bluuebunny/crossref_metadata_2025 huggingface dataset:
Recovery, recrystallization and grain growth in 0.03 C, 1.8 Si, 0.3 Al steels with and without addition of 0.05% of antimony
Authors: Vodopivec Franc , Jenko Monica , Steiner‐Petrovic Darja , Breskvar Bojan , Marinšek Filip
Published: December 2016

The investigation was carried out on two laboratory steels elaborated from identical base materials, one with 0.05% Sb and an industrial steel as‐delivered and after decarburisation. Cold rolled 0.5 mm sheets were prepared by laboratory rolling and investigated after annealing in temperature range 550 to 800°C for 0.5 to 60 m. Antimony has no effect on recovery in temperature range 550 to 625°C. Rare recrystallization nuclei were found at grain boundaries only in the decarburized steel, in all other steels nucleii appeared and grew only inside of deformed grains. At recrystallization finished grains were coarser in antimony and decarburized steels. The explanation is that less numerous nuclei grew for a longer time in the deformed matrix. The size of recrystallized grains was proportional to the square root of the annealing time. Recrystallized grain growth was faster in antimony‐free laboratory and in decarburized industrial steels, while the growth activation energy is very similar in antimony and decarburized steels. The growth activation energy was greater in antimony‐free laboratory and in as‐delivered industrial steels. It was similar to the activation energy of part of the recovery and near to the activation energy of iron self‐diffusion in ferrite. No difference was found in grain growth topology between the antimony and the comparative laboratory steels. Results indicate a similar effect of the presence of 0.05% of antimony and the decreased carbon content in steel.
Effects of bubble expansion on wear of refractory for BOF stirring plugs embedding tuyères
Authors: Yang Qixing , Björkman Bo , Carlsson Göran
Published: December 2016

Single tuyère wear tests of MgO‐C and burnt magnesia bricks were performed to study relations between tuyère characteristics and refractory wear parameters, with emphasis on the wear zone geometry. Either Ar or N2 was used as injected gas and the test temperature for liquid metal was 1400, 1550 and 1700°C. A bubble expansion wear mechanism was proposed for the mechanical wear of tuyère refractory by comparison of bubble radii and the wear zone geometry of refractory bricks and H3BO3 disks. Equations are derived to predict the deep and shear wear zone radii and the refractory wear rate at values of the nominal Mach number up to one. These equations can be used for an optimum design of single‐ and multiple‐tuyère plugs for combined blowing BOF, as well as for optimization of gas stirring operation to reduce the wear of MgO‐C refractory around the tuyère and for the plugs.
Multiple regression analysis of Jominy hardenability data for boron treated steels
Authors: Komenda Jacek , Sandström Rolf , Tukiainen Matti
Published: December 2016

The relations between chemical composition and their hardenability of boron treated steels have been investigated using a multiple regression analysis method. A linear model of regression was chosen. The free boron content that is effective for the hardenability was calculated using a model proposed by Jansson. The regression analysis for 1261 steel heats provided equations that were statistically significant at the 95% level. All heats met the specification according to the nordic countries producers Classification. The Variation in chemical composition explained typically 80 to 90% of the Variation in the hardenability. In the regression analysis elements which did not significantly contribute to the calculated hardness according to the F test were eliminated. Carbon, silicon, manganese, phosphorus and chromium were of importance at all Jominy distances, nickel, vanadium, boron and nitrogen at distances above 6 mm. After the regression analysis it was demonstrated that very few outliers were present in the data set, i.e. data points outside four times the standard deviation. The model has successfully been used in industrial practice replacing some of the necessary Jominy tests.
Representation of thermodynamic properties of quaternary systems using interaction parameters
Authors: Hajra Jnan Prakash , Jayaganthan Rengaswamy , Divakar Mantha
Published: December 2016

Integral excess free energy of a quaternary system has been expressed in terms of the MacLaurin infinite series. The series is subjected to appropriate boundary conditions and each of the derivatives correlated to the corresponding interaction coefficients. The derivation of the partial functions involves extensive summation of various infinite series pertaining to the first order and quaternary parameters to remove any truncational error. The thermodynamic consistency of the derived partials has been established based on the Gibbs‐Duhem relations. The equations are used to interpret the thermodynamic properties of the Fe‐Cr‐Ni‐N system.
Equilibria of Ce‐Al‐O and Nd‐Al‐O in molten iron
Authors: Diao Shusheng , Han Qiyong , Lin Gang , Chen Dong
Published: December 2016

Equilibrium of Ce‐Al‐O or Nd‐Al‐O system in molten iron was studied by separately melting radioactive isotope 141Ce or 147Nd in an Al2O3 crucible filled with pure iron to form 141CeAlO3 or 147NdAlO3 around its inner wall. The content of dissolved Ce or Nd in iron was determined by means of electrolysis in anhydrous electrolyte and radioassay. The concentration of dissolved Al in iron was obtained by photometry and followed by calculation. Activity of oxygen in liquid iron was directly measured by solid electrolyte sensors made of ZrO2(MgO) tube. By extrapolation of data obtained, the temperature dependence of the equilibrium constant of RE‐Al‐O in molten iron, , or of interaction coefficient, may be described as:

urn:x-wiley:01774832:srin01171:equation:srin01171-math-0001
Deep drawable ultra low carbon Ti IF steels hot rolled in the ferrite region
Authors: De Paepe Annick , Herman Jean Claude , Leroy Vincent
Published: December 2016

The control of the amount of solute carbon in ultra low carbon Ti IF steels during ferrite rolling and subsequent recrystallization is of prime importance for the development of an appropriate recrystallization texture and for the production of thin deep drawable hot strips. In the present work, the effect of the solute carbon content and the rolling conditions on the recrystallization texture after ferrite rolling and on the corresponding Lankford value was quantified. Therefore, ultra low carbon Ti IF steels with different sulphur and titanium contents were rolled in the ferrite region, in order to obtain a variation in solute carbon content (from 0 to about 10 ppm) at the ferritic rolling temperatures. It was shown that a deep drawing grade (rmean> 1.4) can be obtained if the chemical composition of the steel guarantees a complete stabilisation of the solute carbon in the austenitic temperature region and if sufficient strain (85%) is given in the finishing train at temperatures lower than about 800°C. It can be concluded that the sulphur and titanium contents have to be chosen slightly higher in comparison to the conventional Ti IF steel grades used for cold rolling and annealing.
Aluminised steel grades with improved coating stability at high temperatures
Authors: De Cooman Bruno C. , Hubert Roger A.
Published: December 2016

The present paper reviews the physical principles, the metallurgical development and the industrial implementation of two new grades of type 1 aluminised sheet steels. The materials are characterised by a much improved high temperature behaviour resulting from the inhibition of the growth of intermetallic phases due to the formation of an AIN diffusion barrier. This diffusion barrier is due to minute amounts of interstitial N (< 20ppm) in the substrate at the time of use under high temperatures of the finished part. An original metallurgical method, which is different from existing or patented metallurgical routes, was used to develop the new products. Two grades were developed, which correspond roughly to the DX52D+AS commercial grade and DX54D+AS deepdrawing grade according to the EN10154 specification.
The influence of nitrogen and orientation on the rolling deformation mechanisms of austenitic single crystals
Authors: Akdut Nuri , Keichel Jörg , Foct Jacques
Published: December 2016

The effect of nitrogen content and initial orientation on the deformation mechanisms of austenitic single crystals was investigated. From a nitrogen alloyed and a nitrogen free single crystal two initial orientations were cut out and cold rolled up to 90% thickness reduction, the corresponding {111} pole figures were measured and the slip traces were analyzed from the longitudinal section.

In one of the nitrogen alloyed austenitic single crystals massive microcrack formation was observed. This observation was discussed in terms of the planarity of slip caused by the interstitially solved alloying element nitrogen. Nitrogen has a strong affinity to dislocations and thus alters the slip character from homogeneous to planar and the slip distribution from single slip to coarse slip. The present investigation proves that the coarse planar slip caused by the alloying element nitrogen in dependency of the initial orientation is responsible for the observed crack formation during rolling. The planarity of slip is also reflected in the measured pole figures. The {111} poles of the nitrogen alloyed single crystals show less scattering and higher maximum intensities than the poles of the nitrogen free single crystals. The differences were attributed to the influence of the nitrogen content on deformation mechanisms.
Chemical potentials of oxygen for three‐phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt
Authors: Take‐uchi Kotaro , E‐naka Takashi , Kon‐no Norimitsu , Hosotani Yozo , Orimoto Takashi , Iwase Masanori
Published: December 2016

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO2 mixture as reference electrode, the equilibrium oxygen partial pressures for three‐phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt were determined as:

‐ log {PO2 (CS + C3S2 + L)/bar} = ‐ 3.22 13000/(T/K) ± 0.05

‐ log {PO2 (C3S2 + C2S + L)/bar} = ‐ 0.92 16400/ (T/K) ± 0.04.

respectively, where CS, C3S2 and C2S indicate CaSiO3(s), Ca3Si2O7(s). and Ca2SiO4(s), respectively.
Dezincification of galvanized steel scrap by electrolyzing
Authors: Ma Zhongting , Chen Qibing , Ni Ruiming , Wei Shoukun
Published: December 2016

To remove and retrieve Zn from galvanized scrap by electrolyzing with caustic solution is experimentally confirmed to be a reasonable approach and the galvanized scrap can be completely purified. The concentrations of NaOH and ZnO, and the temperature of electrolyte are important factors to influence the critical current density of passivation of Zn layer. The electrolyzing parameters such as the applied current density, temperature of electrolyte, and the concentrations of NaOH and ZnO are optimized by experiments.
A study on weldability of zinc‐coated steel sheets in lap joint configuration
Authors: El‐Batahgy Abdel‐Monem
Published: December 2016

The weldability of Zn‐coated steel sheets 0.7 mm thick was investigated using resistance spot welding process. The effect of welding current, welding time and holding time on weld nugget characteristics, microstructure, and mechanical properties was discussed. Then, the possibility of replacing this welding process with laser beam welding was outlined. In this respect, quality of weld joints as a function of zinc removal by grinding prior to welding was evaluated.

It is found that resistance spot welding current and time are the most significant parameters in affecting both expulsion and Zn‐induced porosity. Expulsion was avoided and Zn‐induced porosity was reduced with the decrease in welding current and/or welding time. Zn‐induced porosity was completely eliminated by zinc‐removal by grinding prior to welding. The best weld joint concerning nugget characteristics, soundness and tensile shear strength was obtained using welding current of 10 kA, weld cycle of 20, holding cycle of 18.

Unlike resistance spot welds, high quality of CO2 laser welds free from Zn‐induced porosity could be made without zinc removal by grinding before welding.
Deformation process of a droplet impinging on a hot oxide‐scaled surface above the Leidenfrost temperature
Authors: Hatta Natsuo , Fujimoto Hitoshi , Takuda Hirohiko
Published: December 2016

This paper is concerned with the collision dynamics of a water droplet impinging on a hot surface heated to above the Leidenfrost temperature, focusing upon the case where the impingement side is rough (oxide‐scaled) with an oxide film. The rough surface has been artificially made by rapidly quenching as‐rolled stainless steel by water spraying, after it has been heated to 1000°C in a furnace. A sequence of photographs showing the progressive stages of droplet deformation have been taken on several Weber number conditions. It has been found that the droplet configuration is not axially symmetric around the initial impact point even at an early stage immediately after collision and that the irregularity of the droplet configuration is amplified as the droplet deformation proceeds. With increasing Weber number, the irregularity has been seen to be more remarkable in the later stage and finally the droplet breaks up into some parts. Therefore, the critical Weber number to specify whether or not the droplet is disintegrated on the rough surface has been found to become small compared with the smooth surface case.
Investigations on the rapid solidification of steel droplets in the plasma‐rotating‐electrode‐process
Authors: Wosch Erwin , Prikhodovski Andrei , Feldhaus Stephan , Gammal Tarek El
Published: December 2016

For a better understanding of the solidification structure of the powder produced in the plasma‐rotating‐electrode‐process (Prep) a theoretical model is developed to calculate the solidification time and cooling rate. The relative velocity between particle and surrounding medium is the decisive factor in heat transfer. Cooling rates of up to 106 K/s can be reached for small particles. To investigate the solidification structure the secondary dendrite arm spacing (Das) of the powders is measured. The relation between Das and solidification time given by Kurz is also valid for Prep. The present paper summarizes the results and describes the mathematical model.
Some applications of neural networks for prediction of blast furnace irregularities
Authors: Zuo Guangqing , Ma Jitang , Björkman Bo
Published: December 2016

The on‐line analysis of operational data and prediction of furnace irregularities, though difficult, are essential for the improvement of the control of blast furnace operation. Three models based on artificial neural networks for the recognition of top gas distribution, distributions of the heat fluxes through the furnace wall, and for the prediction of slips have been designed. The off‐line test results showed that a trained perceptron network could recognise various types of top gas profiles. A classifier consisting of a self‐organising feature map network and a learning vector quantizer could classify the characteristic patterns of heat flux distribution; and a model based on a back propagation network could properly predict the probability of upcoming slips in advance. The most important operational variables needed for predicting slips have also been extracted. It has been proved that the neural network used has a good capability of predicting furnace irregularities.
Friction in sheet forming with soft and hard tooling
Authors: Schey John A.
Published: December 2016

Comparative studies were conducted with the drawbead‐simulation (DBS) test on a bare steel, a galvannealed steel, three electrogalvanized steels, and a hot‐dip galvanized steel as representatives of the major classes of steel sheets used in the automotive industry. Drawbeads of bare, plasma‐nitrided and hard chromium‐coated tool steels were prepared with various surface finishes. The zinc alloy Kirksite represented the soft tooling used in die tryout. A low‐viscosity mineral oil, neat and compounded with oleic acid or a borate compound, served as lubricant. Correlation between friction on hard and soft surfaces was governed primarily by the extent and stability of a zinc transfer layer on the hard beads. Kirksite may be regarded as the equivalent of a very stable, more hard and less reactive transfer film. Correlation was generally better when the sheet surface was capable of entrapping the lubricant, when oleic acid (a boundary additive) was absent, borate (a parting compound) was present, and the plowing component of friction was low.
Influence of friction on the material flow during precision forging of helical gears
Authors: Doege Eckart , Neubauer Ingo , Bohnsack Rüdiger
Published: December 2016

At the Institute of Metal forming and Metal forming machine tools (IFUM), University of Hannover, helical gearwheels are produced from cylindrical billets using single state precision forging processes. For a process integrated heat treatment, the workpiece materials need to be carburized already before the forming operation. Thus, in contrast to conventional manufacture, an inhomogeneous case depth distribution is obtained resulting from the material flow during forming. A numerical process simulation with the finite element method (FEM) enables to predict this distribution along the shape of the teeth. The performed experimental and numerical investigations illustrate the influence of friction conditions on the material flow and thus its influence on the case depth distribution.
Some aspects of fracture mechanics research during the last 25 years
Authors: Hagedorn Karl Edgar , Pardun Markus
Published: December 2016

A review is given of the various concepts of fracture mechanics, furthermore of their application to assess the toughness of steels and to guarantee the safety of structures containing cracks. The three most important parameters are the stress‐intensity factor KI for linear elastic fracture mechanics (LEFM), the crack tip opening displacement CTOD and the J‐integral for elastic‐plastic fracture mechanics (EPFM). The ASTM designation E 1820‐96 provides a common method for determining all applicable toughness parameters from a single test, including R‐curves. Many investigations dealt with the numerous influences on these parameters, e.g. specimen geometry arid temperature and strain rate. Various failure concepts have been developed. The method of LEFM based on plane strain fracture toughness KIc is well established for high strength steels or low temperatures. For modern steels with high toughness the more complicated concepts of EPFM have to be applied. Because of the availability of commercial software for FE‐calculations the application of the J‐integral has become widespread in recent years. A number of approximative methods has been elaborated, e.g. CTOD‐design‐curve, BSI PD6493:1991, CEGB‐R6‐method, ETM, Eurocode 3 Annex C. Although the theory of fracture mechanics regards the material as an isotropic continuum the question is of great importance, how its materials parameters depend on the microstructure of the steels. Systematic investigations with the aid of the hot deformation simulator Wumsi showed the favourable material properties of fracture mechanics resulting from thermomechanical treatment. Many models were published for the quantitative correlation between microstructure and toughness parameters, mainly KIc. At the moment the modified Gurson model is in widespread use, which allows the prediction of J‐R‐curves.
Mixing enthalpy measurements in the liquid ternary system iron‐nickel‐chromium and its binaries
Authors: Thiedemann Uwe , Rösner‐Kuhn Michael , Matson Douglas M. , Kuppermann Gunnar , Drewes Karsten , Flemings Merton C. , Frohberg Martin G.
Published: December 2016

The mixing enthalpies of liquid binary iron‐nickel, nickel‐chromium and iron‐chromium alloys were measured by levitation alloying calorimetry. The mixing enthalpy of iron‐nickel alloys is asymmetric and was described by an equation according to the modified quasichemical solution model. Liquid nickel‐chromium alloys were determined to conform to a regular solution model whereas the system iron‐chromium behaves ideally. Based upon the analytical descriptions obtained for the binary systems an isoenthalpy diagram for liquid ternary iron‐nickel‐chromium alloys was calculated. Mixing enthalpy measurements of the concentration section Fe35Ni65 ‐ Cr are in agreement with the model calculation. Iron rich alloys of the system tend to almost ideal behaviour whereas nickel rich alloys are characterized by negative mixing enthalpies up to ‐5 kJ/mol.
Compression of process data with a wavelet method
Authors: Franzen Andreas
Published: December 2016

The subject of this paper is a method for compressing noisy measurement data as far as possible without unacceptable loss of relevant information. This is achieved by transformation into wavelet space and conversion of the wavelet coefficients to small integers. The resulting data file has a high redundancy. Thus, its size can be reduced to some percent of the size of the original data file by standard lossless data compression. The method described is simple and universally applicable.
Water spray cooling of stainless and C‐Mn steel
Authors: Olden Vigdis , Raudenský Miroslav , Onsrud Kristin , Hummel Wolfgang
Published: December 2016

This paper describes laboratory cooling experiments of C‐Mn and stainless steel with a water/air nozzle. Experiments included use of both the steady state and the transient experimental method. The heat transfer coefficient was calculated both analytically and by a numerical method.

The heat transfer coefficient was evaluated as a function of steel surface temperature, water flux, material and water/air flow.

It was found that by increasing the water flux the heat transfer coefficient also increased. The Leidenfrost point was shifted to higher temperatures. Increasing air flow was also found to increase the heat transfer coefficient. Maximum heat transfer coefficient was twice as large for the C‐Mn steel as for the stainless steel.

Comparison of the steady state and transient experimental method showed good agreement in the temperature range 200 – 500°C, and with a water flux of 2I/m2s. Above 500°C it was difficult to obtain stable conditions for the steady state experiments.
Precipitation hardening of HSLA steels
Authors: Militzer Matthias , Poole Warren J. , Sun Weiping
Published: December 2016

A process model to describe the strength contribution from precipitation hardening during coiling after hot rolling has been developed for V and Nb HSLA steels. Experimental measurements of ageing behaviour on the V steel were conducted on coil material which was received in an underaged condition. The size and composition of precipitates was examined on replicas using scanning transmission electron microscopy. The precipitates were observed to be V rich and a substantial increase in precipitate size occurred as a function of ageing time. The modelling approach developed by Shercliff and Ashby for aluminium alloys was extended to microalloyed steels. The model assumes particle coarsening is the rate controlling process and that the precipitates are initially sheared by dislocations with a transition to non‐shearable precipitates at peak strength. After calibration of the model, good agreement was observed between the model predictions and experimental data. A model for ageing in a Nb HSLA steel was also developed using literature values for the ageing behaviour.
Crack susceptibility of medium and high alloyed tool steels under continuous casting conditions
Authors: Flesch Roman , Bleck Wolfgang
Published: December 2016

Hot tensile tests after partial melting of the specimens were carried out on medium and high alloyed tool steels and their mechanical properties (maximum force and reduction of area) were determined in the temperature range between liquidus and 900°C. Cooling conditions and strain rates were varied in this range. The temperature ranges of reduced ductility were determined, the metallurgical reasons for embrittlement were investigated by means of metallographic and microprobe analysis. The crack susceptibility is related to an enrich‐ment of carbon and carbide forming elements in cold and hot working steels, and to the high S content in the segregated zone of the laminate forming steels. The crack susceptibility can be minimized by low strain rates combined with a strong secondary cooling.
Influence of the Al2O3‐contents in the ternary‐systems (FeO, MnO, CaO, MgO)‐ Al2O3‐SiO2 on the course of the mixture gaps in the ternary space
Authors: Schürmann Eberhard
Published: December 2016

In accordance with the previous phase equilibria in the ternary systems (FeO, MnO, CaO, MgO)‐ Al2O3‐SiO2 even small Al2O3‐contents should be sufficient to close the wide mixture gaps in the binary edge systems of FeO‐SiO2, MnO‐SiO2, CaO‐SiO2 and MgO‐SiO2, which are stable in the temperature range from 1700 to 2100‐2200°C. Thermodynamically this acceptance is not impossible but rather improb‐able. Based on phase‐theoretical considerations and the previous results of literature about the course of an unstable mixture gap in the system SiO2‐Al2O3 two thermodynamically founded versions were developed as possible, resulting phase equilibria in the SiO2‐rich, but experimentally not exactly examined part of the mentioned ternary‐systems, and were added to the experimentally secured sections of these systems unproblematically.
Quantification of precipitates in advanced creep resistant 9‐12% Cr steels
Authors: Hofer Peter , Cerjak Horst , Schaffernak Bernhard , Warbichler Peter
Published: December 2016

In this paper a procedure is introduced for the quantification of precipitates appearing in 9‐12°Cr‐steels. Results gained from conventional transmission electron microscopic (TEM) investigations are compared with results from energy filtering transmission electron microscopic (EFTEM) investigations. The study was performed on a creep rupture specimen of the cast material G‐X12CrMoWVNbN10‐1‐1 exposed at 600°C and ruptured after 33000 h. The size distribution of M23C6 carbides, MX phase and Laves phase were measured for both the un‐stressed head and the stressed shank (gauge length) part of the investigated specimen. In particular, problems and sources of uncertainty concerning the quantitative determination of particle parameters in this type of steel are discussed.

It is shown that quantification of the MX‐particles by means of TEM bright field images is hardly possible. The size distributions of M23C6 carbides and MX phase overlap significantly which makes a separation based only on their size nearly impossible. Only Laves phase occupies a different size range. The difference between the size distributions of head and shank is pronounced only for M23C6 carbides. The measured particle distributions obey more closely a log‐normal distribution rather than a normal distribution.
Kinetics of decarburisation of levitating iron drops by oxygen
Authors: Simento Noel , Lee Hae‐Geon , Hayes Peter C.
Published: December 2016

This work is focused on determining the rate controlling mechanisms of decarburisation of iron‐carbon droplets with gas mixtures containing up to 10% oxygen at 1723 K. The results indicate that the decarburisation rate is limited by the transport of oxygen in the bulk gas to the melt surface. The work also shows the absence of any significant resistance to decarburisation from interfacial chemical kinetics or gas phase reactions. Phosphorus in the melt shows no influence on the rate of decarburisation. Chromium has no significant effect on the decarburisation rate.
Production of high carbon ferromanganese using manganese rich slag in the charge
Authors: Eissa Mamdouh , El‐Faramawy Hoda , Farid Gamal
Published: December 2016

The possibility of replacement of the high cost sinter manganese ore by manganese rich slag for the production of high carbon ferromanganese was experimentally demonstrated. The experimental heats were designed and carried out to optimize this replacement through the adjustment of different production parameters. The results of pilot plant experimental heats showed that replacement of 50% of the sinter in the blend (or 25% of the blend) by slag containing 32% Mn and operation under slag basicity 0.9 and low (MgO)/(CaO) ratio of about 0.2‐0.3 are the optimum conditions to attain the highest manganese content in the produced ferromanganese, the highest manganese recovery and the highest metallic yield. The industrial application of reusing manganese slag clarified the economic efficiency of charging manganese slag up to 20‐25% of the blend in reducing the production cost due to reducing the cost of manganese ores. Charging of 20‐25% manganese slag reduces the cost of manganese ores and the total production cost by about 13 and 6% respectively, comparing with the conventional technology (without using manganese slag in the blend).
The tensile failure of mild steel oxides under hot rolling conditions
Authors: Krzyzanowski Michal , Beynon John H.
Published: December 2016

The failure of oxide scales formed on mild steel (mass contents of 0.17% C, 0.13% Si, 0.72% Mn) was investigated using a high‐temperature tensile test technique over the temperature range 830 – 1150°C. Strain and strain rates used were 1.5 – 20% and 0.02 – 4.0 s−1, respectively. The scales were 10 – 300 μm thick. The variations of these test parameters were chosen to approximate the tensile loading of the oxidised surface layer at the slab faces just before roll contact at the upper or lower surfaces. Oxide scales formed cannot be assumed either to be perfectly adhering during tensile loading, in the sense of slipping, or to be fully brittle. Two limit modes leading to oxide spallation have been observed which are strongly influenced by the temperature, strain rate and strain. For the first mode initial through‐scale cracking occurs followed by initiation and propagation of a crack along the oxide‐metal interface between adjacent cracks. The second mode corresponds to the slipping of the oxide scale relative to the metal surface before spallation. The delamination and following slipping of the oxide raft can take place along the interface within the non‐homogeneous oxide scale.
Electrochemical sensors for a continuous determination of aluminium and phosphorus activity in steel
Authors: Borgianni Carlo , Pistelli Maria Ilaria
Published: December 2016

In the present work, two types of electrochemical sensors are described for an on line and continuous measurement of aluminium and phosphorus activity in liquid steel. Sensitivity, reproducibility, response speed and working life are investigated. At 1873 K, data of electromotive force (EMF) vs. Al and P concentrations in liquid steel are obtained for a phosphorus content from 0.001 up to 0.5% and aluminium content from 0.001 up to 0.05%. These data show that a linear relationship exists between the logarithm of the Al and P concentration and the measured EMF. Equilibria related to the P and Al sensors involve 5 and 3 electrons respectively. Taking into account the observed sensitivity and the working life, these sensors can be used for continuous and online control.
Possibilities of counter‐current scrap pre‐heating with melting by use of 100% fossil energy
Authors: Zhang Liuyi , Oeters Franz
Published: December 2016

It shall be found out, how far scrap can be heated without too much oxidation in a shaft with counter‐current flow of scrap and heating gas if the heating gas is stepwise post‐combusted during its rising in the shaft. The scrap is a mixture of plates, cylinders and spheres obeying a log‐normal distribution function of the size. Heat transfer is by convection and radiation. Scrap oxidation kinetics is determined by the phase boundary reaction and by diffusion in the oxide layer. The model calculates the temperature of the scrap size classes and of the gas, and the oxidation of the scrap along the shaft height. The preheated scrap is melted in a smelter. It was found that under steady‐state conditions with a moving scrap heap, about 60% post‐combustion difference between bottom and top of the shaft is possible if the scrap initially has room temperature and is then heated up as far as possible without melting. Scrap oxidation in the shaft is only 0.2% of the production. This is possible by the short residence time of a moving scrap heap in the hot post‐combustion planes where the oxidation rate is high. Calculations for a stationary heap, where the scrap residence time in the hot zones is much longer, showed that here, the oxidation is more than 10 times higher.
Power increase and metallurgical effects during arc heating of liquid steel due to the addition of molecular gases
Authors: Neuschütz Dieter , Hahn Ingo , Spirine Denis , Storsberg Lutz
Published: December 2016

Molecular gases were laterally injected into the gas atmosphere of a pilot furnace containing 200 kg of steel melt and heated by two AC argon plasma arcs. The power increase in the arcs obtained by the injection was 12 % for 20 % N2, 70 % for 20 % CO2, 32 % for 3 % CH4, and 62 % for 3 % C3H8. Mixtures of CO2 and hydrocarbons were also tested. CO2 acted as an oxidizing agent for steel components with oxygen transfer efficiencies of 28 % in the case of slag‐free steel melts and of 10 % in the presence of slag, while the addition of CH4 did not cause any noticeable carbon transfer to the melt.
Surface and interfacial properties of Fe‐30%Cr‐S alloys in contact with alumina
Authors: Chung Yongsug , Cramb Alan W.
Published: December 2016

The surface tension of liquid iron‐30% chromium alloys at 1823 K was determined as a function of sulfur content using the sessile drop technique. The surface tension of iron‐30% chromium alloys decreases with increasing sulfur content and the results can be described by the following equation for sulfur mass contents of greater than 21 ppm: γ = 1592 – 178ln(1 + 145aS)mN/m. The contact angle between the droplet and an alumina substrate was also measured and found to decrease from 142° at 21 ppm sulfur activity to 80° at a sulfur activity of 0.53 (related to the standard state with a mass content of 1%). From these measurements the interfacial energy between liquid iron‐30% chromium alloys and alumina was calculated using Young's equation. The interfacial tension can be described by the following equation: γ = 2026 – 519ln(1 + 29aS)mN/m.
The first shell formation in meniscus free casting
Authors: Courbe Pierre , Jolivet Jean‐Marc , Lesoult Gérard , Perrin Eric , Nilles Paul
Published: December 2016

The meniscus free casting technology was jointly developed by CRM (Centre de Recherches Métallurgiques) and Irsid (Central Research Laboratory of Usinor) in order to significantly improve the surface and subsurface quality of continuously cast long products. This technology realizes a shifting of the meniscus zone upstream of the solidification area by means of a refractory feed‐head located above the mould. In this way, the hydrodynamical perturbations of the meniscus and the meniscus shape do not affect anymore the shell solidification. An important part of the development work was dedicated to the understanding of the solidification mechanisms at the very top of the mould, where the first solidified shell is formed. For that purpose, EMN (Ecole des Mines de Nancy) and Irsid have developed a physical and numerical model of the shell solidification in the new concept. This model takes into account the relative motion between the mould and the product together with two stages of solidification: static near the upper edge of the copper mould and dynamic at the contact of the skin of the cast product. During the casting trials realized at CRM and Irsid, the temperature of the copper on the first 50 mm of the mould and the heat flux extracted were recorded. These values were used to determine the boundary conditions entered into the model. The model calculates the location of the isotherms and the iso‐fraction of solid along the mould wall at each moment of the oscillation cycle. It can predict whether or not the skin is sufficiently solid at the end of the negative strip to be extracted without any damage. When the casting speed increases, the resistance of the skin decreases. In order to alleviate this effect, the influence of the oscillation parameters was studied during continuous casting trials. Sinusoidal and non‐sinusoidal oscillation cycles were investigated. A triangular cycle brings good surface quality for the high carbon grades while a sinusoidal cycle is better suited to the casting of the peritectic and low carbon steel grades. These results are discussed and a guide for the choice of the best oscillation parameters is provided.
Mechanical properties and crack susceptibility of steel during solidification
Authors: Hiebler Herbert , Bernhard Christian
Published: December 2016

The determination of high temperature mechanical properties is a necessity for the better understanding of defect formation during continuous casting of steel. Although a lot of studies have been performed on this topic, some aspects like the influence of cast structure on crack susceptibility are still unclear. The present paper focuses on the effect of carbon on high temperature strength and crack susceptibility. Tensile tests have been performed on steel shells with different carbon content during solidification. The results indicate an important influence of the orientation of the inhomogeneous cast structure towards main stress axis. The initial shell with a thickness of only a few millimetres is more sensitive to defect formation than commonly believed. The critical limits of straining range from about 0.15 to 0.4 %. With increasing shell thickness, the critical strain ascends up to 1.6 %. The detected segregated internal cracks form within the critical temperature range. The strength near solidus temperature is lower than in comparable hot tensile tests, which can also be attributed to the detrimental effect of the inhomogeneous structure. The strength at solidus temperature amounts to 2.5 MPa for higher carbon steels and about 1 MPa for low carbon steels.
Post‐combustion and heat transfer at blowing of oxygen into a carbon monoxide containing slag foam
Authors: Zhang Liuyi , Oeters Franz
Published: December 2016

A combined post‐combustion model (CPM) for smelting reduction processes was developed in a multi‐national research project supported by the European Coal and Steel Commission. The project partners were CSM, Rome, Hoogovens, Ijmuiden, MPI, Düsseldorf, and TUB, Berlin. This paper reports about a heat transfer model developed by TU Berlin within this project. The batch‐type smelting reduction reactor has a two‐layered slag: an upper foamy and a lower less foamy slag. A bubble stream of (CO+H2) gas originating from the iron oxide reduction reaction with coal in the lower slag flows upwards. The rising (CO+H2) gas is post‐combusted by three oxygen jets blown horizontally into the upper part of the slag. A flame zone, and above the flame a mixing and a bubble zone form, in which post‐combustion reaction and transfer of the post‐combustion heat to the slag take place. The modelling of the flame zone was the subject of a previous paper. The present report describes models of the mixing and the bubble zone and of the occurrences in the gas space above the slag. The macro‐kinetics of the overall heat transfer process including slag recirculation and heat transfer from the upper foamy to the lower dense slag are presented further. The model calculations provide information about the distribution of the post‐combustion and the heat transfer processes over the single zones as functions of the important internal process parameters. Further, the oxygen utilisation, the heat efficiency and the temperatures at various locations of the process are described as functions of the ratio of post‐combustion oxygen flow rate to (CO+H2) evolution rate. In all the calculations a specific gas through‐put of carbon monoxide of 3 mol/t•s is assumed. This value corresponds to 510 mol/s for the assumed melt of 170 t. The model shows that heat transfer efficiencies of more than 90 % and slag temperatures of less than 1700°C are possible, if the slag circulation rate is 300 kg/s. Lower circulation rates lead to higher slag temperatures and worse heat transfer efficiencies. Controlled slag circulation is thus an important process tool.
Investigations of the solidification structure of continuously cast slabs
Authors: Weisgerber Bernadette , Hecht Michael , Harste Klaus
Published: December 2016

A study of solidification phenomena performed under industrial conditions is presented. The solidification structure of high carbon, medium carbon and microalloyed steel grades was observed and correlated to casting parameters such as superheat and secondary cooling. Experimental data of dendrite morphology are related to calculated solidification variables. The calculation is based on the solution of the enthalpy balance equation. An expression for the dependence of secondary dendrite arm spacing on solidification variables is proposed for columnar growth. The results are compared to the findings of other authors. The effect of chemical composition on secondary dendrite arm spacing was observed. Therefore the developed relationships are extended to carbon content on the basis of the presented experimental data.
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.
Modelling and simulation of dispersed phase formation in steels
Authors: Prikhodovski Andrei , Maubach Marcus , Hurtado Iñaki , Neuschütz Dieter
Published: December 2016

Modelling has proven to be an efficient way of cutting time and costs associated with the investigation of materials properties. Two examples of thermodynamic modelling are presented which describe different phenomena in steels: the precipitation of carbonitrides and Ti‐based inclusions in IF steels, and the coarsening of dispersed phases in HSLA steels. The underlying mode of describing the phases is the Calphad method, which has been combined with diffusion calculations to give results from both microscopic and macroscopic statistical points of view. The results of the calculations show a good agreement with the experimental data available in literature, and the methodology may be considered as illustrative and extendible to a variety of similar cases.
Examples of microstructure analysis by orientation imaging microscopy
Authors: Friedel Frank , Zimmermann Eva , Klinkenberg Christian , Pircher Hans
Published: December 2016

The properties of cold‐rolled deep‐drawing steels and electrical sheets, as essential products of flat steel production, depend directly on the microstructural state of the ferrite after primary recrystallization. As the traditional method of microstructural description, optical microscopy reaches its limits in describing the recrystallization or recovery state of the ferrite, because any definite and direct information on the texture, type of grain boundaries, and distortions (dislocation density) in the crystal lattice cannot be obtained with this technique. The recrystallization state can be considered by using conventional X‐ray diffractometry to determine macrotexture. In the past microstructural inhomogeneities which, requiring a local description or grain boundaries, could be investigated only by means of transmission electron microscopy (TEM). Nowadays orientation imaging microscopy (OIM), which is based on electron diffraction and which offers an efficient metallurgical investigation technique, links the above mentioned investigation methods and compensates their disadvantages. The efficiency of orientation imaging microscopy in interaction with conventional metallurgical methods was demonstrated on two steels with local microstructural anomalies. Both were cold rolled and annealed. It was shown that recrystallization in the sheet surface of a Ti‐IF steel was inhibited by fine oxidic precipitates. A recovered microstructure with a distinct {001}<110>‐orientation appeared after annealing. In the case of silicon steel it was evident that recovery and recrystallization depended on the initial grain orientations in the former states of production.
VIS‐spectroscopical measurements of the complex dissociation of the tetrahedral Co2+(O2‐)4‐complexes in silicates
Authors: Okretic Stefano , Nowack Norbert
Published: December 2016

By application of the high temperature method for spectrocopical VIS‐absorption measurements developed by the authors, the position and the height of the bands of the Co2+(O2‐)4‐complex have been investigated and analysed for two chosen silicates. The investigations include a temperature range from room temperature up to a temperature above the liquidus temperature (up to 1743 K). The thermic stability (dissociation degree and dissociation enthalpy) of the Co2+(O2‐)4‐complex in the glassy and the liquid state has been determined. With this paper the authors want to contribute to the research on the chemical structure of liquid slags.
Ferritic rolling to produce soft deep‐drawable thin hot strips
Authors: Tomitz Andreas , Kaspar Radko
Published: December 2016

In a conventional production of deep‐drawable sheets of steel, a hot rolling in austenite and a cold rolling at room temperature together with a subsequent recrystallization annealing are applied with a cold strip as a final product. As a cost saving replacement for this, a thin‐gauge hot strip with a required deep‐drawability can be employed. A conventionally (in austenite) hot rolled strip is hardly applicable for this because of its unsatisfactory texture as well as because of the technical difficulties to produce hot strips with sufficiently small thicknesses. As a promising realization of cost saving thin‐gauge deep‐drawable hot strips of steel, a warm rolling can be applied with reduced finish rolling temperatures. In this practice the finish rolling is shifted down into the temperature region of ferrite. In the present work extensive laboratory tests on IF‐ and ELC‐steel were carried out by using the hot deformation simulator Wumsi. By the measurements of the texture development as well as by the computing of r‐values, the process parameters of ferritic rolling and a subsequent direct recrystallization in the coil of these steels could be optimized.