bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of casting‐rolling force of viscous fluid and its technological influence
Authors: Binyu Sun , Hong Zhang , Rong Shi , Baocheng Shen , Yuquan Tong
Published: December 2016

In casting‐rolling process the velocity is very slow and, therefore, the deformed body is still in the state of liquid‐solid viscous flow. The rheological properties of the deformed body are described by the theory of mature hydromechanics. A velocity field was set by the flow function. The pressure field and velocity field of metal flow were combined, based on Navier‐Stokes equation. The distributional formula of the unit pressure in the deformed zone was obtained, and the calculation formulae for mean unit pressure in the casting‐rolling zone were established. In this paper, the influence of absolute draft, radius of casting‐rolling roll and front tension stress on the mean unit pressure had been discussed. Comparison of theoretical data with experimentally obtained values showed good agreement, thus proving the correctness of the theoretical formulae.
The influence of solidification morphology on the high‐temperature mechanical properties of an 18–10CrNi steel
Authors: Scheller Piotr R. , Papaiacovou Panicos , Lin Dong‐Yih , Çöl Mustafa , Dahl Winfried
Published: December 2016

Cylindrical specimens of the grade X4CrNi18‐10 (material no 1.4301) having diameters of 10, 15 and 20 mm were examined on a hot tensile testing unit after partial melting and cooling at different rates. Experiments were performed at temperatures between solidification and 1000°C. As a comparison non‐melted specimens taken from a continuously cast slab were investigated.

In the experiments in which specimens were partially melted the radially solidified area increases with enhancing cooling rate. At cooling rates ≥ 3 K/s it accounts for more than 80 % of the specimen cross‐section. The secondary dendrite arm spacings λ2 range between approx. 30 and 50 μm at these cooling rates. As the radially solidified area increases, strength at zero‐toughness temperature decreases. At lower temperatures, on the other hand, the solidification morphology of these samples had no effect on the mechanical properties. Unlike the results achieved with partially melted specimens, with specimens taken from a continuously cast slab the solidification morphology was found to have a distinct effect. Between 1350 and 1100°C toughness is around 20 % points lower when tensile loading acts transversely to the direction of crystal growth in comparison with axial loading. On the contrary strength is slightly higher. These results show that when investigating the causes of fracture initiation and propagation during and after solidification, the solidification morphology is of prime concern.
Kinetics of phosphorus segregation in 2.7Cr‐0.7Mo‐0.3V steels with different phosphorus contents
Authors: Sevc Peter , Janovec Jozef , Lucas Manfred , Grabke Hans Jürgen
Published: December 2016

The phosphorus grain boundary segregation kinetics during tempering at 680°C and aging at 500°C of 2.7Cr‐0.7Mo‐0.3V steels with phosphorus mass contents of 0.004, 0.014, and 0.027 % was investigated. To determine the grain boundary concentrations of phosphorus the Auger electron spectroscopy was used. Chemical compositions of carbide particles were determined by means of EDX/STEM. Xu Tingdong's and McLean's models of non‐equilibrium and equilibrium segregations, respectively, were used to analyze experimental data. It was shown that a phosphorus grain boundary enrichment during tempering was mainly caused by non‐equilibrium segregation. During aging the mechanism of the equilibrium grain boundary segregation was prevalent. Slow phosphorus segregation kinetics was observed in the experimental steels during aging.
Validity of rate equation based on Langmuir‐Hinshelwood mechanism for gasification of carbon ‐ a reappraisal
Authors: Bandyopadhyay Debajyoti , Ghosh Ahindra
Published: December 2016

Literature review on gasification of carbon by carbon dioxide reveals that the most widely accepted mechanism of gasification is based on the adsorption of oxidizing agent, proposed by Langmuir and Hinshelwood. But few investigators have cast doubt on the validity of the mechanism. In this paper, an attempt has been made to recheck the same with the help of critical analysis of literature information as well as rate data generated by the authors on gasification of electrode graphite and coconut char in different gaseous environments, namely, CO2, CO2‐Ar and CO2‐CO. It has been found that the parameters in the rate equation depend on the type of carbon contrary to the literature postulation that they are universal in nature. Expected linear dependence of rate on gas composition could not be observed under certain experimental conditions. Further, the equilibrium constants of the first elementary step of gasification i.e reversible oxygen exchange step, was found to be widely varying for both, different investigators and for different forms of carbon. Activation energy for the reverse step of oxygen exchange reaction was calculated to be negative tor graphite. Thus, the findings of the present study are not in conformity with the behaviour expected if Langmuir‐Hinshelwood mechanism is valid for gasification of carbon by carbon dioxide.
Contribution to the modelling of stretch reducing of tubes
Authors: Bernardy Paul , Möltner Hermann
Published: December 2016

Computer‐aided simulation is becoming more and more important for the further development of the stretch reducing mill (SRM). The available methods of calculation, however, are not satisfactory. The complete simulation of the process with a finite element method cannot yet be carried out within a reasonable time, whereas the results obtained with the help of simpler models are sometimes very inaccurate. The development of an efficient model aims at considerably improving the relation between expenditure and return as compared with the above‐mentioned methods of calculation. Based on today's knowledge of the process, fundamental extensions have been made to the known conventional SRM model. According to forming history the process model of the extended SRM model is composed of two partial models. The first partial model describes the forming process which takes place in the pass and approximates the real three‐dimensional rolling process with the help of axisymmetric elements. The second partial model describes the behaviour of the workpiece in the space between the stands. The gradual calculation of the deformation in the space between the passes is derived from the equilibrium of forces in axial direction and with the help of suitable hot stress‐strain curve functions. An efficient and fast SRM simulation program has been drawn up on the basis of this extended elementary model. The results obtained were found to correspond very well to the measuring results obtained in numerous rolling trials. The model approach described in this paper can also be applied to other longitudinal rolling processes.
Kinetics of iron oxide reduction from CaO‐MgO‐FeOn‐SiO2 slags by silicon dissolved in liquid iron
Authors: Xie Hui , Schulz Manuela , Oeters Franz
Published: December 2016

At steelmaking temperatures, the kinetics of slag‐metal reactions is usually determined by mass transfer. This occurs in two ways: normal mass transfer which is induced by stirring, and mass transfer by interfacial convection induced by interfacially active elements like oxygen and sulphur. In the present work, mass transfer during the reduction of iron oxide from a basic slag by silicon dissolved in liquid iron was studied under defined conditions of gas stirring by argon in MgO crucibles with 1500 g iron and 250 g slag. The variations of the FeO content in the slag and the silicon content in the iron during the reaction were measured by sampling. Trials were carried out with stirring gas flow rates between 1 and 20.4 l/h(STP). The experimental data were evaluated with the multi‐component transport model in order to determine the mass transfer coefficients of the reaction components. Simultaneously, the coefficients of normal mass transfer were calculated with the boundary layer theory of liquid‐liquid mass transfer for non‐turbulent flow conditions. The measured mass transfer coefficients were by a factor 2.5 larger than the theoretically calculated. The difference indicates the presence of mass transfer by interfacial convection. Mass transfer by interfacial convection is superimposed to normal mass transfer.
Thermodynamics of oxygen behaviour in cobalt‐nickel alloys
Authors: Soltanieh Mansour , McLean Alex , Iwase Masanori
Published: December 2016

In this study the concentration and chemical potential of oxygen in liquid Co‐Ni alloys equilibrated with cobalt‐nickel aluminate spinel solid solutions and alumina have been determined at 1773, 1823 and 1873K as a function of nickel concentration. The oxygen content of the melt has been measured by suction sampling and inert gas fusion analysis. The corresponding oxygen potential has been determined with the following solid state cell: Mo, Mo+MoO2 | (MgO)ZrO2 | (Co, Ni) melt + AI2O3 + (Co, Ni)O·(1+x)Al2O3, Mo.

The effect of nickel on the activity coefficient of oxygen in Co‐Ni alloys has been determined. The results for the activity coefficient have been modelled with Wagner's interaction parameters and also the more recent exponential method of St. Pierre et al. at the three temperatures.
Resistance of 9–20%Cr‐steels against metal dusting
Authors: Grabke Hans Jürgen , Müller‐Lorenz Else Marie , Eltester Burkhard , Lucas Manfred , Monceau Daniel
Published: December 2016

The metal dusting resistance of various 2¼ Cr to 20%Cr steels has been tested in flowing CO‐H2‐H2O atmospheres at 525, 560, 600 and 650°C. For the 2¼Cr‐steel immediately a constant rate of metal wastage is reached, for the high alloy steels the approach to this rate where all surface area is attacked, is more or less retarded by an oxide layer. The formation of a protective Cr‐rich oxide layer is favoured by a high Cr‐content of the steels, by the ferritic structure, by a fine‐grained microstructure, by surface working and by high temperatures – these factors hinder or suppress metal dusting, whereas low Cr‐concentration, austenitic structure, coarse‐grained microstructure, removal of surface deformation by etching and a critical temperature of ≤ 600°C accelerate and enhance metal dusting.
Melting equilibria in the iron‐rich corner of the Fe‐Ni‐Mo system
Authors: Schürmann Eberhard , Djurdjevic Mile , Nedeljkovic Ljubomir
Published: December 2016

Isothermal holding tests were carried out in the Fe‐Ni‐Mo system in the two‐phase region between the liquidus (melt) and the solidus (crystal). The δ and γ liquidus surfaces in the iron‐rich corner of the Fe‐Ni‐Fe3Mo2‐NiMo subsystem, as well as the position of the peritectic line situated between them, could be very accurately established by the experimentally determined isotherms. Based on these results and on the known liquidus lines in the three boundary binary systems, as well as on the known concentration fields of the Fe3Mo2‐NiMo solid solutions, the melting equilibria could be developed with sufficient accuracy in the entire subsystem.
A metallurgical‐thermophysical database system
Authors: Zhang Jiayun , Zhou Tuping , Ma Yongjian , Fang Xueliang , Lei Junbo
Published: December 2016

Using FoxPro and C as programming languages, the framework for developing a computerized metallurgical‐thermophysical database system, Thermophysdata, has been completed at USTB, Beijing, China. Thermophysdata is a user‐friendly system consisting of two major packages, PHYSDBMS, PHYSDPRE. At present, the system can serve users’ data retrievals for a number of physical properties in molten metallic as well as ionic systems. Supported by PHYSDPRE, model optimized physical property values with a satisfactory accuracy are available for a certain amount of molten systems. Based on Chapman‐Enskog's theory, the transport property data for low density gaseous systems could also be predicted.
Determination of dissolved sulfur and Mg‐S, Mg‐O equilibria in molten iron
Authors: Han Qiyong , Zhou Debi , Xiang Changxian
Published: December 2016

Experiments on the extraction of sulfur from the sulfides and oxy‐sulfides such as FeS, MgS, CaS, BaS, RE2S3 and RE2O2S (RE ‐ rare earth metals) by hydrogen reduction were carried out at 600 – 900°C by means of hydrogen reduction‐polarographic analysis method. The reduction degree of various sulfides by H2 at 800°C is in decreasing order as follows: FeS > MgS ≥ RE2S3 > RE2O2S ≥ CaS ≅ BaS. The equilibrium constants for reaction MgS(s) = [Mg] + [S] and MgO(s) = [Mg] + [O] obtained by using vapour‐liquid equilibrium method are: KMgS = 2.0·10−4 at 1873 K, log KMgO = 1.27 ‐ 13670/T, eOMg = 644.5 ‐ 1406000/T.
Reduction of Fe1‐xO in liquid state by H2+Ar mixtures
Authors: Wegrzyn Janusz , Król Leszek
Published: December 2016

The investigations of reducing Fe1‐xO in liquid state with H2+Ar mixtures, in top blowing stream of gas reactor, by using thermobalance method have been carried out. To make the system more homogeneous pure iron crucibles were used in the experiment. The experiments were carried out in the range of gas flow rate V = (5+80) · 10−6 m3/s and in 1723 K. Reduction rate depends on hydrogen partial pressure and flow rate of gas mixture. The logarithm of apparent reduction rate constant is a linear function of logarithm of gas flow rate. In experimental conditions of this work, the initial rate of reduction satisfies the relation . Thus it has been shown that the reduction process is controlled by the mass transfer in the gaseous phase. Sherwood numbers obtained from observed values of reduction rates and empirical equation of the gas‐phase mass transfer rate are correlated by equation . The values of mass transfer coefficient in gas phase calculated from Sherwood numbers are consistent with the values of apparent reduction rate constant and with estimated rate constant of chemical reaction of liquid Fe1‐xO reduction.
Concepts and experiments for characterizing plastic anisotropy of round bars, wires and tubes
Authors: Pöhlandt Klaus , Lange Kurt , Zucko Mishel
Published: December 2016

Starting from axial and radial anisotropy defined in previous publications, concepts for the description of plastic anisotropy of materials having axisymmetric properties (round bars, tubes, wires) are defined. A maximum of three ‐ in most cases even less ‐ independent parameters are needed. For solid materials like round bars it is recommended to use the axial‐radial and the axial‐tangential anisotropy as independent quantities for obtaining the yield locus according to Hill's quadratic yield criterion. Experiments for determining these parameters are described. For tubes, however, in most cases only the radial‐tangential anisotropy can be determined from the transverse contraction in tensile tests. Hence the yield locus can only be obtained in the approximation of the Hosford‐Backofen yield criterion. Effects of the anisotropy parameters on metal forming processes are discussed.
Application of computer modelling in part, die, and process design for manufacturing of automotive stampings
Authors: Thomas William , Altan Taylan
Published: December 2016

Recent studies in sheet metal forming, conducted at universities world wide, emphasize the development of computer aided techniques for process simulation. To be practical and acceptable in a production environment, these codes must be easy to use and allow relatively quick solutions. Often, it is not necessary to make exact predictions but rather to establish the influence of process variables upon part quality, tool loads, material flow, and material thickness variation. In cooperation with its industrial partners, the ERC for Net Shape Manufacturing at the Ohio State University has applied a number of computer codes for analysis and design of sheet metal forming operations. This paper gives a few selected examples taken from automotive applications and illustrates practical uses of computer simulations to improve produtivity and reduce tool development and manufacturing costs.
Development of a new composite flow curve statement
Authors: Lehmann Gunter , Lemke Jürgen
Published: December 2016

A new composite flow curve statement is presented, which allows good approximation of the flow curve and is suitable for numeric simulations. Without restrictions, it holds over the entire range of validity of a flow curve as a function of plastic strain, plastic strain rate and temperature. Simultaneously, it can be used for any material so that it is well suited for material databases. The number of coefficients used is higher than in other flow curve statements; however, the coefficients are calculated more easily and partially by automatic procedures. The described composite statement can be integrated so that it can be employed in analytical calculations, e.g. of force and power requirements.
The effect of double austenitization on the microstructure and fracture toughness of AISI M2 high speed steel
Authors: Ögel Bilgehan , Tekin Erdogan
Published: December 2016

In this study, the effect of double austenitization on microstructure and toughness of AISI M2 high speed steel was investigated. For double austenitization treatment, the specimens, which are hardened initially at 1220°C and quenched in air, were hardened for a second time in the temperature range 1150 – 1050°C. For comparison purposes, another set of specimens is austenitized singly in the temperature range 1150 – 1050°C. Tempering process was carried out between 500 – 640°C. A double austenitization causes a fine carbide precipitation in the matrix, having sizes in the range of 0.10 ± 0.05 μm and volume fractions of between 1 and 6%. It is shown that a double austenitization treatment causes a decrease in fracture toughness (KIc), when compared with single austenitized ones. The reason for the lower KIc values of double austenitized specimens are attributed to these fine carbide precipitates: It is suggested that they limit the plastic deformation capability of the matrix and yield lower fracture toughness values.
Research on the integral hydrobulge forming technology of spheroidal shells
Authors: Zhang Shi‐Hong , Danckert Joachim , Wang Zhong‐Ren , Nielsen Karl‐Brian
Published: December 2016

In the present paper an altemative novel process of manufacturing oblate spheroidal vessels is proposed: the integral hydro‐bulge forming (IHBF) technology of oblate spheroidal shells. A few mild steel and stainless steel oblate spheroidal shells for industrial use were manufactured using this new technology with one of the major diameters as high as 3 m. There is a critical value of the ratio between the vertical diameter and the horizontal diameter of the shell before forming, which can determine whether the shell will be wrinkled during hydro‐bulging. The processes were analysed afterwards, using the explicit finite element code LS‐DYNA3D. The numerical results are discussed and compared with the practical processes. Based on the numerical results a few proposals for the improvement of the IHBF technology of the spheroidal shells are presented.
Residual stresses in rails due to roll straightening
Authors: Finstermann Gerhard , Fischer Franz Dieter , Shan Guoxin , Schleinzer Gerald
Published: December 2016

The knowledge of residual stresses in rails due to roll straightening has become increasingly important for the evaluation of the fatigue behaviour of rails. The residual stresses are induced both by the bending process and the roll contact leading to a very complicated distribution especially near those parts of the surface where the roll contact had taken place. So far, no clear picture has emerged with respect to the residual stress field, either from experiments or from simulations. This study intends to clarify the residual stress distribution by simulation with a fully three‐dimensional model taking into account both the bending and contact process. This work shows that especially in those areas where the roll contact happens compressive residual longitudinal stresses appear on the surface. Furthermore, a very steep gradient of the residual longitudinal stress distribution near the surface is observed which is reported also in very recent X‐ray and neutron diffraction experimental investigations.
Mixing enthalpy measurements of liquid Ti‐Zr, Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys
Authors: Thiedemann Uwe , Rösner‐Kuhn Michael , Drewes Karsten , Kuppermann Gunnar , Frohberg Martin G.
Published: December 2016

The mixing enthalpies of liquid Ti‐Zr, Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys were measured by levitation alloying calorimetry. The mixing enthalpy of Ti‐Zr alloys is slightly exothermic and symmetric with an extreme value of −5.2 kj mol−1. It can be described according to the regular solution model. Experimental investigations of the mixing enthalpies of the strongly non‐ideal binary systems Fe‐Ti, Fe‐Zr and Ni‐Zr had already been subject of earlier works. Based on experimental data temperature dependent descriptions of the mixing enthalpies were calculated with a regular associate model. From the model parameters of the binary subsystems the mixing enthalpy of the respective ternary system can be predicted. Model calculations of the mixing enthalpies of liquid Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys were performed along different concentration sections and compared with experimental data, respectively. A good accordance was observed. The mixing enthalpies of liquid Fe‐Ti‐Zr and Fe‐Ni‐Zr alloys are given at T = 2152 K and T = 1892 K in form of isoenthalpy diagrams, respectively. Moreover, with help of the temperature dependence of the mixing enthalpy the excess heat capacities of the alloys were calculated.
Evaluation of component creep behaviour by means of a threshold approach
Authors: Xu Hong , Maile Karl , Roos Eberhard
Published: December 2016

Creep deformation as well as damage evolution in nut bolt assemblies have been investigated. A damage model was developed, based on a combination of Kachanov theory and critical creep strain threshold. Exceeding the creep strain threshold cause initiation and growth of creep cavities. The model together with a modified Norton‐Bailey creep law was implemented in the user subroutine Creep of the FE code Abaqus. Verification of the computation was done by means of comparison with creep tests of nut bolt assemblies.
Kinetics of inclusion precipitation during steel solidification
Authors: Gaye Henri , Rocabois Philippe , Lehmann Jean , Bobadilla Manuel
Published: December 2016

The precipitation of non‐metallic inclusions (complex oxides, sulphides, nitrides …) during steel solidification is analysed using the multiphase equilibrium code CEQCSI and a nucleation and growth model. The CEQCSI code is based in part on the Irsid slag model, and it provides an evaluation of the composition of inclusions formed at equilibrium, as well as guidelines for industrial treatments in order to reach desirable compositions in semi‐killed steel grades. The nucleation and growth model can be applied to the formation, during steel solidification, of stoichiometric compounds or liquid oxide inclusions. Two particularities of this kinetic model are that nucleation and growth are treated simultaneously, and they compete in consuming the supersaturation at each moment, and that a mixed controlled growth model transport/interfacial kinetics at the precipitate/liquid steel interface is considered. The predicted size distribution of TiN precipitates formed in two steel grades is in good agreement with the results of laboratory experiments. In the case of liquid oxide precipitation, the first calculations indicate that the composition of inclusions can be significantly different from that of inclusions assumed to precipitate under equilibrium conditions.
Solidification structure and micro‐segregation of unidirectionally solidified steels
Authors: Jacobi Hatto , Wünnenberg Klaus
Published: December 2016

Two linepipe steels with carbon mass contents of 0.09 and 0.15% were subjected to steady state unidirectional solidification in a special apparatus. The specimens were positioned in alumina tubes of 15 mm internal diameter, and were pulled downwards at a constant rate, R, from the high temperature furnace. The temperature gradient, G, at the solidification boundary was varied between 5 and 136 K/cm. The dendrite arm spacings measured were quantitatively assessed using the relationship Λ = cRmGn. The exponents m and n for the primary arm spacing, Λ1, are in agreement with theoretical predictions, at m = −1/4 and n = −1/2. Comparison with other steels containing 0.59 % C and 1.48 % C showed that Λ1 increases with increasing carbon content. The exponents m and n for secondary arm spacing are nearly the same, at −0.4 to −0.5. Correlations with local solidification time, θf, show that Λ2 decreases as the carbon content increases. In the δ‐phase regime, coarsening of the secondary arms is possible through remelting. Interdendritic segregation peaks are more quickly reduced in the δ‐phase regime. This is confirmed by the results of electron beam microprobe analyses for segregation. Reduction of the carbon content of linepipe steels reduces the susceptibility to centreline segregation in the continuously cast slabs.
A model of post‐combustion and heat transfer at smelting reduction with a foamy slag
Authors: Di Donato Antonello , Malgarini Giansilvio , Oeters Franz , Zhang Liuyi
Published: December 2016

A smelting reduction reactor with post‐combustion in a foamy stag has two slag layers. In the lower, iron oxide from the slag is reduced to iron by carbon. In the upper, the gas from the reduction is post‐combusted to CO2+H2O. The post‐combustion heat is transferred from the rising post‐combustion gas to the upper slag, and, therefrom, by slag circulation to the lower slag layer where the endothermic reduction reaction takes place. Unavoidably, slag circulation also transfers part of the char into the upper slag where it is oxidised. A kinetic post‐combustion and heat transfer model describes these phenomena. The main process parameters, namely real post‐combustion degree, carbon oxidation, heat transfer efficiency, distribution of temperatures of gas and slag in the single regions of the reactor, coal consumption, and iron production rate are given as functions of the ratio of post‐combustion oxygen to gas evolution rate of the system. The main influences on which heat efficiency and off‐gas temperature as the most important output parameter depend are discussed. Controlled stirring and a regular gas through‐put are of primary importance. The required values are given. A comparison with pilot plant results of the CSM process shows good agreement with the model results.
Oxygen and nitrogen reactions in Fe‐X and Fe‐Cr‐Ni‐X melts
Authors: Ma Zhongting , Janke Dieter
Published: December 2016

A modified ɛ formalism is developed to perform thermodynamic analysis for metallic solutions. The model calculation is successfully applied to describe oxygen and nitrogen equilibria in both liquid iron and alloyed steel melts. Relations between oxygen activities or contents and composition of Fe‐O‐X (X = Si, Cr, Ti and Al) melts are given quantitatively. The results are widely supported by the available experimental results. Nitrogen solubilities in Fe‐Cr and Fe‐Cr‐Ni melts predicted by the present model calculation feature good agreement with experimental results.
Removal of zinc layers from coated steel strip by evaporation
Authors: Franzen Andreas , Pluschkell Wolfgang
Published: December 2016

In this research project, basic investigations on the low temperature reactions of the zinc coating layer were performed in different gas atmospheres in order to develop novel methods for zinc removal from scrap material by baking the material at a moderate temperature. The investigations have shown that zinc evaporates effectively into an inert carrier gas of low oxygen potential. The holding time required is about 5 min at 600°C. The zinc residue remaining on the substrate is low, because the diffusion of zinc in α‐Fe proceeds slowly at the given temperatures. Preliminary experiments with an inductively heated vaporizer of laboratory size led to satisfying zinc removal from shreddered scrap material. This result is a recommendation to develop an industrial pilot plant of this kind.
Reduction of iron oxides from liquid slags using a graphite rotating disc
Authors: Mróz Jan
Published: December 2016

Research work has been carried out on the reduction of FeO from liquid slags of the CaO‐FeO‐SiO2 ternary system using a graphite rotating disc technique. The investigations were conducted on slags with a basicity of CaO/SiO2 = 1.27 and FeO contents of 20 and 60%, at temperatures of 1350 and 1420°C. The calculated viscosity range for these slags is within 2.53 – 0.43 dPa·s. It has been found that the factor controlling the reduction process is diffusion of FeO towards the disc surface, both in the case of the reduction from the slag with 20% FeO and in the case of the reduction from the slag with 60% FeO fraction. The diffusion coefficient of FeO at the reduction temperature of 1350°C is of the order of magnitudes of 10−7 cm2/s, while at 1420°C it reaches the order of 10−6 cm2/s. The calculated thickness values for the limiting diffusion layers range from 8.54·10−3 to 0.70·10−3 cm. It has been found that with increasing reduction rate also Boudouard's reaction starts to be important to the overall reduction rate. The limiting reduction rate at which Boudouard's reaction starts to be important to the entire process is dependent on temperature, being approximately 10.0·10−6 mol FeO/cm2 s at 1350°C, and approximately 15.0·10−6 mol FeO/cm2 s at 1420°C.
Determination of crash‐relevant material parameters by dynamic tensile tests
Authors: Bleck Wolfgang , Schael Ingo
Published: December 2016

The mechanical properties of eight different steels, representing the wide range of steels for automotive application, are determined by accomplishing high speed tensile tests using flat sheet specimens. The steels chosen for investigations are deep drawing grade DC04, high strength steel ZStE340, three dual phase steels with strengths of 600, 800 and 1000 MPa, a TRIP steel and two austenitic stainless steels 1.4301 and 1.4318. Tests are carried out at five different strain rates within the range of 5‐10−3 and 200 s−1, all at room temperature. The results show different strain rate sensitivities according to the different grades of steel. The TRIP steel and both stainless steels show a great potential for energy consumption, when tested at high strain rates.
Study on manufacture of large size pipe elbows by hydro‐bulging tubular single‐curvature polyhedron
Authors: Jianling Dong
Published: December 2016

This paper presents a method to manufacture pipe elbows by hydro‐bulging a tubular single‐curvature polyhedron. The basic idea is: first to build an enclosed tubular single‐curvature polyhedron using sector single‐curvature shell plates; then hydro‐bulge the polyhedron to make the tubular single‐curvature polyhedron deform plastically into a smooth double‐curvature tubular polyhedron; finally to cut the polyhedron into pipe elbows. Main technology steps are: first, to cut steel sheet plates into sheet blanks; second, to form the sheet blanks into single‐curvature cylindrical shells; third, to assemble and weld the single‐curvature cylindrical shells into an enclosed tubular single‐curvature polyhedron; fourth, to hydro‐bulge the polyhedron; fifth, to cut the polyhedron hydro‐bulged to get pipe elbows. This paper also describes a tubular single‐curvature polyhedron hydro‐bulging experiment. The results show that the single‐curvature polyhedron hydro‐bulging technology can be used to manufacture pipe elbows of a large size.
Correction on: Laboratory study of heat transfer through thin layers of casting slag: minimization of the slag/probe contact resistance
Authors: Holzhauser Jörg‐Friedrich , Spitzer Karl‐Heinz , Schwerdtfeger Klaus
Published: December 2016

The heat flux densities through thin layers of casting slag have been measured with a soft cooling heat flux probe which made smooth probe/slag interfaces. Thus the contact resistance was avoided. The evaluated effective thermal conductivities were applied, together with the data on the contact resistance, to compute the “system conductivities” existing in the continuous casting “system” water cooled copper/slag/strand. The refractive index and absorption spectrum were measured and used to deduce functions for the radiative and conductive (phonon) conductivities. Although precise values could not be obtained, due to the many assumptions involved, the data indicate that the conductive conductivity does not change drastically at high temperatures and on melting.
A study of the dissolution of Al2O3, MgO and MgAl2O4 particles in a CaO‐Al2O3‐SiO2 slag
Authors: Valdez Martin , Prapakorn Kritsada , W.Cramb Alan , Seetharaman Sridhar
Published: December 2016

The dissolution behaviour of alumina, MgO and MgAl2O4 particles in a 36%CaO‐21%Al2O3‐42%SiO2 (mass contents in %) slag has been studied using a confocal scanning laser microscope in the temperature range of 1470 ‐ 1550 °C. The double hot thermocouple technique and metallographic examination was also used to characterize the reaction product between the particles and the slag. The total dissolution times for MgO and MgAl2O4 particles decreased with increased temperature and were almost identical (approximately 200 s for a 150 μm diameter particle at 1500 °C.). This phenomenon can be explained by the formation of MgAl2O4 layer on the surface of the MgO particle during dissolution. Alumina dissolution times were slightly longer (approximately 250 s for a 150 μm diameter particle at 1500 °C) than that of MgO and MgAl2O4 particles and no reaction layer was observed on the surface of the particles.
Improved relationship between Vickers hardness and yield stress for cold formed materials
Authors: Tekkaya A. Erman
Published: December 2016

Cold‐formed metal products are increasingly serving as high duty machine parts. Designers and users need to know their properties as accurately as possible. One such product property is the new yield strength, which can be approximated by the final flow stress of the workpiece material during forming. Vickers hardness measurements provide an easy and inexpensive method of evaluating the new local yield stress in cold‐formed workpieces. The well‐known available models given in literature to convert the measured hardness number into the corresponding yield stress have an error of up to 25 %. This is basically due to the facts that cold formed material experiences large plastic strains in the main forming stage, the hardening behaviour is anisotropic and, moreover, the material properties are inhomogeneous especially at the workpiece surface. The purpose of this study is to improve the accuracy of the well‐known available correlation models between Vickers hardness measurements and yield stress. This is achieved by utilizing finite element simulations of the indentation process. The models currently incorporate only the isotropic strain‐hardening behaviour of the work material. The new suggested model decreases the theoretical conversion error to less than 10 %.

The improved model has been verified by experiments. The difficulty in verifying the models is realizing an experiment with a precisely known high plastic strain. In this study, the forward extrusion process was utilized for this purpose. In the forward extrusion process there is one location in the workpiece where the plastic equivalent strain and hence the yield stress is exactly known: the axis of the extrudate. By this method it is possible to obtain strain‐hardening states up to an equivalent plastic strain of 1.6 (!). Hence, making hardness measurements at the axis of extruded workpieces, it was possible to verify the improved relationship up to realistic strain values. The results have shown that the new relationship supplies conversions with a drastically reduced error as compared to the classical relations.
Redistribution of the substitutional elements during σ and χ phase formation in a duplex stainless steel
Authors: Duprez Lode , De Cooman Bruno C. , Akdut Nuri
Published: December 2016

While the kinetics of intermetallic phase formation in duplex stainless steel have been extensively studied for a wide range of compositions, relatively little research has been done on the mechanisms by which the phases nucleate and grow. In this research the emphasis was on the diffusional growth of the sigma (σ) and chi (χ) phases. Intermetallic phase precipitation in a standard DSS type EN 1.4462 was studied in detail at two temperatures: at 850 °C where large amounts of σ phase are formed, and at 650 °C where χ is the main intermetallic phase. The redistribution of the substitutional alloying elements Cr, Mo, Ni, Mn and Si between the ferrite, the austenite and the intermetallic phases was followed by means of scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX). Mn and Si showed no distinct partitioning between the several phases. The diffusion paths of the other elements were found to be determined by two phenomena. On the one hand, the ferrite to austenite transformation causes Mo and Cr to enrich in the ferritic phase and Ni to enrich in the austenite. On the other hand, Mo (σ, χ) and Cr (σ) are removed from the ferrite by intermetallic phase precipitation. At 650 °C, strong Mo enrichments appear at the α‐γ phase boundaries indicating that grain boundary diffusion could be an important mechanism for Mo to diffuse to the growing χ phase.
Mechanism of fluid flow in a continuous casting tundish with different turbo‐stoppers
Authors: Odenthal Hans‐Jürgen , Bölling Ralf , Pfeifer Herbert , Holzhauser Jörg‐Friedrich , Wahlers Franz‐Josef
Published: December 2016

The fluid flow in a continuous casting tundish affects the separation of non‐metallic particles and the cleanliness of the steel. Today, laser‐optical investigations of water models are state of the art and enable detailed information about the effect of baffles, i. e. dams, weirs and turbo‐stoppers, on the flow. In this work 3D‐LDA and 2D‐DPIV‐investigations for different turbo‐stoppers in a water model on a scale of 1:1.7 of a 16 t single strand tundish are presented. Three circular turbo‐stoppers are investigated. Detailed measurements of the mean velocity and turbulence intensity in the tundish with and without turbo‐stopper are shown. With a suitable turbo‐stopper geometry the recirculation area in the tundish centre and short‐circuit flows along the side walls can be avoided and thus more favourable residence time distributions can be obtained. It is shown that the turbo‐stopper produces higher turbulence in the inlet region of the tundish, which is spatially more limited, however, in relation to the flow without turbo‐stopper. Thereby a more homogeneous flow is created at the discharge of the tundish with better conditions for the particle separation. The experimental data yield a good understanding of the flow phenomena in a tundish with turbo‐stopper and are used as validating criterion for numerical simulations (Fluent 5.5) on the basis of the Reynolds equations. The turbulence modelling is based on a two‐equation model (realizable k‐ε model).
Reduction and direct alloying of calcium vanadate
Authors: Yuan Zhang Fu , Huang Wen Lai , Zhu Sheng You , Liao Dai Hua , Hu Hong Fei
Published: December 2016

Based on the reduction law of calcium vanadate, which was explored in the laboratory, the experiments were carried out during direct alloying with calcium vanadate in a high‐frequency induction furnace with a capacity of 25 kg. The average recovery ratio of vanadium was 83.4 %. The tests were also carried out for direct alloying with a briquette of calcium vanadate in a 0.51 electric arc furnace and with cold‐bound pellets of calcium vanadate in a ladle to smelt the low alloy steel with mass contents of about 0.1 % vanadium. The recovery ratios of vanadium were 89.9 % and 86.0 %, respectively.
Metallurgy of continuously annealed high strength TRIP steel sheet
Authors: Matsuda Hiroshi , Kitano Fusato , Hasegawa Kohei , Urabe Toshiaki , Hosoya Yoshihiro
Published: December 2016

The effects of heat‐treatment conditions on mechanical properties are comprehensively investigated to optimise the industrial process of the 590 MPa grade TRIP steel sheet with the metallurgical understanding. The substantial effect of the thermal conditions are first clarified by laboratory investigation, which includes the effects of annealing conditions, cooling conditions from intercritical temperature to austempering temperature and austempering conditions. The results indicate that the optimum annealing temperature is between 800 and 850 °C and the mechanical properties are hardly influenced by the annealing time between 30 and 120 s at an annealing temperature of 825 °C. It is also suggested that the optimum quenching rate is 45 °C/s to obtain the stable properties of the products and the optimum austempering conditions are 425 °C with over 300 s in case of a constant temperature austempering. Based on the laboratory investigation, mill trial is performed using the NKK No.4‐CAL in Fukuyama works. The heat treatment conditions are intentionally varied to examine minutely the stability of the production. The mechanical properties are sensitive to the austempering start temperature, when the austempering temperature is gradually decreased during austempering in the industrial conditions for the stable operation without meanders. Excellent mechanical properties can be obtained by controlling the austempering start temperature between 445 and 460 °C. On the contrary, the properties deteriorate in case of the austempering start temperature over 470 °C although the amount of retained austenite is the same or slightly larger than the material which exhibits excellent properties. This is because the retained austenite is less stable in the high‐temperature austempered material caused by less bainite transformation.
Low‐alloy TRIP steels: a correlation between mechanical properties and the retained austenite stability
Authors: Vasilakos Apostolos N. , Ohlert Joachim , Giasla Katerina , Haidemenopoulos Gregory N. , Bleck Wolfgang
Published: December 2016

In recent years the technology of low‐alloy TRIP steels has considerably advanced. The mechanical properties are characterised by a combination of high yield strength and high uniform elongation as well as enhanced formability. In the present work an effort to correlate mechanical properties with the retained austenite stability was made. Two low‐alloy TRIP steels were investigated. The first of them represents a typical composition of the low‐alloy TRIP steels, while the other one contains aluminum as alloying element. The influence of the heat treatment on the mechanical properties and especially on the amount and stability of the retained austenite was determined. The retained austenite stability was measured with a single specimen technique, in which a tensile specimen was used to determine the MσS temperature with a loading‐unloading procedure. The results showed that there is a strong influence of the stability of the retained austenite on the mechanical properties. Increased stability combined with a high amount of retained austenite, exhibited an increase in both, yield strength and uniform elongation while increased amount of retained austenite with low stability did not show the same good combination of mechanical properties. The results clearly indicate that in order to get the maximum TRIP effect, a good combination of austenite stability and amount is required.
Influence of silicon, aluminium, phosphorus and copper on the phase transformations of low alloyed TRIP‐steels
Authors: Traint Sandra , Pichler Andreas , Hauzenberger Karl , Stiaszny Peter , Werner Ewald
Published: December 2016

Although silicon is very Important to prevent carbide precipitation during annealing of low‐alloyed TRIP‐steels and thus allows the austenite to be stabilized by carbon, it causes problems during processing. Therefore, other alloying elements having a similar effect as silicon have to be considered. Possible candidates to substitute or reduce silicon are aluminium, copper and/or phosphorus, which are supposed to be capable of suppressing carbide formation, too.

The influence of reduced silicon contents in combination with alloying elements being capable of substituting silicon completely or partially on the phase transformations occurring during heat treatment is studied. The results of the investigations are compared with a conventional low alloyed TRIP‐steel. The phase transformations are investigated by dilatometric measurements on cold rolled material. The influence of the cooling rate after the intercritical annealing on the transformation behaviour of the austenite upon cooling and isothermal holding in the bainitic range is studied. The interpretation of the phase transformations are supported by investigations of the microstructure via light microscopy and measuring the content of retained austenite using a magnetic volumetric method.
Forming response of retained austenite in a C‐Si‐Mn high strength TRIP sheet steel
Authors: Streicher Amy M. , Speer John G. , Matlock David K.
Published: December 2016

TRIP sheet steels typically consist of ferrite, bainite, retained austenite, and martensite. The retained austenite is of particular importance because its deformation‐induced transformation to martensite contributes to excellent combinations of strength and ductility. While information is available regarding austenite response in uniaxial tension, less information is available for TRIP steels with respect to the forming response of retained austenite in complex strain states. Therefore, the purpose of this work was to study the austenite transformation behaviour in different strain paths by determining the amount of retained austenite before and after forming. Forming experiments were performed on a high strength 0.19C‐1.63Si‐1.59Mn TRIP sheet steel 1.2 mm in thickness in two different strain conditions, uniaxial tension (ε1 = ‐2ε2) and balanced biaxial stretching (ε1 = ε2). Specimens were formed to strains ranging from zero to approximately 0.2 effective (von Mises) strain. Specimens were tested both longitudinally and transverse to the rolling direction in uniaxial tension, and subtle mechanical property differences were found.

The volume fraction of austenite, determined with X‐ray diffraction subsequent to forming, was found to decrease with increasing strain for both forming modes. Some modification in the crystallographic texture of the ferrite was observed with increasing strain, in specimens tested in the balanced biaxial stretch condition. This trend was not evident in the uniaxial tensile test results. Slight differences were found in the transformation behaviour of the austenite when formed in different strain conditions. More austenite transformed in specimens tested parallel to the rolling direction than transverse to the rolling direction in uniaxial tension. The amount of austenite transformed during biaxial stretching was determined to be greater than the amount transformed in uniaxial tension for specimens tested transverse to the rolling direction at an equivalent von Mises strain. The amount of austenite that transformed in biaxial tension, however, was comparable to the amount of austenite that transformed in specimens tested longitudinal to the rolling direction in uniaxial tension.