were quantitatively determined for blowing step I (pure oxygen blowing) and reduction step R (pure argon blowing). The predominant mechanism is ejection of metal and slag droplets by bursting of bubbles at the bath surface. Dust formation via the vapour phase in AOD steelmaking is of less importance than previously expected, the relative amount is only about 3 %. During the addition of fluxes through the converter mouth, the entrainment of solids plays a role, too.
Recent advances in steel cleanliness
Authors: Höfer Friedrich , Abratis Horst , Geck Hans‐Günter , Patel Pervez
Published: December 2016

At Klöckner Edelstahl in Georgsmarienhütte improvements in steel cleanliness mentioned in this report were concentrated on the tundish and pouring channel. Sealing of the tundish with inert gas curbed reoxidation so that total oxygen after about 1 minute of casting was around 10 ppm, whereas this value was reached only after 25 minutes of casting in the case without inert gas sealing. Reoxidation in the pouring channel may be a danger because of the high pressure drops recorded. Therefore, stringent measures must be observed to prevent reoxidation in the tundish and the pouring channel.
New reference materials for electrochemical on‐line sensors to measure steel bath composition
Authors: Dimitrov Stefan , Ranganathan Srinivasan , Weyl Axel , Janke Dieter
Published: December 2016

Further efforts have to be made to develop reliable sensors for on‐line measurements in steel melts. Accurate performance of conventional sensors with a Cr‐Cr2O3 reference over extended periods is disturbed by polarization effects mainly at the solid electrolyte/oxygen reference interface. A promising way to minimize or eliminate this problem is to reduce the flux of ionic oxygen across the solid electrolyte by applying oxygen references featuring oxygen potentials close to the actual oxygen potential of the steel melt. In search of oxygen references with 's lower than that of Cr‐Cr2O3 mixtures, EMF measurements were made to determine the equilibrium oxygen pressures of the systems Cr‐CaO‐CaCr2O4, Cr‐MgO‐MgCr2O4, Cr‐Y2O3‐Y2Cr2O6, and Nb‐NbO. It is shown that the use of these reference materials enables correct on‐line measurements in fully‐killed steel baths over periods of 4 hours at least.
The risk of hydrogen embrittlement in high‐strength prestressing steels under cathodic protection
Authors: Isecke Bernd , Mietz Jürgen
Published: December 2016

High strength prestressing steels in prestressed concrete structures are protected against corrosion due to passivation resulting from the high alkalinity of the concrete. If depassivation of the prestressing steel occurs due to the ingress of chlorides the corrosion risk can be minimized by application of cathodic protection with impressed current. The risk of hydrogen embrittlement of the prestressing steel is especially pronounced if overprotection is applied due to hydrogen evolution in the cathodic reaction. The present work considers this risk by hydrogen activity measurements under practical conditions and application of different levels of cathodic protection potentials. Information on threshold potentials in prestressed concrete structures is provided, too.
Correlations between infrared emission and structure of silicates in the temperature range between 1000 and 1600°C
Authors: Mausbach Klaus , Nowack Norbert , Schlegelmilch Franz
Published: December 2016

It is possible to build a radiation cell which allows the investigation of thin molten salt layers. One may draw conclusions from the infrared emission spectra to the structure of molten salts. The influence of different cations on the structure of silicate melts both in and near the molten state is detectable. The existence of free O2−‐ions is not necessary for the description of the properties of a silicate slag. The basicity of a slag depends on the strength of the bond of the oxygen ions to the silicate network. The basicity of a molten silicate melt can be determined by the use of infrared emission spectroscopy.
Reaction processes in the interior of an MgO‐carbon brick with boron carbide additive
Authors: Rymon‐Lipinski Tadeusz , Wolf Peter
Published: December 2016

This paper deals with oxidation protection afforded to carbon‐containing refractory materials by boron carbide. Following the previous tests on the stability of B4C at high temperatures and on the microstructural characteristics of a fired MgO‐C brick, now the reactions, which are to be expected in the interior of the brick, in a neutral atmosphere are discussed. The results of the theoretical consideration and the experiments carried out provide evidence that MgO is unstable in the presence of boron carbide as from approx. 1300°C. Similar instability is shown by magnesium borate, which is reduced by carbon as from about 1300°C. In both reactions, reactive gases occur (Mg vapour and B2O2), which prevent its ingress and hence oxidation of the carbon by binding the oxygen. As well as the dense layer of borate melt on the brick surface, this phenomenon is obviously responsible for the high efficiency of the boron carbide as an antioxidant for MgO‐C materials.
Application of thermodynamic computations to the solution behaviour of niobium and vanadium carbonitrides
Authors: Eckstein Hans‐Joachim , Fennert Mario , Ohser Joachim
Published: December 2016

On the basis of well‐known thermodynamic equations, a model is proposed which allows the computation of both the solution behaviour and the composition of the carbonitride precipitates of the microalloying elements in steel. Apart from the concentration of the microalloying elements and the carbon and nitrogen content, the following aspects were taken into account: the non‐stoichiometric composition of carbonitrides, a regular solution behaviour of the mixture of carbide with nitride, the effect of third elements on the activity of carbon and nitrogen, the possible primary binding of nitrogen by aluminium. The calculation is based on the knowledge of the solubility products of pure carbides and nitrides. Comparison with experimental results of carbonitride precipitates in microalloyed niobium and vanadium steels support the model‐based predictions concerning the temperature‐dependent composition and solubility of carbonitrides under equilibrium conditions.
Texture development of strip cast ferritic stainless steel
Authors: Raabe Dierk , Hölscher Martin , Dubke Mathias , Hanke Karl‐Heinz , Pfeifer Herbert , Lücke Kurt
Published: December 2016

The textures and the mechanical properties of a strip cast, cold rolled and recrystallized ferritic stainless steel with 16% Cr have been investigated and compared to conventionally processed hot band. The strip cast initial material exposed three improvements. First, the textures were weaker and more homogeneous through the sheet thickness. Second, it revealed a higher Lankfort value and third, the complete elimination of the ridging phenomenon.
The use of thermal analysis techniques for the validation of phase transformation models
Authors: Bodin Andre , Marchal Piet D.
Published: December 2016

In the study of the phase transformation of steel several methods can be used to obtain information about the behaviour of steel during heating and cooling. In this research several conventional methods, e.g. dilatometry, were studied together with an in‐situ thermal analysis method (ISTA). This method, which can be applied to any cooling curve, enables us to draw conclusions as to the transformation behaviour of the steel. Using a continuous annealing simulator (Casim) a range of cooling rates can be investigated with the resulting mechanical properties.

It will be demonstrated that ISTA can be performed on the results of a variety of experimental techniques and therefore under very different experimental conditions. It is possible to investigate transformation behaviour and mechanical properties on a single test piece. Using the pressurized air cooling of the Casim proves to be a good compromise between the possibilities of determining the mechanical properties and flexibility in cooling conditions of the specimens.
The influence of thermomechanical treatment on the transformation behaviour of steels
Authors: Kaspar Radko , Lotter Ulrich , Biegus Christian
Published: December 2016

The effect of thermomechanical treatment on the γ – α‐transformation in steel has been reviewed. It has been shown that the thermo‐mechanically conditioned austenite significantly influences the kinetics of transformation due to the differences in the formation of product phases. An enhanced nucleation during the diffusion controlled transformation, as a result of austenite grain refinement and/or austenite strengthening, leads to a substantial refinement of the microstructure (ferrite grains, pearlite nodules). The deformation substructure of austenite may strongly affect the shear mechanism of the diffusionless transformation, which leads to finely fragmented martensite crystals. Such differences in the transformation characteristics result in different formation temperatures of transformation products and so to the changes in CCT diagrams.
Modelling of the anisotropy of Young's modulus in polycrystals
Authors: Klinkenberg Christian , Raabe Dierk , Lücke Kurt
Published: December 2016

The crystallographic orientation distribution of cold rolled and recrystallized low‐carbon deep drawing steel is quantitatively investigated by means of the series expansion method and the technique of model component fit. The results of both methods are utilized to describe the elastic properties of the inspected sheets. The application of the model components allows a very good approximation of the course of Young's modulus and corresponds to experimental results as well as to the predictions stemming from the series expansion method. In addition to the influence of peak‐type texture components also the impact of complete and incomplete fibre‐type texture components on the course of Young's modulus is inspected.
A thermodynamic model for composition and chemical driving force for nucleation of complex carbonitrides in microalloyed steel
Authors: Samoilov Andrej , Buchmayr Bruno , Cerjak Horst
Published: December 2016

The extent and degree of dispersion of carbonitrides in high strength low alloy (HSLA) steels is controlled by nucleation and growth processes. A thermodynamic model is presented enabling calculation of the composition of the carbonitride embryo as well as the chemical driving force for nucleation (CDF) in the austenite region of a multicomponent microalloyed steel. The analysis made for a Nb‐Ti HSLA steel indicates that the critical carbonitride nucleus is richer in N and Ti than the bulk precipitate at equilibrium at a given temperature and the difference increases when the holding temperature decreases. The results also show that the Ti addition has an optimum value defined by the maximum in the ratio of bound Ti and Nb to their total content. The maximum CDF correlated with the minimum Ti content sufficient to form a carbonitride at the austenitizing temperature.
Measurements of bubble plume behaviour and flow velocity in gas stirred liquid Wood's metal with an eccentric nozzle position
Authors: Xie Yongkun , Oeters Franz
Published: December 2016

The distribution of gas fraction and the flow field of gas‐stirred liquid metal in steel ladles at eccentric injection of the stirring gas through the bottom of the vessel were measured in melts of 437 kg liquid Wood's metal. The melts had a temperature of 100°C. The bath height was 37 cm and the vessel diameter 40 cm. The blowing nozzle was positioned at half of the vessel radius. Gas flow rates were between 100 and 800 cm3(STP)/s. The gas fractions were measured by electrical resistance probes. The flow velocity of the liquid metal was determined by magnet‐probes. The gas fraction and the velocity distribution in the plume were found to have a Gaussian shape. The cross‐section of the plume is ellipsoid, as the plume width in the direction of the radius was a little smaller than the width in the direction perpendicular to it. Moreover the plume was inclined to the wall. The results which were found for the plume are mathematically described. The flow field at eccentric gas‐stirring consists of one great loop, which fills almost the entire vessel. This is contrary to centric blowing, where for aspect ratios of the ladle in the order of 1, a toroid is formed in the upper and a dead zone exists in the lower part of the vessel. The consequences of this behaviour, especially for mixing in the melt, are discussed.
Steady state model for current and temperature distributions in an electric smelting furnace
Authors: Sridhar Eunny , Lahiri A. K.
Published: December 2016

A two‐dimensional mathematical model has been developed for predicting current and temperature distributions in an electric smelting furnace. The current distribution is calculated by solving differential equation for magnetic field intensity Hθ with A.C. input. Temperature distribution in the furnace is evaluated by solving the equation for conservation of energy. The data used for the model is based on the ferro manganese production. The effect of various operating parameters such as electrode depth, electrical conductivity of the charge and the slag on the power consumption, heat loss, slag and top gas temperatures have been studied in the present model.
Influence of hydrodynamic lubricant entrainment on friction effects in cold rolling
Authors: Pawelski Oskar , Rasp Wolfgang , Draese Stephan
Published: December 2016

The cold rolling process is decisively influenced by the mechanisms of lubricant supply to the deformation zone. Rolling tests with thin aluminium sheets were performed based on a theoretical model of the hydrodynamic entrainment of lubricant. Aluminium was used as a model material for steel in order to get a soft rolling stock to enlarge the hydrodynamic effect. The rolling conditions were chosen so that changes in friction conditions could definitely be traced back to a hydrodynamic effect in the inlet zone. The changes in friction conditions were demonstrated by significant rolling parameters, dimensionless similarity numbers, and alterations of the surface structures of the rolled test sheets. The conclusions indicate some tribological problems in cold rolling.
Effects of solution treatment temperatures on microstructure, tensile and fracture properties of Co‐free 18 Ni maraging steel
Authors: Sinha Parameshwar Prasad , Tharian Thomas , Sivakumar Dhenuvakonda , Sarma Dharba Subhramanya
Published: December 2016

The study presents the influences of solution treatment temperatures (S.T.T.) on microstructure, tensile and fracture properties of 18 Ni cobalt free maraging steel. The results are thoroughly discussed in light of the prevailing microstructural conditions as revealed by optical and transmission electron microscopy, and detailed scanning electron fractography. It is found that tensile strength in both unaged and aged conditions is independent of solutioning temperature and, consequently, grain size. However, the tensile ductility, CVN and KIC in aged condition get severely affected with the increase in S.T.T. because of a change occurring in the martensitic lath morphology from blocky to stringer type. This transition in the martensitic morphology starts at the prior austenitic grain size of 35‐40 μm and is completed at 120‐130μm. Solutioning at 1323 K followed by air cooling, however, results in thermal embrittlement of the steel due to grain boundary precipitation of TiCN. The prior austenitic grain size in this reaction plays only an indirect role. Based on these results, it has been suggested that the existing controversies on the effect of S.T.T. grain size on tensile ductility and fracture behaviour of maraging steels can be rationalized if the changes in martensitic lath morphology are considered as an important variable.
Orientation dependent surface segregation of antimony on non‐oriented electrical steel sheet
Authors: Jenko Monika , Vodopivec Franc , Grabke Hans Jürgen , Viefhaus Helmut , Praček Borut , Lucas Manfred , Godec Matjaž
Published: December 2016

The surface segregation of antimony was studied using AES on a 1.8% Si steel alloyed with different mass contents of Sb (0.052 and 0.1%). The dependency of surface segregation on grain orientation and on the presence of other solute atoms (S. P. C, Al. Si) were investigated under UHV conditions in the temperature range from 450 to 900 °C.

The results lead to an explanation for the formation of a texture rich in (100)‐grains in Si steel caused by the presence of Sb. Also grain boundaries were analysed by AES after annealing at 850, 700 and 550 °C for different times. Since the grain boundary segregation was negligible one can conclude that the texture formation results from orientation dependent surface segregation of Sb causing differences in surface energies and stabilities of different grains.
Microstructure and mechanical properties of rapidly solidified Fe‐25%Cr‐5%Al ribbons produced by planar flow casting
Authors: Jiménez José A. , Frech Wolfgang , Ruano Oscar A. , Frommeyer Georg
Published: December 2016

Catalyst substrate foils of the highly oxidation resistant Fe‐25Cr‐5Al alloy (mass contents in %) with a thickness ranging from 40 to 180 μm have been produced by planar flow casting. The rapidly solidified ribbons showed a monophase ferritic microstructure of columnar grains. The grain size determined over a section parallel to the ribbon wheel side ranged from 5 μm for the thin ribbons (40 μm) to 18 μm for the thicker ones {180 μm). This anisotropic columnar solidification microstructure exhibits a strong <100> fiber texture, with the fiber axis nearly perpendicular to the plane of the ribbon. The position of the maximum in the pole figure was tilted from the center point toward the casting direction. Results of uniaxial tensile tests showed that only the yield stress data of the ribbons in the as‐cast condition are reproducible, whereas the ultimate tensile strength and the elongation to failure data show a wide scatter band. The fracture mode exhibits ductile features such as glide bands and dimples.
Temperature dependence of the microscopic cleavage fracture stress
Authors: Jüde‐Esser Christoph , Grimpe Fabian , Dahl Winfried
Published: December 2016

The microscopic cleavage fracture stress which could be responsible for dramatic failure is commonly seen as a temperature independent material property. But a dependence on temperature was found in several former investigations. In this work new studies on cleavage fracture with low carbon steel C 10 were performed. The stress was determined with double‐edge notched tensile (DENT) specimens at different temperatures and various crosshead speeds. In addition tests were made with four‐point bend specimens (SENB4) according to Griffiths and Owen. A significant influence of temperature on the microscopic cleavage fracture stress was found. The explanation for this result is seen in terms of the thermal activation of dislocation movement, which is needed to produce the critical conditions for fracture. As temperature independence is proposed from the “Local Approach” a check up of this procedure is given and limitations of the “Weakest Link‐model” are shown.
The influence of tempering on cleavage fracture stress and transition behaviour of bainitic 2.25Cr1Mo steel
Authors: Holzmann Miloslav , Vlach Bohumil , Man Jiří , Krejčí Jan
Published: December 2016

The effect of tempering on the mechanical properties and on the cleavage fracture stress of bainitic 2.25Cr1Mo steel was studied in a variety of structures with the Hollomon‐Jaffe parameter M ranging between 18.23 × 103 and 21.70 × 103. The rapid decrease in yield stress and UTS was observed up to value M = 20 × 103. For values M > 20 × 103 the reduction of yield stress and UTS slows down. The cleavage fracture stress continuously decreases with increasing value of M. Concurrently, the changes in dislocation density and in carbide size, morphology and distribution were observed. Various theories of cleavage origin of tempered bainitic microstructures are discussed. The transition temperatures, determined from impact Charpy test, reach minimum at M = 20 × 103. Using Orowan's theory of initiation of the brittle fracture in steels, the minimum of transition temperatures may be explained by the different reduction rates of cleavage fracture stress and yield stress with value of M.
Austenite reversion in 18 Ni Co‐free maraging steel
Authors: Sinha P. P. , Sivakumar D. , Babu N. S. , Tharian K. T. , Natarajan A.
Published: December 2016

The mechanism of austenite reversion in 18 Ni Co‐free maraging steel (250 grade) has been established by conducting extensive X‐ray diffraction (XRD) and transmission electron microscopy (TEM) under differently aged conditions. It has been proposed that contrary to the precipitate dissolution mechanism suggested for the initiation of austenite reversion in 18Ni‐8Co‐5Mo type maraging steels, the initiation of transformation of martensite to austenite in this type of maraging steel is due to the diffusion of Ni from matrix to the dislocations and other defect structures on prolonged/high temperature ageing. This results in local enrichment of Ni which lowers both AS and MS temperatures of the region. Lowering of these transformation temperatures is responsible for the early reversion of martensite to Ni‐enriched stable austenite which, on subsequent cooling to room temperature, does not transform back to martensite.
Simulation of the behaviour of voids in steel plates during hot rolling
Authors: Pietrzyk Maciej , Kawalla Rudolf , Pircher Hans
Published: December 2016

The prime objective of the work is to predict the behaviour of voids in the steel slab during hot rolling and to assess the tendency of the void to closure, depending on the process parameters. The rigid‐plastic thermal‐mechanical finite‐element program is used for the purpose. The model which simulates the general case of deformation of a single void in a matrix undergoing plastic deformation is developed. This model allows the investigation of the influence of the stress state on the void's behaviour. Finite element calculations carried out for the industrial hot plate rolling process supply information regarding the stress state during rolling depending on the process technological parameters. These data are used as boundary conditions in the void's closure model and, in consequence, allow the analysis of the influence of rolling technology on the void's behaviour.
Thermal expansion and crown evaluations of rolls in rolling processes
Authors: Tseng Ampere A. , Tong S. X. , Raudensky M. , Chen T. C.
Published: December 2016

An understanding of the thermal expansion of work rolls is essential to the proper control of the flatness of a rolled strip in operating a modern, high‐speed rolling mill. In this paper, an analytical solution has been developed to provide the thermal displacements and expansions of the roll. The thermal expansion data, in turn, can be utilized to estimate the thermal crown for shape control and contributes to alleviating many shape problems of the rolled product. The thermal displacement potential function has been used to solve the governing partial differential equations for the thermal displacements. The general stress function is then obtained to modify the displacement potential solution to satisfy the boundary conditions of the free roll surface. To demonstrate the accuracy and reliability of the solution developed, the results of the present solution have been compared with previously published numerical and experimental results at typical rolling conditions; good agreement has been found between them. A parametric study is then performed to provide the required information for proper control of the roll and strip shape in operating a high‐speed rolling mill.
Calculation of some parameters of polyhedron bulging process
Authors: Jianling Dong
Published: December 2016

Single‐curvature polyhedron bulging technology for manufacturing spherical vessels is to build spherical vessels by assembling and welding sheet blanks of zero‐curvature and single‐curvature into a polyhedron, then gradually bulging the polyhedron into a spherical vessel. With the technology, heavy presses and large dies are not needed, so spherical vessels can be built at low cost. In order to make a polyhedron after being bulged satisfy given dimension requirements of the spherical vessel, it is necessary to calculate wall thickness and diameter of the polyhedron under bulging pressure.

In this paper, wall thickness decrement and deflection of a point on a single‐curvature polyhedron during bulging are measured, it proves that the wall thickness decrement is much smaller than the deflection. Under the assumption that wall thickness of a polyhedron keeps constant during bulging, the constant‐area spheritaxis principle is put forward. With this principle, methods of calculating diameter, wall thickness of a polyhedron and pressure under which the polyhedron becomes a spherical vessel are got. Besides, other applications of the principle are also given.