bluuebunny/crossref_metadata_2025 huggingface dataset:
Bestimmung des Grenzumformgrades mit dem Torsionsversuch
Authors: Kliber Jiri , Schindler Ivo , Kubiński Wiktor , Kuźmiński Zbigniew
Published: December 2016

Die Bestimmung des Grenzumformgrades eines Stahles, der während der plastischen Verformung nicht überschritten werden kann, ist von großer Bedeutung. Die vorliegende Arbeit berichtet über Ergebnisse von Warmtorsionsversuchen, aus denen der Grenzumformgrad als Funktion von Temperatur und Umformgeschwindigkeit ermittelt wurde. Die Versuche wurden an den Stählen X 10 CrNiTi 18 9, 10 CrMo 9 10, X 10 CrNiMoTi 18 12, X 20 CrMoV 12 1 und X 2 NiCrNb 25 18 durchgeführt.
Microstructure of the heat‐affected zone in 17–4 PH stainless steel
Authors: Bhaduri Arun Kumar , Venkadesan Srinivasan
Published: December 2016

The microstructure of the heat‐affected zone (HAZ) in bead‐on‐plate welded 17–4 PH stainless steel was studied with special reference to the roles of prior heat treatment and heat input during welding. The HAZ in solution‐annealed condition consists of three different microstructural zones containing: (i) retransformed martensite and reformed austenite; (ii) overaged martensite; and (iii) under‐aged martensite. In aged condition the HAZ consists of zones (i) and (ii), while in overaged condition it consists almost entirely of zone (ii). The HAZ in solution‐annealed and aged conditions is characterised by steep gradients in hardness, while in overaged condition it has uniform hardness throughout. A good correlation was obtained between the calculated temperature distribution in the HAZ and the observed microstructural features.
Carburization of hot metal by industrial and special cokes
Authors: Gudenau Heinrich Wilhelm , Mulanza Jean Paul , Sharma D. Ganpath Ram
Published: December 2016

In the present paper, a study has been made of carbon dissolution from industrial cokes and specially treated cokes in hot metal. With these results obtained together with earlier investigations, a model is now presented, which attempts to explain carbon pick‐up from coke by hot metal. Factors relating to hot metal, coke and experimental conditions are included in the model. An attempt is also made to quantify carbon dissolution behaviour from coke in hot metal in comparison with that of pure graphite. It was determined, that the carburizing ability of cokes can be modified by controlling the ash compositon. The results of the special cokes indicate clearly that the presence of iron oxide is favourable for carburization. Some additives, i.e. CaO, MgO, SiO2 and Al2O3 reduce significantly the dissolution of carbon.
Thermodynamics of Mn–Fe–C and Mn–Si–C system
Authors: Ni Ruiming , Ma Zhongting , Wei Shoukun
Published: December 2016

The solubility of C in Mn melts with different contents of Si and Fe at 1400 and 1500°C was determined. With these data the interaction coefficients eSiC, eFeC, eCC as well as γoC were evaluated. The standard free energy of solution of C in liquid Mn based on 1 wt.% solution standard at 1400 and 1500°C were calculated, respectively. The solubility of C in liquid Mn formulated in relation to temperature was made as to the conformability of the present results with those given in the literature.
Bildung und Wachstum von Ermüdungsrissen in Druckbehältern – experimentelle und rechnerische Bestimmung
Authors: Keller Hans Peter
Published: December 2016

Im Rahmen von Schwellversuchen an acht Hochdruck‐Transportbehältern aus 34 CrMo 4 konnte die Bildung von Ermüdungsrissen an Starterkerben am besten mit der Gleichstrompotentialmethode, aber auch mit Kerbaufweitungsmessungen, erfaßt werden. Da die zur Rißbildung erforderliche Anrißlastwechselzahl mit Konstanten aus der Literatur für einen ähnlichen Werkstoff nur ungenau zu berechnen war, wurden aus den Versuchen geeignetere Konstanten abgeleitet.

Mit einem auf der Basis bruchmechanischer Beziehungen aufgestellten relativ einfachen Rißwachstumsprogramm wird die Lastwechselzahl zur Ausbreitung halbelliptischer Oberflächenrisse in Behältern unterschätzt, wenn die Lastgrenzen beim Schwellvorgang konstant bzw. die Unterlast angehoben wurde. Bei Absenken der Oberlast ist die Unterschätzung deutlich größer, da die Verringerung der Rißgeschwindigkeit durch das von der hohen Last erzeugte Druck‐Eigenspannungsfeld nicht berücksichtigt wird.
Anomalies in creep‐curves of martensitic 9–14% chromium steels under long‐term loading
Authors: Schirra Manfred , Anderko Kurt
Published: December 2016

In creep tests within the temperature range 550–700°C short regimes of elevated creep rate within the strain range 2% were observed at variants of the tempered martensitic chromium steel X 18 CrMoVNb 12 1 (DIN 1.4914). These result in undesirable time yield limit‐curves which may even exhibit a retrograde shape. A correlation could be found between the creep anomaly and the ratio of the minor alloying elements AI and N. A recommendation is given for a necessary addition to the existing alloy specification.
Microstructural modelling of the creep behaviour of particle‐strengthened superalloys
Authors: Reppich Bernd , Heilmaier Martin , Liebig Karin , Schumann Gerhard , Stein Klaus‐Dieter , Woller Thomas
Published: December 2016

The steady‐state creep of particle‐strengthened systems is predicted from the matrix behaviour within the framework of the threshold stress concept. A procedure is outlined for estimation of the hardening parameter σp reflecting the effect of the particles. Unlike previous suggestions neither questionable nor restrictive simplifications are assumed for σp and the stress exponent nm of the particle‐free matrix. The proposed approach is exemplified with γ’ precipitation‐strengthened Ni‐based superalloy Nimonic PE 16 crept at 810°C. The matrix creep data and, in particular, the needed nm‐values are measured on single‐phase Nichrome reference alloys.
The creep curve of austenitic steels X 6 CrNi 1811 and X 8 CrNiMoNb 1616 after stress changes
Authors: El‐Magd Essam , Shaker Chaled
Published: December 2016

The present investigation aims at a better understanding of the relation between creep rate and time in terms of the internal back stress as a structural parameter. The formulation of the creep rate is based on the fundamental Orowan equation. The average dislocation velocity was derived by a theoretical consideration of the required effective stress in dependence of free activation enthalpy. A relation for the mobile dislocation density was determined by fitting the experimental results to calculated data. The determination of the internal back stress in the different creep stages was carried out on austenitic steel X 6 CrNi 18 11, X 8 CrNiMoNb 16 16 and on pure aluminium. It was found, that the knowledge of the behaviour of the internal stress after stress changes allows an exact description of the corresponding creep rate curve.
Experimental and numerical investigations of the creep behaviour of the dissimilar weldment GS‐17 CrMoV 5 11 and X 20 CrMoV 12 1
Authors: Buchmayr Bruno , Cerjak Horst , Witwer Michael , Maile Karl , Theofel Heinrich , Eckert Wilhelm
Published: December 2016

In the collaborative programme between MPA, Stuttgart, and the Institute for Materials Science and Welding Technology at the Technical University, Graz, within the framework of COST 505 “Materials for Steam Turbines”, the creep‐rupture behaviour of the dissimilar weldment 1%CrMoV/12%CrMoV was investigated. Independent of the effects given by the welding process, weld metal and post weld heat treatment, the fine‐grained zone in the HAZ of the lower alloyed steel grade was life‐determining after long‐time creep loading. The decarburized coarse grained HAZ near the fusion line is critical at higher stress levels, e.g. breakdowns.
Influence of oxide scales on heat transfer in secondary cooling zones in the continuous casting process, part 1: heat transfer through hot‐oxidized steel surfaces cooled by spray‐water
Authors: Köhler Christian , Jeschar Rudolf , Scholz Reinhard , Slowik Jacek , Borchardt Günter
Published: December 2016

For the cooling of steels in the continuous casting process it is necessary to know the heat transfer from the solidifying strand to the cooling water to enable calculation of the secondary cooling zone. Previous investigations have only determined this variable for non‐oxidizing metallic surfaces. For many steels cast in practice, however, the formation of oxide layers prevents a direct transfer of the previous results. In the present research the influence of the oxide layers on the heat transfer has been investigated for spay‐water cooling. Results have shown that heat transfer in the range of stable film boiling is determined for a constant spray‐water temperature in the same way as for non‐oxidizing metals, i.e. using the water mass flux density ·s only. The changed surface qualities resulting from the oxide formation cause the Leidenfrost temperature, however, to shift considerably to higher values.
Cyclic work hardening and formation of dislocation substructures during low‐cycle fatigue of tempered dual‐phase steels
Authors: Mediratta Shree Ram , Ramaswamy Vaidyanath , Singh Vakil , Rao Rama
Published: December 2016

A C‐Mn‐Si dual‐phase steel, containing 33.8% lath martensite of 0.45% C content (called steel 1), was tempered at 200, 460 and 650°C and designated steels J, K and L, respectively. Sheet specimens of 3 mm thickness and 10 mm gauge length pertaining to steels I, J, K and L were subjected to tensile and low cycle fatigue testing at room temperature. The steels I, K and L show cyclic softening while the steel J exhibits a small cyclic hardening. The cyclic stress response varies significantly at higher and lower applied strain amplitudes for each of the steels which has been discussed in terms of competing processes of hardening and softening during strain cycling. The value of the cyclic strain hardening exponent decreases continuously in the order steels I>J>K>L. Varied dislocation substructures form at higher and lower strain amplitudes during cyclic deformation.
The application of optical basicity to dephosphorization equilibria
Authors: Bergman Åke
Published: December 2016

Es werden Ergebnisse dargestellt, die zeigen, daß die optical basicity of metallurgical slags. Optical basicity is applied to phosphate capacity data and optical basicity is found to be a very sensible measure of basicity. The application of optical basicity to CaO‐saturated slags is examined and discussed.
Experimental determination of the jet effect for blowing oxygen into the melting bath of electric arc furnaces
Authors: Jeschar Rudolf , Matschullat Thomas , Kehse Georg
Published: December 2016

Recent practice with electric arc furnaces has been the injection of oxygen through nozzle positioned on the bottom of the furnace. This type of furnace places certain requirements on bottom injection. To enable a constant coupling of the energy over the electrodes, a calm bath surface must be guaranteed. On the other hand, a good mixing of the bath is required to avoid any thermal lamination in the bath. The latter condition in particular is prerequisite for a maximum melting capacity. When judging the effect of the jet on the bath, it must be taken into account that the oxygen disintegrates directly after entering the bath and merely transfers its impulse to the liquid melt. This jet effect is described by the calculation method introduced below which is adjusted to the actual behaviour using simulation tests. In this connection, changes in the jet consistency caused by the formation of carbon monoxide have not yet been considered. Parallel to this, the mixing of the bath was determined by conductivity measurements. In these experiments, the bath level xf, the vessel diameter D and the blown‐in water mass‐flux mw were changed. A comparison of the results for fountain height and mixing time formed the basis for the development of an optimization concept for bottom‐blowing nozzles in electric arc furnaces.
Solubility of titanium nitride in delta iron
Authors: Kunze Joachim
Published: December 2016

Titanium nitride in microalloyed steels can be formed already in delta iron, as can be shown by thermodynamical calculations basing on measurements of the solubility in austenite or in the melt. The solubility products calculated with respect to delta iron differ up to one order of magnitude. Therefore, between 1420 and 1510°C a direct measurement was performed on pure Fe–Ti–N alloys yielding a solubility product (related to the composition TiN1,0) of log LTiNα/δ = −17205/T + 5.56. It is identical with that one calculated from the solubility in liquid iron.

The differing results of calculations basing on the solubility in austenite are attributed to incorrect data of the Gibbs free solution energy of titanium in austenite. Starting from the present measurements and from the data reported with respect to pure titanium and to the nitrogen solubility a Gibbs free solution energy GTi,γH(x) – GTi,γR = −40294 − 13.66. T[J/mole] was deduced which is more negative than previous data.
Investigation of strain‐inhomogeneities during hot flat rolling – influences on the microstructure evolution
Authors: Lachmann Lutz , Zouhar Gustav
Published: December 2016

In this paper results of the influence of the material flow on the microstructural evolution of austenite during hot flat rolling are presented. Material flow is investigated by means of rolled specimens, which are prepared with a square‐grid in the middle of the plate. Analyses of the microstructure were applied to elucidate the evolution of the prior austenite structure in thickness direction of the rolled specimens. The inhomogeneous deformation in thickness direction in combination with algorithms for the calculation of the microstructural evolution gives more detailed information on the occurrence of microstructural inhomogeneities compared to the usually applied strip‐model.

The inhomogeneous deformation over the thickness of a rolled sheet can be described with sufficient accuracy by means of the strain model according to Zouhar and Lachmann.
Untersuchungen des Zeitstandverhaltens von Schweißverbindungen der Werkstoffe X 20 CrMoV 12 1 und GS‐17 CrMoV 5 11
Authors: Kußmaul Karl , Eckert Wilhelm
Published: December 2016

Untersucht wird das Zeitstandverhalten gleichartiger Schweißverbindungen des Werkstoffs X 20 CrMoV 12 1 sowie ungleichartiger Verbindungen zwischen diesem und dem Werkstoff GS‐17 CrMoV 5 11. Bei quer entnommenen Kleinproben zeigt sich ein Abfall der Zeitstandfestigkeit gegenüber dem Grundwerkstoff. Große Querproben aus einer ungleichartigen Verbindung weisen eine höhere Zeitstandfestigkeit auf als entsprechende Kleinproben. Zur Klärung der in den Schweißverbindungen auftretenden Spannungs‐ und Dehnungsumlagerungen wurden inelastische Finite‐Elemente‐(FE‐)Berechnungen durchgeführt. Dabei wurde das Zeitdehnverhalten von Grundwerkstoffen, Schweißgut und thermisch simulierten Gefügen der Wärmeeinflußzone berücksichtigt. Die Anwendung spannungsbezogener Kriterien zur Bestimmung der Anrißdauer der Proben auf die FE‐Ergebnisse läßt eine Voraussage des Versagensorts sowie eine sichere Abschätzung der Versagenszeit zu.
The basic concepts of texture investigation in polycrystalline materials
Authors: Bunge Hans‐Joachim
Published: December 2016

Polycrystalline materials consist of grains which may have different sizes, shapes and arrangements to be observed under the microscope as well as different crystal orientations observed by diffraction methods. The orientation parameters of the crystallites are subsumed under the term texture. The main textural quantities are the orientation distribution function ODF of the crystallites and the misorientation distribution function MODF of grain‐ and phase boundaries. Textures are being formed in materials by all kinds of anisotropic solid state processes and they have influence on all kinds of anisotropic material properties. Textures can be measured grain‐by‐grain or using polycrystal diffraction methods. The appropriate radiations are X‐rays, electrons and neutrons.

Finally, some examples are given concerning martensitic transformation in FeNi‐alloys, shape memory alloys, cross‐rolling of Armco‐iron, biaxially stretched polyethylene, and HTc superconductors.
Modelling deformation texture formation by orientation flow fields
Authors: Klein Helmut , Bunge Hans‐Joachim
Published: December 2016

Model calculations of the development of straight and cross‐rolling textures were carried out. The texture is represented in terms of a series of expansions. The changes of the texture coefficients by a small deformation step can be expressed in terms of the coefficients themselves multiplied by a texture change matrix [α].

Integration over the deformation degree η from any starting texture thus gives the deformation texture formation. In the present calculations, the fully constrained Taylor model was used (but other models can equally well be chosen). This model has no unique solutions for most orientations, i.e. it allows several different orientation changes for the same starting orientation. It was shown that this effect is essential in order to obtain model textures which do not only agree in type but also in magnitude with experimental textures.
Influence of hot‐rolling conditions on texture development in deep‐drawing steels
Authors: Därmann‐Nowak Cornelia , Engl Bernhard
Published: December 2016

As the textures of deep‐drawing sheet steels are important for certain material properties the purpose of this paper was to take a closer look at the hot‐rolling, cold‐rolling and annealing textures of different deep‐drawing steel grades. Several Al‐killed mild steels and vacuum‐degassed Ti‐IF steels have been hot rolled in the mill varying the finishing temperature (FT). After coiling, cold rolling and short‐time annealing the textures at different thickness levels have been measured by means of (110)‐pole figures and orientation distribution functions (ODFs).

For both steel groups the textures at the surface of the hot strip exhibit a more or less pronounced shear type character. Towards the mid‐thickness level (with lower FT more clearly) typical (cold‐) rolling textures exist characterized by a strong {001}<110> orientation and in the Ti‐IF steels additionally by a significant {112}<110> orientation density. In the case of high FT cold rolling and annealing lead to favourable {111}‐textures where deep‐drawing application is concerned. For the Al‐killed steels lowering FT results in diffuse recrystallization textures whereas in the Ti‐IF steels a sharp texture with near {223}<582> orientations can be observed which have not been known for these steels before. The results prove that the hot strip textures can be of great importance for the resulting annealing textures and the according material properties.
Textures in steel sheets
Authors: Bleck Wolfgang , Großterlinden Rolf , Lotter Ulrich , Reip Carl‐Peter
Published: December 2016

Steel sheets frequently exhibit pronounced textures influencing the product properties by causing anisotropies. In the present paper a survey is given of the typical textures in steel sheets in the final and also in the intermediate stages of the manufacturing process. In order to quantify and characterize textures the method of ODF is used, which also allows a simple representation of the main texture features by plotting the pole density along texture fibres. For hot‐rolled strip the textures of mild unalloyed and high‐strength microalloyed steels are considered for different finish‐rolling temperatures including rolling in the γ/α dual phase region. Besides the textures in the middle‐section the surface textures are also dealt with. The cold‐rolling texture is investigated with regard to the influence of hot‐band texture and grain size for unalloyed mild deep‐drawing grades and IF‐steels. The recrystallization texture of different deep‐drawing qualities is presented together with results of the influence of N‐fixation on the texture determined r‐values.
Automatic measuring system for textures with sample change by means of a robot arm
Authors: Großterlinden Rolf , Lotter Ulrich , Thoma Christian
Published: December 2016

The existing texture measuring device of the research department of Thyssen Stahl AG has been retrofitted and automated to make it possible that ODF analyses may be used more comprehensively in steel development, despite the high efforts required for measuring and evaluation. Now it is possible to automatically measure series of up to 10 samples. All measuring processes are controlled by step motors by a computer, which also collects the measured data. Samples are changed by a robot arm, which replaces the measured sample by a new one taken from a special sample magazine. Both the evaluation and the output of data and graphics are also performed by series and automatically on a second computer. Because of the new investigation device, up to 12 ODF measurements per day are possible, while the costs are reduced to one fifth of the former level.
Metallkundliche Untersuchungen am Grundwerkstoff und an Schweißverbindungen des 9%‐Chromstahles X 10 CrMoVNb 9 1
Authors: Brühl Fritz , Cerjak Horst , Schwaab Paul , Weber Heinz
Published: December 2016

Umfangreiche Untersuchungen zur Ausweitung des Einsatzbereiches warmfester ferritischer Stähle mit 9 bis 12 % Cr auf 600 °C führten zur Entwicklung des Stahles X 10 CrMoVNb 9 1 (P 9 1 bzw. T 9 1 nach ASTM‐A 335). Wegen der hohen Einsatztemperaturen treten unter Zeitstandbeanspruchung Gefügeänderungen auf, die am Grundwerkstoff und an Schweißverbindungen metallkundlich untersucht wurden.

Im üblichen Lieferzustand weist der Stahl T 9 1 ein Gefüge aus angelassenem Martensit mit Ausscheidungen von Chromcarbiden M23C6 auf den Grenzen der Martensitlatten und feinen, sowohl kohärenten wie inkohärenten Niob‐Vanadin‐Carbonitriden vom Typ MX im Korn auf. Unter Zeitstandbeanspruchung scheidet sich weiteres M23C6 und MX sowie zusätzlich die Laves‐Phase aus. Die kohärenten MX‐Ausscheidungen beginnen zu überaltern. Erholung und Rekristallisation werden beschleunigt. Das Zeitstandverhalten dürfte im wesentlichen durch die MX‐Ausscheidungen bestimmt werden, wobei das Mengenverhältnis der Elemente Vanadin, Niob, Kohlenstoff und Stickstoff von erheblicher Bedeutung sein sollte.

In Schweißverbindungen bildet sich die Zeitstandschädigung in der Regel in der WEZ nahe der Grenzlinie zum unbeeinflußten Grundwerkstoff aus. In diesem Bereich führt die kurzzeitige Erwärmung auf Temperaturen wenig über A1 zur Bildung eines kohlenstoffarmen Austenits, da praktisch noch keine Carbide in Lösung gehen. Nach der Abkühlung liegt dann ein sehr weicher Martensit vor, der zudem beim üblichen Anlassen auf Temperaturen um 750 °C praktisch vollständig rekristallisiert.
Metallographic examination of the heat‐affected zone of a test weld in a type X 20 CrMoV 12 1 steel
Authors: Kussmaul Karl , Gaudig Wolfgang , Haas Siegfried
Published: December 2016

Metallographic examination of a similar test weld in a type X 20 CrMoV 12 1 steel revealed a martensitic phase within the heat‐affected zone of the base metal adjacent to the fusion boundary. As a consequence, the heat‐affected zone displayed an excess microhardness compared with the unaffected base metal. It is shown that the occurrence of this martensitic phase can be correlated with segregations in the base metal. Due to its martensitic nature, this phase can be transformed to α‐ferrite and carbide by an additional tempering treatment subsequent to the standard post‐weld heat treatment. By this additional tempering treatment the uniformity of the microstructure of the heat‐affected zone can be considerably improved.
Steel quality and analytical precision in plate production
Authors: Humbert Jean
Published: December 2016

This paper reviews the analytical quality requirements in the field of heavy‐plate production. The concept of process capability is used as a help to balance the analytical accuracy of the laboratory against the demands of the customer, those of the steel plant and those of the order‐processing and planning center.
Simulation of metal flow and heat transfer during hot rolling of bimetal plates
Authors: Pietrzyk Maciej , Dyja Henryk
Published: December 2016

Coupled thermomechanical finite element model is applied to simulate metal flow and temperature distribution during hot rolling of bimetal plates. Calculations are carried out for various reductions and dimensions of the plates. Two possible versions of the boundary conditions are assumed. The first considers the case when special guides or tensions prevent bending of the sample before entering and after exit from the roll gap. The second allows free bending of the plate on both sides of the mill. Results of calculations include distributions of strain rates, strains, roll pressure, friction forces and temperatures during rolling. Calculated rolling force and torque are compared with the experimental data. Several conclusions regarding the metal flow and heat transfer in various rolling conditions are drawn.
Strains in the tube‐sinking process evaluated by the finite element method and experimental technique
Authors: Sadok Lucjan , Pietrzyk Maciej , Paćko Marek
Published: December 2016

Rigid‐plastic finite element model of the tube‐sinking process is validated by comparison of the results of calculation with the experimental data. Brief description of the model is presented in the paper. Experimental tube sinking was performed for copper samples. Mesh‐measurement method was used to determine the strain distributions experimentally. Typical results of calculations and measurements of various process parameters are presented. The results confirm the predictive abilities of the model.
Structural superplasticity of a fine‐grained and rapidly solidified ultra‐high carbon‐alloy tool steel X 245 VCr 10 5
Authors: Frommeyer Georg , Speis Hans‐Josef
Published: December 2016

The fine‐grained ultra‐high carbon‐alloy tool steel X 245 VCr 10 5, containing large volume fractions of special vanadium and chromium carbides within a ferritic solid solution matrix has been produced by rapid solidification – meltatomization – and powder metallurgical techniques. This steel exhibits structural superplasticity in the temperature regime from 900 to 1150°C at initial strain rates of about ∊̇ = 10−3 s−1. High strain‐rate sensitivity parameters of m > 0.4 and uniform tensile elongations up to 950% were recorded. The dominant deformation mechanism in the superplastic region is grain‐boundary sliding accommodated by lattice diffusion. The failure of superplastically strained samples is caused by interlinkages of cavities at matrix/carbide interfaces.
Numerical computation of flow phenomena in gas‐stirred ladle systems
Authors: Balaji Devulapalli , Mazumdar Dipak
Published: December 2016

Quasi‐single‐phase mathematical models as applied to the ladle hydrodynamics have been analysed rigorously. It is shown that choice of convergence criteria, nodal configuration and differencing schemes all influence the computed results significantly and consequently, results independent of these numerical parameters must first be established to draw any useful conclusion. Several quasi‐single‐phase computational procedures reported in the literature to study the gas‐injection‐induced flow phenomena have been critically examined. To this end, experimentally measured bulk flow‐fields, plume‐rise velocity and gas voidages have been compared with those predicted numerically. Such comparisons indicate that the bottom injection phenomena (viz., bulk flow, plume‐rise velocity, and gas volume fraction within the plume etc.) can be adequately represented by assuming bubble slippage and considering a constant rise velocity in the two‐phase region in the numerical solution scheme.
Beschreibung von Ver‐ und Entfestigungsvorgängen am Beispiel austenitformgehärteter Stähle mit Hilfe von Fließkurven
Authors: Bleckwedel Axel , Schrader Hartmut , Kunze Hans‐Dieter
Published: December 2016

Fließkurven beschreiben das Formänderungsvermögen von Werkstoffen. Gleichzeitig liefern sie Informationen über die Wechselwirkung zwischen der Ver‐ und Entfestigung, wobei diese beiden Eigenschaften temperaturabhängig sind.

Fließkurven wurden an Stählen aufgenommen, die sich im wesentlichen in ihrem Kohlenstoffgehalt unterscheiden. Die Bestimmung der Formänderungsfähigkeit erfolgte bei Temperaturen, die denen entsprechen, bei denen eine Austenitformhärtung vorgenommen wird. Die mathematische Beschreibung der Fließkurven läßt erkennen, daß zunächst mit steigender Umformtemperatur die Verfestigungsrate abnimmt. Der Kohlenstoffgehalt erhöht dagegen die Verfestigungsrate. Die dynamische Erholung wird mit wachsender Umformtemperatur beschleunigt, ebenso mit steigendem Kohlenstoffgehalt.
Analysis of heat flow and microstructure evolution during spray deposition of Fe‐3C‐1.5Mn alloy
Authors: Singh Siddh Nath , Mishra Nirmalendu S. , Ojha Shambhu Nath
Published: December 2016

A theoretical model for the concomitant solidification of droplets and preform during spray deposition has been proposed, based on heat‐flow analysis. It has been unambiguously demonstrated that cooling rates approaching those in the rapid solidification (RS) regime can only be achieved when the droplets are still in free flight during the deposition process. The cooling rates in the droplets range from 104–106 Ks−1 depending upon their size for the experimental conditions employed in the present studies. In contrast, the model predicted cooling rates for the deposits in the region of 103–104 Ks−1. A hypoeutectic Fe‐3C‐1.5Mn‐0.3Si has been chosen as an experimental alloy for studies relating to microstructural characterization. The microstructure of powder developed fully during solidification of droplets in free flight revealed dendritic morphology of the metastable austenitic phase, whereas the spray‐deposited alloy exhibited characteristic homogeneous and refined substructure. The evolution of microstructure during spray deposition as also during atomization has been compared and discussed by invoking the proposed model.
Studies on the behaviour of mist jet and its cooling capacity of hot steel surface
Authors: Koria Satish C. , Datta Indrani
Published: December 2016

The present study is concerned with the design of mist nozzle to produce air/water mist jet, and to investigate the behaviour of mist jet and its capacity to cool the hot steel surface. The behaviour of the mist jet is studied by collecting water at different axial distances. Radial water flux profile is correlated with a Gaussian type of distribution function under a wide range of experimental conditions. Maximum water flux in the mist jet is correlated with the downstream axial distance and water‐loading ratio. Water‐loading ratio is found to influence water flux more strongly than axial distance. Radius of the mist jet is correlated with the downstream distance. It is found that the mist jet cools a crack‐sensitive steel without Cracking and, at the same time, produces a martensite type of structure.
Experimental studies on the bath oscillation during gas blowing into liquids, part 2: measurements in a converter model
Authors: Xie Yongkun , Oeters Franz
Published: December 2016

Experimental studies on the wave motion during gas blowing into liquid iron in a converter model were carried out on the systems water/air and Wood's alloy/nitrogen under various blowing conditions. Variables of the measurement were the gas flow rate and the configuration of nozzles. The measured results showed that a wave motion appears only if the gas flow rate exceeds a critical value which depends on the nozzle configuration. The blowing conditions for wave formation can be characterized by the relation of the bath depth to the vessel diameter and by the gas flow rate. The frequency or the oscillation period of the wave is independent of the gas flow rate. The amplitude of the wave follows a logarithmic function of gas flow rate.
Evaluation of friction under hot working conditions in a high temperature test rig
Authors: Lundberg Sven‐Erik , Waldén Bertil
Published: December 2016

A new high temperature test rig was designed and constructed. In a first series of tests it was shown that by proper choice of testing parameters, wear mechanisms similar to those in rolls in operation could be achieved. By comparison of frictional values evaluated from experiments in the test rig to values evaluated from ring upsetting tests, an attempt is made to establish the high temperature test rig experiments as a method for simulation of the tribological situation in hot rolling. The coefficient of friction μ was evaluated and fairly good agreement was found with frictional values from ring upsetting tests. However, it is doubtful whether μ is a relevant measure of friction in hot working processes, and in the ring upsetting tests also the friction factor m was evaluated. Evaluation of m‐values from the test rig experiments might be possible. However, such an evaluation claims both a correct shear yield stress value of the hot material and a relevant description of the contact surface area. Since no plastic deformation occurs in the test rig a “semi‐plastic” state must be established and verified. Different attempts can seem realistic, but it is obvious that the evaluation of m, using a “semi‐plastic” state can be manipulated by the choice of conditions by calculating the shear yield stress. Furthermore, it is not clarified whether the Hertzian theory of elastic contacts is valid for a temperature of 1000°C. Thus m‐values evaluated from the test rig have no meaning and the frictional conditions must be characterized by the coefficient of friction μ.

Since both relevant frictional and wear conditions are obtained, the high temperature test rig can be used for simulation of roll wear and for the development of new, more wear resistant roll grades.
Effect of deformation conditions on the transformation of micro‐alloyed medium‐carbon forging steels
Authors: Kaspar Radko , Hoppe Harald , Pawelski Oskar
Published: December 2016

The CCT diagrams of three medium‐carbon steels without and with microalloying by vanadium and titanium were constructed by applying direct cooling of as‐deformed austenite. Deformation parameters corresponding to those of industrial forging were varied with a laboratory simulation technique by using the plane strain hot compression test. The effect of microalloying, deformation, and deformation temperature on the amount of structural substituents was quantified. For practical application of the study the as‐forged controlled cooling conditions were determined to achieve the desired bainite‐free ferritic‐pearlitic microstructure with beneficial mechanical properties.
Investigations concerning quantitative determination of local damage in ductile materials
Authors: Holland Dirk , Kong Xianming , Schlüter Norbert , Dahl Winfried
Published: December 2016

Ductile fracture of metallic materials can be described by void nucleation, growth and coalescence. The first coalescence of voids defines crack initiation. A quantitative description of material damage by the means of continuum‐mechanics is a very current theme. Using Gurson's model and the yield equation modified by Needleman and Tvergaard a quantitative description of damage condition is possible by connecting stress triaxiality and void volume fraction. In this paper failure curves, in which the effective plastic strain is plotted as a function of stress triaxiality, will be generated by a new yield equation, which is a further development of the Gurson model. The failure curves will be shown for crack initiation and other damage situations. An advantage of the further developed yield equation, compared with the conventional one, can be seen in the fact that not one constant, which is independent of the material, but several material specific values are used. These values can be determined by density measurements at different void volume fractions. The procedure for determination of failure curves will be shown and subsequently test results will be discussed.
On the geometry of fatigue crack closure
Authors: Stüwe Hein‐Peter , Pippan Reinhard , Shan Guo Xin
Published: December 2016

Long fatigue cracks frequently grow at a much lower rate than short cracks because they are closed during part of the stress cycle. The critical crack length for the transition from “short” to “long” depends on the amplitude of stress intensity ΔK and on the stress ratio R. This dependence is explained using a numerical study of the crack flank contour.
Experimentelle Untersuchungen der Strömungen, Turbulenz und Teilraumausbildung an Kaltmodellen gasgerührter Mischreaktoren
Authors: Junk Gerhard , Nonte Thomas , Steinmetz Eberhard , Wilhelmi Herbert , Schlösser Gereon
Published: December 2016

Im Rahmen dieser Arbeit wurden theoretische und experimentelle Untersuchungen an Wasser‐ und Quecksilbermodellen bodengeblasener Reaktoren durchgeführt, um ein mathematisches Modell zur Beschreibung der Durchmischungsvorgänge weiterzuentwickeln. Dieses mathematische Modell beruht auf der Einteilung des Gesamtsystems in Subsysteme, die als ideale Mischer miteinander im Stoffaustausch stehen. Die Strömungsverhältnisse sowie ungefähre Anzahl, Lage und Größe der Teilräume wurden unter Variation der Gasvolumenströme, der Gefäßdurchmesser und der Füllstandshöhen zunächst mit Hilfe des Lichtschnittverfahrens erfaßt. Lichtschnittuntersuchungen mit Fluoreszen als Tracer dienten zur Beobachtung des Mischverhaltens der Einzelteilräume sowie zur Bestimmung der Gesamtmischzeiten. Mit einem Laser‐Doppler‐Anemometer wurden sowohl die großräumigen als auch die lokalen Strömungs‐ und Turbulenzprofile ermittelt. Aus den so erhaltenen Daten wurden die genaue Lage und die Größe der Teilräume sowie die Stoffaustauschströme zwischen diesen bestimmt. Weiterhin wurden Konzentrationsmessungen an Quecksilbermodellen durchgeführt. Der Vergleich dieser Messungen mit den an Wassermodellen erhaltenen Strömungs‐ und Turbulenzprofilen führte zu einer Einteilung in fünf Teilsysteme, mit der bei Anwendung des mathematischen Modells gute Übereinstimmung zu gemessenen Werten erzielt werden konnte.
Low‐cycle fatigue of X 2 NiCoMo 18 12 and X 10 NiCrAITi 32 20
Authors: Detert Klaus , Adolfs Rainer
Published: December 2016

The low‐cycle fatigue and short crack‐growth behaviour of an ultra‐high strength maraging steel and a high‐nickel austenitic steel have been studied. The tests were performed in a laboratory environment at room temperature in push‐pull cycles with constant strain amplitudes of 0.25 to 2 %. Short crack‐growth investigations were performed using bending specimens loaded by a resonance bending machine. Crack growth was measured using the replica method.

The cyclic and tension stress strain behaviour has been compared. Fatigue tests were interpreted according to the recommended practice of ASTM‐E 606‐80. First microcracks were observed after 10 to 70 % of the fatigue life.
Trends in the development of grain‐oriented electrical sheet
Authors: Bölling Fritz , Günther Klaus , Böttcher Andreas , Hammer Brigitte
Published: December 2016

Thin gauge, high silicon content, perfect crystal orientation and small domain wall spacings are the fundamental features of an ideal electrical steel sheet with minimum core loss and maximum polarization. For achieving these properties in the fabrication process, very exact control of secondary recrystalliration is necessary, which becomes more and more difficult with decreasing sheet thickness and increasing silicon content. In the present paper the influence of the starting conditions – i.e. the primary recrystallized grain structure and precipitation distribution – on selective grain growth and Goss‐texture formation is described. For RGO and HGO typical differences in the primary grain size, critical inhibitor diameter and amount of primary Goss‐grains have been observed. By increasing the knowledge about the physics of electrical steel sheet, the fabrication process and magnetic properties have been continuously improved in the past. Today, new techniques of strip production like thin strip casting are an important aspect for further development offering very promising perspectives on new possibilities of texture control.
A new approach in texture research: local orientation determination with EBSP
Authors: Engler Olaf , Gottstein Günter
Published: December 2016

A new technique for convenient measurement of crystallographic orientation of small volumes in bulk samples is introduced. It makes use of electron back scattering patterns (EBSP) in the SEM. The principle of pattern formation as well as measuring and evaluation procedure are introduced. The method offers a viable procedure for obtaining information on the spatial arrangement of orientations, i.e. on orientation topography and thus, provides a new level of information on crystallographic texture. The application of EBSP is demonstrated by two examples, namely for investigation of nucleation of recrystallization and microstructure evolution during high‐temperature fatigue.
Mullite as an electrochemical probe for the determination of low oxygen activity in liquid iron
Authors: Suito Hideaki , Inoue Ryo , Nagatani Akihiro
Published: December 2016

Oxygen activities in liquid iron deoxidized with aluminium were measured at 1873 K, using a mullite electrolyte having a Cr‐Cr2O3 reference mixture. These results were compared with those obtained using commercial tube‐type ZrO2‐8 mol% MgO and plug‐type ZrO2‐9 mol% MgO probes, along with oxygen activities calculated from analysis. Oxygen activities from EMF measurements using mullite and plug‐type probes were found to be in agreement with those calculated from the Al/AI2O3 equilibrium and those estimated from analyzed oxygen contents. Polarization effect due to electrochemical oxygen transport was observed in a commercial tube‐type ZrO2‐based probe. Supersaturation in liquid iron deoxidized with aluminium was also measured at 1873 K.
Mathematische Teilraummodelle zur Beschreibung der Durchmischungsvorgänge in gasgerührten Reaktoren
Authors: Jank Gerhard , Nonte Thomas , Steinmetz Eberhard , Wilhelmi Herbert
Published: December 2016

Das mathematische Modell baut auf einer Untergliederung des Gesamtreaktors in Teilräume auf, die untereinander im Stoffaustausch stehen. Jeder einzelne Teilraum wird als idealer Mischer betrachtet. Die Austauschvorgänge zwischen den einzelnen Teilräumen werden durch konstante Kopplungskoeffizienten dargestellt. Die Massenbilanz für den einzumischenden Stoff liefert ein homogenes Differentialgleichungssystem zur Bestimmung der Konzentrationsverläufe in den einzelnen Teilräumen. Verschiedene mathematische Modelle für die Zerlegung der Teilräume werden vorgestellt. Experimentelle Untersuchungen ergaben eine Einteilung in fünf Teilräume. Der Vergleich der berechneten Mischzeiten mit experimentell bestimmten Werten zeigt sehr gute Übereinstimmung.
Influence of particles on recrystallization textures of ferritic stainless steels
Authors: Raabe Dierk , Lücke Kurt
Published: December 2016

Five microalloyed ferritic steels with a Cr content of 10 to 17 % were cold rolled and recrystallized. Steels with a high volume fraction of Nb and Ti precipitations revealed a deviation from the typical {111} fibre texture. The new main component {557}<583> was explained by particle induced growth selection.
Strengthening and toughening treatment of steel used as the material of multistation progressive dies
Authors: Tang Yuan‐qi
Published: December 2016

The Cr12MoV steel was chosen as the material of multistation progressive dies, and its impact toughness and hardness were measured, following different heat treatments. Based on experimental results, a practical technology carried out in vacuum is recommended as the strengthening and toughening treatment for these dies: 980°C oil pre‐quenching, oil quenching again at 980°C, final tempering at 200°C for 1 hour, and then air cooling. This treatment makes the steel have fine austenitic grains and carbide particles, and thus leads to good combination of strength and toughness such that the service life of the dies is increased.
Formation and effects of slag foaming in smelting reduction
Authors: Gudenau Heinrich Wilhelm , Wu Keng , Nys Stefan , Rosenbaum Heinz
Published: December 2016

Research was carried out on the foaming phenomenon in the bath of the smelting reduction process with a hydrodynamic model and with high‐temperature experiments. There are two mechanisms of slag foaming: when foam is generated by injected gas, the height of the slag foaming can be regulated. Contrarily, the production of gas during the reduction of iron oxides causes slag foaming which can hardly be controlled. High temperature as well as low slag basicity reduce the foam stability. In smelting reduction a large slag volume is expected. A rinse‐spot in the slag layer, which can prevent slag foaming, disappears under these conditions. Wall‐effects play an important role for the foam stability.
Experimental investigations on the consumption of graphite electrodes doped with various oxides
Authors: Kyas Anke , Fleischhauer Jörg , Steinmetz Eberhard , Wilhelmi Herbert
Published: December 2016

In order to reduce the burning off of electrodes in electric arc furnaces it is necessary to decrease the specific thermal load at the tip in the arc attachment area. This can be achieved by minimizing the work function of the electrode materials, whereby the peak temperature is reduced. The work function of doped graphite electrodes was investigated under conditions prevailing during standard industrial practice in order to achieve transferable results. The measurement equipment developed to meet this requirement bases on a design, which first was put forward by Bade & Yos. By measuring the peak temperature of the electrode and its current density the value of the work function of the material was calculated with a modified Richardson equation. Starting from materials with well‐known values of the work function, to verify the accuracy of the experimental method and the mathematical model, those of pure and doped graphites were determined. The additives, oxides as a rule, result in a significant reduction in electron work function in the case of magnesium, calcium and cerium oxides.
Investigations on the fluiddynamic and thermal process control in ladles
Authors: Neifer Martin , Rödl Sigurd , Sucker Dietrich
Published: December 2016

Inert gas stirring of the melt in the ladle is a proven engineering process measure in secondary steelmaking. It is employed to ensure the specified homogeneity of the melt in terms of composition and temperature. The achievement of these objectives is essentially contingent on the flow conditions in the melt. The present paper deals with the results of numerical computations of the bubble movement and velocity field generated by such a gas stirring process. The distribution of alloy elements and the temperature field in the melt are computed on the basis of real temperature‐dependent fluid properties. The results of the numerical computations are compared with corresponding results of model trials and expressed in a form usable for operating plants. In addition, recommendations are made with regard to the scale‐up of model trial results to full‐size ladles under actual operating conditions.
Mechanical properties of type 304 stainless steel sheet produced by twin‐roll strip casting process
Authors: Takuda Hirohiko , Kikuchi Shiomi , Hatta Natsuo , Kokado Jun‐ichi
Published: December 2016

Tensile properties and formability of type 304 stainless steel sheets which were cast by a twin‐roll type strip caster and thereafter cold‐rolled are examined and compared with those of conventionally processed sheets. The results exhibit that the strip casting processed sheets have mechanical properties almost equal to the conventional ones. Furthermore, it is found that the degree of plastic anisotropy caused by crystallographic anisotropy in the present sheets is weaker than that in the conventional ones.