bluuebunny/crossref_metadata_2025 huggingface dataset:
Localised corrosion behaviour of high and low nitrogen Cr‐Mn steels
Authors: Srinivasan Ahila , Reynders Brigitte , Grabke Hans Jürgen
Published: December 2016

It is well established that addition of nitrogen to steels improves the pitting corrosion resistance of steels. To elucidate the role of nitrogen, electrochemical and surface analytical studies were carried out on Cr‐Mn steels with low (0.0075 %) and high (0.9 %) nitrogen contents. The incubation time for pitting, measured in sodium sulphate solutions containing different concentrations of chloride was higher for the high nitrogen steel. The pit initiation process was found to be first order with respect to chloride concentration. The passive current density was one order lower than that of nitrogen free steel. The grain broundary attack observed in low nitrogen steel was not present in high nitrogen steel. XPS analysis indicated nitrogen enrichment at the surface in the passive layer. This may be one reason for the higher pitting resistance of nitrogen containing steel besides formation of ammonium ions and rising pH.
Decomposition of hypo‐eutectoid Fe‐C austenites; a numerical diffusion model
Authors: Silalahi V. M. Mesnan , Onink Marcel , van der Zwaag Sybrand
Published: December 2016

A numerical model is presented which describes the growth rate of ferrite during the decomposition of austenite in Fe‐C alloys. The growth rate is modelled assuming carbon diffusion in austenite as the rate determining mechanism. The effect of the definition of the diffusion coefficient of carbon in austenite on the growth rate is shown. The model is used to examine the effects of initial carbon concentration, the local carbon concentration in austenite at the interface and the initial austenite grain size on the growth rate. Good agreement between theoretical results and both new and existing experimental data was observed.
Austenite stabilization from direct cementite conversion in low‐alloy steels
Authors: Haidemenopoulos Gregory N.
Published: December 2016

Transformation induced plasticity (TRIP) effects associated with austenite dispersions in low alloy Fe‐Mn‐Si steels can be enhanced by austenite stabilisation. Austenite which forms during conventional intercritical annealing does not possess the required stability in order to exhibit TRIP effects. In this work, thermodynamic calculations indicated that it is feasible to form austenite by a cementite to austenite conversion which occurs under paraequilibrium conditions, i.e with partition of carbon but with no partition of substitutional alloying elements. In this way the austenite inherits the manganese content of cementite and is chemically stabilised. A treatment consisting of a two‐step annealing has been examined. In the first step, soft annealing, an Mn‐enriched cementite dispersion in ferrite is formed. In the second step, intercritical annealing, austenite nucleates on the cementite particles, which are consumed to form austenite. It was experimentally determined that this austenite has been enriched in manganese and carbon and, therefore, is stabilised. The conversion reaction is followed by the conventional austenite nucleation at ferrite grain boundaries. This austenite is lean in manganese and is not stable. The net effect of the two‐step annealing treatment is a significant austenite stabilisation relative to simple intercritical annealing, indicating a potential for enhanced TRIP effects in this class of steels.
Development of a new ceramic inclusion separator for steel melts
Authors: Raiber Klaus , Hantusch Jan , Hammerschmid Peter , Janke Dieter
Published: December 2016

The majority of steels produced by continuous casting is fully Al‐killed. Ceramic foam and multi hole filters have been tested so far in laboratory and small scale production experiments to lower the total oxygen content of steel melts. The use of such filters in tundishes has hitherto been limited by their insuffiicient mechanical and thermal durability over extended periods. Owing to their small pore sizes, these filters allow a high inclusion separation efficiency, but a limited mass throughput. Therefore a technique is looked for to extract non‐metallic inclusions efficiently from the melt at higher mass throughputs. Further ideas led to a new ceramic inclusion separator which has been tested in small scale experimental runs. To verify the flow and separation process, a water model has been built and numerical modelling was applied. The results of the molten steel experiments, the water model and the mathematical modelling are described and compared to each other. For the small scale it is confirmed that the new experimental device may yield high filtration efficiencies.
Conditioning of austenite by hot working of microalloyed forging steels
Authors: González‐Baquet Ignacio , Kaspar Radko , Richter Johannes
Published: December 2016

On four grades of medium carbon V‐bearing steels with additional Ti and Nb microalloying hot deformation tests were conducted as a simulation of hot forging. The aim of the study was to suggest general guidelines for the design of deformation patterns and cooling conditions of austenite. Both the resulting flow stresses and the strengthening/softening behaviour were taken into consideration. The maximum flow stresses appear to be insensitive both to the variation of microalloying and to the design of the deformation schedule over the range tested. Nevertheless, large differences can be achieved regarding austenite strengthening, especially its residual value at the begin of the γ‐α‐transformation which is decisive for the subsequent transformation process. A substantial effect of the final deformation temperature and the type of microalloying was ascertained.
The Solution kinetics of zirconium in liquid steel
Authors: Argyropoulos Stavros A. , Sismanis Panagiotis G.
Published: December 2016

Zirconium cylinders were immersed into liquid steel and their mass‐transfer rates were measured under static and dynamic conditions. The cylinders were suspended from a load cell, and the apparent weight of the dissolving specimen as well as temperatures at various locations in the samples were measured continuously during immersion and recorded with a data acquisition System. From the weight measurements, the mass‐transfer rate was deduced. In the assimilation of zirconium in liquid steel two periods were identified, i.e. the steel shell period and the free dissolution period. Immediately upon immersion the steel shell period Starts and when this period ends the free dissolution period commences. During the steel shell period, a shell of frozen steel wraps around the cylinder following its initial immersion. When zirconium cylinders were immersed into liquid steel, a reaction was detected at the steel shell/zirconium interface. This reaction took place almost immediately after immersion. The intermetallic Compounds Fe2Zr and FeZr2 were identified as reaction products. The experimentally measured mass transfer rates during the free dissolution, under quiescent and inductively stirred steel baths, were very similar. Under the experimental conditions used, the rate Controlling step of zirconium dissolution in liquid steel is reaction controlled.
Modifications of iron and manganese on the melt equilibria of binary systems – a critical assessment
Authors: Schürmann Eberhard
Published: December 2016

To determine the influences of modifications of an element on the melt equilibria of binary systems, quite specific requirements have to be met in relation to the configuration of the stable and unstable equilibria lines, and these are indicated at the onset. In relation to modifications of iron, they enable clear conclusions to be drawn as to their influences, and enable critical assessment of the influence of the manganese modifications on the melt equilibria, regarded as dubious, in the systems Fe‐Mn and Mn‐Si, and also in manganese‐rich Mn‐X systems with X = Pd, Ta, Rh, In, Sb, Ru, Cu. They also enable absent or incorrectly drawn stable and unstable melt and transformation equilibria of the systems Fe‐Mn and Mn‐Si to be effectively supplemented. A critical thermodynamic assessment of the measured manganese vapour pressure curves provides important indications as to the stable and unstable melt and transformation equilibria of the manganese modifications.
Measurement of viscosity, density and surface tension of metal melts
Authors: Friedrichs Hans Adolf , Ronkow Leonid Wladimirowitsch , Zhou Yongmao
Published: December 2016

A modified procedure for measuring viscosity, surface tension and density of metallic melts, using a gas bubble viscosimeter, is presented. The principle of measurement is based on the relation between rate of ascent of a gas bubble in the melt and the melt viscosity. The rate of bubble ascent is determined by registering the moment of detachment by pressure measurement in the lance and the moment of arrival of the bubble at the melt surface by video film and an image processing system.

The procedure is tested and the limits of its application are determined by comparative measurements on reference metals.

After tests on reference metals, measurements are taken of the viscosity, density and surface tension of Al‐Cu alloys in the temperature range 960 – 1465 K with copper contents of 12.23 to 58.5%. The relationships between these values and temperature and composition of the melt are investigated, and corresponding approximation formulae derived.
Kinetics of decarburisation of levitating liquid iron drops by carbon dioxide
Authors: Simento Noel , Lee Hae‐Geon , Hayes Peter
Published: December 2016

Decarburisation experiments were carried out by levitating liquid iron droplets in a flowing gas stream containing carbon dioxide at 1723K. Decarburisation of liquid iron droplets by carbon dioxide can be adequately described by the mixed control of gas phase mass transport and dissociative chemisorption of carbon dioxide. Carbon monoxide in the gas phase does not have any significant effect on the rate of decarburisation. The rate of decarburisation decreases significantly with increase in sulphur content in the melt and this effect can be quantitatively explained using the Langmuir isotherm. Adsorption coefficient of sulphur is found to be 200. Influence of phosphorus and chromium in the melt on the rate of decarburisation is negligibly small.
FEM‐analysis of the friction process in section drawing
Authors: Drossel Welf‐Guntram , Hildebrand Martin , Pawelski Oskar
Published: December 2016

It is necessary to gain more detailed information about the real frictional conditions in the section drawing process to improve the drawing techniques and to expand the producible section assortment. A deformed surface grid allows to describe local displacements on the workpiece used later on as boundary conditions in an FEM‐calculation. With the knowledge of local frictional coefficients an increase in friction coefficient in drawing direction with curved cross‐sections can be stated. Sharply edged cross‐sections show an additional increase in friction coefficient in the range of high local deformation, i.e. near the edges. This fact influences both the material flow in the forming zone and the straightness of the section. An analysis of the surface topography change by friction and deformation declares the computed distributions of the friction coefficient.
Low carbon manganese steels microalloyed with vanadium and nitrogen
Authors: Eissa Mamdouh , EI‐Fawakhry Kamal , Mekkawy Mohamed , Hussein Abdul Hamid , Tawfik Ahmed
Published: December 2016

With the objective of studying the effect of vanadium and nitrogen microalloying on microstructure and strength of low carbon steels with different manganese contents, three series of low carbon steels (0.1% C) with manganese content (between 0.8 and 3.5%), vanadium content (up to 0.17%) and nitrogen content (up to 0.025%) have been designed and investigated in the hot forging condition using a preheating and finish forging temperatures of 1200 and 950°C, respectively.

Steels with a manganese content up to 2.3% revealed ferrite‐pearlite structures, whereas higher manganese contents from 2.7 to 3.5% resulted in the formation of bainitic structures. A pronounced effect of manganese on the mechanical properties of steels was detected at lower manganese contents < 1.5%, due to solid solution and grain refining effects, and higher manganese contents > 2.3, due to bainite formation. Manganese content in the range of 1.5‐2.3% had less pronounced effect due to solely solid solution hardening.

Vanadium microalloying effectively increased the strength of steels through solely precipitation strengthening or both precipitation strengthening and grain refining effect. The effectiveness of vanadium was greatly enhanced by increasing the nitrogen content. The grain refinement of vanadium‐nitrogen microalloying seems to be due to inhibition of austenite grain growth as a result of precipitation of vanadium nitride in austenite during forging. Precipitation strengthening of these steels is achieved by precipitation of vanadium carbide and nitride in ferrite or bainite.

Nitrogen enhanced the precipitation strengthening of vanadium microalloyed steels which could be attributed to the finer vanadium nitride dispersion precipitates compared with vanadium carbide. Up to 70% of the total nitrogen content of steel precipitates as vanadium nitride which could be achieved with V/N ratio of about 6‐7.

Microalloying of low carbon‐manganese steels (0.1% C and 1.8% Mn) with 0.15% vanadium and 0.025% nitrogen was found to be effective in attaining high levels of yield and ultimate tensile strengths of 835 and 940 N/mm2, respectively in the forging condition.
Thermodynamic properties of alumina‐saturated iron‐carbon‐bismuth alloys
Authors: Chang Lewen , Malhotra Sandeep , Schlesinger Mark E.
Published: December 2016

Using direct and indirect equilibration methods, the solubilities of iron in molten bismuth and those of bismuth in molten iron‐carbon alloys have been measured over the temperature range 1473‐1873 K. The Henrian behaviour of bismuth in molten ferrous alloys allows the calculation of its activity coefficient, which in turn facilitates modelling as a function of temperature and carbon content, using the unified interaction parameter formalism developed by Pelton and Bale. The modelling results generate the expression: .

A model has also been developed expressing bismuth content in molten iron‐carbon alloys as a function of temperature and composition: .
Hot compression testing of mild steel industrial reheat furnace scale
Authors: Tiley John , Zhang Yimin , Lenard John G.
Published: December 2016

The deformation of reheat furnace scale, formed on mild steel slabs in an industrial reheat furnace, was investigated using a high temperature compression test technique, over the temperature range of 650–850°C. Strain was nominally 30% for all tests, conducted at two strain rates, 0.1 and 1.0 s−1. The mill scale samples were 6mm thick, ground to obtain cylindrical compression test pieces. The test parameters were chosen to demonstrate the deformation behaviour of a porous scale at temperatures similar to the entry conditions to the finishing stands of a hot strip mill. Oxide scales are generally assumed to be brittle at these temperatures. In the present tests the scale deformed in a linear‐like elastic/plastic manner under these conditions. Although cracking occurred, the samples remained intact as the deformation proceeded. Below 650°C the scale was crushed to a powder immediately after the start of the compression process.
Development of new deep drawing steels by doping with surface active elements
Authors: Beyer Gerhard H. , Grabke Hans Jürgen
Published: December 2016

In this study, the effects of doping with the surface‐active elements Ge, Te, Se, As, Sb and Sn in atomic mass contents of 10 to 200 ppm on the texture and drawability of an IF‐steel (FeP06, DIN‐EN 10130) and an ELC‐steel (FeP05, DIN‐EN 10130) were investigated. Twenty‐six ingots were produced by melting and doping in a vacuum‐induction furnace, followed by forging, hot‐rolling and cold‐rolling. The cold‐rolling reduction was ɛ = 72 %. Recrystallization annealing was performed in a batch‐annealing simulation furnace. Subsequently, the orientation distribution function (ODF) and the α, γ, η‐fibre textures of both the cold‐rolled and recrystallized state were measured by means of an X‐ray diffraction goniometer and compared with the undoped reference material.

The results indicate that the IF‐steel specimens doped with 100 ppm Te and Se show a significantly enhanced γ‐fibre {111}<110>‐{111}<112> texture compared to the reference specimen. Also the ELC‐steel specimens showed a higher γ‐fibre by doping with atomic mass contents of 10 to 100 ppm Se and Te. To investigate whether the drawability has been improved, Lankford‐value (rm and Δr) measurements by means of tensile tests were applied. The compositions with improved γ‐fibre also showed higher r‐values and therefore confirmed the results of the texture measurements. Se doping was found to be especially beneficial in texture and drawability for both investigated materials. The growth of selenides and tellurides at the surface of Ti4C2S2‐ and Ti2S‐ precipitates was observed by means of scanning transmission electron microscope linescans equipped with field emission gun (STEM‐FEG). Doping with Sb and Sn rendered no notable improvement of the materials, and Ge and As proved to affect the mechanical properties unfavourably.
A semi‐discrete approach to modelling and control of the continuous casting process
Authors: Guo Baozhu , Xia Xiaohua , Camisani‐Calzolari Ferdinando Roux , Craig Ian K.
Published: December 2016

Starting from a partial differential equation describing the heat transfer in the continuous casting of steel, the Kirchhoff transformation is used to obtain a more simplified governing heat equation. A boundary state and control transformation is then introduced to obtain a nonlinear heat equation with boundary control. The semi‐discrete approximation is applied in the investigation to obtain an ordinary differential equation model. The derived lumped parameter control model can be used to get an approximate solution for the system as well as for finite dimensional system control studies. Finally, local controllability is proved for the system using a linearization technique.
Explicit models of thickness profile and tension stress distribution for process control applications
Authors: Jelali Mohieddine
Published: December 2016

This contribution aims to present a compact and efficient model for the calculation of strip thickness profile and shape which refers to the tension stress distribution. The model is derived from appropriate combination and generalisation of analytical approaches well known in the published literature. The basis for the model is given from analytical solutions of the gaugemeter, roll force and tension stress differential equations linearised about the actual operating point. A novel profile and flatness prediction algorithm is developed which leads to more efficient solutions for cold and hot rolling mills. The resulting algorithm has substantial advantages over the traditional models in its efficient computation, and hence, provides an opportunity for real‐time implementation in advanced model based control systems.
An exponential hardening model for anisotropic sheet metals
Authors: Hu Weilong
Published: December 2016

A new exponential hardening rule is brought forward to apply for planar anisotropy strain‐hardening sheet metals. Three exponential hardening relations measured along the rolling direction, 45°‐angle and 90°‐angle direction against rolling direction are just the special cases of this model. Based on this model to solve some plastic deformation problems for anisotropic strain‐hardening materials, some functions and calculating results, such as constitutive relations, forming limit characteristic, springback and other parameters associated with these types of materials, should be more likely to approach real states. So this anisotropic strain‐hardening model is very important for applying sheet metal forming simulation.
Engineering approach to modelling the multiaxial creep and damage behaviour of compact tension geometry specimens of a 12 Cr steel at 550° C
Authors: Gaudig Wolfgang
Published: December 2016

Theoretical creep equations including tertiary creep were determined by fitting uniaxial constant load creep test results. Additionally, a new strain/time hardening rule was established. This theoretical approach was implemented in a finite‐element routine, and the load line displacement of a Cs20‐specimen of a 12 Cr steel under constant load was calculated as a function of time. The results were compared to experimental findings and correlated with creep damage by cavitation.
Prediction of gas‐liquid two‐phase mixture flow in a vertical pipe with a sudden expansion in diameter
Authors: Hatta Natsuo , Omodaka Masaaki , Nakajima Fumitaka , Fujimoto Hitoshi , Takuda Hirohiko
Published: December 2016

The principle of gas‐lift pumps is applied to vacuum‐decarburization with the RH (Ruhrstahl Heraeus) process to circulate molten steel. Gas‐lift pumps are also applicable to the transportation of molten iron/steel between different refining processes. This paper treats theoretical analysis of steady‐state flow characteristics of gas‐liquid two‐phase mixtures rising in a vertical pipe with an abrupt expansion of its diameter. The system of governing equations is based upon a one‐dimensional multi‐fluid model. Flow pattern transitions are taken into consideration. A new numerical procedure to predict the flow characteristics at the sudden expansion has been proposed. Experiments have also been performed for several conditions to confirm the applicability as well as the validity of the present numerical model. It has been found that the predictions agree reasonably well with the experimental data. Next, the effect of the sudden expansion of pipe diameter on the pump performance was investigated numerically. As a result, it has been confirmed that the sudden expansion of pipe diameter contributes to improve the pump efficiency.
The temperature equilibrium during hot tensile tests of stainless steels
Authors: Lin Dong‐Yih , Dahl Winfried
Published: December 2016

Real temperature equilibrium within specimens is the basis of reliable results of hot tensile tests. These tests were undertaken with cylindrical specimens of a ferritic stainless steel AISI 430 and an austenitic stainless steel AISI 304. The specimens with diameters of 10, 15, 20 and 25 mm were partially melted. The cooling rates after holding by a maximum temperature varied between 0.5 and 3.0 K/s. Temperature was measured continuously at the specimen center and 3 mm under the specimen surface during the whole test process.

Tests with the smallest specimen diameter and under a slow cooling rate of 0.5 K/s had even temperature distribution in the radial direction of the specimen so that no duration time is required at any test temperature. Such identical temperature distribution in the cross‐section of specimens were changed in different ranges when the specimen diameter was enlarged or the cooling rate was increased. The necessary duration time for the temperature equilibrium in the radial direction of specimens is explained in detail in this study that can help the reliability of hot tensile test.
A study of nitrogen solubility in Na2O‐B2O3 slag
Authors: Kong Sang‐Jin , Hwang Ho‐Yong , Lee Hae‐Geon
Published: December 2016

The nitrogen solubility and nitride capacity of a Na2O‐B2O3 slag system were investigated in a concentration range of Na2O mass contents up to 40 % at 1373K. The solubility of nitrogen in Na2O‐B2O3 slag was found to be proportional to the oxygen partial pressure to the power of −3/4, and it was also found to increase with increasing reaction temperature. The nitride capacity of the slag decreased with increasing Na2O content. From the experimental results it was concluded that nitrogen dissolution into Na2O‐B2O3 slags (Na2O mass contents < 40 %) occurs by its reaction with both free oxygen ions and with oxygen ions incorporated with the network.
Viscosity of slags
Authors: Mudersbach Dirk , Drissen Peter M. , Kühn Michael , Geiseler Jürgen
Published: December 2016

The experimental determination of the viscosity of slags proves to be difficult. Therefore models for calculation have been developed. The Urbain‐III‐model is very often used for slags. In order to further improve its accuracy, the Forschungsgemeinschaft Eisenhüttenschlacken (FEhS) modified this model by adjusting the coefficients of Weymann's temperature relation in dependence of the CaO/SiO2‐basicity of the slag: η = A.T.exp(103.B/T) with A = f (C/S‐basicity); B = f (xoxides). Viscosities calculated by means of this modified model fit well with measured values. It has been shown that the application of this model enables the optimisation of metallurgical reactions and processes. Furthermore it should be possible to optimise those properties of the solidified slag which are influenced by the viscosity of the liquid slag. Thus the production of construction materials could be further improved to fulfil the highest quality requirements.
Effect of equal channel angular pressing on structure and mechanical properties of a low carbon steel
Authors: Shin Dong Hyuk , Jeong Won Sik , Kim Jongryoul , Paik Young‐Nam
Published: December 2016

Experiments were conducted on a plain low carbon steel with an initial grain size of ~ 30μm to investigate the changes of microstructure and mechanical properties by repetitive equal channel angular pressings. Under the pressing conditions of giving a strain of ~ 1 and rotating samples 180° between each pass, the yield strength significantly increases from 310 to 750 MPa after single pass, and it reaches 1050 MPa after 12 passes. The increment of yield strength gradually decreases as the number of passes increases. The examination of microstructure by transmission electron microscopy shows that ferrite consists of parallel bands of elongated subgrains having a width of 0.3 μm and a length of 2 μm after a single pass. The subgrains are further divided by boundaries with low angle misorientation on subsequent passages. Low angle boundaries turn to high angle boundaries without noticeable grain refinement as the number of pass increases. In addition, lamellar cementites in pearlite are broken up into fragments within a pearlite colony. Analyses of structural and mechanical changes in a plain low carbon steel by equal channel angular pressing indicate that the strength enhancement is mainly due to the grain refinement of ferrite.
Computational thermodynamics and slag modelling applied to steel elaboration
Authors: Gaye Henri , Lehmann Jean , Rocabois Philippe , Ruby‐Meyer Fabienne
Published: December 2016

A bibliographical review of the most recent developments in slag modelling approaches is presented. It covers the period posterior to the publication in the 2nd edition of Slag Atlas of the comprehensive review by Kowalski, Spencer and Neuschütz of thermodynamic models and databases for calculation of phase diagrams and thermodynamic properties of slags. The trends in using this information in computational thermodynamics software/database packages are outlined. Industrial applications based on examples pertaining to various iron‐and steelmaking reactors are discussed. These applications made essentially with the Irsid slag model and the CEQCSI software concern steel refining or microalloying by slag‐metal reactions in the ladle, steel‐refractories interactions, and inclusions control in steels.
Strip properties and processing in twin roll casting of stainless and low carbon steels
Authors: Lindenberg Hans‐Ulrich , Brückner Gabriele , Tacke Karl‐Heinz
Published: December 2016

Metallurgical features of the twin‐roll strip casting process are discussed. The as‐cast structure of two austenitic stainless steels is evaluated using EPMA and metallography. Cleanness levels as reached in twin‐roll strip casting are compared with conventional and thin slab casting. In‐line annealing is described as a method for grain refinement. The scale layer on twin‐roll cast strip is characterised for low carbon and stainless steels.
Reduction of MnO from molten slags with liquid steel of high carbon content
Authors: Vargas‐Ramirez Marissa , Romero‐Serrano Antonio , Chavez‐Alcala Federico , Zeifert Beatriz , Hallen‐Lopez Manuel
Published: December 2016

This work estimated the reduction of MnO in slags of the CaO‐SiO2‐FeO‐CaF2‐MnO system and liquid steel with the initial composition (mass contents) 0.75 %Mn, 0.16 % Si and 0.5 to 2.0 % C, as an alternative to introducing Mn to the steel melt. The slag basicities (CaO/SiO2) In the experiments were 2 and 3. MnO was obtained from manganese ore. The experiments were carried out in an open 10 kg induction furnace using Al2O3‐based refractory at 1873 K. The oxygen potential was measured throughout the experiments with a galvanic cell (ZrO2‐solid electrolyte with a Cr/Cr2O3 reference electrode).

The MnO reaction mechanism was analysed in terms of the slag basicity, the silicon and the initial carbon contents in the melt. The rate and the degree of MnO reduction were found to increase with the increasing of initial carbon content; however, the effect of slag basicity was less important. A kinetic analysis of the process was performed using a coupled reaction model.
Quantitative assessment of segregates in continuously cast slabs by electron probe microanalysis
Authors: Preßlinger Hubert , Mayr Michael , Kaltenbrunner Thomas , Lettner Josef
Published: December 2016

Due to the limited solubility of individual elements in the crystal lattice of steel, an enrichment of the residual melt and furthermore a formation of micro and macro segregates will appear during solidification of the steel melt. Depending on the chemical composition of the steel, the operation parameters of the casting plant and the slab dimension, the segregates will be formed with different intensities. The knowledge of the segregation effects is imperative for further processing of slabs and the subsequent products.

The electron probe micro analyser (EPMA) makes feasible an objective assessment of the segregates due to solidification over the entire slab thickness. This is carried out by concentration mapping (CM), which is a method for the quantitative determination of element distributions over certain areas on the sample. In this paper some results taken from an investigation on steel grade 13 CrMo 4–5 are presented, and some casting technological measures derived from these results are proposed.
Steel Desulphurisation and Sulphur Bonding in Solidified Ladle Slags
Authors: Posch Wilhelm , Preßlinger Hubert , Mayr Michael , Klepp Kurt O. , Hiebler Herbert
Published: December 2016

It was investigated in which form sulphur is bonded in ladle slags. For this purpose, the mineralogical phases of the ladle slags were qualitatively and quantitatively evaluated by means of a microprobe. This slag characterisation allowed reconstructing the bonding of sulphur into the phases of the ladle slag. Moreover, the reaction process with regard to the ionic theory as well as the structural formula for the mechanism of sulphur bonding were discussed.

The bonding of sulphur into calcium aluminate slags is determined by the sulphide ion content in the slag as well as by the ratio of (CaO)/(Al2O3). Calcium sulphide separates only if the slag contains a large number of sulphide ions. When Ca12Al14O33 is separated the sulphide ion is successively integrated into the lattice. The crystal lattice of Ca12Al14O33 is characterised by an open, three‐dimensional anionic network composed of aluminium‐oxygen tetrahedrons linking the edges. In this network, large interstitial spaces are formed, which may be filled with calcium ions on the one hand and statistically with a free oxygen or sulphide ion on the other hand.
A Model Based on the Assessment of Intrinsic Creep Resistance Concept
Authors: Vassilas Nikolaos I. , Baxevani Eleni A.
Published: December 2016

In the present study a simple model is proposed to assess creep behavior. The model is applied to experimental results performed on austenitic steel X8 CrNiMoNb 16 16. The model is based on a modification of the Levy‐Mises equation for plasticity to consider creep time effects, introducing as a parameter the intrinsic creep resistance. The assessment of creep behavior applied for monotonic and two stages loading data is good. The model could assess negative creep strain rates as well as damage accumulation observed as an increase of the minimum creep rate after each reloading at the same stress level in two stages tests.
Numerical Study of Gas‐Solid Flow in the Raceway of a Blast Furnace
Authors: Feng Yu‐Qing , Pinson David , Yu Ai‐Bing , Chew Shen J. , Zulli Paul
Published: December 2016

This paper presents a numerical study of gas‐solid flow in a blast furnace raceway using a 2D slot cold model. Numerical experiments are conducted by combining the discrete element method for the solid phase with computational fluid dynamics for the gas phase. The motion of particles caused by lateral gas blasting under conditions similar to that in the blast furnace process is examined at a particle scale. Combustion and associated solids movement around the raceway are simulated by extraction of particles from the bottom of the bed. The effect of bed height or solid pressure is considered by imposing a downward force on the top layers of particles in the bed. It is shown that depending on the gas velocity, the bed can transit from a fixed bed to a fluidized bed or vice versa. Two zones can be identified in such a bed: a stagnant zone in which the particles remain at their initial positions, and a moving zone in which particles can move in various flow patterns. In particular, if the gas velocity is in a certain range, the moving zone is formed just in front of the gas inlet, giving the so‐called raceway in which the particles can circulate. The effects of gas velocity, solid pressure and solid extraction are quantified. The fundamentals governing the gas‐solid flow and the formation mechanisms of a raceway are discussed in terms of particle‐particle and particle‐fluid interaction forces.
Evolution of Globular Microstructure in New Rheocasting and Super Rheocasting Semi‐Solid Slurries
Authors: Uggowitzer Peter J. , Kaufmann Helmut
Published: December 2016

Based on the solidification theory for metal alloys, a simple recipe for the controlled processing of globular microstructures without external stirring is presented: Firstly, small solidification nuclei must be distributed homogeneously throughout a melt. In New Rheocasting (NRC) these nuclei are formed by forced homogeneous nucleation due to partial quenching of the melt, while in Super Rheocasting (SRC) the nuclei are “second phase particles” in specially designed alloys, which are grown in a controlled fashion in a certain temperature range. Potential alloy compositions for SRC are provided. Secondly, given these melts with small particles in them, globular growth can be assured by utilizing the Gibbs‐Thomson “self healing effect” and slow further cooling to allow diffusion in the melt and to suppress constitutional supercooling. This simple recipe is applicable to various ferrous and non‐ferrous alloys. If an SRC alloy is cooled more rapidly than necessary for globular growth of the primary phase, but is held sufficiently long in the SRC range for dispersoid formation, these dispersoids can act as potent grain refiners and possibly enhance elevated temperature properties. A combination of both processes by using SRC alloys in the NRC equipment may lead to pressure tight castings with low porosity and finer grain structure than can be achieved with NRC on its own, and consequently, better mechanical properties.
Semi‐Solid Rheoforging of Steel
Authors: Seidl Ingold , Kopp Reiner
Published: December 2016

To produce steel components with complex shapes excessive machining is necessary frequently since high pressure die casting of steel is not industrially applied. Forming steel in the semi‐solid state can in principle produce new components and geometries which cannot be realised by conventional closed die forging. Semi‐solid forging of steel combines the possibility of producing geometries not conventionally forgeable in one forming operation and of adding further functions during the same operation. In previous investigations on thixoforming of steels, the semi‐solid steel was generated by reheating precursor material billets. An alternative approach for generating semi‐solid steel from the liquid state with subsequent forging operation is presented in this paper for the first time. The steel grades X210CrW12 cold work tool steel and 100Cr6 bearing steel are molten and driven into a globular semi‐solid state using a cooling slope and a cup. By cooling the steel into the semi‐solid range instead of heating it, the required process temperatures are lower than in the process route via heating. Therefore, the load on the dies in a semi‐solid forging operation is decreased. Suggestions for the respective layout of the process are made for both steel grades. Future potentials and challenges to be solved are discussed, showing advantages especially in the field of high melting point alloys such as steels. This technique enables to produce pre‐shaped semi‐solid billets to optimise the materials flow and the homogeneity of the mechanical properties.
Adhesion and Thermal Shock Resistance of Al2O3 Thin Films Deposited by PACVD for Die Protection in Semi‐solid Processing of Steel
Authors: Kurapov Denis , Schneider Jochen M.
Published: December 2016

In this work thin Al2O3 films were deposited on hot working steel AISI H11 by plasma assisted chemical vapour deposition (PACVD). The effect of the AlCl3/O2 ratio in the gas mixture and the substrate temperature on the film hardness and constitution of the deposited films was investigated by nanoindentation and X‐ray diffraction, respectively. Within the investigated process parameter window thin films containing either the γ‐Al2O3 or the α‐Al2O3 phase were grown. The performance of these Al2O3 coatings for the semi‐solid processing of steel was studied with respect to hardness, adhesion and resistance to thermal shock. The maximum critical load of 50 N as determined by scratch testing was achieved after plasma nitriding of the substrate. No cohesive or adhesive coating failure could be detected after 1000 thermal shock cycles at a contact temperature of 1170±30 °C. Based on the here presented adhesion and thermal shock data it can be concluded that the Al2O3 thin films are suitable candidates for the die protection during semi‐solid processing of steel.
An automated Thixo‐Forging Plant for Steel Parts
Authors: Küthe Fabian , Schönbohm Alexander , Abel Dirk , Kopp Reiner
Published: December 2016

The scope of the article is to describe the automated production of a thixoformed steel part. The production plant was set up within a prototype initiative at the Institute of Metal Forming in cooperation with the Institute of Automatic Control of RWTH Aachen University and industrial partners. Preliminary experiments showed that the quality of the formed parts varied to a great extent due to changing production conditions since the handling of the billet was carried out manually. To eliminate the possible disturbances introduced by the manual handling of the billet, an automation concept has been elaborated in order to guarantee a defined production environment. An industrial robot (KUKA) fulfils the handling tasks like the feeding of the induction coil with the feedstock material and the placing of the heated billet into the hydraulic press. The removal of the formed part from the press is realised by a simple mechanical device in order to be able to use only one gripper. The design of the gripper ensures a minimal heat loss during handling. The induction coil, the gripper system and the cavity are flooded with inert gas in order to prevent scaling. The sequence control for the production of a part is realised on the controller of the robot which provides sufficient PLC functionality and can be easily equipped with the required I/O components to trigger the different automation components.
TEM Investigations of Fine Niobium Precipitates in HSLA Steel
Authors: Béreš Miloslav , E.Weirich Thomas , Hulka Klaus , Mayer Joachim
Published: December 2016

Commercially produced 0.03 % C, 0.08 % Nb, 0.01 % Ti high strength low alloyed (HSLA) steel in the form of 20 mm thick plates was investigated. The steel was thermomechanically processed and the mechanical properties of the steel were evaluated by tensile testing. Using analytical and high resolution transmission electron microscopy the distribution, morphology, composition, crystal structure and particle size of niobium and titanium carbonitrides were observed and identified in these steels. The distribution of the precipitates was found to be nearly random, with occasional occurrence of precipitation free zones. Complex agglomerates with a cubic TiN seed crystal overgrown by a cubic NbC particle were the most commonly observed precipitates. Further TEM analysis in the accelerated cooled and tempered specimens in 1/4 plate thickness did not reveal any evidence that additional precipitation in the ferrite occurred. Precipitation in ferrite was only detected after subsequent cold deformation and tempering of the same samples. By a combination of EFTEM, STEM, HRTEM in addition to EDX spectroscopy, a large population of strain induced NbC precipitates with fcc crystal structure ranging in size down to 2 nm were identified in the ferrite matrix.
Review of ECSC research work in ironmaking
Authors: Mülheims Klaus , Peters Michael , Lüngen Hans Bodo
Published: December 2016

The Treaty of the European Coal and Steel Community (ECSC), which expired in 2002, states in its Article 55 to promote technical and economic research with respect to the production and growing application of coal and steel. The results of funded research projects shall be made available to all representatives and partners concerned. For the European steel industry Article 55 was the basis for building up a steel research programme covering topics from raw materials to steel application and instigated a European network of researchers from the steel industry, research institutes and universities.

On the basis of these research and development activities carried out by the ECSC steel research, the iron and steel industry has shown important advances in technology and environmental compatibility. Furthermore, the ECSC steel research has contributed to nearly all important technological developments. The main objective of the ECSC steel Research and Technology Development (RTD) programme was to sustain and develop the Community steel industry's competitiveness.

The following report describes fundamental developments and activities within the framework of ECSC research with particular respect to hot metal production in the last 15 years.
Microstructure and Deformation Behaviour of Iron‐Rich Iron‐Aluminium Alloys with Ternary Carbon and Silicon Additions
Authors: Herrmann Jutta , Inden Gerhard , Sauthoff Gerhard
Published: December 2016

The microstructure, hardness, yield stress, fracture strain, and brittle‐to‐ductile transition temperature of Fe‐Al alloys with Al contents of 12‐18 at.% Al, which are in the range of the so‐called K‐state with possible short‐range ordering reactions, and with ternary additions of carbon and silicon were studied with respect to the effects of possible impurities on the hardening of Fe‐Al alloys. It was found that perovskite‐type Fe3AlC carbide particles precipitate even in alloys with low C and Si contents; they are controlled by prior heat treatments and strongly affect the deformation behaviour.
Interfacial Convection and Mass Transport in Thin Liquid Layer
Authors: Scheller Piotr R.
Published: December 2016

Investigations into the phenomenology of convection flows next to the interface between two liquids have been carried out in laboratory experiments using various liquids. Then convection flows have been observed in industrial tests during continuous casting. The results show that the motional velocity of volume elements next to the interface due to disturbances of interfacial tension (produced by mass and charge transfer) depends on liquid layer thickness and on liquid properties. A new dimensionless number is introduced to describe this manner of convective flow; it is also suitable for evaluation of experimental results. Furthermore, a dimensionless function is theoretically developed to describe the relation between convective flows near the interface in the slag layer and mass transport.

Casting powders melt on the surface of the liquid metal forming a liquid slag layer. Samples taken during casting have revealed convective flows in the flux layer and mass exchange with the liquid metal. Coefficients of the developed dimensionless function have been determined empirically for Ti‐transport from the interface into the flux layer.
Development of Non‐coke Ironmaking Processes in China
Authors: Wei Guo , Shen Fengman , Shen Yansong , Hao Xiaojing , Zhao Qingjie
Published: December 2016

Development of non‐coke ironmaking process in China is presented. It is concluded that coal‐based rotary kiln is still the main process for direct reduced iron (DRI) production in the near future in China. The most important problems of DRI production in China are small production scale and heavy environment pollution. Now the gas‐based shaft furnace process has become one of the significant processes of DRI production in China. The market demand for DRI production in China is continuously increasing. Due to the tense supply of coking coal and its heavy environmental load, more steel plants in China will use smelting reduction (SR) technology.
A Blast Furnace Prediction Model Combining Neural Network with Partial Least Square Regression
Authors: Hao Xiaojing , Shen Fengman , Du Gang , Shen Yansong , Xie Zhi
Published: December 2016

The prediction of the important running variables of blast furnaces (BF) has been a major study subject as one of the most important means for monitoring the BF state in ferrous metallurgical industry. In this paper, a prediction model for BF by integrating a neural network (NN) with partial least square (PLS) regression is presented. The selection of influencing operational parameters of BF on variables to be predicted is developed according to the minimization of residuals based on the theory of path analysis. The selected influencing parameter data series are processed as the inputs of the prediction model. In order to validate this prediction model, the silicon content in hot metal of BF is taken as the variable to be predicted. The model is trained and evaluated with industrial data, and the results show that it works well. Further modification of this prediction model is also discussed to improve its industrial application.
Energy Consumption in Smelting Reduction
Authors: Fang Jue , Wang Xingjuan , Guo Li , Liu Peixiao
Published: December 2016

The concepts of theoretical gas utilization ratio, smelting heat of iron ore and effective calorific value of coal were introduced in this work. The practical gas utilization ratio and the gas consumption in the shaft of a reduction unit for smelting reduction were discussed. The Corex process was optimized and the energy consumption was minimized according to the relationship of gas production in the smelting unit and the degree of iron ore reduction in the reduction unit. It was proven that the most important factor for saving energy in smelting reduction process is to use coal with suitable effective calorific value for the smelting heat of iron ore.