bluuebunny/crossref_metadata_2025 huggingface dataset:
A new procedure for measuring the thermal diffusivity of non‐metallic melts at high temperatures
Authors: Friedrichs Hans Adolf , Ronkow Leonid Wladimirowitsch , Zhou Yongmao
Published: December 2016

A new procedure for measuring the thermal diffusivity of non‐metallic melts at high temperatures has been developed, and a measuring set up based on thermography and the use of a CO2 laser has been constructed. The working efficiency of the measuring procedure, together with the accuracy and reproducibility of the measured values have been checked by measurements on synthetic slags. The thermal diffusivities of synthetic slag (38% CaO – 38% SiO2 – 19% Al2O3 – 5% Fe2CO3) at temperatures from 1648 to 1740 K lie between 2.6×10−7 and 3.0×10−7 m2s−1. The mean deviation of measured values is about ±6%. The advantages of this new procedure are compared with usual laser flash methods and possible error sources are discussed.
Measurement of aluminum or silicon activity in Fe‐Ni (< 30 %) alloys using mullite and ZrO2‐based solid electrolyte galvanic cell
Authors: Li Guangqiang , Inoue Ryo , Suito Hideaki
Published: December 2016

Using mullite (3Al2O3·2SiO2)‐tube type and ZrO2 (MgO mole fractions of 9 %)‐plug type solid electrolyte, the activities of Al in the Fe‐15, 29% Ni‐0.002 to 0.84% Al (mass contents in%) alloys were measured at 1873 K in an Al2O3 crucible, and those of Si in the Fe‐13, 28% Ni‐0.13 to 2.3% Si alloys were measured at 1823 K in a mullite crucible with an excess of SiO2. The interaction coefficients of and were determined as −0.0173 ± 0.0052 and 0.00021 ± 0.00007, respectively, and those of and were determined as 0.0094 ± 0.0049 and −0.00008 ± 0.00004, respectively. The oxygen activities obtained by the EMF measurements were compared with those obtained from the contents of analyzed oxygen. The oxygen activities in the Fe‐Ni‐Al alloys were found to be supersaturated. The interaction coefficients of and were determined as 0.0027 ± 0.0012 and 0.00012 ± 0.00004, respectively, from the contents of analyzed oxygen in Fe‐Ni‐Si alloys.
Radial gas distribution in the blast furnace top
Authors: Timmer Ron , Droog John , Flierman Gerard , Steeghs Antoine
Published: December 2016

Blast furnace process control heavily depends on good control of burden and gas distribution. For many blast furnaces this control relies on measurements with fixed above‐burden probes. Therefore, an accurate knowledge of the gas flow between stockline and above‐burden probes is of paramount importance. Measurements in the blast furnace top and calculations with a mathematical model are used to shed more light on the gas flow in the blast furnace top. It turned out that complex gas flows cause several differences between data at stockline level and at above‐burden probe level. There is an acceleration of gas in the furnace centre due to the much higher temperature there. Gas from the colder intermediate region is therefore attracted towards the centre. There is hardly any influence of the inclination of the stockline. It is advisable to make the distance between stockline and above‐burden probes as small as possible or to use some form of in‐burden measurement.
Prediction of the continuous cooling transformation diagram of some selected steels using artificial neural networks
Authors: Vermeulen Willem , van der Zwaag Sybrand , Morris Peter , de Weijer Ton
Published: December 2016

Continuous cooling transformation (CCT) diagrams play an important role in the description of the transformation behaviour of steels. The experimental determination of a CCT diagram is a very time consuming and expensive task. It would therefore be very attractive to be able to predict CCT diagrams from the chemical composition of the steel and its austenitising temperature. In this article the use of artificial neural networks for the prediction of the transformation start and finish lines in CCT diagrams is described. The data were selected from a single source: The vanadium steels, atlas of continuous cooling transformation diagrams [4].

Three neural networks with different numbers of hidden nodes (5‐10‐15) were trained. The number of hidden nodes did not significantly influence the accuracy in the prediction. The network with the least number of hidden nodes (5) was therefore chosen for the evaluation of the performance of the neural networks. This neural network was able to predict the general trends in the CCT diagrams quite well. The relative standard deviation in the prediction of start and end temperatures of each transformation depended on the cooling rate. For the high and low cooling rates it was ∼ 40°C, for the intermediate it rose to 90°C for the ferrite start formation and to 75°C for the other diffusional transformations (pearlite and bainite).

The accuracy of the predicted CCT diagram was primarily restricted by the modest quality of the input data used to train the neural network.
Calculation of liquidus temperature of low and high alloyed iron base melts from their chemical composition by means of the equivalence factors
Authors: Schürmann Eberhard , Djurdjevic Mile , Nedeljkovic Ljubomir
Published: December 2016

Liquidus temperature of a steel is calculated from its chemical composition according to the so far proposed procedures by simply summing up the iron melting point lowering effects of all in the steel contained elements Xi, as they are given by approximating the iron liquidus curves with the straight lines in the corresponding binary Fe‐Xi systems. The intensification of the iron melting point lowering effect with the increasing concentration of each element contained in the steel has not been at all or only partly taken into account in this approach. This is the reason why the calculated steel liquidus temperatures are not accurate enough.

In the here proposed new calculation procedure the iron melting point lowering effect of an alloying element Xi is first translated into an equivalent effect of carbon in the Fe‐C system by converting the concentration of Xi into an equivalent concentration of carbon taken as a reference element. The carbon equivalent iron melting point lowering effect of all elements contained in the steel including carbon is then evaluated by summing up the calculated equivalent carbon concentrations of all elements together with carbon into a fictitious total equivalent carbon concentration. A so calculated total equivalent carbon concentration has made it possible to determine with a good accuracy the steel liquidus temperature along the stable δ/α or γ liquidus lines in the Fe‐C system. The success of a melting point calculation is strongly dependent on the accuracy of the equivalence factor equations for each alloying element. They are derived by relating the iron liquidus line in the binary Fe‐Xi system to that in the Fe‐C phase diagram.
Modelling of oxygen activity in Fe‐Ni‐Cr melts
Authors: Laag Thomas , Ohser Joachim , Janke Dieter
Published: December 2016

The subject of this study is the thermodynamics of oxygen dissolved in Fe‐Ni‐Cr liquid alloys. The introduced model is based on a power series to express the logarithm of the activity coefficient of oxygen.

The activity coefficients have been computed from experimental data found in literature. With the help of the described model it is possible to predict the activity coefficient for an arbitrary composition of the Fe‐Ni‐Cr melt and for temperatures between 1525 and 1625°C. The results are compared with data published in literature. The analytical description of the activity coefficient widely agrees with the available experimental data.
Infrared emission spectra (FTIR) and crystallisation studies of the glassy CaO·MgO·2SiO2‐slag (900 – 1200°C)
Authors: Mausbach Klaus , Nowack Norbert , Schlegelmilch Franz
Published: December 2016

The application of Fourier‐transform‐infrared spectroscopy (FTIR) as a method for in‐situ measurements of the spectral emission coefficient is described. During the transformation of the glassy Silicate slag 26CaO + 24MgO + 50SiO2 (mole fractions in %) in the temperature range 900 up to 1200°C into the crystalline diopside the emssion coefficient changes in a characteristic way. Using this method the temporal development of the crystallisation is measured and evaluated.
A comparison of two procedures for computation of the thermal Stresses in not rolled beams
Authors: Boyadjiev Ilia , Lam Yee‐Cheong , Thomson Peter
Published: December 2016

The thermal stresses and deflections in not rolled steel beams can be modelled by using a finite element approximation to the three‐dimensional case based on two dimensional analysis. This is significant because a finite element model of thermal stress in a long beam would require very long computational times in the general case. An iterative method is employed in early analyses [1…5]. The problem is considered one‐dimenssional – the transverse stresses are neglected and the longitudinal stress only is computed. This approximation can result in significant errors when the magnitude of the transverse stresses is comparable with that of the longitudinal stress. Such is the case in industrial practice for instance in accelerated water cooling of Channels or air cooling of rails after hot rolling. One of the most comprehensive simplified finite element thermal stress analyses of hot rolled beams of complex cross sectional geometry is that offered by Abouaf, Marcelin and Chenot [6; 7]. Initially, generalised plane strain was assumed and two additional parameters, namely the curvature and a unit deformation of the fibre at the origin of the coordinate System, were included directly in the Solution. The above method requires Solution of a System of equations in which the stiffness matrix has to be utilised on three occasions. This is computationally expensive, because usually 80% or more of the total Solution time is used for solving the system of equations in which the stiffness matrix participates. In this paper the iterative method described in [1…5] is extended to include the transverse stresses in the analysis. In addition material nonlinearity is taken into account by using the von Mises’ plasticity theory. The system of equations is solved only once for an increment of stress in the elastic range. The present paper offers a comparison between the two procedures.
Effect of hot strip processing during direct charging of thin slabs on the properties of cold strip of LC‐steel
Authors: Bruns Hartmut , Kaspar Radko
Published: December 2016

Direct charging of thin slabs of low carbon steel (0.05%C) was investigated by using laboratory tests on a thin‐slab‐casting Simulator linked with the hot deformation Simulator (Wumsi). Starting with a different initial thickness of simulated thin slabs (45 down to 25 mm) the total strain ɛ∑ was varied. Hot deformation schedules (with and without roughing) with different finishing temperatures TF lead to some differences in the hot strip microstructure. Nevertheless, after cold rolling and batch annealing, a rather uniform pancake‐structure and a pronounced {111}‐texture were achieved in the cold strip without any significant relation to the processing routs. The measurement of final mechanical properties proved that a good deep drawability of cold strip can be achieved with direct charging of thin slabs, well comparable to that after a conventional cold charging of thick slabs.
UV/VIS‐spectroscopy of aluminates in liquid and solid oxide slags
Authors: Mausbach Klaus , Nowack Norbert , Schlegelmilch Franz
Published: December 2016

Structural information of liquid oxide melts including statements concerning their basicity are important not only for the metallurgy of steelmaking but also for the refractory industry, for ceramic productions and for glass manufacturing. After the introduction of infrared emission spectroscopy of liquid melts up to 1600°C it is now possible to receive UV/VIS‐spectra of these melts in different atmospheres. The comparison to already published spectra is possible by recording spectra of quenched samples at room temperature with the same optical system as the high temperature ones.

The suitability of the Fe‐ and Cr‐Ions as test‐ions for the indications of the features of liquid aluminate melts is discussed. A new spectroscopical method for the investigation of melts above 1450°C was developed. Octahedral‐coordinated Fe3+ causes intensive charge‐transfer (CT) absorptions in the melts. These CT‐bands shift towards higher wavelengths and get broader and more intensive at higher temperatures; the results are discussed by the use of the Urbach‐approximation. The CT‐bands of Cr(VI) are attached to various chromate species. The properties of liquid silicates will be the subject of a later investigation.
Finite element analysis of formability of a few kinds of special steel sheets
Authors: Takuda Hirohiko , Fujimoto Hitoshi , Kuroda Yoshito , Hatta Natsuo
Published: December 2016

Deep drawing processes of various special steel sheets are simulated by the rigid‐plastic finite element method. To predict the forming limit a criterion for ductile fracture is applied. From the histories of stress and strain in each element calculated by the finite element simulation, the fracture initiation site and the critical stroke are predicted by means of the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the finite element analysis combined with the ductile fracture criterion is useful to predict the forming limit in a wide range of sheet steels.
Precipitation of titanium nitride in low‐alloyed steel during solidification
Authors: Kunze Joachim , Mickel Christine , Leonhardt Monika , Oswald Steffen
Published: December 2016

The microsegregation of titanium and manganese and the precipitation of titanium nitride during dendritic solidification were investigated on an Fe‐0.051%Ti‐0.77%Mn alloy. Carbon and nitrogen were introduced into the liquid sample via the gas phase. The material solidifies as delta ferrite at a carbon mass content of about 0.08% but predominantly as austenite at ≥ 0.3%.

At ferritic solidification, an about 3fold enrichment of the titanium in the residual melt between secondary dendrite arms is attained by segregration, whereas in the corners between some dendrites or grains in maximum a 10fold enrichment was detected. TiN particles of 0.5 to 1.0 μm size are formed only in the regions of maximum segregation where the supersaturation is higher than 15fold. An equal supersaturation has been calculated for homogeneous nucleation in the melt. The number of particles is moderate at 0.016% nitrogen but low at 0.008%.

At austenitic solidification, the titanium content in the residual melt increases to more than the 30fold of the starting value. Particles formed in the melt grow to diameters in the 2 μm range.
Quantitative model of the effect of quenched and tempered structure, 0.2‐% proof stress and grain size on fracture appearance transition temperature Fatt
Authors: Finkler Helmut
Published: December 2016

The transition temperature for the notched‐bar impact strength considerably varies as a function of the steel composition, the quenched and tempered (QT) structure and associated grain size as well as the 0.2‐% proof stress. To get a better insight into how these parameters affect the transition temperature, the Fatt of many steels resulting from identical quenching, but different tempering treatments was evaluated and a quantitative model developed. The correlation between similarly QT steels and the 0.2‐% proof stress can be described by similar parables, the summits of which lie on a straight line. The position of these peaks on the straight line is determined by the QT structure and the grain size. As the influence of the grain size is assumed to be the same for all QT structures, a measured Fatt ought to be sufficient to know the correlation between grain size and yield strength for a given QT structure. For evaluation purposes, it has been shown practical to characterize the QT structure on the straight line by the Fatt for the grain size dm = 1 mm. The influence of the QT structure proper is determined by the strongly varying correlation between carbide lamellae and grain size, which is independent of the grain size. This carbide lamellae size is thus ascribed the role of a critical crack size.
Application of the fracture mechanics safety analysis to structural steel sections
Authors: Kalinowski Britta , Beltrami Christine , Dahl Winfried , Feldmann Markus , Sedlacek Gerhard
Published: December 2016

This contribution presents a fracture mechanics safety analysis with finite element models applied on I‐beams with defects in the tension flange. The moment rotation at room temperature was observed in the light of the toughness behaviour in front of initial notches. The results show very early crack initiation due to very large initial defects. The experiments were accompanied by a fracture mechanics safety analysis employing FEM. However, in temperature ranges of buildings plastically designed beams are subjected to sufficient rotation capacity, i.e. rotational ductility could be found.
Influence of microalloying on the mechanical properties of medium carbon forging steels after a newly designed post forging treatment
Authors: González‐Baquet Ignacio , Kaspar Radko , Richter Johannes , Nußbaum Georg , Köthe Alfred
Published: December 2016

For more than twenty years the classical quench and tempering of medium carbon Cr‐alloyed steels has been substituted in the production of drop‐forged parts for the automotive industry by a direct continuous cooling of less expensive V‐microalloyed steels with lower carbon content. However, this simplified treatment has serious limitations concerning the yield strength and ductility if compared with the properties after quench and tempering. On a group of such V‐bearing steels additionally microalloyed with Ti and Nb and with different N contents, an alternative two‐step‐cooling (TSC) strategy after forging, combined with an additional annealing (AN), has been applied. This new post forging treatment results in a significant improvement of the final mechanical properties. The paper is focused on the particular contributions of a different microalloying in the optimized deformation schedules to improve mechanical properties after TSC + AN. The aim of this additional microalloying is to achieve a more homogeneous distribution of ferrite in the final multi‐phase microstructure due to a proper austenite conditioning as well as to make a full use of the strengthening potential of vanadium in these forging steel grades.
Modelling of the effects of strain‐induced martensitic transformation on the mechanical behaviour in drawn tubes
Authors: Luksza Janusz , Majta Janusz , Ruminski Maciej
Published: December 2016

The objective of this paper is to demonstrate the ability of a computer simulation to analyze the development of microstructure and finally to predict mechanical properties of two‐phase steel after strain induced martensitic transformation. A model of a tube sinking process was coupled with closed form equations describing the mechanical properties of stainless steel. The influence of the martensitic transformation on mechanical behaviour was also noted in uniaxial tension tests and hardness measurements. First, the non‐uniformity of deformation was modelled by the finite element method where the mechanical description of metal flow was based on the model of two‐phase material. Secondly, a series of drawing and tension tests were carried out in order to identify the inhomogeneity of mechanical properties (yield strength, tensile strength, hardness) as a function of mechanical and thermal conditions given in each test. The investigation was focused on the case where the conical dies were used. With a combination of an amount of deformation and die geometry, based on the microstructure development the final relationships were established. Finally, it was shown that the correlation between the process parameters and the development of the resulting microstructure can be effectively described using proposed models.
Prediction of the measured temperature after the last finishing stand using artificial neural networks
Authors: Vermeulen Willem , Bodin Andre , van der Zwaag Sybrand
Published: December 2016

In this report the development of an artificial neural network, capable of predicting the temperature after the last finishing stand of a hot strip mill for a certain class of steels, is described. Three neural networks with different numbers of hidden nodes (3, 5 and 7) were trained. The relative standard deviation in finish temperature as predicted by the best performing neural network model (7 hidden nodes) was just over 25% smaller than that of the linear Hoogovens model. This improved accuracy can be explained by the incorrect assumption in the Hoogovens model of linear dependence of the finishing temperature on some input parameters.

With the trained neural network, the influence of the various input parameters on the finishing temperature could be examined. The dependencies predicted by the neural network can be approximated by a linear fit and are a factor 2 lower for all input parameters.

It is conceivable that operation of the mill using an artificial neural network for the prediction of the finishing temperature would have resulted in smaller operational fluctuations.
Dilatation measurements of plain carbon steels and their thermodynamic analysis
Authors: Qiu Caian , van der Zwaag Sybrand
Published: December 2016

Dilatation of the low‐carbon steels with small additions of mass contents of Mn (up to 1.50%), Si (up to 0.347%), Nb (up to 0.053%), and V (up to 0.082%), was measured at a heating rate of 3°C/min, and the experimental results were compared with calculations based on thermodynamic models. The differences between experiments and calculations were analysed. It was found that the thermal expansion of pearlite and of austenite in the steels exhibits almost linear temperature dependencies, and these dependencies are described very well by the present calculations. During the transformation of pearlite to austenite, contraction of the steels may occur due to the dissolution of cementite within a narrow temperature range. The dilatation of the steels during the transformation of ferrite to austenite depends on the competition between the thermal expansion and the transformation process, and it finally leads to an increase in the length change to a maximum followed by a decrease down to the temperature at which the transformation is completed. For some steels, however, a certain amount of ferrite may remain in the samples during heating even at temperatures well above that of the minimum dilatation. This will affect the determination of the A3 temperature, and makes the expansion of the steels deviate from the true expansion behaviour of austenite.
Mathematical modelling of divided blast cupola
Authors: Viswanathan Nurni Neelakantan , Srinivasan Mandayam Nayachavadi , Lahiri Ashok Kumar
Published: December 2016

A pseudo 2‐D mathematical model has been developed to simulate a cupola with one row and two rows of tuyère. The simulation results predicted higher spout temperature and combustion ratio for cupola with two rows of tuyère compared to that with one row. Further, the model has been used to study the effect of the distance of separation between the two rows of tuyère on cupola performance. The computed results shows that the spout temperature increases with tuyère level separation and attains the maximum at an optimum distance of separation between two rows of tuyère. Above the optimum, the spout temperature starts decreasing. The exit gas temperature and combustion ratio increases monotonously with the increase in tuyère level separation. These results agree well with the reported experimental observations. The mechanism behind the improved cupola performance with two rows of tuyère has been deduced from the computed temperature and composition profiles inside the cupola.
Determination of the interfacial heat transfer coefficient in a metal‐metal system solving the inverse heat conduction problem
Authors: Mehrotra Surya Pratap , Chakravarty Apratim , Singh Prabhdeep
Published: December 2016

Simulation of several industrial processes involving solidification of metals requires characterization of heat transfer coefficient at the solidifying metal/metal‐substrate interface. In the present investigation an attempt has been made to estimate this heat transfer coefficient, hc, using simulated experiments in which the heat transfer from a heated stainless steel block (simulating solidifying metal) to a water cooled copper block (simulating metal‐substrate) is monitored by continuously recording temperatures at a few internal locations both within the metal block and the substrate block. The problem of determining the interfacial heat transfer coefficient is recognized to be an inverse heat conduction problem (IHCP). A numerical method is employed to solve IHCP and to determine the hc from the transient history of temperatures at a few locations. The effect of the physical nature of the interface, as well as the cooling conditions prevailing at the outer surface of the substrate on hc is examined and discussed. While the physical nature of the interface, i.e. roughness on the metal as well as the substrate surfaces, has a significant effect on hc, the cooling conditions have only a marginal effect. The hc in the present investigation remains more or less time invariant.
Modelling and simulation of deformation zone in cross rolling mill
Authors: Zhiqiang Li , Yuqiu Lu , Shouli Lu
Published: December 2016

Based on the three‐dimensional models of the deformation zone of Accu‐Roll mill described in this paper, simulative software is developed on a PC computer by means of 3‐D solid method. Any sections of the deformation zone can be viewed at any position and in any direction so that it is very convenient to analyze characteristics of cross‐rolling deformation zone and to pre‐set process parameters.
Thin strip casting of steel with a twin‐roll caster ‐ correlations between process parameters
Authors: Büchner Achim Rüdiger
Published: December 2016

Thin strip casting of steel according to Bessemer is now being investigated world‐wide in many institutions. In order to optimize, stabilize and scale up the process, a better understanding is needed. So there is a large interest in model descriptions. The best treatment by an exact analytical solution of the heat transfer equations is not possible due to its complexity. Instead, several numerical calculations have been carried out with good accuracy, but due to the large number of influencing parameters they are very often not generally applicable. The treatment in this paper is a compromise: the physical problems are solved by use of some approximations; thus analytical approaches with sufficient accuracy and general applicability are obtained. First the geometry of the pool and of the solidification is studied. An important result of this is that the pool must be treated in two different parts with strongly different heat transfer behaviour. In the upper part no solid bridges occur, and the rolling force cannot be transmitted. Thus the heat transfer into the rolls is hampered and can be described according to Newton. In the lower part there are solid material bridges to transmit the roll force, although a full solidification is not yet completed. The heat transfer into the rolls is much improved, and is now ideal. Then important process parameters as pool height, rolling force, and strip temperature are calculated and results are compared with data obtained from Fe6.3%Si experiments.
Final solidification, centre segregation and precipitation phenomena in continuously cast round billets
Authors: Jacobi Hatto , Wünnenberg Klaus
Published: December 2016

Archimedes’ principle was applied to strand lengths of up to 14 m of round 177 mm diameter billets to determine cavity volume V (in cm3/m) for a series of tubemaking steels. Under steady state casting conditions, V depends primarily on the chemical composition and solidification behaviour of the steels. Averages ranged up to in an extreme case (bearing steel; vC = 2.0 m/min). Stopping the strand and abrupt lowering of withdrawal speed made it possible to artificially induce individual shrinkage cavities with peak values of V = 45 cm3/m. In the round mould, subsequent necking of the liquid crater is initiated in this process. Whisker‐like and icicle‐like dendrites can be observed in horizontally formed macroscopic shrinkage cavities.

The liquid crater is broken off by periodic bridging (the mini‐lingot model). As permeability decreases, the bridges deflect downward in a U‐shape under the ferrostatic load. The residual inter‐dendritic melt is squeezed out in this plastic deformation process. Some bridges ultimately break. This interpretation is based on comprehensive CMA studies and concentration maps.

Cores taken from the centre of a strand of bearing steel were submitted to various heat treatments between 1100 and 1350°C. Homogenization occurs below solidus (T < 1225°C). Carbides dissolve and sulfides become globular. Spatial segregation, on the other hand, increases, above solidus. In the extreme case at 1350°C/30 h, the residual melt at the grain boundaries migrates practically completely from the surface zone to the centre of the cylindrical sample (40 mm diameter). The propellent forces for this macro‐heterogenization are provided by the activity gradient from the cylindrical surface to the centre and minimization of interface energy γ/I.
New post forging treatment of medium carbon microalloyed steels
Authors: Kaspar Radko , Gonzälez‐Baquet Ignacio , Richter Johannes , Nußbaum Georg , Köthe Alfred
Published: December 2016

In drop forging of parts for the transport industry the classical quench and tempering (QT) of alloyed steels is nowadays substituted by direct continuous cooling (CC) of microalloyed steels with elimination of quench cracking and expensive straightening and stress relieving cycles. Nevertheless, there are some limitations on strength and toughness achievable by this technique. On two commercial medium carbon (0.3%C) steels microalloyed with vanadium or vanadium and titanium, modified forging parameters and a new two‐step cooling (TSC) strategy combined with an additional annealing were applied. Some increase in manufacturing costs, when compared to CC, can be justified by a significant increase in strength and ductility. The improvements attainable through such a modified treatment give evidence of the large potential of multi‐phase ferrite‐containing microstructures as a substitute of a tempered martensite.
Application of a micromechanical damage model to the analysis of ductile fracture of a thermomechanically treated steel with different microstructures
Authors: Pardun Markus , Hagedorn Karl Edgar , Kaspar Radko , Memhard Dieter
Published: December 2016

A possibility to characterize the different stages of the process of ductile fracture from a more microscopic point of view are micromechanical damage models. On a steel 27MnSiVS6 microalloyed additionally with titanium, which belongs to the group of the microalloyed precipitation hardening ferritic‐pearlitic steels, different states of microstructure (ferrite‐pearlite, tempered martensite, bainite) were produced using thermomechanical treatment. On such specimens fracture mechanics tests were done with side‐grooved 1/2 CT‐specimens and the results were compared with those obtained by a numerical simulation based on the modified Gurson model. A good agreement between calculated and measured JR‐curves also for a thermomechanical treated steel with separations was found. The critical distance Ic has a great influence on the results of this numerical model. A qualitative relation between this parameter and the average inclusion spacing, which depends on the microstructure, was found.
The influence of prior ageing on creep damage development in two variants of Alloy 800
Authors: El‐Magd Essam , Frères Patrick , Nicolini Guido , Schuster Hans , Ennis Phil J.
Published: December 2016

The influence of high temperature thermal ageing treatments on the development of intercrystalline creep damage in two variants of Alloy 800 has been investigated. Ageing up to 3000 h and creep testing were carried out at 800 and 900°C. The high temperature behaviour of the 800HT variant is discussed with reference to the effect of heat treatments on the microstructure. The metallographic methods by which the creep damage was quantitatively determined are described. The growth rate of intercrystalline microcracks was described using a statistical model and the dependence of crack growth rate on the thermal history for both 800HT and 800H was determined. The carbide precipitation and growth processes were determined as functions of the exposure temperature and duration. The results showed the three characteristic stages, precipitation, growth and coarsening (Ostwald ripening). The largest increase in the intergranular creep damage was found in Alloy 800HT within the first 1000 h, in which the precipitation of chromium carbides on the grain boundaries is substantially completed. The comparison between the two variants showed significant differences in the damage development. 800HT exhibited at 800 and 900°C higher creep crack growth rates with increasing exposure duration, but in 800H this effect was not clearly identified.
Circulation rate of liquid steel in RH degassers
Authors: Ahrenhold Frank , Pluschkell Wolfgang
Published: December 2016

Vacuum‐decarburization with the Ruhrstahl‐Heraeus process is used for the production of ultra‐low carbon steels. One important aspect of the RH process is the circulation of liquid steel between the degassing unit and the transport ladle. Thus, supervisory control of the RH treatment requires precise mathematical modelling of the circulation rate. In this work, a numerical model of the circulation flow is described in detail.

This newly developed model as well as a frequently used semi‐empirical equation are compared with measured data. It is shown that the numerical model is in far better accordance with the measured data than the semi‐empirical equation. The numerical model is then applied to data of a conventional RH treatment. Special emphasis is put on the coupling of circulation rate and reaction rate. Both, circulation rate and reaction rate, are calculated as a function of time.
Controlling homogeneity and reproducibility in the production of heavy plates
Authors: Streißelberger Alois , Flüß Peter , Kolling Alfons
Published: December 2016

To derive a representative assessment of the achieved level of control in the production of heavy plates the increasing relevancy and the various aspects of homogeneity and reproducibility criteria, the role of process control and the investigation methods have to be considered. The aspects of fitness for use and of fabrication are driving forces for a narrow control of plate properties, which includes the homogeneity within all parts of a delivered plate and also the repeatability of properties from plate to plate produced for the same specification or order. With view to the specified range of composition, process parameters and mechanical properties adapted target ranges are defined. The steps of production are controlled and monitored by process computers. So the desired level of the capability of the process can be assured. This is a prerequisite for process control.
Investigation into tribology of cold strip rolling
Authors: Rasp Wolfgang , Häfele Peter
Published: December 2016

The key factors which determine the friction as well as the surface quality of the rolled strip are the amount of oil which is entrapped in the roll bite and the roughness of strip and roll. In the present paper, the influence of the hydrodynamic and the roughness effect on the entrained film thickness and on the friction conditions in the roll gap have been examined theoretically and experimentally. For the experimental validation of the theoretical findings, rolling tests with thin aluminium sheets are carried out. The main parameters for the hydrodynamic effect, l.e, the rolling speed, base viscosity and yield stress, and the ones for the surface effect, l.e, the surface roughness and its orientation, have been systematically varied throughout the experiments.
Metal flow in bearing section during extrusion process of L, C and T sections
Authors: Kiuchi Manabu , Yanagimoto Jun , Mendoza Victor
Published: December 2016

Conventionally, various metal sections are extruded using flat‐faced dies. This results in metal flow‐related defects such as bending, twisting, tearing and thinning. As a result, time consuming and expensive post‐extrusion operations are needed to obtain acceptable dimensional quality of the product. This paper describes the application of a newly developed rigid‐plastic FEM code to the extrusion of sections and shows the results of metal flow simulation. The results are used for predicting the geometric defects and reducing them through modification of the bearing land and the position of die opening. This procedure is applied to the extrusion of L, C and T sections and the influence on the metal flow of some variables like friction coefficient, aspect ratio of product's cross‐section, bearing land length and position of die opening is studied. The results are presented making emphasis on the study of the axial velocity distribution in the bearing land.
Comparison of the light‐weight potential of different materials used under bending loads
Authors: Neumann Peter
Published: December 2016

In transportation and many other technologies weight reduction brings about economical and environmental advantages. Therefore, materials are increasingly being judged according to their weight saving potential. In the case of structural materials, which have to withstand given stresses, a classification based on density alone (light metals) falls short, since the crucial parameter is the ratio between density and strength. In the case of parts loaded in bending the situation is complicated by the fact that e.g. the elastic stiffness of such parts (of a given length) does not only depend on their volume but also on their shape. It will be shown in this paper that the usual comparison of the weight saving potential of different materials under bending loads is strongly shape biased, favouring the more compliant material. An un‐biased comparison reveals, however, that e.g. the weight saving potential of high strength steels and aluminium alloys is comparable ‐ also if used for bending parts.
Analysis of the motion of a flat jet in a direct strip casting feeding system
Authors: Holmberg N. Anders , Åkerstedt Hans O.
Published: December 2016

The motion and shape of a vertically falling flat rectangular jet of liquid metal issuing from an inclined plane is analysed numerically and analytically. The jet is affected by surface tension and gravity. The main interest in this problem originates from the technological application of the direct strip casting process, which is a novel process to cast steel strips in a thickness range from 2 to 15 mm with a minimum or no hot‐rolling. In this process the liquid metal is fed onto a single endless horizontal belt that runs between two rollers. The bottom of the belt is cooled by water. One of the techniques to feed the liquid metal is down an inclined plane. Due to disturbances in the flow, for instance slag in the liquid metal, the jet issuing from the inclined plane may split into two or several jets. The large convergence of the individual jets causes an unfavourable non uniform distribution of the liquid metal over the belt.

In the analysis of the present paper it is shown, using an expansion in the inverse Froude number, that the convergence of a single jet depends to zero order on the inverse square root of the Weber number We−1/2 = (γl(ρw02 h0))1/2. Small convergence of the jet is found for large Weber numbers, which can be accomplished with a large initial velocity w0.
Quantification of macrosegregation in continuously cast steel structures
Authors: Komenda Jacek , Runnsjö Gunilla
Published: December 2016

Macrosegregation was investigated in longitudinal sections of continuously cast, experimental slabs of austenitic stainless steel and carbon‐manganese steel. The macro‐mapping technique was applied to investigate austenitic stainless steel slab sections. The method was based on electron probe microanalysis that was applied in a step‐point mode to locally investigate segregation areas. The same stainless steel specimens and carbon‐manganese steel specimens were etched to reveal the segregation structure. The macrosegregation in three carbon‐manganese steel slabs was represented by etch‐prints. The quantitative investigation of structure was performed directly on the macroetched specimens and on the etch‐prints. The morphology of macrostructure was characterised by new parameters: segregation factor M, width of a segregation band W0.5, centreline segregation intensity C and the heterogeneity index H. The segregation factor M was proportional to the inhomogeneity in segregate size distribution and to the segregate area fraction. W0.5 was defined as the area where the segregate area fraction is greater or equal to half of the maximum value of measured area fractions. Parameter C equal to a ratio Mmax/W0.5, represented the intensity of centreline segregation. The heterogeneity index H was based on the measurements of mean size of segregates and the mean free path within segregate areas. For a homogeneous structure the heterogeneity index is zero and it increases with growing inhomogeneity of a macrostructure.
Simultaneous refining of phosphorus and sulfur from hot metal utilizing recycled sinter ore dust
Authors: Pak Jong‐Jin , Kim Eui‐Jun , Jung Woo‐Gwang
Published: December 2016

An experimental study is carried out to determine the possibility of utilizing the recycled sinter ore dust for refinging flux for hot metal. The dust has good physical and chemical properties as an injection powder, however, it contains masses of about 0.24% S and a substantial amount of sulfur which can be picked up by the hot metal during the injection treatment. Therefore, sinter ore dust is mixed with burnt lime, fluorspar and sodium carbonate to increase the sulfide capacity of the flux. The fluxes are tested for hot metal dephosphorization and desulfurization in laboratory and plant scale experiments. The fluxes show an excellent dephosphorization efficiency without sulfur pick up. In case of the flux containing sodium carbonate masses of 10%, sulfur in hot metal is simultaneously removed. In addition, a higher manganese yield in hot metal is obtained in case of a sodium carbonate containing flux at the end of injection treatment.
Reduction of hematite compacts by H2‐CO gas mixtures
Authors: Moon II‐Joon , Rhee Chang‐Hee , Min Dong‐Joon
Published: December 2016

The reduction behaviour of hematite compacts by H2‐CO gas mixtures was investigated at 1073‐1223 K. The total porosity, pore size distribution and surface area of the compact was measured using mercury pressure porosimeter. The reduction tests were carried out using Cahn balance. The reduction behaviour could not be described in terms of a single rate‐determining step; the reduction process was initially controlled by the chemical reaction at the oxide/iron interface, controlled by the intraparticle diffusion through the reduced layer towards the end of reduction, and the mixed control, in between. Over the whole range, the reduction rate decreased with CO content in the gas mixture. The chemical reaction rate constants were two to three times higher for H2 reduction than those of CO reduction, and the effective diffusivities of H2 reduction were three to four times higher than those of CO reduction. Values of activation energy for chemical reaction were found to be 19.8‐42.1 kJ/mol depending on the gas compositions; 100% CO showing the lowest.
Dissolution behaviour of manganese ore in basic oxygen furnace type slag
Authors: Jung Woo‐Gwang , Chen Zhao‐Ping , Sohn Ho‐Sang , Pak Jong‐Jin
Published: December 2016

In order to improve manganese yield during the reduction process of manganese ore in blowing practices employing less slag at BOF, the dissolution behaviour of manganese ore in slag has been studied in an experimental scale. The effect of temperature, slag composition, addition of CaF2, and pre‐treatment of manganese ore was examined for the dissolution behaviour of manganese ore into BOF type slags. The precipitation of (Fe,Mn)O phase in slag was observed during the addition of manganese ore. The dissolution rate of manganese ore into molten slag increased with temperature, and also increased with the initial contents of FeO, MgO and MnO. However, the effect of slag basicity was not evident on the dissolution rate of manganese ore into slag. The addition of CaF2 and pre‐treatment of Mn ore were very effective to promote the dissolution of manganese ore into slag.
Thermoelectric properties of the Fe‐Al and Fe‐Al‐Si alloys for thermoelectric generation utilising low‐temperature heat sources
Authors: Ono Katsutoshi , Kado Masaki , Suzuki Ryosuke O.
Published: December 2016

The iron is intrinsically a p‐type conductor. When aluminum with three valence electrons is added to the iron, the d‐subbands are occupied by electrons, so alloying with the aluminum transforms the iron to the n‐type conductor, hence the p‐n junction is made possible. Furthermore, when silicon is added to the n‐type Fe‐Al alloy, this alloy returns to the p‐type conductor. Therefore, the thermoelectric p‐n junctions with high thermoelectric power have been recognised (figures in % refer to mass contents):

Fe(p) – Fe12%Al(n): α=38μV/K and Fe12%Al12%Si(p) – Fe12%/Al(n): Δα=70μV/K.

Thermoelectric generation offers the possibility of a gigantic electric power generation utilising low‐temperature sources of energy below 700 K such as exhaust heat from the central‐station steam‐electric plant, solar heat and terrestrial heat. The immense production of electricity by this principle is made possible exclusively by means of the conversion materials consisiting of the iron and iron‐based alloy because the generator can be manufactured on an efficient mass production basis, and the alloys mentioned above will meet this requirement. In this paper, the thermoelectric properties of these alloys such as Seebeck coefficient, thermal conductivity and electrical resistivity were experimentally determined in the temperature range between 300 and 700 K to provide basic data on the conversion materials with respect to the thermoelectric generation utilising low‐temperature heat sources.
Mixing phenomena inside the ladle during RH decarburization of steel melts
Authors: Ahrenhold Frank , Pluschkell Wolfgang
Published: December 2016

The RH (Rheinstahl‐Heraeus) process is in widespread use to produce ultra‐low carbon steel by vacuum treatment. Among other factors, the decarburization rate is effected by mixing phenomena inside the ladle. Thus, supervisory control of the RH treatment requires an adequate and precise representation of the mixing conditions. In this work, mixing is characterised by concepts of chemical reaction engineering. Different sizes and geometries of RH installations are taken into account using similarity criteria. A simple model is derived from the experimental results and detailed numerical flow computations. For this model, a mathematical function of mixing is developed which can be incorporated into supervisory control systems.