bluuebunny/crossref_metadata_2025 huggingface dataset:
Zur Kinetik der verschleißinduzierten Wasserstoffeffusion aus unlegiertem Stahl
Authors: Pyun Su‐Il , Kim Jong‐Sang
Published: December 2016

Unter Anwendung elektrochemischer und massenspektrometrischer Methoden wird in der vorliegenden Arbeit versucht, sowohl die einzelnen Beiträge zur verschleißinduzierten Wasserstoffeffusion quantitativ zu erfassen wie auch den Zusammenhang zwischen der verschleißgeförderten Wasserstoffeffusion und der Wasserstoffanreicherung in oberflächennahen Bereichen zu erforschen. Haftungsverschleiß‐ und Furchungsverschleiß‐induzierte Wasserstoffeffusionsmechanismen sind meistens auf die mechanische Abtragung der wasserstoffangereicherten Schichten bzw. auf die Thermodiffusion aus diesen Schichten zurückzuführen. Nach einem Anlaufstadium stellt sich ein Gleichgewicht zwischen dem effundierenden und dem eingefangenen Wasserstoff ein. In diesem Stadium erfolgt die Wasserstoffeffusion mit stationärer Geschwindigkeit.
Beitrag zur Korrosion weicher, unlegierter Stähle in Natronlauge
Authors: Langenscheid Gerhard
Published: December 2016

In diesem Bericht werden Untersuchungsergebnisse mitgeteilt, die einen Beitrag zur Klärung des Korrosionsmechanismus weicher Stähle in heißer, konzentrierter Natronlauge darstellen.

An Stahlproben der Sorte St 12, aber mit C‐Gehalten von 0,06 bis 2,27%, wurden in 70°C heißer, gesättigter Natronlauge Stromdichte‐Potential‐Kurven aufgenommen. Neben einem Stromdichte‐Maximum bei ca. ‐0,85 V (UH), das der Ferritauflösung zuzuordnen ist, trat ein zweites Maximum bei ca. ‐0,68 V auf, das mit dem Zementitgehalt der Legierungen linear zunimmt und durch die Zementitauflösung verursacht wird. An Proben aus St 12 mit 0,06 % C, bei denen durch eine geeignete Wärmebehandlung die Ferritkorngrenzen stark mit Zementit belegt waren, wurden unter einer Zugspannung von 0,85 · Rm in der o.a. Natronlauge Korrosionsversuche von 100 h Dauer durchgeführt. Im Potentialbereich des ersten Maximums (‐0,87 bis ‐0,82 V) trat nur ein Angriff des Ferrits ein. Korngrenzen wurden nicht angegriffen. Bei höheren Potentialen (über ‐0,75 V) erfolgte zunehmend die Bildung interkristalliner Risse, verursacht durch die Auflösung des Korngrenzenzementits. Bei ‐0,68 V kam es nach 60 h zum Bruch.

Nach diesen Untersuchungen wird die interkristalline Korrosion weicher Stähle in heißer, konzentrierter Natronlauge durch aktive Auflösung des Korngrenzenzementits verursacht.
Measurements on the local properties of the vertical heterogeneous buoyant plume
Authors: Koria Satish C. , Singh Sarbjit
Published: December 2016

An electroresistivity sensor probe is developed and used to measure gas fraction and bubble frequency in turbulent air/water plume formed during upward injection of gas. The measured gas fraction and bubble frequency profiles at different axial positions in the plume are found to exhibit good similarity. It is found that the axial gas fraction decreases and plume radius increases with increase in axial distance. From the values of axial gas fraction and plume half radius, turbulent viscosity of liquid in bubble plume is determined and is found to be several times higher than the molecular viscosity.
Effect of weld heat input and creep strain on the elevated temperature and crack growth properties of austenitic steels
Authors: Kanbach Helmut , Detert Klaus , Rukwied Armin
Published: December 2016

A potential material class for use at 600°C and more, e.g. for steam turbines with improved thermal efficiency, are austenitic steels. Using these steels with welded joints, it is to be considered that, by superposition of weld residual stresses and service stresses, extensive creep strains – and in the worst case crack formation – can occur locally. To assess the influence of these effects on service behaviour, different material states of CrNi‐steels and Incoloy 800 were investigated with respect to strength, ductility and, especially, to crack and creep crack growth in the temperature range around 600°C. It is shown that creep embrittlement, not microstructural changes as effected by weld heat input, causes heat affected zone (HAZ)‐reheat cracking. Creep embrittlement can be avoided by special design and fabrication rules.
Erwärmung von Brammen und Knüppeln ohne Randentkohlung durch Kohlenstoffrestauration
Authors: Schüppstuhl Ernst Ludwig , Jeschar Rudolf
Published: December 2016

Die Erwärmung von kohlenstoffreichem Stahl in oxidierenden Atmosphären führt zur Randentkohlung. Anhand eines vereinfachten mathematischen Modells wird nachgewiesen, daß die Randentkohlung unmittelbar im Anschluß an die Erwärmung wieder rückgängig gemacht werden kann. Das Wärmgut wird hierzu nach Erreichen der Ziehtemperatur in einer kohlenstoffabgebenden Atmosphäre wieder aufgekohlt. Das Verfahren wird als Kohlenstoffrestauration bezeichnet.

Für die Guterwärmung kann ein weitgehend konventionell aufgebauter Wärmofen verwendet werden. Die Kohlenstoffrestauration findet in einem zweiten Ofen statt, dessen Atmosphäre durch Teilverbrennung geeigneter Brennstoffe erzeugt wird. Eine Wärmeübertragung an das Gut ist in diesem Ofen nicht vorgesehen. Die Brennstoffe müssen so zusammengesetzt sein, daß bei ihrer Teilverbrennung erstens eine ausreichende thermische Enthalpie freigesetzt wird, mit der die Atmosphäre auf die Wärmguttemperatur erwärmt und Wärmeverluste ausgeglichen werden können und daß zweitens das teilverbrannte Gas noch aufkohlend gegenüber dem randentkohlten Stahl wirkt. Es wird gezeigt, daß Brennstoffe mit einem Atomverhältnis von Wasserstoff zu Kohlenstoff von H/C < 2 beide Bedingungen im allgemeinen gleichzeitig erfüllen.

Wärmofen und der Ofen zur Kohlenstoffrestauration sind energetisch gekoppelt, indem das verbrauchte noch brennfähige Aufkohlungsgas im Wärmofen als Brennstoff eingesetzt wird. Die Kohlenstoffrestauration erfordert deshalb einen geringeren Energieaufwand als bisher übliche Verfahren zur Wiederaufkohlung von Stahl. Der Zeitbedarf für die Kohlenstoffrestauration ist aufgrund der hohen Prozeßtemperatur der Wärmzeit des Gutes ähnlich.
On the trueness of total boron contents of some certified reference steel samples
Authors: Ambrose Alan D. , Harine Michel , Staats Gotthard , Weichert Edgar
Published: December 2016

In order to obtain true values for the boron content of steel samples, the need for complete dissolution of all boron phases present in the steels is stressed and the importance of an appropriate calibration procedure is also emphasised. The results of international research by ECISS/TC20 using direct spectrophotometry with curcumin (pr EN 10 200) have been compared with those of the curcumin method after separation by 2‐ethyl‐1.3‐hexanediol‐chloroform extraction and those of the 1.1'‐dianthrimide method after distillation of the boron methylester by means of an all‐quartz apparatus. The results obtained were independent of the method of determination.
The CaS solubility in the CaO bearing slags
Authors: Uo Motohiro , Sakurai Eiji , Tsukihashi Fumitaka , Sano Nobuo
Published: December 2016

The CaS solubility and sulfide capacity for the CaO–SiO2–CaF2 and CaO–Al2O3–SiO2 systems have been measured at 1300°C and 1400°C, respectively.

With the CaO–SiO2–CaF2 system, the slag doubly saturated with CaO and 3CaO · SiO2 has the highest CaS solubility of 12.5 wt.%. On the liquidus the slag always has a higher CaS solubility than when it is not on the liquidus. The sulfide capacity was confirmed to decrease with increasing SiO2 content.

With the CaO–Al2O3–SiO2 system, the CaS solubility was found to depend only on CaO content. A good correlation between the sulfide capacity and the CaS solubility was observed as expected from theory.

The temperature dependence of CaS solubility in those systems was also discussed.
Kriechrißverhalten typischer Kraftwerksbaustähle
Authors: Granacher Joachim , Tscheuschner Reinhard , Maile Karl , Eckert Wilhelm
Published: December 2016

Zur Auslegung und Überwachung von Hochtemperaturbauteilen für Kraftwerke und thermische Anlagen werden Kenntnisse über das Kriechrißverhalten unter langzeitiger Beanspruchung benötigt. Auf der Basis von Kriechrißversuchen sind für wichtige Kraftwerksbaustähle geometrie‐ und beanspruchungsunabhängige Beschreibungen zur Kriechrißeinleitung und zum Kriechrißfortschritt zu gewinnen.

An vier Kraftwerksbaustählen wurden mit Proben unterschiedlicher Form und Größe Kriechrißversuche in einem weiten Beanspruchungsbereich durchgeführt. Dabei wurden Kriechrißgeschwindigkeiten bis herab zu 5 · 10−5 mm/h bei Versuchsdauern bis zu 14 000 h erreicht.

Die Kriechrißgeschwindigkeit der bei 550°C untersuchten Stähle 30 CrMoNiV 4 11, X 22 CrMoV 12 1 und X 20 CrMoV 12 1 läßt sich mit dem Parameter C2* in deutlich engeren Streubändern beschreiben als mit den Parametern C1* und Kl. Nur für den bei 450°C untersuchten Stahl X 12 CrNiMo 12 2 eignet sich der Parameter Kl besser zur Beschreibung der Kriechrißgeschwindigkeit.

Die Kriechrißeinleitung läßt sich mit einem Zwei‐Kriterien‐Diagramm abschätzen, das für größere Proben und damit vermutlich auch für größere Bauteile eher überkonservativ ist.
Temperaturverteilung in der berohrten Kesselwand eines Konverterkühlkamins
Authors: Gudenau Heinrich Wilhelm , Dahl Winfried , Koerfer Markus , Scheiwe Michael
Published: December 2016

In der vorliegenden Arbeit wurden zunächst die verschiedenen Möglichkeiten zur Bestimmung zweidimensionaler Temperaturverteilungen in eng berohrten Kesselwänden diskutiert. Es zeigte sich, daß erst die Anwendung der Finite‐Element‐Methode den Zugang zu Lösungen des Temperaturfeldes unter Berücksichtigung der Temperaturabhängigkeit der Werkstoffeigenschaften, der Instationarität der äußeren thermischen Belastung, des Energiespeichervermögens des Werkstoffes und der speziellen geometrischen Merkmale berohrter Kesselwände eröffnet. Dabei wurde die Einbettung der Kesselrohre in den Prozeßablauf des LDAC‐Verfahrens durch geeignete, zeitabhängige thermische Randbedingungen simuliert. Zur graphischen Dokumentation der numerischen Rechenergebnisse wurden Linien gleicher Temperatur über den aus der Kesselwand gewonnenen Modellausschnitt gelegt. Die feuerraumseitige Rohrscheitellage erwies sich als die thermisch gefährdetste Zone.
Investigations concerning the crack resistance behaviour of thick‐walled components under thermal shock loading
Authors: Roos Eberhard , Guth Wolfgang
Published: December 2016

Pressurized thermal shock tests carried out on a thick‐walled hollow cylinder (NKS3) and on the HDR pressure vessel are subject of this investigation. With the NKS3 thermal shock test the behaviour of a 360° circumferential crack subjected to axisymmetrical cooling was examined. After 7 min crack initiation and stable crack growth occurred. At the HDR reactor pressure vessel circumferential cracks in the cylinder wall were loaded by thermal‐shock strip cooling (ΔT = 280 K) starting from operational conditions (p = 106 bar, T = 310°C). The numerical analyses are in good agreement with the experimental results, provided the triaxiality of the stress state in front of the crack tip as well as the branches of the crack on the HDR cylinder are also taken into consideration.
Rißwachstum warmfester Werkstoffe unter überelastischer Wechselverformung bei erhöhter Temperatur
Authors: Kullik Matthias , Maile Karl
Published: December 2016

An den warmfesten Stählen 13 CrMo 4 4 und 28 CrMoNiV 5 9 wurden Rißwachstumsuntersuchungen im Ermüdungs‐ bzw. Kriechermüdungsgebiet durchgeführt. Dabei sollte der Einfluß einer Vorbehandlung der Werkstoffe in Form einer Zeitstandbeanspruchung auf das Rißwachstum untersucht werden. Die Werkstoffe wurden dazu bei 560°C mit 2 % Kriechdehnung vorbeansprucht. Der Rißfortschritt je Zyklus wurde in Abhängigkeit von Probenform, Temperatur, Spannungsverhältnis, Versuchsfrequenz und Haltezeiten bestimmt. Für Kompaktproben beider Werkstoffe wirkt sich bei Ermüdungsversuchen die Zeitstandvorbeanspruchung nicht auf das Rißwachstum aus. Für mittengeschlitzte Flachproben führt sie jedoch zu einem starken Anstieg der Rißfortschrittsrate. Der Einfluß des Spannungsverhältnisses ist probenabhängig und kann bei einer modifizierten Auswertung vernachlässigt werden. Die Abhängigkeit von der Versuchsfrequenz ist oberhalb 0,005 Hz gering. Haitezeiten von 90 min Dauer bei Lastumkehr führen jedoch zu einem wesentlich schnelleren Rißwachstum.
Precipitation effects in austenitic stainless weld metals
Authors: Borst Karin , Pohl Michael
Published: December 2016

Creep‐rupture specimen of similar welded joints of X6 CrNi 18 11 (1.4948/AISI 304) and X6 CrNiMo 1713 (1.4919/AISI 316) show only low elongation after longtime testing. The reason for this loss of ductility was found by metallographic investigations.

The weld metal of five joints had ferrite contents from 3 to 7.5%, due to a primary ferritic solidification. During creep testing in the temperature range from 500 to 800°C carbide precipitation takes place at the austenite‐ferrite grain boundaries, because delta ferrite is not in a state of equilibrium at these temperatures. After carbon has been used up, the remaining delta ferrite changes into sigma phase, if its alloying element content is high enough. In the upper temperature range, coagulation of sigma phase is dominating. At these large particles grain boundary migration is hindered. During the grain boundary sliding sigma phase particles break and initiate creep cracks. In fully austenitic weld metal sigma precipitation starts at austenite – austenite grain boundaries. During creep testing, void formation starts at sigma particles. Growing of voids leads to grain separations.
Crack growth in welded turbine materials at elevated temperatures
Authors: Kanbach Helmut , Rukwied Armin , Detert Klaus
Published: December 2016

Due to thermal gradients and load changes steam‐turbine casings suffer combined creep‐fatigue loading. Creep and fatigue portions depend on service conditions. Special interest is focused on the behaviour of creep‐fatigue cracks, originating from potential defects due to construction and manufacturing weldments, on residual lifetime assessment. The project deals with the crack‐growth behaviour at 530°C and r.t. of welded and unwelded heat‐resistant cast steels: 1% CrMoV‐cast (GS‐17 CrMoV 5 11, two melts: low and high V‐content) and 12% CrMoV‐cast (G‐X 22 CrMoV 12 1). The crack planes of CT‐specimens investigated, taken from manual arc‐welded plates, were situated in the heat‐affected zone (HAZ). The fatigue, creep and combined creep‐fatigue crack‐growth behaviour was investigated by means of low‐frequency (0.5 and 0.05 Hz) tests, holding‐time (20 min) tests and constant load tests up to about 5 000 h.

Metallographic investigations show that in the case of both 1% and 12% CrMoV‐cast weldments the preferred crack path lies in the outest, i.e., the high tempered and not α/γ transformed region of the HAZ. A strong increase on the crack‐growth rate at 530°C is exerted by dominant creep portions. In the case of the 1% CrMoV‐cast this acceleration becomes important at stress intensity ranges higher than about 25 MPa√m with some higher sensitivity of the HAZ. For the 12% CrMoV‐cast creep dominance begins at about 50 MPa√m. No differences for the HAZ and the base material were found for this material.
Fields of activity of the Institute of Energy Process Technology of the Technical University of Clausthal
Authors: Jeschar Rudolf , Pötke Wolfgang , Scholz Reinhard
Published: December 2016

The report presented here is a description of the main fields of activity of the Institute of Energy Process Technology of the Technical University of Clausthal. The institute investigates both fundamental problems and those arising in the industrial practice in the field of high‐temperature technology for the areas of heat and mass transfer, thermodynamics, flow technology, combustion and chemical kinetics.

The production process in a metallurgical plant, including the areas of blast furnace, steel work, continuous casting and heating furnaces in the rolling mill as well as heat treatment plants, is taken as a basis to expound on the current activities of the institute in greater detail. This volume informs on the results of investigations concerning the areas of blast furnace, steelwork and continuous casting. The following volume will contain the themes from the remaining two areas of production mentioned above, which will be supplemented by investigations into the minimization of the energy consumption in continuous furnaces for the ceramics, lime and cement industries and into the low‐pollutant combustion of difficult fuels.
Investigations of gas‐particle‐lance flows at high velocity for the injection of solid in melting baths
Authors: Orlowski Reiner , Scholz Reinhard
Published: December 2016

For the injection of gas and solid into molten masses using lances the situation at the lance outlet is a boundary condition for the mixing in the melting bath and therefore an important parameter for the energy and mass exchanges which take place there. In the scope of the main research programme of the Deutsche Forschungsgemeinschaft named “Mischung mit Energie‐und Stoffumsatz in schmelzmetallurgischen Systemen”, a mathematical model is to be developed at the Institut für Energieverfahrenstechnik der Technischen Universität Clausthal, which should make it possible to calculate the situation at the outlet of a lance operating with gas and solid, using operational and geometrical parameters (pressure at lance intake, amount of solid, length and diameter of lance) which can be freely chosen.
Heat transfer with film quenching of vapourizing liquids
Authors: Köhler Christian , Specht Eckehard , Jeschar Rudolf
Published: December 2016

The heat transfer for film quenching was investigated theoretically and experimentally. With the aid of a mathematical model analytical equations were deduced, with which the locally transferred heat‐flux density and the local thickness of the vapour film can be calculated during stable film boiling. The equations were confirmed by experimental results. Accordingly, the heat transfer can be technically influenced only by the velocity of the water leaving the nozzle. With increasing jet velocity of the water not only the transferred heat flux during stable film boiling becomes higher but also the thickness of the vapour film becomes smaller, so that the film collapses earlier, causing the Leidenfrost temperature to shift to higher values.
Magnetic properties of non‐oriented magnetic steel at medium frequencies
Authors: Lex Albert , Huneus Hans
Published: December 2016

The magnetic properties of non‐oriented magnetic steel are specified at a frequency of 50 or 60 Hz. The effect of increasing the frequency of the magnetizing field upon the specific total loss, the field strength and the specific apparent power is demonstrated. Regarding the non‐oriented steel at 50 Hz total loss comprises mainly hysteresis loss, whereas the eddy‐current loss of most of the grades amounts to less than 40%. The approximately square increase of the eddy‐current loss with frequency means that at 400 Hz the total loss is determined by the resistivity. For excitations up to a peak polarization of 1.6 T increasing sheet thickness results in an increasing field strength at 400 Hz. While at 50 Hz low‐alloyed grades have a lower field strength above 1.3 T, at 400 Hz the field strength of the high‐alloyed grades is more favourable up to 1.4 T. With respect to the apparent power, the square of which is proportional to the copper losses, there is an advantage of the higher alloyed grades up to 1.5 T.
The generation of stress and strain during the quenching of steel plates in polyalkylene glycol solutions
Authors: Allen Frances Sarah , Fletcher Alfred John , King Susan
Published: December 2016

An examination has been made of the effect of increasing polyalkylene glycol concentration on the generation of thermal stress and strain in steel plates of a high hardenability steel 835M30, using a viscoelastic‐plastic mathematical model. The results obtained from these quenched specimens suggest that the residual stresses and strains were not greatly affected by concentrations of the proprietary Aquaquench 1250 within the range 5% to 25%, although the addition of up to 5% of this solution did markedly reduce the residual stress and strain. At the same time the reduction in the Aquaquench 1250 from 25% to 5% greatly reduced the duration of the vapour blanket stage of the quench, so it might be possible to produce a fully martensite structure in a lower hardenability steel without adversively affecting the level of stress and strain at the end of the quench.
Electrical conductivities of M3P2O8 (M = Ca, Ba)
Authors: Ohshita Hiroshi , Fujiwara Hiroyasu , Iwase Masanori
Published: December 2016

Two‐probe conductivity measurements made for M3P2O8 (M = Ca, Ba) suggested that the electrical conduction of these phosphates would primarily be due to the migration of Ca2+ and Ba2+ ions. At relatively low temperatures and high oxygen partial pressures, in contrast to Ca3P2O8, however, Ba3P2O8 shows partial electronic conduction.
Texture analysis by electron diffraction
Authors: Schwarzer Robert A.
Published: December 2016

Electron diffraction methods for the determination of individual grain orientations and selected area diffraction (SAD) pole figures are briefly reviewed. The standard techniques of orientation determination grain‐by‐grain are the interpretation of selected‐area electron spot and microbeam Kikuchi diffraction patterns with a transmission electron microscope (TEM). Electron‐transparent thin samples are required. Specimen areas smaller than 500 nm or 10 nm in diameter, respectively, can be studied. Alternatively, selected area pole figures can be measured on a TEM. This technique is similar to the conventional transmission x‐ray method. The orientations of grains in a bulk sample are obtained with a scanning electron microscope (SEM) from back‐reflection Kikuchi patterns (i.e. electron backscattering patterns) or from channelling patterns. Spatial resolution is approximately 1 μn or 5 μm, respectively.

Individual grain orientation and pole figure measurements can be performed on‐line by interfacing the electron microscope with a computer. Outstanding advantages of texture measurement by electron microscopy over x‐ray and neutron diffraction are the ability to image the microstructure of the sampled area which complements texture measurement, and the high spatial resolution in diffraction and imaging modes. Experimental results of individual grain orientation measurement may be represented by inverse pole figures, orientation distribution functions, and misorientation distribution functions.
Graphical representations of orientations and ODFs by Rodrigues vectors
Authors: Neumann Peter
Published: December 2016

The most commonly used representation of orientations in the space of the Euler angles has two serious deficiencies: 1) The invariant volume element has a singularity at ϕ = 0.2) In the case of cubic symmetry the common representation has a threefold ambiguity. Both disadvantages can be avoided by using the representation by Rodrigues vectors which is the geodesic projection of the quaternion representation and is characterized by mathematical simplicity. Especially, all symmetry induced subspaces are bounded by piecewise plane surfaces, and all fibre textures are represented by straight lines. With the help of examples it is demonstrated that the graphical appearance of real textures is simpler in the Rodrigues representation.
Einfluß des Sauerstoffs auf die Ausbildung von Aluminiumoxiden in Eisenschmelzen
Authors: Steinmetz Eberhard , Andreae Christoph
Published: December 2016

Die Ausbildung und Beeinflussung von Aluminiumoxiden bei Reoxidation wurden in Laborschmelzen mit einer kombinierten Sauerstoff‐Meß‐ und Dosierzelle untersucht. Die Konzentrationsgrenzen und die Stoffstromdichten, die für die Bildung bestimmter Einschlußformen bestimmend sind, wurden in vordesoxidierten Proben ermittelt. Zusätzlich wurde das Verhalten bei veränderlichen Sauerstoffstromdichten und bei gleichzeitiger Beaufschlagung mit Sauerstoff und reinem Aluminium von gegenüberliegenden Seiten aus untersucht. Aus den generellen Richtungen der Stoffströme darf möglicherweise nicht auf die örtlich aktuellen Stoffströme geschlossen werden, da bestimmte Einschlußformen an zunächst nicht erwarteten Stellen, aber reproduzierbar, auftraten. Grenzflächenaktive Wirkung des in Eisen gelösten Sauerstoffs ist als Ursache nicht auszuschließen.

Umbildungen in der Morphologie oder Auflösungen von schon gebildeten Phasen fanden – zumindest unter den hier vorliegenden Versuchsbedingungen – nicht statt, wohl aber Neubildungen an anderen Orten nach der bekannten Abfolge der Einschlußbildung.
Influence of alloying elements and metalloids on the emulsion and separation behaviour of steel and slag
Authors: Gammal Tarek El , Hinds Geoffrey , Schoneberg Ulrich
Published: December 2016

With the aid of surface and interfacial tension data it has been possible to clarify the effect of the elements nickel, titanium and sulphur in steel and titanium oxide and sulphur in slag on the emulsifying or separating tendencies of liquid steel/molten slag phases. This has been related to the tendency of (scattered) liquid steel films to adhere to gas bubbles crossing the interface, which in turn leads to the formation of metal droplets in the slag phase. Nickel containing steels tend to form emulsions, whereas titanium, both dissolved in the steel and as titanium oxide in the slag, tends to suppress adherence of the steel to the bubbles and promotes steel/slag separation. Sulphur containing steels show also an emulsifying tendency in contact with both sulphur containing and sulphur free slags. With sulphur present in the slag, however, the opposite effect is observed, so that, as sulphur transfer proceeds between the steel and the slag during desulphurization, the emulsifying tendency is markedly reduced, leading to steel/slag separation.
Bestimmung des gelösten Kohlenstoffgehaltes in feuerverzinktem Stahlblech mit dem Torsionspendel
Authors: Fuchs Axel , Haeussler Eberhard N.
Published: December 2016

Zur Bestimmung des gelösten Kohlenstoffgehaltes an streifenförmigen Feinblechproben wurde ein Torsionspendel vom Collette‐Typ aufgebaut. Grundlagen, Meßprinzip und Aufbau des Geräts werden beschrieben. Anhand einer Eichreihe und unter Anwendung der beschreibenden Statistik wurde eine Nachweisgrenze von 1,7 · 10−4 Massenanteilen in % ermittelt. An betrieblich feuerverzinktem Feinblech wurde der Einfluß der Ofenaustrittstemperatur und des Gesamtkohlenstoffgehalts auf den gelösten Kohlenstoff untersucht. Danach nimmt mit steigender Ofenaustrittstemperatur der Gehalt an gelöstem Kohlenstoff deutlich zu. Dagegen nimmt der Gehalt an gelöstem Kohlenstoff mit zunehmendem Gesamtkohlenstoff ab.
Geometrische und kinematische Grundlagen beim Ringwalzen
Authors: Koppers Ulrich , Kopp Reiner
Published: December 2016

Der Radial‐Axial‐Ringwalzprozeß unterscheidet sich grundlegend vom Längswalzen. Infolge der kontinuierlichen Walzenzustellungen in zwei Walzspalten ist er instationär. Erst ein kinematisches Prozeßmodell erlaubt die sichere Verfolgung der sich ständig ändernden Prozeßbedingungen und ermöglicht eine nach umformtechnologischen Kriterien geführte Prozeßbeeinflussung mittels eines Prozeßrechners. Die Kinematik und Geometrie des Walzprozesses wird analysiert und mathematisch formuliert. Die dieses Bewegungssystem darstellende Differentialgleichung wird entwickelt. Sie beschreibt die Verknüpfung von Walzgeschwindigkeit, Ringgeometrie und den Formänderungen in den beiden Walzspalten. Hierauf basierend werden die Funktionen der Ringquerschnitte entlang des Ringumfanges abgeleitet. Das entwickelte adaptive Prozeßmodell wird mittlerweile mit Erfolg industriell unter den vielfältigsten Produktionsbedingungen eingesetzt. Die mit dem Einsatz sich einstellende Transparenz des Ringwalzprozesses hat neben den neuen technologischen Anwendungen eine wesentliche Vereinfachung in der Bedienung und eine Reduzierung bisheriger Fehlermöglichkeiten erbracht. Neue Prozeßüberwachungsmöglichkeiten für die Maschinendiagnose sind ebenso ein wichtiger Fortschritt.
Prediction of the creep behaviour of metallic materials under step loading using a simple mechanical model
Authors: Pantelakis Spiros G. , Batsoulas Nikolaos D. , Kermanidis Theodor B.
Published: December 2016

The creep exposure of metallic parts usually occurs under time‐variable loading conditions. For the prediction of creep behaviour under step loading a simple mechanical model is employed. The model is based on the time dependence of the material structure during creep. Therefore, the characteristic parameters of the model are considered to be functions of time and are correlated with the time dependence of the material structure parameters. For the definition of these functions a structure mechanical model has been employed. The mean internal material resistance has been considered as an appropriate structure parameter. The characteristic parameters of the model are defined in each step loading on the basis of the change of the internal stress derivative.

For the verification of the model prediction the numerical results are compared with experimental results of the austenitic steel X 8 CrNiMoNb 16 16 for the orthogonal cyclic stress function.
Metallurgical results from a 30‐t AC plasma ladle furnace
Authors: Neuschütz Dieter , Schubert Karl‐Heinz , Bebber Hans J.
Published: December 2016

In a 30‐t ladle furnace equipped with three A.C. transferred arc‐plasma torches for a power input of 6 MW, the influence of argon plasma heating on the chemical composition of a number of steel grades from carbon to chromium‐nickel steels was investigated. The concentrations of carbon, manganese, chromium and nickel remained virtually constant even for extra‐long heating periods of 2 hours. Silicon melting loss was appr. 0.03%/h, comparable to conventional ladle furnaces. Nitrogen pickup proved to be negligibly small, although the N2 partial pressure in the furnace was about 0.5 bar. Since the slag is well heated up by the plasma flames, a metal desulphurization is noticed, the extent of which depends on the basicity of the slag. At the slag/gas interface, equilibrium is established with the slightly oxidizing furnace atmosphere, leading to sulphur transfer from slag to gas via SO2.
Experiments on the development of non‐oxidizing fluxes for continuous steel casting
Authors: Hammerschmid Peter , Janke Dieter
Published: December 2016

An attempt has been made to eliminate easily reducible oxide components, such as SiO2, TiO2, alkaline oxides and Fe2O3 and thereby exclude oxygen sources from casting fluxes. The new casting fluxes are based on CaO, Al2O3, MgO, SrO with limited amounts of alkaline and alkaline earth fluorides. Melting behaviour, viscosity, Al2O3 solubility and wear of submerged nozzles is essentially the same as that of conventional casting fluxes. The new fluxes also tend to undergo glassy solidification.
Model experiments on mass transfer in ladle metallurgy
Authors: Mietz Jürgen , Schneider Stefan , Oeters Franz
Published: December 2016

Model experiments on mass transfer in gas‐stirred ladles were carried out in reactors of different geometric dimensions. The model system consists of: water, cyclohexan as model slag, iodium as element to be extracted from water into slag phase, and compressed air as stirring gas.

The experimental results show that when using an eccentric bottom nozzle, rate constants of mass transfer are always smaller than with centric gas injection. Centric stirring leads to comparatively larger increases of rate constants if a certain gas flow rate is exceeded. Both results can be explained by different emulsification conditions of slag phase.

Theoretical calculations of residence times show that mainly the emulsification of small droplets taken along by the recirculation flow is responsible for accelerations of mass transfer in gas‐stirred ladles.
Thermomechanical properties of iron and iron‐carbon alloys: density and thermal contraction
Authors: Jablonka Angela , Harste Klaus , Schwerdtfeger Klaus
Published: December 2016

For the modelling of strains und stresses arising during solidification data on the mechanical and thermal properties of the steel are needed. Data on density and on related properties of iron and iron‐carbon alloys in the literature were evaluated giving the thermal contraction as a function of temperature and carbon content.
Nitride capacities in CaO–SiO2 and CaO–SiO2–Al2O3 melts
Authors: Tomioka Katsutomo , Suito Hideaki
Published: December 2016

Nitride capacities, , defined by (mass‐% N) · in the CaO–SiO2 and CaO–SiO2–AI2O3 melts were measured in the temperature range of 1 723 to 1 923 K by a gas‐slag equilibration technique using CaO, Al2O3, and Mo crucibles. Nitrogen content in slag, (mass‐% N), was proportional to oxygen partial pressure, , to the power of −3/4 at constant nitrogen partial pressure, . The values for increased linearly with increasing temperature and increased with the content of nitride formers, SiO2 and Al2O3, but the effect of SiO2 on value was found to be greater than that of Al2O3. The activity coefficients of Si3/4N in the CaO–SiO2 melts tended to increase with increasing the content of SiO2.
Comparison of interrupted and uninterrupted creep rupture tests
Authors: Granacher Joachim , Oehl Markus , Preußler Thomas
Published: December 2016

Characteristic differences between the interrupted and the uninterrupted creep‐rupture test are shown. Possible reasons for different test results are analysed. Specially designed comparison tests indicate that the results based on the different test methods remain within an expected scatterband dictated by inaccuracies of the testing techniques.
Chemical behaviour of nitrogen in metallurgical slags
Authors: Wenz Heike , Janke Dieter
Published: December 2016

According to previous experimental work, nitride capacity CN, in opposition to sulfide capacity CS, decreases with increasing optical basicity of metallurgical slags. This tendency is also confirmed by the contradictory behaviour of the free energy changes of oxide‐nitride and oxide‐sulfide transformation reactions as a function of basicity.

From the present metal‐slag equilibrium studies, denitrogenation potentials PN = %(N)/{%[N] · %[Al]} were obtained characterizing denitrogenation efficacy of slags at given compositions and temperatures. From these potentials, factors were derived which mark the effects of individual slag components. It was found that these factors feature the same basicity dependence as nitride capacities CN and denitrogenation potentials PN. The factors are increased, e.g., as less basic oxides are increasingly present in the slag phase in the order BaO → SrO → CaO → MgO.
Dephosphorization of Mn‐based alloys
Authors: Ma Zhongting , Ni Ruiming , Zheng Chongjie , Wang Jinshu
Published: December 2016

The critical oxygen partial potential of dephosphorization in liquid Mn‐base alloys under oxidizing or reducing conditions has been determined by thermodynamic analysis. Under oxidizing conditions, thermodynamic conditions to achieve dephosphorization and avoid manganese oxidizing were given. The results of thermodynamic analysis show that BaO‐base slag can be an effective dephosphorization agent for Mn‐base alloys. Under reducing conditions, the high degree of dephosphorization in Mn‐base alloys can be obtained based on thermodynamic analysis. In experimental work, BaCO3 was added to remove phosphorus from Mn–Fe–C melts. The time needed for equilibration of the dephosphorization reaction of Mn–Fe–C melts was determined at 1573, 1623 and 1673 K. The refining results were experienced as dephosphorization efficiency ≠p = (%[P]0 − %[P])/%[P]0. Moreover, the effect of the initial content of Si and C on ≠p was investigated. ≠p in the Mn–Fe–C melts was also given as a function of temperature. Dephosphorization reaction in Mn–Fe–C melts is of first order.
Relation between microstructure and some mechanical properties of dual‐phase medium‐C–Cr cast steel
Authors: El‐Ghazaly Saied A. , Abbas Mohamed A. , Ibrahim Khalid
Published: December 2016

The influence of dual‐phase structure (ferrite + martensite) on the impact toughness and rate of abrasive wear for as‐cast and normalized steel (0.29 C, 1.15 Mn, 0.9 Si and 0.95% Cr) is investigated. The increased grain refinement and the well arranged lamellar packets of martensite and ferrite obtained during intercritical quenching (from 810°C) of normalized and prequenched (from 880°C) steel created a satisfactory combination between toughness and abrasive wear resistance over those measured for intercritically quenched as‐cast steel with or without prequenching.
Studies on kinetics of strain ageing in Nb, Ti, V‐bearing HSLA steels and a dual‐phase steel
Authors: Panda Ashok Kumar , Ganguly Ratan Indu , Misra Somnath
Published: December 2016

Strain‐ageing behaviour of different high‐strength low‐alloy (HSLA) and dual‐phase steels was investigated. Single factor experiments were carried out to decide on the range of variation of variables for construction of the matrix of experimental design. Quantitative relationships between time and temperature of ageing (within a narrow range) at constant pre‐strain, with increase of yield strength after strain ageing was developed in the form of regression equations by applying statistical design of experiments. Validity of these equations was checked by statistical method as well as by random experiments. Activation energies for strain ageing of these steels were determined by using the developed regression equations. These values were in close agreement with the values reported by other investigators.
Martensitic high‐nitrogen steels
Authors: Berns Hans
Published: December 2016

Interstitial nitrogen considerably improves the corrosion resistance of low‐tempered martensitic stainless steels. It may be introduced into the bulk by pressure melting or powder metallurgy and into a surface layer by case hardening. The new high‐nitrogen steels (HNS) are suitable for stainless tools and bearings.

High‐tempered HNS are outstanding due to a fine dispersion of stable nitrides, which improve the hot and short time creep strength as well as the toughness. This may be used in hot‐work tooling. Long time testing will have to prove whether HNS offer advantages in fossile power plants.
Fractality and reversibility of ferrous martensite
Authors: Hornbogen Erhard , Skrotzki Birgit
Published: December 2016

Martensite formation is characterized by a diffusionless structural phase transformation from austenite to martensite, associated with a considerable amount of lattice variant shear γγα ≍ 0.2. Ferrous martensite shows all possible features connected with the transformation. Different modes of initiation of the martensite formation are possible. The reasons for the burst phenomenon can be considered as an analogy to discontinuous yielding. The transformation only procedes if further thermodynamical driving force is provided by cooling or shear stress. In some cases fractal microstructures are formed in which several fragmentations can be recognized. In contrast to shape memory alloys, steels usually do not show reversibility of the reverse α → γ transformation. The factors which favour reversibility have been defined. Knowledge of these is necessary for the development of iron‐base shape‐memory alloys.
Calculation of phase equilibria for AISI M2 high‐speed steel
Authors: Golczewski Jerzy , Fischmeister Hellmut F.
Published: December 2016

Thermo‐calc computations have been made for the iron‐rich corner of the system Fe‐Cr‐Mo‐W‐V‐C to obtain phase equilibria for AISI M2 high‐speed steel (German designation S‐6‐5‐2). The calculations describe the main transformation temperatures of this steel with good accuracy. The phases which are present during austenitization and their volume fractions are also correctly accounted for. The solidification sequence of the M2 steel, and in particular the occurrence of M2C in the ledeburitic eutectic, can be explained if the segregation of alloying elements and carbon in the interdendritic spaces is taken into account. The secondary hardening precipitates can be described in satisfactory approximation on the basis of local two‐phase equilibria between each carbide and the matrix, indicating that their compositions are essentially determined by the nucleation process.
Retained austenite in the cracking process of steel on the working rolls of the cold sheet rolling mill
Authors: Pacyna Jerzy
Published: December 2016

It was proved that the volume fraction of retained austenite (RA) in the quenched samples of the 0.80%C, 1.80%Cr, 0.23%Mo, 0.17%V steel on the working rolls of cold sheet rolling mills depends on their sizes. During tempering of this steel at 160°C the RA is stabilized so strongly that it is transformed neither by means of stresses nor strains. It was computed that in this steel, every 1% by volume of RA increases its fracture toughness (Klc) by about 5%. Under conditions of dynamic loading the power of effect of RA is increased to about 7%.
Possibilities of influencing the γ‐α‐transformation products of hot‐rolled pearlitic steels
Authors: Lang Cestmir , Kaspar Radko , Koschlig Manfred
Published: December 2016

Controlled alloying, optimum configuration of the rolling schedules, and a suitable cooling strategy make it possible to broadly influence the microstructure and mechanical properties of higher‐carbon steels. Increasing the manganese content and microalloying with vanadium delay the diffusion‐controlled γ‐α‐transformation, and the increase in the amount of pearlite improves strength properties. Lowering of the finishing temperature refines the austenite microstructure, and increases the level of residual strengthening that remains in the austenite. This changes the amount of ferrite and improves the resistance to brittle fracture. Applying a cooling interruption step in the ferrite formation temperature range also permits an additional variation of the amount of ferrite. The extent to which recalescence develops during the formation of pearlite can bring about significant changes in the pearlite morphology and hence influence strength and toughness properties. Accelerated cooling to a low coiling temperature, as a further process‐related modification, promotes the formation of bainite, obtaining high strength properties without any mentionable loss of toughness.
Bruchzähigkeit niedriglegierter Stähle mit heterogenen Martensitgefügen
Authors: Dlouhý Ivo , Garasim Julian A. , Škarek Jiří
Published: December 2016

Für niedriglegierte MnSiCrMoV Versuchsstähle mit drei verschiedenen Kohlenstoffgehalten wurde der Einfluß der heterogenen Martensitgefüge, die durch Schnellaustenitisierung des ferritisch‐carbidischen bzw. martensitischen Ausgangsgefüges und anschließendes Abschrecken und Anlassen erzeugt wurden, auf die mechanische Eigenschaften untersucht. Verglichen mit homogenem Martensit ist die Bruchzähigkeit bei martensitischem Gefüge mit geringem C‐Gehalt, das Reste ungelöster Carbide bei allen untersuchten Stählen aufweist, ohne größeren Festigkeitsverlust angestiegen. Im Versuchsstahl mit 0,3 % C führt das martensitische Gefüge, das Mikrobereiche mit erhöhtem Anteil an Carbidbildnern enthält, zu einer gleichzeitigen Erhöhung von Festigkeit und Bruchzähigkeit. Das erblich modifizierte Martensitgefüge weist deutlich höhere Festigkeiten – um etwa 150 MPa – auf, ohne daß die Bruchzähigkeit beeinträchtigt wird. Gleichzeitig wird die Übergangstemperatur um etwa 50°C erniedrigt.
The effect of loading rate on the strength and toughness of fine‐grained structural steels
Authors: Kussmaul Karl , Dernier Thomas
Published: December 2016

The effect of loading rate on the strength and deformation characteristics of tensile tested smoothed round bar specimens and on linear‐elastic and elastic‐plastic fracture toughness values was investigated. Test materials were a high toughness melt of the fine‐grained structural steel 20 MnMoNi 5 5 and two model materials of reduced toughness. The strain rate was varied between ∊̇ = 10−3and 103s−1in the tensile tests, the loading rate betweenK̇= 1 and 2 · 106MPam1/2s−1in the fracture toughness tests. The true‐stress true‐strain curve is shifted to higher stresses with increasing strain rate. A reduction of the deformation characteristics was only observed in cases of extremely reduced toughness. However, no brittle fracture at nominal stresses below yield was found in the tensile tests with smoothed specimens. Contrary to that all fracture mechanics tests showed a reduction of the crack initiation toughness with increasing loading rateK̇.
Investigation on the effect of Zn on the behaviour of S in the iron bath smelting reduction process
Authors: Li Hong‐jie , Tokuda Masanori
Published: December 2016

A computer program system was developed to simulate the smelting reduction ironmaking process. In this study, the effects of zinc, temperature, and post combustion ratio of the gas generated from the smelting reduction furnace on the behaviour of sulphur in the iron bath smelting reduction process were investigated from the thermodynamic point of view. The simulated results indicated that even a very small amount of zinc could introduce sulphur into the dust in the form of ZnS, which would effectively prevent the sulphur from entering the outlet gas. Moreover the deposited ZnO would accumulate continuously in the system in case of all dust being recycled.
Physico‐chemical aspects of the behaviour of inclusions in steels
Authors: Gatellier Christian , Gaye Henri , Lehmann Jean , Pontoire Jean Noël , Riboud Paul Victor
Published: December 2016

Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with a precise control of the composition, morphology and plasticity of oxide and sulphide inclusions that remain in the product. In liquid metal, the composition of complex inclusions can be monitored by appropriate deoxidation practice, calcium treatment and/or slag‐metal reaction. Further transformation may occur during solidification or heat treatments prior to hot‐rolling: reaction between oxides and sulphides, as well as crystallization of oxides. An analysis of these factors, and of tools (thermodynamic models and laboratory experiments) which have been developed to comprehend and control them is presented.
Prediction of an iron oxide concentration in the induction smelting process
Authors: Gupta Govind Sharan , Sundararajan Thirumalachari , Chakraborti Nirupam
Published: December 2016

Induction smelting process, ISP, is a direct smelting process in which self‐fluxed composite pellets (made of iron ore, brown coal and lime) are melted in a single phase induction furnace in conjunction with top blown oxygen. A mass transfer model to predict the concentration of iron oxide, has been developed for this process. Transient mass balance equation with complex boundary conditions has been worked out by adopting a relatively new approach known as the cell model approach. These equations have been solved numerically using finite difference technique to obtain the iron oxide concentration profile in the induction smelting process. Numerical and experimental results obtained for the iron oxide concentration show a reasonable agreement with each other.
Optimizing structure, toughness and wear performance of 15 % Cr cold work cast tool steel
Authors: El‐Ghazaly Saied Azab
Published: December 2016

A series of six Cr‐, Cr + Mo‐, Cr + Mo + V cold work cast tool steels were produced and investigated for microstructure, impact toughness and both experimental and industrial abrasive wear. Grain refinement of the steel matrix even in as‐cast condition was obtained on using 2.3 % Mo + 0.9 % V and that ensured increasing impact toughness and abrasion resistance. An optimum impact toughness of about 85 J‐cm−2 was obtained in air quenched (970°C) and tempered (450°C) Mo + V containing steels in which area fraction of carbides reached 38 %. The abrasion resistance improved in case of steels tempered at 250°C and had fine grain structure.