bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the Master Curve Approach for the Irradiation Embrittlement Evaluation of Pressure Vessel Steels
Authors: Viehrig Hans‐Werner , Böhmert Jürgen
Published: December 2016

The Master Curve (MC) approach and the associated reference temperature, T0, as defined in the test standard ASTM E1921, is rapidly moving from the research laboratory to application in integrity assessment of components and structures. T0 is the index temperature for the universal MC, which considers the toughness behaviour of a specific material. “The Structural Integrity Assessment Procedures for European Industry” (SINTAP) contain a MC extension for analysing the fracture behaviour of inhomogeneous ferritic steels. This paper presents the application of the MC approach to the T0 determination of different types of Russian WWER‐type reactor pressure vessel (RPV) steels. In addition the SINTAP‐MC approach was applied to determine an alternative reference temperature, TR.

The influence of different microstructures and compositions within one type of RPV steel and the effect of irradiation with fast neutrons on T0 are experimentally evaluated. In general the MC based T0 is about 72 K below the Charpy V‐notch transition temperature related to an impact energy of 48 J. The paper demonstrates the application of MC based T0 and TR as an alternative reference temperature for neutron embrittled RPV steels used in the RPV integrity assessment.
Effect of Processing Conditions on Mechanical Properties of a Ti Interstitial Free Steel
Authors: Alvarez M.A. Vicente , Perez Teresa , Actis Fernando , Seré Pablo , Cervellini Gabriel
Published: December 2016

The effect of thermal cycle, cold reduction and temper rolling on texture, microstructure and mechanical properties of a Ti‐added IF steel is presented. Sheets with different cold reductions were annealed using cycles with temperatures, heating rates and soaking times including extreme annealing conditions like continuous and batch regimes. Microstructure is characterized by equiaxed grains of about 17 to 20μm, being independent of the annealing cycle applied. As a function of the processing variables, texture depended mainly on heating rate and cold reduction degree, showing little dependence on soaking time or temperature. Despite the great differences between batch and continuous annealing cycles, yield strength, ultimate tensile strength and hardening coefficient n show little variation between these extreme regimes. This characteristic makes this steel almost insensitive to annealing conditions, strongly differing from other deep drawing materials like Al‐killed steels. The influence of texture on r‐value was studied using a Taylor‐based model which showed good agreement with experimental relationships. Finally, temper rolling of annealed materials was simulated with elongations varying from 0.5 to 7%. This resulted in an important increase of YS and a decrease of n, but had a deleterious effect on stretchability.
Semi‐Solid Processing of Metal Alloys
Authors: Aguilar Julio , Fehlbier Martin , Grimmig Tilman , Bramann Horst , Afrath Carsten , Bührig‐Polaczek Andreas
Published: December 2016

Semi‐solid metal casting is an innovative technology for the production of near‐net‐shape parts with demanding mechanical properties. The paper describes different processing routes and materials for semi‐solid‐metal casting (SSM), which have been investigated and also partially developed at the Foundry‐Institute of Aachen University.

The standard thixocasting process for aluminium, highly reactive magnesium alloys and steel alloys with high melting points was investigated under variation of a wide range of process parameters. Specially adapted pre‐material production and reheating methods were developed for different materials and their application and future potential is pointed out. The thixocasting experiments were executed on a modified high pressure die‐casting machine with a specially designed “step‐die” providing wall thicknesses from 0.5 to 25 mm. The mechanical properties were tested in dependence of the wall thickness and the metal velocity. The results of these examination show high tensile strength values in combination with very good elongations.

The rheocasting process is a new SSM‐forming method with liquid melt as feed‐stock and a high recycling potential. The research results of RCP‐technology (Rheo‐Container‐Process) invented at the Foundry‐Institute and of the Cooling‐Channel‐Process for aluminium and magnesium alloys are promising and are presented in this paper.

Studies on semi‐solid processing of magnesium alloys and mixtures of them were conducted by ThixomoldingTM. To establish the most adequate process parameters, the temperature and the mixture relations were varied. Using a mould for tensile test specimens, the mechanical properties and the microstructure evolution could be evaluated. The chemical composition of the different phases was determined using SEM and EDX technologies. Evaluations of the flowing properties were conducted using a spiral mould with a total length of 2m and a cross section of 20mm x 1.5mm.
Casting of High Alloy Steels in the Mushy State
Authors: Bramann Horst , Afrath Carsten , Grimmig Tilman , Fehlbier Martin , Bührig‐Polaczek Andreas
Published: December 2016

In order to broaden the field of application for the innovative thixocasting process, much research is dedicated to the thixocasting of high melting point alloys. The wide property range of modern high alloy steels combined with the productive semi‐solid die casting process opens up new fields of application. The Foundry Institute of the Aachen University has therefore been concentrating on the research of the possibilities and limits of high pressure die casting of high alloy steels in the semi‐solid state. This paper gives an overview of the current work dedicated to thixocasting of steel alloys by a high pressure die casting machine at the Foundry‐Institute of the Aachen University of Technology.

In order to understand and describe the material properties in the semi‐solid state, basic test specimens have been investigated. Weak points of tool preheating as well as directional solidification of the produced parts can be controlled by numerical simulation of the temperature distribution inside the dies. In consideration of the outstanding flow properties of semi‐solid steels more complex geometries with accurately defined applications are now being investigated. Extensive metallographical analyses of the pre‐material, the reheated billets and the produced parts have been done to evaluate the viability of the process. The mechanical properties of the specimens outline the outstanding potential of the thixocasting process.
Thixoforging of Steel Using Ceramic Tool Materials
Authors: Behrens Bernd‐Arno , Haller Björn , Fischer Dirk
Published: December 2016

Today thixoforming processes are mainly established in the production of parts made of aluminium alloys. Compared to high melting alloys the process temperature is low and thus the process is easier to handle. Because of process temperatures up to 1470°C thixoforming of steels demands a sophisticated process control and adapted tool materials. In this field there is still a large need for research. This paper deals with experiences made at the IFUM concerning the thixoforging of steel. The use of ceramic tool materials for thixoforging of steel is presented. For this purpose hybrid dies where a ceramic insert is prestressed with a hot working steel shrink ring as well as different stamp geometries were developed and built up. Different ceramic materials from Si3N4 to ZrSiO4 were tested and evaluated. To prevent an unwanted cooling and oxidation of the slug during its transfer, the transfer is carried out encapsulated in high temperature resistant crucibles that can provide a protective atmosphere. The suitability (e.g. thermo shock resistance) of different materials for the use as transport crucibles was also subject of this research work.

The forming experiments were carried out with the institute's hydraulic press. The process logic controller of this press offers the appropriate flexibility and various control modes needed for a sophisticated and reproducible filling of the die. In this way the die filling process of different steels can be tested.
Model Tests and Analysis of Corrosion Resistance of Ceramic Tool Dies for Steel Thixoforming
Authors: Münstermann Simon , Telle Rainer
Published: December 2016

Contact corrosion and cyclic melt corrosion test results of silicon nitride (Si3N4) ceramics in contact with semi‐solid and molten steel alloys are analysed in view of steel thixoforming applications. Corrosion effects are identified and model tests are evaluated by comparison of corrosive attack on steel thixoforming dies in application‐relevant forming experiments. The performed corrosion experiments show that a reaction zone of up to 20 μm thickness forms on the ceramic in model tests and forming experiments, respectively. Si3N4 ceramics reveal sufficient corrosion resistance in small‐scale forming series. Results show good agreement of contact corrosion tests with thixoforming experiments. Comparability of cyclic melt corrosion tests with thixoforming applications is limited by the casting powder used to prevent oxidation of steel melt.
Effects of Pre‐Processing on Thixoformability of Steel Grade 100Cr6
Authors: Bülte Raimund , Bleck Wolfgang
Published: December 2016

Thixoforming is a new manufacturing technology which has been widely investigated for aluminium alloys. The thixoformability of steel and especially the impact of different pre‐processing is subject of this paper. For the thixoforming process it is of special interest to obtain the required fraction liquid content between 20 and 40%, a globulitic microstructure and low process temperatures. Therefore, steel primary material from three different processing routes was compared. The primary materials are rolled bars, laboratory cast billets and laboratory cast billets with liquid core reduction. The melting behaviour of the different materials was investigated by using Differential Thermal Analysis (DTA). Furthermore the materials were reheated into the solid‐liquid range and quenched to monitor the development of the microstructure. No significant differences between the three different pre‐processing routes could be determined with regard to thixoforming. Thus it seems possible to start thixoforming with as‐cast primary material.
Thixoforging of Steel Alloys ‐ Facility Requirements for Industrial Application
Authors: Siegert Klaus , Messmer Guenther
Published: December 2016

The article describes some important considerations for an industrial application for the thixoforging of steel alloys. Extensive experience in the forming of aluminium, brass and steel alloys was made with the automated thixoforging unit set‐up at the Institute for Metal Forming Technology. After a brief description of the thixoforging unit, the cycle of automated thixoforging is explained. Beside the demands of reheating in an inert atmosphere, some aspects of process monitoring are described. In relation to this, the installed industrial vision system is presented.

The requirements for batch production dies in automated units are focused upon. The results of the experimental forming of steel alloys with two different materials for the thixoforging dies are presented. A comparison of both alloys 1.2714 and CuCrZr is made.
Advanced Processing and Properties of Thixotropic Formed Components Based on Partially Melted Magnesium
Authors: Wagener Wolfram
Published: December 2016

Contrary to the manufacture of aluminium components in the semi‐solid, thixotropic state the production of magnesium based components by semi‐solid techniques is still uncommon. For this reason, the advantage of this production method is analysed with regard to the commercial magnesium alloy AZ80. The objective of this research is semi‐solid‐casting (SSC) of AZ80 for the production of a light weight component in near‐net‐shape quality and with advanced properties.

Using extruded primary feedstock material, the behaviour and the advantages are investigated. Billets with a weight of up to 2 kg are heated up into a semi‐solid state. To avoid any risk of self‐ignition of the material an automatic, temperature controlled induction heating system is used. To achieve an optimum homogeneous grain structure the induction heating power is varied making use of a process control system based on power‐time‐curves. The heated billets are transported in the soft semi‐solid condition from the induction heating system to a die casting machine to produce components with wall thickness’ between 2 and 10 mm. After forming of the components, the influence of heat treatment on the grain structure and especially on the mechanical properties is determined to provide parts with optimised characteristics.

To compare the properties of the special globular grain and microstructure, the results of various static and dynamic tests are analysed. It is found that components can be manufactured with a magnesium alloy in a thixotropic state in near‐net‐shape quality, with low porosity and with excellent mechanical properties like elongation of up to 15%.
Micro Semi‐solid Manufacturing ‐ A New Technological Approach towards Miniaturisation
Authors: Steinhoff Kurt , Weidig Ursula , Weikert Jan
Published: December 2016

One of the most important prerequisites to meet the increasing demand for efficient technologies for micro‐part production is constituted by the ability to overcome existing process limitations by new innovative technological approaches. By the introduction of a new process variant based on a hybrid material condition between solid and liquid state, such an approach is presented. This micro semi‐solid manufacturing technology, so‐called Micro‐Thixoforming, was initiated, on the one hand, by being aware of the technological limits of existing micro‐forming and micro‐casting processes and, on the other hand, by a comprehensive understanding of the special rheological mechanisms of metallic materials in semi‐solid state finally establishing the desired potential to follow the trend towards miniaturisation with drastically reduced process restrictions. However, this promising potential can only be successfully exploited when the initial idea, which is based on phenomenological considerations, can be transferred to a process technology with sufficient practical relevance. Therefore, the presented new integrated process concept for Micro‐Thixoforming is particularly characterised by the application of unconventional solutions for the main process steps: raw material conditioning, thermal pre‐processing, semi‐solid forming and thermal post‐processing. To give an indication of the innovative character of the chosen practical solutions liquid metal jet technology, LASER‐induced plasma shockwaves and high pressure water jet should be mentioned. However, what is even more important in this context is the ability not only to realise a process concept but, beyond that, to recognise the further potential regarding new strategies for material design arising from the availability of this process. Such a strategy e.g. consists of utilising the well‐known segregation effect, which notably often is negatively associated with semi‐solid forming. However, for the envisaged technological approach, controlled segregation aims at a defined adjustment of functionally graded properties for the produced micro part.
Structure of Liquid Slags and Ultraviolet/Visible Reflection Spectroscopy of Molten and Glassy Silicates (Fe2O3‐CaO‐SiO2)
Authors: Nowack Norbert , Zebger Ingo , Pfeifer Frank
Published: December 2016

The first part of this work is a description of the molecular structure of liquid silicates. From the knowledge of the chemical bond, the Men+···O2− bond distance and the Men+/O2− coordination number, the Men+···O2− bond polarity (Me=Ca, Mg, Al, Fe…) of liquid oxide slag systems is derived. There exists a connection between this value and the activity coefficient of an oxide component. We illustrate this connection for important slag systems.

The second part of this work deals with the reflectivity of liquid silicates in the ultraviolet and visible spectral range using the reflection angle 0°. For these considerations, we have developed a spectroscopic reflection method (impulse‐flash‐technique). We have investigated the systems CaO‐FeOn‐SiO2 with Fe2O3 ‐contents above 24% (mass percent) and a CaO‐Fe2O3‐flux with an Fe2O3‐content of 60% in the temperature range from 1400 °C to 1500 °C applying an oxygen partial pressure of pO2 = 0.21 bar. The increased reflectivity in the ultraviolet spectral range is based on the very intensive electron transfer (charge transfer bands: CT) from the oxide ion (bound to the respective matrix) to the Men+‐ion (Men+=Fe3+, Mn2+..). The increased reflectivities in the visible spectral range are due to d‐d‐transitions in the Men+‐ion located in Men+‐O2− ‐complexes. This can be proven in the following way. The reflection bands in the visible range are much less pronounced than the CT‐bands in the UV range. In liquid slags complexes with the coordination number 4, Fe3+(O2−)4 were found. In glassy silicates, complexes with the coordination number 6 dominate. The reflection spectra have been analysed quantitatively and related to the molecular structure of the liquid and glassily solidified systems.

In the present work, we describe a quantitative correlation between the reflectivity in the UV range and the molar Fe3+‐content. The basic investigations for recording the redox state of liquid silicates during a running metallurgical process are part of this work.
Microstructure and Tensile Properties in Dual Phase and Trip Steels
Authors: Bleck Wolfgang , Papaefthymiou Spyros , Frehn Andreas
Published: December 2016

Advanced high‐strength steels, like dual phase and TRIP steels, have gained much interest for automotive application. The complex microstructures in dual phase steels, and even more critical, the metastable microstructure in TRIP steels, do not follow the well‐established traditional microstructure‐property relationships for deep drawing steels. The volume fraction of the different phases, the phase distribution, and the stability of metastable phases influence significantly the forming potential.

This paper discusses the correlation between different microstructural features and the mechanical properties. The tensile test properties of dual phase steels are governed by the martensite volume fraction, the martensite hardness and to a much smaller extent the martensite island diameter. Both in dual phase and more pronounced in TRIP steels the retained austenite content plays a vital role in determining the formability. The stability of the retained austenite can be described by different methods, it needs to be adjusted according to the forming temperature and the type and amount of strain. In general, multiphase steels require a very strict microstructure control in order to develop predictable forming behaviour.
On the Relationship between Mechanical Properties and Mechanisms of Plastic Deformation in Metastable Austenitic Steels
Authors: Pétein Arnaud , Jacques Pascal J.
Published: December 2016

The requirements of the automotive industry for materials exhibiting increased structural performances are continuously increasing. These materials must remain ductile during the forming operations while also exhibiting improved strength and energy absorption capacities.

New highly alloyed steel grades have been studied for a few years now, due to their exceptional mechanical properties resulting from interactions between dislocation plasticity, transformation plasticity and mechanical twinning.

This study deals with the mechanical properties of steel grades presenting high manganese compositions. At room temperature, several phase transformations (γ→α', γ→ɛ and ɛ→α′) were found to occur when the samples are deformed. The effect of different annealing conditions on the mechanical properties and the transformation sequence is analysed. The evolution of the work‐hardening of the samples is interpreted in connection with the kinetics of the phase transformations.
On the Behaviour of Hematite and Graphite Blend during Ball Milling and Heating Up Reduction of Milled Mixture
Authors: Raygan Shahram , Khaki Jalil Vahdati , Aboutalebi Mohamad Reza
Published: December 2016

The effect of ball milling under argon and air atmospheres on the reaction behaviour of the mixture of sintered hematite and graphite was investigated. Thermo‐gravimetry / differential thermal analysis (TG‐DTA) was adopted to determine the effect of milling time on the reduction process during heating up under Ar atmosphere. The samples were heated at a constant heating rate of 10 °C/min from room temperature up to 1100 °C and maintained at this temperature for 30 minutes.

TGL (thermo‐gravimetry loss) curves showed a decrease of onset temperature of reduction with increase of milling time. XRD patterns of milled samples at room temperature revealed that the peaks of graphite disappeared after 48 hours milling. This represents the transformation of crystalline structure of graphite to the amorphous structure. By increasing the milling time to 72 hours, magnetite peaks appeared in the XRD pattern as a result of reduction of hematite with graphite during milling. However, the amount of magnetite formed during milling process increased as milling proceeded. The powders milled under Ar atmosphere became more active than the powders milled under air and consequently the carbothermic reduction of hematite in powders milled under Ar atmosphere was observed at lower temperatures compared with air‐milled powders. It was observed that the reduction time of hematite in powder mixture was decreased with increase of sintering time of hematite prior to milling.
Evaluation of Desulphurization Flux in CaO‐Al2O3‐BaO‐CeO2‐MgO System
Authors: Shibata Etsuro , Nakamura Takashi , Nishida Takeshi , Endo Mitsunori , Itou Hideyuki , Takasu Tomio
Published: December 2016

The flux of the CaO‐Al203‐BaO‐CeO2‐MgO system as a desulphurization flux containing no fluorine for the secondary metallurgy process was evaluated in this study. The flux composition was designed using the eutectic compositions of the binary systems. The melting and desulphurization abilities of the fluxes were evaluated by measuring their liquidus temperatures and the distribution ratios of sulphur between the fluxes and the carbon‐saturated iron or stainless steel. The lowest liquidus temperature of 1325°C was obtained by adding 5.7 mass% MgO to the 80mass%A‐20mass%B flux. (A: 12CaO‐7Al2O3, B: BaCeO3+12mass%Al2O3). The distribution ratios of sulphur and sulphide capacities of the fluxes in this study were higher than those of the commercial product of calcium aluminate flux. This means that the CaO‐Al2O3‐BaO‐CeO2‐MgO fluxes developed in this study have higher desulphurization and melting abilities compared with the commercial product of calcium aluminate flux.
Stresses in Refractory Lined Circular Vessels and Pipes
Authors: Fischer Rudolf H.
Published: December 2016

The determination of stresses with refractory lined vessels etc. must take into account the interrelatedness of both components, the shell and the lining. The necessary equations, displayed elsewhere, are clearly represented step by step. Tension stresses within the refractory are imaginary and can be traced only by calculation. They may be attributed to the shell, if only the equilibrium of forces is preserved. The effect of joint gaps within the refractory can also be calculated by introducing imaginary temperature reductions. To conclude, this report presents an example accompanying all comments and dealing with refractory wear as well.
Thermodynamic Criteria for the Selection of Alloys Suitable for Semi‐Solid Processing
Authors: Balitchev Evgueni , Hallstedt Bengt , Neuschütz Dieter
Published: December 2016

In this work the suitability of alloys for semi‐solid processing was investigated using numeric simulation. The simulation was based on equilibrium calculations, Scheil‐Gulliver calculations and, when necessary, diffusion simulations. For this purpose a new parameter was introduced in addition to the commonly used selection criteria. With the new parameter, the thixo ranges ΔT40–60 and ΔT20–40, the specific demands of the different semi‐solid processes thixocasting and thixoforging can be considered. On the basis of thermodynamic simulation, the conventional aluminium alloys A356, AA6082 and A319, the steels 100Cr6, HS6‐5‐2 and X210CrW12 and a number of experimental aluminium‐lithium based alloys were evaluated according to the selection criteria. The thermodynamic calculations showed a large sensitivity of the course of the solidification with respect to variations in the contents of the alloying elements. This shows the necessity of keeping a tight composition control on alloys for semi‐solid processing. For aluminium alloys in particular silicon has to be monitored closely and for steels carbon and chromium.
Ring Rolling Research at the Dresden University of Technology – its History from the Beginning in the 70s to the Present
Authors: Ficker Thomas , Hardtmann André , Houska Mario
Published: December 2016

The paper presents a brief history of ring rolling development at the Dresden University of Technology (DUT) from the 70s to the present. The technological scope covers the techniques explored at the DUT: Tangential profile ring rolling, axial profile tube rolling/roll plunging and the TRENPRO® method to produce shaped rings. Starting from the state of the art, technological principle, range of application and machine‐oriented implementation of these techniques are described. Furthermore, other common ring rolling variants, such as axial profile ring rolling, skew‐rolling and radial‐axial ring rolling, are taken into consideration. Finally, the authors provide a summary of problems still to be solved and ways to refine and disseminate the “ring rolling” discipline, assessing the rolling methods’ potential as extremely forward‐looking.
High‐Pressure Sheet Metal Forming of Large Scale Structures from Sheets with Optimised Thickness Distribution
Authors: Kleiner Matthias , Homberg Werner , Krux Rainer
Published: December 2016

In order to manufacture components optimised in regard to lightweight construction, the use of innovative forming processes like high‐pressure sheet metal forming (HBU) in combination with the use of tailor rolled blanks (TRB) as innovative semi‐finished materials is a promising solution. To realise a sufficient forming process reliability, at first, investigations on the seal system were carried out. Hereby, a non‐adjustable as well as a new adjustable seal system have been investigated and qualified as sufficient solutions for this process depending on thickness ratio and thickness gradient within the TRB. One typical workpiece geometry which offers a promising lightweight potential and which can be manufactured from TRB with the HBU‐process is the class of body structures. Therefore, an idealised large scale structure has been designed and investigated in theoretical (numerical) and experimental research. The research work has shown that this large scale structure can be manufactured sufficiently by the HBU of TRB.
Rotary Blanking ‐ a New Manufacturing Process
Authors: Hoffmann Hartmut , Schweitzer Michael , Schmidt Thomas , Hein Christoph
Published: December 2016

Rotary blanking is a method of blanking and punching with rotating tools whereby the cutting tools are fixed to a pair of rollers performing a continuous blanking operation on a strip of sheet metal. The purpose of this paper is to outline the determining conditions under which the rotary blanking process takes place and to discuss advantages, restrictions, applications and optimization of this technology.
Activity of Chromium Oxide in CaO‐SiO2 based Slags at 1873 K
Authors: Morita Kazuki , Tsukiashi Koji , Kimura Munekazu , Sano Nobuo
Published: December 2016

Thermodynamic properties of chromium oxides in molten slags are very important for optimization of stainless steel refining processes as well as reduction processes of chromium ores. The solubility of chromite into molten slags has been found to vary drastically with oxygen partial pressure and slag composition in the former studies by the authors. In the present study, activity data and redox equilibria of chromium oxides measured under moderately reducing conditions, PO2= 6.95×10−11 atm, at 1873 K are summarized. For the CaO‐SiO2‐CrOx system, the activity coefficient of chromium oxide increased with increasing basicity and the optimized slag composition for stainless steel refining is assessed as that saturated with CaCr2O4 and Cr2O3 using the phase relations determined. On the other hand, the presence of MgO and Al2O3 brings about different behaviour of chromium oxide activity and redox equilibria and the 44 mass per cent CaO ‐ 39 mass per cent SiO2 ‐11 mass per cent Al2O3 ‐ 6 mass per cent MgO slag is recommended to reduce the chromium oxidation loss in the practical stainless steel refining process at 1873 K.
Oxidation State of Titanium in CaO‐SiO2‐TiOx Slags at 1873K
Authors: Ariyo Chris , Gonzalez Pablo , Holappa Lauri
Published: December 2016

Oxidation state of titanium was determined in CaO‐SiO2‐TiOx slags in the composition range 25‐53 percent CaO, 27‐46 percent SiO2, 10‐55 percent TiOx at 1873K using gas equilibration method.

In the experiments, slags with different titanium oxide contents were equilibrated with a known carbon monoxide and carbon dioxide ratio. The results were used to determine the Ti3+ and Ti4+ contents as well as the activity coefficient ratio of corresponding oxides in the slag.

The dependence of the activity coefficient ratio as a function of oxygen partial pressure was determined.
Evaluation and Control of Iron and Steelmaking Slags through Electrochemical FeO Sensor
Authors: Iwase Masanori , McLean Alexander , Katogi Ken , Kikuchi Yoshiteru , Wakimoto Kazumasa
Published: December 2016

One of the greatest obstacles to the application of physical chemistry principles to the elucidation of slag‐metal reactions is a lack of knowledge of activities of the reacting species. To a large extent, oxygen potential of the slag phase governs iron and steelmaking practice. Without oxygen control by means of appropriate sensors, the behaviour of the other elements cannot be managed. In this paper, measurements of the FeO activity with various types of electrochemical FeO sensors will be described together with examples of their applications for improved strategies toward better practice for ladle metallurgy and sulphur and manganese distributions between slag and metal phases during steelmaking. Measurements of FeO activity have also been made in order to improve dephosphorization reactions. This type of work has led to significant reduction in volume of slag generated within the steelmaking vessel, which in turn, has important implications for refractory wear, metal yield, alloy recovery and improved productivity. Finally an on‐line sensor is described which permits the oxygen potential to be determined for both the metal phase and the slag phase during steelmaking in the BOF.
MnS Precipitation Behavior in Re‐Sulfurized Steels with Intermediate Levels of Sulfur
Authors: Valdez Martin Emiliano , Wang Yan , Sridhar Seetharaman
Published: December 2016

This paper presents results on the quantification of MnS precipitation during solidification of steels with intermediate levels of sulfur (0.05%) using a Confocal Scanning Laser Microscope (CSLM) equipped with a gold image furnace. The precipitation of MnS was observed in the liquid pools remaining in between advancing dendrites at the end of solidification. It was observed that MnS precipitated during cooling on existing mixed‐oxide particles of AI, Si and Ca. The rate of precipitation was seen to accelerate at two distinct points, once when the steel was molten and once during solidification.
Influence of the Lining on the Thermal Behaviour of a Teeming Ladle
Authors: Volkova Olena , Janke Dieter
Published: December 2016

Exact knowledge of the thermal behaviour of the steelmaking ladle is essential for an effective performance of the secondary metallurgical treatment. In order to predict the influence of working parameters, some thermal ladle models have already been developed and presented. The development of new complicated thermal ladle models or the mathematical description of modelling are important. Nevertheless exact model studies of the influencing factors on the thermal state of the ladle are of similar significance. Especially for ladle modernisation concepts, when the lining layer thickness is changed or new refractory materials are used, the question arises if there is an influence of modernisation on the thermal state of the ladle, heat losses or steel melt temperature. The selected refractory materials represent a decisive factor. The thermal properties of the wear‐resistant lining influence the temperature changes and heat losses in the ladle, whereas the properties of the back and insulating lining are accountable for the steel shell temperature of the ladle. The thermal state of the ladle as a function of the real inner ladle lining has already been investigated. The present work is concentrated on the influence of the real back lining and insulating lining.
Minimizing the Distortion of Steel Profiles by Controlled Cooling
Authors: Pietzsch Robert , Brzoza Miroslaw , Kaymak Yalçin , Specht Eckehard , Bertram Albrecht
Published: December 2016

A complex thermomechanical model is introduced for the simulation of the transient fields of temperature and stresses during the quenching of steel products. The material behaviour is an extension of the classical J2‐plasticity theory with the extension of temperature and phase fraction dependent yield criteria. The coupling effects, i.e., dissipation of mechanical energy, transformation induced plasticity (TRIP), and phase transformation enthalpy, are considered. The model is used for the determination of the optimal cooling or quenching for reducing the distortion in the long steel profiles. The simulation results are presented in order to investigate the effects of material properties, boundary conditions, profile size and geometry. In the simulations, L‐, T‐ and U‐profiles made of steel C45 and steel C80 are considered. It is demonstrated that with a higher cooling rate in the mass lumped regions of the profiles, the distortion can be reduced.
Reoxidation of Ni‐ and Ni‐Fe‐Alloys by Al2O3‐SiO2 Refractory Materials
Authors: Lachmann Stefan , Loh Jürgen , Wahlers Franz‐Josef , Scheller Piotr R.
Published: December 2016

Reactions at the refractory/melt interface during ingot casting of Ni‐ and Ni‐Fe‐alloys were studied. The casts were performed using different alumino‐silicate bricks as refractory materials. Samples taken from the casting channel before and after casting were investigated using light and scanning electron microscopy with XPS. Thermodynamic calculations were performed with FactSage and the results were compared with the results from industrial tests. After the melt has infiltrated the surface layer of the bricks, refractory corrosion starts with an attack of Mn and Mg of the melt on SiO2 and Fe2O3 of the refractory bonding matrix. Despite the presence of elements with higher oxygen affinity in the melt, low‐melting alumino‐silicate phases are predominantly built by the reaction with Mn and Mg. In a second step this liquid phase either traps non‐metallic inclusions from the melt or, at higher contents of Zr, Ti, Mg, Y etc. in the melt, causes massive reoxidation and inclusion formation. The refractory materials investigated show an increasing trend for reoxidation with an increasing amount of SiO2 in glassy phases of the refractory bonding matrix. By the use of a refractory material with higher mullite content in the bonding matrix or by use of alumina bricks a strong reoxidation of the melt and intense inclusion formation can be avoided. These observations are also valid for other alloys with higher contents of elements with high affinity to oxygen.
Centre Segregation, Soft Reduction and Oxide Cleanness for Large Diameter Line Pipe with Highest Demands on HIC
Authors: Cappel Jürgen , Flender Reinhard , Höffken Rolf , Kemper Gerhard , Wünnenberg Klaus
Published: December 2016

Starting material to meet maximum demands requires low centre segregation and excellent oxide cleanness. Comparative tests were performed for this purpose on an oval‐bow caster with a 5 m radius and a vertical bending machine with a 3 m vertical section and a 9 m radius. Both types of machine are capable of producing an excellent strand‐centre quality provided strand support system settings are well monitored. Oxide cleanness is superior in slabs cast on the vertical bending machine; the inclusion band is further from the surface than on the bow caster. Sulphur prints are not suitable for inspection purposes, whereas MIDAS (Mannesmann Inclusion Detection by Analysing Surfboards) is able to detect macroscopic inclusions with certainty.
Metallurgy, Microstructure and Properties of a New Nitride Strengthened Nickel‐Chromium Superalloy
Authors: Brill Ulrich
Published: December 2016

The nitrogen content of Ni‐base superalloys for high temperature service is generally kept below about 0.05 wt.‐% to avoid detrimental precipitation of nitrides. These nitrides are said to have a harmful influence on mechanical properties and workability of these alloys. However, some recent studies and research conducted with nitrogen strengthening of Ni‐Cr‐alloys have resulted in an alloy with excellent physical and mechanical properties. The applied PESR (Pressurized Electro‐Slag Remelting)‐Technology provided up to 1.0 wt‐% nitrogen in a NiCr7030‐alloy.The homogeneously distributed nitrides prevent the alloy from excessive grain growth thus providing stable mechanical properties, i.e. impact toughness even after long term exposure. The new alloy easily exceeds Rm= 850 MPa at room temperature and 600 MPa at 600 °C as relevant design values. This paper introduces this new alloy with its very special metallurgy, microstructure, and its physical and mechanical properties.
Choking Phenomena of Gas‐Powder Flows at Sonic Velocity
Authors: Li Qiang , Zou Zongshu , Tan Shengming
Published: December 2016

Choking phenomena of gas‐powder flows in a horizontal constant cross‐section duct are experimentally studied using three kinds of powders: Al2O3, hollow Al2O3 (H‐alumina) and Al, with different physical properties such as densities, specific heat capacities and thermal conductivities. The relationship between the mass flowrate and inlet stagnant pressures is analysed and the apparent sonic velocity (ASV) of gas‐powder flows is defined. The influences of physical properties of powders on the ASV are obtained by the comparison between the experimental results of different powders. Two characteristic parameters, the effective specific heat capacity (ESHC) of solid phase and the effective isentropic exponent (EIE) of the mixture, are defined to describe the choking phenomena. The ESHC is not only measured through experiment but also calculated by numerical method. The calculated results are well consistent with the measured ones. As a preliminary application test for choking phenomena ‐ in order to uniform the pulverized coal injection (PCI) into a blast furnace ‐, a model PCI system with two branch pipes was set up and tests were carried out to verify the choking effect. The test results show that, during choking, the PC flow rates in the branch pipes can be well equalized no matter how much the downstream conditions differ from each other.
A Clean Technique to Recover Vanadium from Converter Slag
Authors: Dong Yuanchi , Yu Liang , Li Liaosha
Published: December 2016

As an important secondary raw material, V‐bearing converter slag is of great interest for vanadium recovery. An economic, clean, and novel technique to recover valuable elements, such as vanadium, from waste slag involves three steps: (1) The selective concentration of the desirable element in a specific mineral phase (2) The selective coarsening of the mineral phase by precipitation and growth to a critical grain size in molten slag; (3) The selective separation of the enlarged mineral phase from the tailings by ore dressing or hydrometallurgical processes. Vanadium in the modified converter slag was concentrated into a specifically designed mineral phase called the V‐concentrated phase. This phase can be separated from the other slag phases by ore dressing.
Chromium Oxide Reduction from Slag by Silicon and Magnesium
Authors: Gutiérrez‐Paredes Juliana , Romero‐Serrano Antonio , Plascencia‐Barrera Gabriel , Vargas‐Ramírez Marissa , Zeifert Beatriz , Arredondo‐Torres Víctor
Published: December 2016

Experimental and theoretical studies were performed in order to estimate the effect of the basicity of the slag as well as the amount of reducing agents on the reduction of chromium oxide from a slag in contact with molten steel at 1600 °C. The aim of this work was to compare the efficiency of magnesium and silicon as reducing agents of Cr2O3. The slag system contained CaO, MgO, SiO2, CaF2 and Cr2O3 together with Fe‐alloys (Fe‐Si or Fe‐Si‐Mg). The maximum Cr yield was about 81% with Fe‐44%Si‐9%Mg and 88% with Fe‐75%Si. That means that the reducing effect of Mg was much better than that of Si. Some experiments were conducted to study the effect of initial Cr in steel on the chromium oxide reduction reaction. Three initial Cr contents were tested (0.15, 2 and 4 mass%). It was found that chrome was partially bound into stable spinel phase MgO·Cr2O3 in the final slag.

Thermodynamic estimations were made to determine the effect of process temperature, slag basicity and the amount of reducing agents in the slag on the Cr recovery. The efficiency of Cr reducing agents increased in the order: Si, Al, Ca and Mg. The Cr yield increased with slag basicity and amount of reducing agents.
FEM Study of Fatigue Response of 3‐Sheet Spot Welded Joints
Authors: Collin Tania , Melander Arne
Published: December 2016

The commercial software used for predicting fatigue strength for load‐carrying spot welds in sheet structures, like car bodies, is mainly developed for two‐sheet joints. The purpose of this work was to study the fatigue properties of three‐sheet spot welded joints with a dimensioning method used in the automotive industry and to compare such computational results to those obtained from a more accurate method and to experimental data. Eleven three‐sheet, single spot welded specimens were studied using a structural stress approach, followed by shell element simulations, similar to those used in commercial software. These results were compared to calculations based on fine meshed solid element models. Fracture mechanics was used to evaluate the loading conditions at the spot welds. Comparison between the results from the different methods and experimental results for three shear loaded specimens, consisting of triple sheets, found in literature showed good correlation. The shell element method in shear loaded cases gives stress intensities within +35% to ‐5% of the solid element method results. In peel loaded cases the results differ up to ‐60%, an under‐estimation that leads to an increase of estimated fatigue life up to 65 times.
Quench and Partitioning Steel: A New AHSS Concept for Automotive Anti‐Intrusion Applications
Authors: De Cooman Bruno C. , Speer John G.
Published: December 2016

A new type of high strength, high toughness, martensitic steel, based on a newly proposed Quench and Partitioning (Q&P) process, is presented. This high strength martensitic grade is produced by the controlled low temperature partitioning of carbon from as‐quenched martensite laths to retained inter‐lath austenite under conditions where both low temperature transition carbide formation and cementite precipitation are suppressed. The contribution focuses on both the current understanding of the fundamental processes involved and includes a discussion of the technical feasibility of large‐scale industrial production of these steels as sheet products. The Q&P process, which is carried out on steels with a lean composition, should be implemented easily on some current industrial continuous annealing and galvanizing lines. In addition, martensitic Q&P sheet steel is characterized by very favourable combinations of strength, ductility and toughness, which are particularly relevant for high strength anti‐intrusion automotive parts.
Niobium in Engineering Steels for Automotive Applications
Authors: Klinkenberg Christian , Trute Sebastian , Bleck Wolfgang
Published: December 2016

In the last decade, the European niobium consumption in automotive strip and sheet has more than tripled. The development of high strength and advanced high strength steel grades for strip and plate products focused upon constantly increasing strength levels combined with excellent fatigue properties as well as formability and weldability. Until now, the high potential of microalloyed steel has not been used to the same extent in forgings and springs. This paper reviews automotive components as transmissions, suspensions and springs highlighting new material solutions for special steels having optimized processing and in‐use properties. Special consideration is given to the metallurgical background as well as to examples for the processing and application of niobium microalloyed steel in forgings and springs from low carbon and higher carbon containing steels. Niobium metallurgy permits the reduction of carbon to meet more stringent end‐user requirements demanding high strength combined with improved toughness, fatigue strength and weldability at a competitive manufacturing cost.
Utilization of Waste Wood for Production of Iron, Carbon Monoxide and Hydrogen without generating Carbon Dioxide
Authors: Matsuda T. , Takekawa M. , Hasegawa M. , Ikemura Y. , Wakimoto K. , Ariyama T. , Iwase M.
Published: December 2016

National legislation within Japan has increased the need for the development of new process technologies that will utilise waste wood materials. The present study is aimed at generating some fundamental data with respect to the reduction of iron oxide by waste wood. By using a high frequency induction furnace, mixtures of wood + Fe2O3 were heated very rapidly to temperatures between 1673 and 2073K in a stream of argon. Gas chromatographic technique applied on exhaust gases escaping from the furnace revealed that the gaseous reaction products consisted mainly of carbon monoxide and hydrogen. On the other hand, conventional chemical analysis and X‐ray diffraction technique made on condensed‐phase reaction products detected the presence of Fe‐C alloys, solid carbon (char) and ferrous oxide, depending upon the atomic ratio of C/O within wood + Fe2O3 mixture. Thus, the reaction products consisted of metallic iron, ferrous oxide, char, CO, CO2, H2O, H2 and CH4, depending upon C/O atomic ratio within the mixture and the experimental temperature. The results were in good agreement with values calculated from thermodynamic equilibrium.
Twin Roll Casting of Steel Strip ‐ Experiments and Model Considerations on Strip Spottiness
Authors: Büchner Achim R.
Published: December 2016

Thin strip casting of steel through a twin‐roll caster demands the production of a perfectly homogeneous strip. This requirement is often not fulfilled due to non‐uniform heat contact between the solidifying strip and the rolls in the pool, which leads to temperature inhomogeneities visible at the strip behind the rolls (spottiness). The effect of spottiness is described from experimental observations in terms of contrast between dark and hot spots and of the mean diameter of the hot spots. The contrast is found to depend on roll material, surface roughness and roll velocity. A general dependence on the temperature difference between melt and rolls is observed.

Calculations of heat transfer in the liquid and solid pool explain the hot‐dark‐temperature differences. The spottiness visible on the strip after leaving the rolls is initiated in the liquid pool, but it is enlarged by rolling contact differences in the solid pool. A model consideration based on thermally caused bending of the solidified material layers leads to a good coincidence with experimental data of the heat transfer coefficient at hot spots.