bluuebunny/crossref_metadata_2025 huggingface dataset:
Columnar to Equiaxed Transition (CET) in castings – Part I: Determination of the CET from cooling curves
Authors: Lipton Jan , Heinemann Wilfried , Kurz Wilfried
Published: December 2016

Description of columnar to equiaxed transition (CET) during dendrite solidification by a qualitative model. Evaluation of cooling curves in an organic alloy by applying the model. Verification of the model by precise temperature measurements.
Ausheilmechanismen von Kriechporen bei nachträglicher Wärmebehandlung
Authors: El‐Magd Essam , Jäger Klaus
Published: December 2016

Wachstumsgeschwindigkeit von Korngrenzporen während Zeitstandbeanspruchung durch Diffusion, durch Kriechverformung oder durch gekoppelten Mechanismus. Aussintern der Poren während einer nachträglichen Wärmebehandlung durch Diffusion. Modell zur Porenschrumpfung durch Rückkriechen des umgebenden Materials.
Experiments on the mass transfer between two immiscible phases by a top and bottom blown converter model
Authors: Schlarb Heinrich , Frohberg Martin G.
Published: December 2016

The mass transfer of caprylic acid between water and oil was studied at a top and bottom blown converter model. A model law was deduced from the experiments. It was observed that the oil phase presents itself nearly completely in droplet form at higher blowing rates. This observation allowed the determination of the mass transfer coefficient at 2.26 · 10−4 [ms−1]. A value of equal magnitude can be calculated of spheres being flown around. The rotational speed of the bath corresponds to earlier measurements.
Kinetics of the carburization of iron alloys in methane‐hydrogen mixtures and of the decarburization in hydrogen
Authors: Grabke Hans Jürgen , Müller Else Marie , Speck Heinz Valentin , Konczos Geza
Published: December 2016

The surface reaction kinetics have been investigated for the reaction

CH4 (gas) = C (dissolved) + 2H2 (gas)

on Fe and Fe‐M foils (M = Mn, Cr, Co, Ni, Sn) at temperatures between 800 and 1000°C. The resistance relaxation method was applied in a flow apparatus. The following rate equation was observed for the rate of carbon uptake

urn:x-wiley:01774832:srin00635:equation:srin00635-math-0001

where is the carbon concentration and k and k′ are the rate constants for carburization and decarburization respectively. For Fe, Fe‐10 Ni and Fe‐10 Co the value of v = 3, for the alloys with > 20% Ni as well as for all Fe‐Mn and Fe‐Cr alloys the value v = 4 results from the measurements, which indicates differences in the rate determining step. With increasing Cr, Mn, Ni, Co content the rate constants k and k′ increase.

The decrease of the equilibrium carbon concentration with increasing Ni content in Fe‐Ni alloys is correlated to a fast increase of k′ and a slow increase of k with increasing Ni content. Beyond the minimum of at about 70 wt.% Ni both rate constants show a strong increase. By holding Ni at high carbon activities (aC > 0.7 at 1000°C) segregation of carbon induces a surface reconstruction which is characterized by formation of (111) planes and which reduces the reaction rates.

The increase of the equilibrium carbon concentration in the systems Fe–Mn and Fe–Cr with increasing content of alloying element is correlated to a slow increase of k′ and a fast increase of k with increasing Mn or Cr content.

Sn segregates to the surface and retards the reaction rate by blocking the reaction sites for the surface reaction, similar to the effects of P and S.
Resistivity of electrical sheets in high temperatures
Authors: Soiński Marian
Published: December 2016

The paper presents changes in electric resistivity ϱ, dependent on the temperature T for oriented and non‐oriented electrical sheets. The analysis of temperature changes on the temperature coefficient of resistivity α was performed for different sheet grades. Various methods were used to mathematically describe empirical data obtained. The influence of non‐metallic inclusions and crystallographic dislocations on the resistivity value was detected. For the sheets under examination, the values of residual resistivities ϱr (at 4.2 K) and ideal resistivities (at 400 K) were provided.

It was suggested that apart from the value of the temperature coefficient of resistivity α, the value of residual resistivity ϱ, be used to classify sheets of different chemical constitution. This seems to be of particular significance for better material characteristics on view of newly designed electric machines adapted to operate in ever higher temperatures.
Influence of non‐uniform material properties and water cooling on current density and temperature profiles in arc furnace electrodes
Authors: Bullerschen Klaus , Wilhelmi Herbert , Wimmer Wolfgang
Published: December 2016

The influence of the simplifying assumption of constant electrical conductivity on the modelling of current density and temperature profiles in arc furnace electrodes is investigated in comparison with calculations taking into account the complete interdependence of electrical and thermal effects. With respect to the accuracy of the calculated values for UHP arc furnace electrodes it is shown that the classical theory for the skin effect using the approximation of constant electrical conductivity is inferior to an exact numerical evaluation, especially concerning the current distribution. A two‐dimensional thermal analysis is performed for combination electrodes consisting of a water cooling shank and a graphite wearing part, in order to demonstrate the cooling effect for the reduction of graphite consumption. In the electrodes considered here, the cooled region in the wearing part covers an axial distance in the order of one electrode diameter.
Mathematische Beschreibung der MgO‐Sättigung in komplexen Stahlwerksschlacken beim Gleichgewicht mit flüssigem Eisen
Authors: Schürmann Eberhard , Kolm Ingo
Published: December 2016

Zur Verminderung des Feuerfestverschleißes wird bei der Stahlerzeugung der MgO‐Träger Dolomitkalk als Schlackenbildner eingesetzt. Dies erfordert genaue Kenntnisse der in Abhängigkeit von der Schlackenzusammensetzung und der Temperatur löslichen MgO‐Gehalte, um metallurgisch wirksame, gut flüssige Schlacken zu gewährleisten.

Die MgO‐Sättigungsgehalte in Stahlwerksschlacken wurden bei niedrigen, durch das Gleichgewicht mit flüssigem Eisen festgelegten Sauerstoffpartialdrücken experimentell bereits durch eine große Anzahl von Sättigungsschmelzen untersucht, bedurften jedoch einer einheitlichen und auch komplexe Schlacken umfassenden Beschreibung. Alternativ zu schwer lesbaren graphischen Darstellungen wird daher eine numerische Beschreibungsform entwickelt, welche zunächst die MgO‐Gehalte auf der Magnesiowüstit‐Sättigungsfläche im reinen Vierstoffsystem MgO—FeOn—CaO—SiO2 bei 1600°C mit Hilfe eines Gleichungssystems in Abhängigkeit von der Schlackenzusammensetzung erfaßt.

Die Gültigkeit der Beziehungen wird sodann auf Mehrstoffsysteme mit mehr als vier Komponenten erweitert, indem Gehalte an MnO, P2O5 und Al2O3 entsprechend ihrer spezifischen Wirkung auf die MgO‐Löslichkeit entweder als verdünnend eliminiert (MnO) oder in äquivalente SiO2‐Gehalte umgewertet werden (P2O5, Al2O3). Auf diese Weise wird das reale, komplexe Mehrstoff‐Schlackensystem in ein bezüglich der MgO‐Sättigungsgehalte äquivalentes Quasi‐Vierstoffsystem MgO*—FeOn*—CaO*—SiO2* überführt. Der Temperatureinfluß kann durch einen auf 1600°C bezogenen Korrekturfaktor berücksichtigt werden.

Die vorgestellten Gleichungen ermöglichen es, die in technischen Schlacken löslichen MgO‐Gehalte in einem weiten Konzentrations‐ und Temperaturbereich zu berechnen.
Erfassung von Rißbildung und Rißwachstum von Oberflächenrissen mit Potentialmethode, Aufweitungsmessung und Schallemission
Authors: Keller Hans Peter , Merker Wolfgang , Morsi Mohamed
Published: December 2016

In der vorliegenden Arbeit werden Ergebnisse vorgestellt, die im Rahmen eines Forschungsprogrammes bei sieben Behälterversuchen und den entsprechenden begleitenden Untersuchungen gewonnen wurden. Ein Ziel der Arbeit war, Verfahren und Versuchstechniken zu entwickeln, die eine zuverlässige Einbringung von Rissen in gekerbte Behälter durch pulsierenden Innendruck erlauben. Dabei standen zwei Probleme im Vordergrund: Die experimentelle Erfassung der Rißbildung im Kerbgrund und die Bestimmung der Tiefe von Oberflächenrissen während der Schwellbeanspruchung. Bei den Versuchen hat sich gezeigt, daß die Entstehungsphase von Oberflächenrissen mit Potentialmethode, Aufweitungsmessung und Schallemission erfaßt werden kann. Zur Verfolgung des Tiefenwachstums haben sich Potentialmethode und Aufweitungsmessung bewährt. Für diese Verfahren werden Kalibrierkurven in übertragbarer Form angegeben, welche die Meßgrößen Potential bzw. Aufweitung mit der Rißtiefe verknüpfen. Mit derartigen Kurven kann die Einbringung von Oberflächenrissen in Behälter und Platten vollautomatisch überwacht werden. Darüber hinaus ergibt sich für die Potentialmethode im Rahmen der zerstörungsfreien Prüfung die Möglichkeit, die Abmessungen örtlich bekannter Oberflächenfehler abzuschätzen.
The continuous analysis of molten steel by means of chemical reactions/aerosol generation and atomic emission spectrometry
Authors: Golloch Alfred
Published: December 2016

For the continuous analysis of molten steel there are three fundamental alternatives to attain information about the concentrations of elements in the melt. The method of continuous sampling and analyzing the material of the sample stream outside the melt is chosen for investigation in the present work.
Phase equilibrium in the system ZrO2 + MgO + P2O5 at 1573 K
Authors: Iwase Masanori , Ichise Eiji , Kitaguchi Hitoshi
Published: December 2016

Phase equilibrium in the system ZrO2 + MgO + P2O5 near ZrO2—MgO edge was established at 1 573 K. Within the composition range investigated pseudoternary compounds were not detected, while two compatibility triangles for ZrO2 + MgO + 3MgO · P2O5 and ZrO2 + 3 MgO · P2O5 + 2ZrO2 · P2O5 were determined.
Process conditions and oxidation behaviour of high speed steel ribbons during rapid quenching
Authors: Löser Wolfgang , Stephani Günter , Fiedler Hans
Published: December 2016

Oxygen absorption has been investigated in rapidly quenched ribbons of high speed steel produced by a single roller PFC‐technique. The average oxygen content of the master alloy was 130 ppm. After melt spinning, there was an increase in the oxygen level from 700 to 10 000 ppm depending on the ribbon thickness and on the ribbon‐roller contact length. Using IR‐temperature measurements, the oxygen content correlates with the ribbon temperature at the ribbon‐roller separation point. The oxygen levels rise with increasing ribbon thickness or decreasing contact length. Quenching rates are strongly affected by the wetting conditions of the solidifying ribbon at the roller surface. Secondary oxidation was interpreted using a phenomenological model for the scale constant which produced calculated data in reasonable agreement with the experimental results. Aspects for process improvement are also discussed.
On the reaction mechanism of the carburization and decarburization of α‐iron in CH4/H2‐mixtures
Authors: Sobe Gerhard , Polei Veronika
Published: December 2016

The surface reaction of the carburization and decarburization of α‐iron in CH4/H2‐mixtures has been investigated by a method using the radioactive isotope 14C. Experimentally two different kinetic equations have been confirmed and discussed in detail:

urn:x-wiley:01774832:srin00846:equation:srin00846-math-0001

In accordance to 1) the kinetic equation (1) is explained by a slow reaction: .

For the kinetic equation (2) the adsorption, respectively the desorption of CH4, is considered to be the most slow partial step. The correlation of the carburization with the adsorption is supported by the relations:

urn:x-wiley:01774832:srin00846:equation:srin00846-math-0003

Thus can be regarded as Ea, the activation energy of the adsorption. Its value was determined at 109 kJ/mol being equivalent to 1.1 eV, which is characteristic for a chemisorption.

Further it was established, that the rate of the decarburization according to equation (2) increases with decreasing temperature, i.e. the (apparent) activation energy proved to be negative. This is explained by the fact that before its rate‐controlling desorption the CH4‐molecule first of all must be formed step‐by‐step and by the assumption that for thermodynamical reasons the surface concentration of CH4 increases very much with decreasing temperature.

The range of validity of the kinetic equations (1) and (2) can be limited to each other as follows:

– The kinetic law (1) is established especially at higher H2‐pressures and at surfaces with low, but effective impurities. The impurities simultaneously result in a high decline of the reaction rate.

– The kinetic law (2) is valid especially at lower H2‐pressures.
Effect of carbon content in CrMoV hot working tool steel
Authors: Berns Hans , Wendl Franz
Published: December 2016

The aim of this work was to find out whether a reduction of carbon content would reduce the amount of segregated eutectic carbides and improve ductility and toughness. Quenched and temperted specimens of steel X 40 CrMoV 5 1 (∼AISI H 13) were tested at carbon contents of 0.42 and 0.27%. Tensile and short time creep tests were carried out at elevated temperatures. Toughness was derived from unnotched, notched and precracked specimens over a temperature range. Stable fatigue crack growth was measured in CT specimens at room temperature and in thermal fatigue specimens.

As expected, ductility and toughness are raised by reducing the carbon content. At the same time a favourable improvement of hot strength and creep resistance appears, causing a lower thermal fatigue crack velocity. These beneficial effects are due to the higher alloy content in solution after hardening.

It is proposed to test a steel X 28 CrMoV 5 1 for intricate tools in practical application and learn more about its wear behaviour.
Properties of through hardening bearing steels produced by BOF blowing metallurgy and by electric arc furnace with ladle metallurgy
Authors: Baum Rudolf , Böhnke Kurt , Boeckers Tilman , Klemp Harald
Published: December 2016

Melting in EAF and BOF‐TBM and different methods of aluminium deoxidation in the subsequent ladle treatment result in a similar degree of cleanness. With respect to micro‐inclusions the air melted ingot and continuous cast steels achieve nearly the same level as remelted steels. Considering macro‐inclusions there still remains a decisive difference: remelted steel is sure to be free from macro‐inclusions, whereas some occasionally occur in air melted steel.

The random test and metallographic evaluation systems do not allow uniform classification of the various steel groups. None of the applied methods can determine definite inclusion contents. The number and sizes of the evaluated types of inclusions only can define the statistical probability of their occurrence in a larger lot of heats. Up to now they cannot be related to the fatigue behaviour of the steels. Therefore, further investigation is necessary to reveal the effect of critical sizes and chemistry of the various inclusions on the fatigue behaviour. First tests reveal that the machinability seems to be governed by the carbide grain sizes more than by the sulphur contents in the investigated range of 0.003‐0.015%. The comparison of test results in terms of cleanness and segregation shows that continuous casting should allow the same application as ingot casting.
Schnelle Untersuchung kleinster Oxidmengen mit RFA
Authors: Grisar Ulrich , Bensmann Bernhard , Kampe Hubert , Rosemann Johannes
Published: December 2016

Das bekannte Verfahren zur Analyse von ca. 1 mg beruht auf spektralanalytischen Messungen, die einen hohen Arbeitsaufwand erfordern. Bei der RFA werden für die eigentliche Messung nur kleine Massen gebraucht; durch geeignete Aufbereitung gelingt es, die gewonnenen Oxide in die nötige dünne Schicht zu bringen. Eine korrekte Kalibration ist möglich. Damit ist die erforderliche Genauigkeit, die sich aus dem metallurgischen Untersuchungsziel ergibt, zu erreichen. Der Arbeitsaufwand ist wesentlich kleiner als bei den beschriebenen Verfahren.
Spinel deoxidation equilibria in the Fe—Mn—Al—O system – experiment and computation
Authors: Pandit S. Shashidhara , Jacob K. Thomas
Published: December 2016

The concentration and chemical potential of oxygen in liquid Fe—Mn alloys equilibrated with the spinel solid solution, (Fe, Mn)Al2+2xO4+3x, and α‐Al2O3 have been determined at 1873 K as a function of manganese concentration. The composition of the spinel phase has been determined using electron probe microanalysis. The results are compared with data reported in the literature. The deoxidation equilibrium has been computed using data on free energy of solution of oxygen in liquid iron, free energies of formation of hercynite and galaxite, and interaction parameters reported in the literature. The activity‐composition relationship in spinel solid solution was derived from a cation distribution model. The model is in excellent agreement with the experimental data on oxygen concentration and potential and the composition of the spinel phase.
Viscosity estimation of slags
Authors: Urbain Georges
Published: December 2016

The viscosity of silicate melts and slags is a property difficult to measure accurately using sophisticated apparatus, it is both time consuming and expensive. The use of models to estimate the viscosity is the first step to be carried out, mainly with metallurgical slags involving numerous components. The proposed model is an experimental one based on accurate data for pure binary and ternary melts. From this data, using a simple hypothesis on the behaviour of unusual compounds, it is possible to estimate the viscosity of a complex melt. This estimation is used as a first approximation and can be amended, if necessary, by only a few direct measurements.
Ausscheidungsverhalten von nichtrostenden ferritisch‐austenitischen Stählen mit höheren Molybdän‐Gehalten
Authors: Tacke Gerhard , Köhler Heinz Jürgen
Published: December 2016

Ferritisch‐austenitische Stähle mit Cr‐Gehalten von 20 bis 28%, Nickel‐Gehalten von ca. 5% und Molybdän‐Gehalten zwischen 1,5 und 6% wurden auf ihr Ausscheidungsverhalten unter Berücksichtigung von Wärmebehandlungsquerschnitten bis 200 mm □ untersucht. Mit steigendem Molybdän‐Gehalt nimmt die Ausscheidungsmenge zu. Die in den C‐armen N‐legierten Versuchsstählen dabei auftretenden Phasen sind

– kubisches Nitrid des Typs CrN mit 40–80% Cr, bis zu 45% V+Nb und 20% Mo bezogen auf den metallischen Anteil (100%); die Phase wurde im Ferrit und auf Korn‐ und Phasengrenzen beobachtet,

– hexagonales (CrMo)Nxmit ca. 80% Cr und 8% Mo, welches nur auf Korn‐ und Phasengrenzen vorliegt,

– tetragonale Z‐Phase (CrMo)2Nb2N2mit ca. 35% Cr, 45% Nb, 20% (V/Fe/Mo), die im Austenit fein und im Ferrit grob ausgeschieden vorliegt,

und eine kohärente MoFe‐Phase im Austenit einiger Stähle.

Im Gegensatz zu den IK‐kritischen Carbiden des Typs Cr23C6in den austenitischen und ferritischen Stählen binden die o.a. Nitridphasen vergleichsweise weniger Cr bzw. Mo ab, nicht zuletzt durch Einbau von V und Nb anstelle des Cr. Mit steigendem Wärmebehandlungsquerschnitt nimmt die Menge an Ausscheidungen erwartungsgemäß zu. In 0,2 μm Abstand von Nitriden wurden in Stählen mit Matrix‐Gehalten von 27 bzw. 25% Cr auch bei größeren Querschnitten nur geringe Verarmungen von 5–6% Pkt. gemessen. Bei Mo‐Gehalten von >5% wird bei Abkühlung größerer Querschnitte (200 mm □) σ‐Phasenbildung beobachtet. Zudem wurde eine Fe‐reiche kubische Phase eines bisher unbekannten Typs auf Korngrenzen beobachtet.
Fatigue crack growth in an as‐rolled dual‐phase steel
Authors: Chen Daolun , Wang Zhongguang , Jiang Xiaoxia , Ai Suhua , Shi Changxu
Published: December 2016

Fatigue crack propagation behaviour of an as‐rolled dual‐phase steel is investigated over a wide range from 10−10 to 10−6 m/cycle in a 3.5% NaCI solution and laboratory air under different load ratios. It was found that the as‐rolled dual‐phase steel studied in the present investigation shows good resistance to fatigue crack growth in laboratory air. The threshold values decrease with increasing stress ratios, which is consistent with the competition model proposed previously. The threshold value obtained using a 3.5% NaCI solution is higher than that in the laboratory air owing to the wedge effect of corrosion products within the crack. Fatigue crack growth rates in the higher ΔK range obey the Paris formula in each case within this study.
A microstructural characterization of scale formed on austenitic Fe–29.7Mn–8.7Al–1.04C and duplex Fe–29Mn–10Al–0.4C alloys in oxidizing‐sulfidizing environments
Authors: Tjong Sie Chin
Published: December 2016

Austenitic Fe–29.7Mn–8.7Al–1.04C and duplex Fe–29Mn–10Al–0.4C alloys were exposed to the SO2–O2 mixed gas environments at 900 °C. The morphology of the scales formed on these alloys under oxidizing‐sulfidizing conditions were examined by SEM and X‐ray mapping techniques. The results showed that the addition of carbon up to 1 wt.% to the Fe–29.7Mn–8.7Al–1.04C alloy led to the formation of internal sulfidation and intergranular oxidation in the mixed oxidant gas environments. On the other hand, no evidence of intergranular oxidation could be detected in the duplex Fe–29Mn–10Al–0.4C alloy with lower carbon concentration.
An investigation of the lattice parameters of α‐(Fe, P) alloys
Authors: Hattendorf Heike , Büchner Achim R. , Inden Gerhard
Published: December 2016

In this investigation the lattice parameters of α‐(Fe, P) alloys are measured very accurately. By comparison with literature it is concluded that the distribution of P‐atoms in Fe is not always random and varies with heat treatment.
Some aspects on MgO solubility in complex slags
Authors: Bergman Åke
Published: December 2016

A magnesia capacity is defined, CMg2+ = (%Mg2+)/aMgO and its relation to optical basicity is examined and discussed. The solubility of MgO in complex slags, in equilibrium with magnesiowustite, is derived from the activity of MgO in the magnesiowustite and from the magnesia capacity as given by the slag's optical basicity. It is found that the activity of MgO in the magnesiowustite can be derived from [%O] assuming ideality in the FeO–MgO system at 1600°C. It is also found that the MgO saturation contents in complex slags are accurately derived from the equation:

urn:x-wiley:01774832:srin00273:equation:srin00273-math-0001

In addition, the relation between the magnesia capacity and the capacities of vanadium and phosphorus is examined and the relative basicity of the oxides is discussed.
Slag foaming in smelting reduction processes
Authors: Ito K. , Fruehan Richard J.
Published: December 2016

In order to understand the effect of slag composition on foaming in the smelting reduction process, slag foaming was quantitatively studied for CaO–SiO2–FeO slags in the temperature ranging 1250–1400 °C. It was found that slag foaming could be characterized by a foaming index Σ which is equal to the retention or travelling time of the gas in the slag and by the foam life. The effects of P2O5, S, MgO and CaF2 on foaming were studied. As expected slag foaming increased with increasing viscosity and decreasing surface tension. The results were extrapolated to bath smelting process to predict the foam height. Slag foaming heights as high as 3–5 meters are predicted for a typical operation.
Experiments on the smelting reduction of oxides of iron, chromium and vanadium and their mixtures with argon/methane‐plasmas
Authors: Vogel Dietmar , Steinmetz Eberhard , Wilhelmi Herbert
Published: December 2016

The analysis of the smelted alloys and final slags reveals a preferential reduction of iron oxides. This result as well as the influence of an increasing amount of iron oxide in the mixtures on the degree of reduction, is in accordance with thermodynamic calculations.

In order to give a detailed description of the kinetics of the smelting reduction, it is necessary to obtain more information on the transport properties of oxide‐ and gas phases as well as the changing partial pressures of the oxygen in melted oxides during the reduction period. Reduction of oxides with a low oxygen partial pressure, for example chromium‐, vanadium‐ and titanium oxides, by use of hydrocarbon gases mainly leads to carbon monoxide as product gas. The high temperatures reached in plasma processes increase this decomposition. Therefore, the hydrogen in the reduction gas can only be the transport medium for the main reducing agent carbon.

On the other hand, high reduction temperatures favoured the kinetics of carbonmonoxide formation. Furthermore, higher temperatures lower carburization, which is a great advantage for the production of ferroalloys such as ferrochromium or ferrovanadium.

The experiments show that it is possible to take advantage of thermal plasmas for melting and reducing of metal oxides and mixtures respectively, even for the high‐melting chromium oxide. It seems to be possible to melt steels with a high content of alloying elements in a one‐step procedure. For this reason, smelting reduction processes with plasma may be attractive for the production of high‐alloyed steels in small and flexible steel plants.
Application of ion chromatography in steel industry
Authors: Tusset Vittorino , Hancart Jules
Published: December 2016

Most steel plant laboratories in the Benelux‐countries are equipped with ICP‐AES and AA‐spectrometers dedicated to the analysis of samples in solution, mainly for the quantitative determinations of cations. These methods, however, are hardly suitable for the analysis of anions; hence, the interest in applying the ion chromatography method for the determination of these ions. The “Centre de Recherches Métallurgiques” studied different applications of ion chromatography (I.C.) in steel industry laboratories. In this paper, four major applications of this technique are described: analysis of waste waters, determination of the anions in surface treatment baths, analysis of rolling mill coolants, and analysis of sulphur in steel.
Investigation of die stresses and die deflections in forging axisymmetric parts
Authors: Hirt Gerhard , Altan Taylan
Published: December 2016

In this study, two examples were investigated. The first was cold coining of a thin circular disk where the effect of elastic die deflections upon the tolerances of the formed part was evaluated. In the second example, the die stresses and die deflections were estimated for the upper die in hot closed‐die forging of a flange‐shaft type part. The predicted results in the first example showed good agreement with experimental data. Thus, it was illustrated that the methods used and discussed in this study are reliable to estimate die stresses and deflections. It is expected that additional work is necessary to develop a practical procedure for predicting the failure and fatigue life of cold and hot forging dies.
The predictive capabilities of a thermal model of flat rolling
Authors: Lenard John G. , Pietrzyk Maciej
Published: December 2016

The predictive capabilities of a thermo‐mechanical model of flat rolling are substantiated by comparing its results to measurements obtained from laboratory tests. Time‐temperature profiles, temperature and strain rate distributions are computed. The model proves to be successful. Differences between calculated and measured temperature values are found to be less than 10%.
Effect of thermomechanical processing on structure and properties of low carbon steels
Authors: Panigrahi Bimal Kumar , Ramaswamy Vaidyanatha , Bhan Suraj
Published: December 2016

The microstructure of one plain carbon and two microalloyed steels has been refined by two different thermomechanical processing schedules in a laboratory rolling mill. The factors controlling the structural refinement have been investigated. The results indicate that a combination of single/two stage rolling prior to reaustenitization treatment and finish rolling in the (α + γ) region followed by controlled cooling improves the mechanical properties by refining the ferrite grain size.
Studies on the correlationship between structure and physical properties in the buoyant plume rising in liquid
Authors: Koria Satish C. , Singh Sarbjit
Published: December 2016

In this study the correlations are developed to determine the fundamental properties of the plume, i.e. gas fraction and plume half‐radius as a function of upstream gas‐injection parameters and downstream axial distance. All other properties such as plume radius, volumetric flow rate of liquid, turbulent viscosity and eddy‐mixing length are expressed in terms of gas fraction and plume half‐radius. The eddy‐mixing length is calculated and the calculations have shown that the length changes just marginally with an increased gas‐injection rate. The implication of this finding is discussed in terms of the effects induced by submerged gas injection in the liquid bath.
Investigations to determine the maximum permissible cooling velocity for ceramic components made of alumina
Authors: Honcamp Stefan , Jeschar Rudolf
Published: December 2016

The presented paper discusses the problems of heat stress arising as a result of instationary temperature fields (thermally induced stresses) in ceramic components and includes the results of both theoretical and experimental investigations to determine the critical cooling velocity for cylindrical bodies made of alumina.

The theoretical and experimental results are compared to show that calculating the stresses using the linearized elasticity theory is sufficiently accurate. The fracture condition is determined so that the fracture stress ascertained in a 4‐point‐bending experiment is defined as the maximum bearable tensile stress. The statistical theory according to Weibull is applied to transform this fracture stress onto the type of stress occurring during the cooling experiments. In addition to a short derivation of the equations for thermally induced stresses with temperature‐dependent material values, this paper also describes the determination of the relevant material values and, in particular, that of the temperature dependencies necessary for the calculation. The experimentally determined results show, in addition to the influence of the thermal diffusivity of the material, a quadratical dependence of the critical cooling velocity on the size of the body, as is also to be expected from an analytical solution to the stress equation.
Effect of niobium on hot ductility of low C‐Mn‐steel under continuous casting simulation conditions
Authors: Zhen Lu , Hongtao Zhang , Baorong Wu
Published: December 2016

The effect of niobium on hot ductility of low C‐Mn steel under continuous casting simulation conditions in the range from 700°C to 1 000°C was investigated on a Gleeble‐1500 tester by using in‐situ melting and solidification method. It was found that the ductility trough becomes deeper and wider as Nb content increases. The steel has more refined structure and is more sensitive to interdendritic fracture as Nb content gets higher. The segregation of impurities or alloy elements and formation of sulphides and Nb‐compounds in the interdendritic regions promote the interdendritic fracture.
Correlation of microstructure and failure initiating sites in an AISI M2 high‐speed steel using Vickers indentation
Authors: Ögel Bilgehan , Tekin Erdogan
Published: December 2016

In this study, the relation of crack initiation and propagation to microstructure was shown in an AISI M2 high‐speed steel using Vickers hardness indentation. Observations were carried out on the cracks generated from the corners of the square pyramid indentation in both the as‐quenched, the quenched and tempered specimens. It is shown that cracks are nucleated from the corners of the indentation by either cleavage of the carbide or by decohesion between the carbide and the matrix, depending on the size of the carbide. A nucleated crack propagates by tearing of the martensitic matrix between the cracked carbides ahead of the indentation corner. It is shown that the crack resistance of the M2 steel is determined by the toughness of the matrix rather than the size and distribution of the carbides in the matrix.
Mathematical model for on‐line heat treatment of steel bars
Authors: Morales R. D. , Toledo Miguel , López A. G. , Tapia A. C. , Petersen C.
Published: December 2016

A mathematical model to predict steel bar thermal behaviour during continuous quenching after the finishing mill has been developed. The model includes process variables, such as finishing rolling speed, finishing temperature, rod size and chemical composition, water flowrate and mechanical design of the cooling device. It was found that empirical correlations for the heat‐transfer coefficient belonging to water spray systems are suitable to simulate fast cooling employing submerged water‐cooling tubes. Martensite depth is strongly influenced by the bar diameter and water velocity inside the submerged tube. Mist spray systems are not as effective as submerged tubes for cooling steel bars, although, the initial cooling rates are higher. The % volume of martensite is a direct function of the self‐tempering temperature, and independent of the fast cooling device.
Effect of structural factors on the creep properties of modified chromium steels
Authors: Foldyna Václav , Jakobová Anna , Říman Riša , Gemperle Antonín
Published: December 2016

The precipitation strengthening of modified chromium steels is effected predominantly by M23C6 carbides. In molybdenum‐modified 9% chromium steels, creep resistance depends on the dispersion of the M23C6 carbides and on the molybdenum content in the solid solution. There is no point in increasing molybdenum contents of molybdenum‐modified steels above approximately 1 wt.%. In vanadium‐modified steels precipitation strengthening is effected both by M23C6 carbides and by VCxNy carbonitrides. If the amount of nitrogen in solid solution is insufficient, this reduces the volume fraction of VCxNy in the structure and thus impairs the creep resistance of the steel. It is advisable to restrict the aluminium and titanium contents in the vanadium‐modified chromium steels.
Subgrain growth during creep of a tempered martensitic 12% Cr‐steel
Authors: Blum Wolfgang , Straub Stefan
Published: December 2016

The results of Nilsvang, Eggeler and llschner on subgrain growth in X 20 CrMoV 12 1 during creep are interpreted in terms of dynamic subgrain growth. It turns out that relatively large strains are needed to establish the steady‐state subgrain structure, implying that the technically relevant part of creep occurs in the transient range.
Improvement of mechanical properties of pearlitic and pearlitic‐ferritic steels by deformation‐induced changes of microstructure
Authors: Kaspar Radko , Gasterich Hans‐Jörg , Hagedorn Karl Edgar
Published: December 2016

By using laboratory simulation tests thermomechanical processing, based on a post‐transformation hot deformation with accelerated cooling, was employed on two steels with 0.46 and 0.76% C. Finer pearlite interlamellar spacing, reduced proeutectoid ferrite, and partially spheroidized pearlite bring about a substantial increase of strength without loss of toughness and ductility.
Investigation of the thermodynamic properties of Ni‐AI intermetallic compounds by an EMF method
Authors: Wang Jiansheng , Engell Hans‐Jürgen
Published: December 2016

The partial molar free energy of aluminum in β‐NiAl intermetallic compounds was determined from 41.3 to 67.8 at.% nickel in the temperature range from 788 to 1005°C by an EMF method. The partial molar free energy and enthalpy of nickel, the mixing free energy and enthalpy and the free energy of formation of the different compounds in the Ni‐Al‐system were calculated.
Life prediction based on the propagation of short cracks
Authors: Vehoff Horst , Neumann Peter
Published: December 2016

The growth of short and long fatigue and creep‐fatigue cracks was examined in various steels. The experiments were carried out to test if recent models for creep‐fatigue crack growth can be applied to describe the influence of strain rate on the growth of large and small cracks. Damage parameters were derived from these crack‐growth laws for the life prediction under complicated loading. These parameters were applied to predict the life of smooth specimens cycled at different temperatures and deformation rates. Compared to conventional life predictions better predictions were obtained presumed the growth mechanism of the short cracks did not change for the range of temperature and strain rates in question.
Combined decrease of sulphur, nitrogen, hydrogen and total oxygen in only one secondary steelmaking operation
Authors: Bannenberg Norbert , Bergmann Bernd , Gaye Henri
Published: December 2016

The development of a matured metallurgical process allows the reduction of the sulphur, nitrogen, hydrogen and total oxygen content to the lowest values in only one secondary metallurgical step during treatment in a ladle tank degassing unit. By careful adjustment of a lime‐saturated ladle top slag at the beginning of the vacuum treatment, it is possible to obtain a desulphurization degree of more than 95%. The process of nitrogen removal by a stirring gas can be described with a dynamic model in excellent agreement with plant trials. The nitrogen content after vacuum treatment depends mainly on the nitrogen content before vacuum, the stirring gas quantity and the sulphur content. The achievable hydrogen contents mainly depend on the stirring gas quantity and dehydrogenisation can be described by the same model used for denitrogenisation. By a cleanliness stirring after the vacuum treatment under a nearly SiO2‐free‐, lime‐alumina slag, saturated with lime, the total‐oxygen content can be lowered to less than 20 ppm.
A parametric study of the accelerated cooling of steel strip
Authors: Filipovic J. , Viskanta Raymond , Incropera F. P.
Published: December 2016

To gain insight into the effects of various parameters controlling the thermal behaviour of a quenched steel strip during the process of accelerated cooling by an array of planar water jets, a parametric study has been performed using a previously developed and validated mathematical model. The behaviour of the strip was characterized by its coiling temperature, top and bottom surface temperature variations and heat extraction in the jet impingement region, top surface heat extraction in the film boiling region, and top and bottom surface thermal penetration depths. Parametric variations included cooling system design conditions, such as the top and bottom nozzle widths, and operating conditions such as the top nozzle discharge velocity, the cooling water temperature, and the ratio of volumetric water flow rates applied at the top and bottom surfaces. The effects of steel strip parameters such as strip thickness and strip velocity were also considered.
Kinetics of steel melting in carbon‐steel alloys
Authors: Specht Eckehard , Jeschar Rudolf
Published: December 2016

For the melting of scrap metal in baths with a high carbon content, in which the melting temperature lies below the bath temperature, a model is being developed which is based on the coupling of mass and heat transfer. It will be shown that the mass transport determines the melting rate only for very low bath temperatures. Furthermore, it will be discussed how the melting efficiency is influenced by the supplied energy flow and mass transfer in the bath.
Tests on the oxidation‐inhibiting effect of CaB6 in refractory MgO‐C materials
Authors: Rymon‐Lipinski Tadeusz , Schmelzer Bettina , Ulitzka Stanislaus
Published: December 2016

The oxidation‐inhibiting action of B4C as an antioxidant is to be attributed to two possible mechanisms. The first describes the formation of reactive gases (Mg vapour and B2O2) that react with oxygen reducing its partial pressure in pores of the material. The second mechanism results in the formation of a borate layer which includes carbon between the oxide grains and thus protects it from further oxidation. The present study made an examination as to whether these mechanisms also play a part in the use of CaB6. The results confirm the pattern of chemical behaviour in MgO‐C materials with boron‐containing antioxidants recorded in previous tests. However, the temperature at which the protective effect begins lies in this case at about 200°C lower when compared to B4C. It is obviously due to the formation of a eutectic melt in system MgO‐CaO‐B2O3 at approx. 1080°C.
Development of a numerical model simulating the desulphurisation of liquid steel
Authors: Reifferscheid Markus , Pluschkell Wolfgang
Published: December 2016

A comprehensive numerical model is developed simulating the batch process of liquid steel desulphurisation. Special emphasis is placed on the exact figuring of real process engineering conditions. The model includes time dependent intensive parameters such as the aluminium content and the oxygen content of the liquid steel as well as the temporal course of the CaO‐, CaS, Al2O3‐component activities in the refining top slag. Mass transfer coefficients are derived from practical experience.

The computations prove the outstanding influence of the stirring intensity on the rate of the refining reaction. Its progress is delayed by the dissolution of the lime charge at the beginning of the stirring treatment. The simulation model can also be applied to optimize the desulphurisation process with respect to stirring time, state of deoxidation and amount of refining slag.
Kinetic model for reduction of iron oxide in molten slags by iron‐carbon melt
Authors: Paul Amitava , Deo Brahma , Sathyamurthy Narayanasami
Published: December 2016

Rate of reduction of iron oxide in iron and steelmaking slags by mass contents of dissolved carbon (>3%) in molten iron depends upon activity of FeO, temperature, mixing of bulk slag and other experimental conditions. A general kinetic model is developed by considering mass transfer of FeO in slag, chemical reaction at gas‐metal interface and chemical reaction at gas‐slag interface, respectively, as the three rate controlling steps. A critical analysis of the experimental data reported in literature has been done. It is shown that in the case of slags containing mass contents of less than 5% FeO, the reduction of FeO is controlled by mass transfer of FeO in slag plus chemical reaction at gas‐metal interface; when slags contain more than 40% FeO, the reduction of FeO is controlled by chemical reaction at gas‐metal interface plus chemical reaction at gas‐slag interface; at intermediate FeO mass contents (between ∼ 5 and 40% FeO), the reduction of FeO is controlled by all three steps, namely, mass transfer of FeO in slag, chemical reaction at gas‐metal interface and chemical reaction at gas‐slag interface. The temperature dependence of rate constant for the gas‐slag reaction is obtained as:

In k2 = –32345.4(&6128)/ T + 19.0(&3.42); σlnk2,1/T = &0.3.

where k2 is expressed in mol m‐2 s‐1 bar‐1. The mass transfer coefficient of iron oxide in bulk slag is found to vary in the range 1.5 × 10‐5 to 5.0 × 10‐5 m/s, depending upon the slag composition as well as experimental conditions.
Phase transformations during tempering of the Fe‐15Cr‐1Mo martensites containing nitrogen or carbon
Authors: Berns Hans , Bugajchuk Sergej Nikolaijevitsch , Duz Vladimir Andrejevitsch , Ehrhardt Rüdiger , Gavriljuk Valentin Gennadijevitsch , Petrov Yuri Nikolaljevitsch , Yakubzov Igor Arkabijevitsch
Published: December 2016

Hardness measurements, dilatometry, internal friction measurements, Mössbauer spectroscopy and transmission electron microscopy are utilized in order to study the effect of tempering on the microstructure of a stainless martensitic steel containing 15% Cr, 1% Mo and 0.6% N. A similar carbon steel containing 15% Cr, 1% Mo and 0.6% C is used for comparison. Tempering of alloy Fe‐15Cr‐1Mo‐0.6N in the low temperature range of 353‐473 K leads to formation of hexagonal ∊‐nitride (Fe,Cr)2N, which is followed by precipitation of the orthorombic ∊‐nitride (Fe,Cr)2N at temperatures of 573‐773 K. The hexagonal nitride Cr2N is precipitated at 923 K and preferably formed at grain boundaries. The alloy Fe‐15Cr‐1Mo‐0.6C shows the expected tempering behaviour. ∊‐carbide (Fe,Cr)2C and cementite (Fe,Cr)3C are precipitated during low temperature ageing, followed by the formation of Cr7C3 carbides after the temperature has risen to 873 K. With a similar interstitial content the amount of retained austenite in the nitrogen martensite is nearly twice as high as in the carbon one. Furthermore, the thermal stability of the retained austenite of the nitrogen alloy is substantially higher than that of the carbon steel.
Kinetics of iron oxidation with water vapour at temperatures between 1300 and 1450°C
Authors: Yan Chengyu , Oeters Franz
Published: December 2016

In this paper measurements of the kinetics of iron oxidation in H2O‐containing gas mixtures of various compositions in the temperature range of 1300 to 1450°C, and metallographic examinations are described. The reaction product is solid wustite below and liquid iron saturated iron oxide above 1377°C, this temperature being the incongruent melting temperature of iron saturated wustite. The experiments were carried out by measuring the weight increase during the oxidation of an iron specimen connected to a thermo‐balance with a platinum wire. The water vapour was generated by means of a water vapour saturator. The rate law is linear in the beginning of the single experiment and later becomes parabolic. The linear law was interpreted as being caused by two resistances connected in series: the transport of the oxidising gas through the adjacent gas boundary layer, and the phase boundary reaction at the oxide interface. The parabolic law was interpreted as being determined by the transport of iron ions and vacancies through the growing oxide layer. The resistance of gas transport becomes negligible above a certain critical gas velocity which is, for example, 23 cm/s at 1342°C. The temperature‐dependent values of the phase boundary reaction rate constant were calculated with the help of known theories from the results of those experiments in which the gas velocities were above the critical value for gas transport at the respective temperatures. The parabolic law did not apply, when the oxidation product was liquid as under these circumstances the formed oxide dropped off the specimen during the experiment and hence, became no thicker than 22 μm. For all the experiments the oxide layer was composed of wustite, even when the oxygen potential of the reaction gas was far higher than that for equilibrium of the gas with wustite and magnetite. The surface structure of the oxide layer and the grain sizes varied with temperature. At lower temperatures the grains were relatively small while at higher temperatures they became extremely large up to a diameter of 6 mm.
Effect of sulfur on supersaturation in aluminum deoxidized liquid iron
Authors: Tanabe Jun , Suito Hideaki
Published: December 2016

The effect of sulfur addition on supersaturation observed in aluminum deoxidized liquid iron was studied at 1873 K, by using CaO‐Al2O3 slags in an alumina or lime crucible. The contents of supersaturated oxygen for a given aluminum level were not influenced by the addition of sulfur (mass contents of 1×10−5 ∼ 0.42%) in the experiments where the sample was rapidly quenched. However, in the experiments in which the sample was cooled from 1873 to 1723 K at a cooling rate of 2.7 K/min, the effect of sulfur on supersaturation was observed for mass contents of more than 0.01% sulfur. The critical supersaturation for alumina precipitation was discussed based on the variation of the interfacial energy between liquid iron and alumina.
Flow dynamics in thin slab caster moulds
Authors: Honeyands Thomas , Herbertson Joe
Published: December 2016

This study investigated the dynamic fluid flow phenomena that occurred in water models of a thin slab caster mould. The flow of fluid caused significant surface waves and was observed to be strongly oscillatory. The magnitude and the period of oscillation of these waves represent potential quality constraints in thin slab casting. The oscillation mechanism is explained in terms of the dynamic balance/imbalance between the pressure gradient across the jet emerging from the SEN and the opposing momentum of the recirculating, entrained flow.