bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of EAF Off‐Gas Post Combustion in Dedusting Systems using CFD Methods
Authors: Tang Xin , Kirschen Marcus , Abel Markus , Pfeifer Herbert
Published: December 2016

To comply with the increasingly strict environmental regulations, the poisonous off‐gas species, e. g. carbon monoxide (CO), produced in the electric arc furnace (EAF) must be treated in the dedusting system. In this work, gas flow patterns of the off‐gas post combustion in three different dedusting system units were simulated with a computational fluid dynamics (CFD) code: (1) post combustion in a horizontal off‐gas duct, (2) post combustion in a water cooled post combustion chamber without additional energy supply (no gas or air/oxygen injectors) and (3) post combustion in a post combustion chamber with additional energy input (gas, air injectors and ignition burner, case study of VAI‐Fuchs GmbH).

All computational results are illustrated with gas velocity, temperature distribution and chemical species concentration fields for the above three cases. In case 1, the effect of different false air volume flow rates at the gap between EAF elbow and exhaust gas duct on the external post combustion of the off‐gas was investigated. For case 2, the computed temperature and chemical composition (CO, CO2 and O2) of the off‐gas at the post chamber exit are in good agreement with additional measurements. Various operating conditions for case 3 have been studied, including different EAF off‐gas temperatures and compositions, i. e. CO content, in order to optimize oxygen and burner gas flow rates. Residence time distributions in the external post combustion chambers have been calculated for cases 2 and 3. Derived temperature fields of the water cooled walls yield valuable information on thermally stressed parts of post combustion units.

The results obtained in this work may also gain insight to future investigation of combustion of volatile organic components (VOC) or formation of nitrogenoxide (NOx) and permit the optimization of the operation and design of the off‐gas dedusting system units.
Improved Cold Formability by Thermo‐Mechanical Rod Rolling
Authors: Kienreich Robert , Buchmayr Bruno
Published: December 2016

Usually, unalloyed medium carbon steels and 1% chromium steels for cold heading applications are produced by hot rolling, subsequent controlled cooling and soft annealing. It is shown that by thermomechanical rod rolling and slow air cooling at the loop cooling conveyor the tensile strength can be lowered to such an extent so that cost‐intensive soft annealing procedures are not required. The effects of the processing parameters on the microstructural evolution and final mechanical properties of steel grades 23MnB4 and 1% Cr‐steels like 32CrB4, 37Cr4 and 41 Cr4 are tested by a Gleeble machine. Using a microstructural process model, called CAROD, the entire rolling and cooling process has been optimized.
Softening Behaviour after Deformation in the Austenite‐Ferrite Two‐Phase‐Region
Authors: Bleck Wolfgang , Herzig Caroline , Venkatraman Mahadevan
Published: December 2016

Detailed knowledge of the material behaviour during austenite decomposition is of great importance for the development of new strategies in hot strip rolling, like direct and hot charging or ferritic rolling, as well as for the development of new steel grades. Especially the influence on flow curves, precipitation behaviour and microstructure in the hot strip is relevant.

Two steels were investigated with regard to their softening behaviour in ferrite, ferriteaustenite and austenite region. An Avrami type modelling approach, based on the experimental softening results and the microstructural investigation was applied to model the softening in the two‐phase‐region. Thus the quantitative prediction of the softening can be found as a function of temperature, strain rate and interpass time.
Microstructural Aspects and Optimization of Thin Slab Direct Rolling of Steels
Authors: Kaspar Radko
Published: December 2016

By using a thin slab casting simulator combined with the hot deformation simulator WUMSI, laboratory tests were performed to investigate the microstructure processes and mechanical properties in the process of thin slab direct rolling (TSDR). The paper shows the possibilities to improve the initial as‐cast state of microstructure prior to hot rolling (microvoids, dendritic structure, austenite grain size, state of precipitation). The main part of the study is dedicated to the role of microalloying and sulphur for the austenite grain control and for the precipitation hardening in the final structure. On examples of selected low carbon steel grades the effect of the variation of the process parameters of hot rolling and cooling on the microstructure and mechanical properties is presented.
A Contribution to Scale Growth during Hot Rolling of Steel
Authors: Schwerdtfeger Klaus , Zhou Shunxin
Published: December 2016

This work was carried out in context with the development of strip casting by the single‐belt process. In this new process the casting is directly connected with hot rolling which must be carried out at lower speed than in conventional hot rolling, to match the casting rate. It is of interest to theoretically study the effect of low rolling speed on operational parameters and materials behaviour, among them scale formation. In the present investigation it is demonstrated that, under the conditions of hot rolling, the oxidation of iron in air is governed by a mixed mechanism involving diffusion in the oxide and transport of molecular oxygen in the gaseous boundary layer. An algorithm has been formulated for the description of the deformation behaviour of the scale in the roll bite. Scale formation was computed for conventional finishing rolling with a seven stand mill and for in‐line hot rolling of strip produced by the single‐belt process. It is found that the final scale thickness in the single‐belt casting/in‐line hot rolling process is about twice that in conventional hot rolling, for the same strip thickness behind the last stand.
Master Curve Approach: Effects of Last Revision of ASTM E 1921 and Application for different Constructional and Pressure Vessel Steels
Authors: Buchholz Jörg , Dahl Winfried , Langenberg Peter
Published: December 2016

The introduction of the Master Curve Approach enables the description of the scatter of the fracture toughness behaviour of ferritic and martensitic steels in the temperature transition region and in the lower shelf. The Master Curve Approach was standardized in the ASTM E 1921 and is meanwhile widely applied. A main advantage is the clear determination of an objective toughness criterion, the reference temperature T
0, while compensating the scatter of results and existent size effects. Within the last revision ASTM E 1921‐02 some modifications were made which will be exemplified in this article. The current revision and the former ASTM 1921‐97 are compared and the effects are shown at some examples. Censoring and different data selection will be regarded concerning its sensibility to the T
0–temperature determination by the example of a a pressure vessel steel.
The Behaviour of Selenium Impurities During the Addition of Se‐Containing Manganese to Steel Melt
Authors: Aboutalebi M. Reza , Isac Mihaiela , Guthrie Roderick I.L.
Published: December 2016

Manganese is an important alloy addition for alloy steels. It is normally added to steel melts as ferromanganese. However, for the adjustment of melt composition, manganese metal is used as a trimming addition since it has lower levels of impurities than ferromanganese. The manganese used for this purpose is obtained from the electrolytic processing route wherein selenium‐containing additives are added to the electrolyte bath to improve the current efficiency. This practice introduces selenium to the manganese metal. Given that selenium and its compounds are potentially toxic and damaging to the work place and environment, effluents have to be treated in a controlled manner. In order to determine how selenium typically distributes between molten steel, slag and gas phases, a laboratory‐scale experimental study was carried out to evaluate the deportment of selenium following the addition of selenium containing manganese to the steel melt. Contaminated commercial manganese metal, as well as Mn‐Al‐Se spiked briquettes with different selenium contents were added to steel melts at 1600 °C. Selenium recovery to the solidified steel samples varied from 16% to 75%, depending on selenium levels of additions. Owing to the high vapour pressure of selenium, significant amounts of the selenium added to the melt evaporated, reacting with air to form selenium dioxide. SEM analysis of the solidified steel samples revealed that the selenium was largely present as manganese selenide (MnSe) in the form of spherical inclusions within the iron matrix. A thermodynamic assessment on the potential formation of possible selenium compounds within the steel melt suggests that the most stable selenium compound under the test conditions is MnSe, in accord with experiments.
Understanding the Properties of Oxide Scales on Hot Rolled Steel Strip
Authors: Bolt P. Henk
Published: December 2016

Surface quality and downstream processability of hot rolled strip depend on tertiary scale thickness and composition at all process stages, from secondary descaling to the cold coil. TGA oxidation experiments provided the basis for quantitative modelling of scale growth during finishing hot rolling of low carbon steels (with or without Si or P). Finishing temperature (FT), gauge, and (particularly at the edges) coiling temperature (CT) are the main influence factors with respect to scale thickness. Based on HTXRD oxidation trials and microscopic analyses, trendlines are presented that roughly predict the final scale composition as a function of CT, for the coil centre and the edges. It appears that a CT of 400‐600°C, in combination with a coil centre position, is favourable for decomposed wustite, which is the preferred component for a good scale ad‐ and cohesion. Retention of wustite, the most preferred phase in the roll bite but very brittle at room temperature, is promoted by relatively high CTs (particularly with a coil quench) and by very low CTs. Hematite is formed at the edges in case of a high CT. This extremely hard phase is unwanted at any stage.
Prediction of Material Spreading in Hot Open‐Die Forging
Authors: Knap Matjaž , Kugler Goran , Palkowski Heinz , Turk Radomir
Published: December 2016

Prediction of spreading during the hot open‐die forging process is a key issue in the optimal control of forging technology. Exact measurements of the cross‐sectional shape and dimensional changes during forging in industry are very complicated and demand large financial investment, but on the other hand, their contribution to optimization during the forging phase is not essential. Hence the only reasonable choice is to make optimization during the technological planning stage, i.e. before the actual forging. The use of physical simulations and results from forging in the laboratory has confirmed that the ratio between the contact area length and work piece width is not the only influence on material spreading. Additionally, two geometrical parameters, the ratio between the width and the height of the cross‐section and the relative deformation, as well as the temperature of the forged piece must be considered. It is important to treat each material in the model separately.

For prediction of spreading two approaches were chosen, i.e. description in the form of a function in which the coefficients are specific for each grade of steel, and prediction by the application of the neuronal network approach (CAE NN – Conditional Average Estimator, Neural Networks). Each of the approaches has its own characteristics: prediction with CAE NN is more accurate than the description in the form of a function, but the latter is more suitable for modelling hot open‐die forging technology.
The Rheological Behaviour of Metallic Suspensions
Authors: Modigell Michael , Pape Lars , Hufschmidt Markus
Published: December 2016

The knowledge of the rheological behaviour of metallic suspensions is an important issue when simulating die filling in thixoforming processes. Therefore rheological experiments like step‐change in shear rate tests, shear stress ramps and oscillation experiments have been carried out to characterise the flow behaviour of semi‐solid alloys exemplarily for A356 and Sn‐15%Pb. The material exhibits a yield stress and shows shear‐thinning and thixotropic flow behaviour, which is strongly influenced by the solid fraction, the particle shape and size and the degree of particle agglomeration. The instantaneous response on a change in shear rate was observed and pretends shear‐thickening properties. All experiments were carried out in a Couette rheometer. The experimentally gained data are well fitted to a model approach, which consists of a modified Herschel‐Bulkley law and accounts for the time‐dependent effects by introducing a structural parameter κ.
Two‐Phase Simulations as a Development Tool for Thixoforming Processes
Authors: Modigell Michael , Hufschmidt Markus , Petera Jerzy
Published: December 2016

Semi‐solid metal alloys are employed in Thixoforming processes. In the mushy state alloys, consisting of spherical solid particles suspended in a liquid matrix, show shear thinning thixotropic behaviour and exhibit a yield stress. Beyond this the flow behaviour is influenced by the solid fraction, which is dependent on the slurry temperature. Due to the complex flow behaviour of metallic suspensions new concepts of die and process design are required to guarantee a reproducible high quality of the produced parts. To this end a non‐isothermal two‐phase model has been developed and implemented into a proprietary developed FEM software. The model bases on a modified Herschel‐Bulkley approach and comprises the entire non‐Newtonian behaviour of semi‐solid alloys. A specially designed die filling experiment is used to validate the numerical simulation. The experimental set‐up allows to observe the moving flow front during die filling and to measure the pressure. The filling experiments are carried out with various filling velocities and die temperatures.
Numerical Modelling of Semi‐Solid Flow under Processing Conditions
Authors: Kirkwood David H. , Ward Philip J.
Published: December 2016

During the industrial process of semi‐solid forming (or thixoforming) of alloy slurries, typically the operation of die filling takes around 0.1s. During this time period the alloy slug is transformed from a solid‐like structure capable of maintaining its shape, into a liquid‐like slurry able to fill a complex die cavity: this involves a decrease in viscosity of some 6 orders of magnitude. Many attempts to measure thixotropic breakdown experimentally in alloy slurries have relied on the use of concentric cylindrical viscometers in which viscosity changes have been followed after shear rate changes over times above 1s to in excess of 1000 s, which have little relevance to actual processing conditions and therefore to modelling of flow in industrial practice. The present paper is an attempt to abstract thixotropic breakdown rates from rapid compression tests between parallel plates moving together at velocities of around 1m/s, similar to industrial conditions. From this analysis, a model of slurry flow has been developed in which rapid thixotropic breakdown of the slurry occurs at high shear rates.
Mathematical Modelling of Fluid Flow in a Continuous Casting Tundish with regard to Extraordinary Casting Conditions
Authors: Bruch Christian , Valentin Peter
Published: December 2016

The quality of the steel (degree of cleanness in the finished material) can be influenced to a great extent by the flow conditions in the continuous casting tundish and the resulting conditions for the separation of non‐metallic inclusions. Whereas in the literature a lot of numerical simulations about the flow patterns of regular casting tundishes have been published, the effects of disturbances like the absence of a strand or the progressive wear of the flow control devices in the tundish on the flow behaviour will be investigated here. It will be shown that the absence of single strands exerts much less influence on the total flow behaviour in the tundish than variances of the flow control devices.
Friction Forces between Mould and Strand Shell during Billet Casting
Authors: Valentin Peter , Bruch Christian , Horn Andreas C.
Published: December 2016

During continuous casting processes lubrication between mould and strand shell is very important for reaching and maintaining a good surface quality of both the as‐cast strand and the finished product. The lubrication is influenced by the properties of the mould powder but also by the friction forces caused by the periodic movements of mould and the descending strand shell. In the present research measurements were carried out to investigate the friction forces during 150 mm sq. billet casting of different steel grades using mould powder or granules and submerged entry nozzles. The friction forces reached values up to 6 kN. Since friction forces are depending on upward and downward movements within the mould‐strand‐system, the evaluation of a rheogram shows the typical change of pressure and tension. Maximum friction forces arise during the positive strip time of the rising mould, introducing tensions and cracks in the as‐cast strand. On the other hand lowest frictions forces are generated by the descending mould within the negative strip time leading to the healing of faults in the as‐cast strand. These industrial experiments indicate a correlation between friction forces and surface quality of as‐cast strands.
Study on the Design of the Soft Reduction Unit of High‐Speed Billet Casters
Authors: Thome Ralf , Harste Klaus
Published: December 2016

The production of continuously cast products that display very low centre segregation and thus more homogeneous properties is an important objective, particularly for high‐speed continuous casting of billets, in meeting increasingly stringent quality requirements. In addition to the well known methods of reducing macro‐segregation in continuous casting, inline deformation of the partially solidified strand, already used successfully in slab and bloom casting, offers an alternative for producing material with low segregation level. The present report considers the feasibility and effectiveness of mechanical soft reduction for the continuous casting of billets. The structural design of the soft reduction unit as a stand or segmental construction was investigated, as well as the influence of varying roll diameters. A strand of the existing billet caster S4 was modified for this purpose and soft reduction tests were conducted on spring steel grade 54SiCr6 at casting speeds between 3.30 and 3.60 m/min. The conclusions drawn from the test results as regards roll diameter, required reduction rate and necessary reduction force formed the basis for designing the soft reduction unit of the new billet caster SO that went in operation in March 2004.
Assuring Microstructural Homegeniety in Dual Phase and Trip Steels
Authors: Rivera‐Díaz‐del‐Castillo P. E. J. , van der Zwaag S.
Published: December 2016

The presence of ferrite/pearlite bands in dual phase and TRIP assisted steels is a consequence of microchemical segregation which causes mechanical properties anisotropy. Such inhomogeneous phase distribution produces a lowering of the mechanical properties such as fracture behaviour. This anisotropy is commonly not accounted in micromechanics computations which often assume a random distribution of phases in the solid. The present paper deals with an integral model for this undesirable band formation accounting for the solute segregation caused by solidification, microcomponent diffusion present in the austenitisation process, and the nucleation of the transformed phase in segregated regions. In the present work, the model was applied to two industrial grade dual phase steels and two TRIP assisted steels. The influence of such parameters on band formation is summarised in a number of “band prevention plots”, which are aimed at providing the optimum processing conditions for ferrite/pearlite band prevention.
Modelling of Transformations in TRIP Steels
Authors: Katsamas Antonis I. , Haidemenopoulos Gregory N. , Aravas Nikolaos
Published: December 2016

Industrial processing of low‐alloy Transformation Induced Plasticity (TRIP) steels involves various stages of heat‐treating, such as Intercritical Annealing (IA) and Bainitic Isothermal Treatment (BIT), in order to produce a dispersion of retained austenite (γR) particles and bainite (αB) in a ferritic matrix (α). Retained austenite then transforms to martensite (α′) during forming processes undergone by the steel. In the present work an effort was made to model these stages of processing, i.e. IA, BIT and the γR→α′ strain‐induced transformation. Simulation of heat‐treatment stages was implemented using computational kinetics methods. Investigation of the strain‐induced gMR→α′ transformation kinetics was performed by means of a simple analytical model. Simulation of IA and comparison with available experimental data showed that the amount of austenite (γ) forming during IA reaches the values predicted by thermodynamic equilibrium only at high annealing temperatures (>825°C). It was also observed that kinetic and thermodynamic predictions set a lower and an upper limit, respectively, within which the actual amount of austenite experimentally observed is contained. Results from the simulation of the BIT indicated considerable carbon enrichment, and thus stabilization of γR, in agreement with recent experimental observations. As regards the strain‐induced gMR→α′ transformation, the analytical model employed in the present work was fitted to available experimental results, showing reasonably good adaptation to the kinetic behaviour of the microstructure during plastic deformation.
Reaction Kinetics of Coke and some Carbonaceous Materials with CO2 and Coke Strength after Reaction
Authors: Kawakami Masahiro , Mizutani Yukitaka , Ohyabu Takayuki , Murayama Kengo , Takenaka Tosihide , Yokoyama Seiji
Published: December 2016

The reaction rate per unit mass of wood char was an order of magnitude larger than that of coke and graphite and that of glassy carbon was an order of magnitude smaller than the latter. However, the reaction rate per unit surface area of wood char was smaller than that of graphite. The reaction of coke proceeded homogeneously at temperatures lower than 1373 K, while the reaction was restricted to the surface layer at higher temperatures. The tensile strength of coke after reaction decreased with the reaction degree at 1273 K, but was not changed or even increased at 1573 K. This is due to the fact that at 1573 K the core of the sample was not attacked by CO2 but strengthened by further crystallization.
Recycling of By‐Product Pellets as Burden in the Blast Furnace Process: A Lab and Pilot Scale Investigation
Authors: Robinson Ryan , Sundqvist Ökvist Lena
Published: December 2016

Cold bonded by‐product briquettes have been recycled in the blast furnace at SSAB Tunnplåt in Luleå since 1993. Recently, much effort has been made to increase the recycling of by‐products. One such project deals with the development of a cold bonded by‐product pellet (CBP) agglomerated from very fine dusts. The pellets used in these tests are produced from a blend containing BF flue dust, filter dust, briquette fines and BOF coarse dust as well as cement binder.

The pellets were tested in the laboratory by reduction tests, softening and melting tests, thermo gravimetric analysis, differential thermo analysis, and mass spectrometry measurements. The test results indicate that the CBPs can disintegrate during reduction in the BF shaft, are self‐reducing to a high extent and, as a supplement to the normal ferrous burden, they show quite good softening and melting properties. A pilot scale test in LKAB's experimental blast furnace was performed. CBPs were charged with rates of 150 kg/tHM, 299 kg/tHM and 344 kg/tHM respectively during test periods 1, 2 and 3. The blast furnace operation was very stable during test period 1 with 150 kg CBP/tHM, but the burden descent and gas distribution were disturbed during the periods with greater CBP burden content. The rate of reducing agents was significantly decreased and slag amount was increased when CBPs were charged.
Inclusion Growth and Removal in Gas‐Stirred Ladles
Authors: Söder Mats , Jönsson Pär , Jonsson Lage
Published: December 2016

A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas‐stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical‐cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical‐cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical‐cap bubbles (assuming plane contact between the inclusion and the bubble).
Galvanizability of Complex Phase High Strength Steel
Authors: De Bruycker E. , De Cooman B.C. , De Meyer M.
Published: December 2016

Complex phase (CP) steels have very high ultimate tensile strengths, resulting from the use of specific alloying elements, which improve the hardenability but cause difficulties when applying a zinc coating by means of continuous hot‐dip galvanizing. The galvanizability of a cold rolled 1000MPa complex phase steel was investigated by monitoring the surface chemistry before dipping and evaluating the quality of the zinc coatings applied by a laboratory hot‐dipping simulator. Two steel compositions with different Cr levels were used. The influence of the most important production parameters, the annealing temperature and the dew point of the annealing atmosphere, was investigated. Both steel compositions were galvanizable, but both the surface appearance and zinc coating adhesion were improved when low Cr contents were used. At a low dew point of ‐30°C, Cr, Mn and Si segregated to the surface and the presence of Mn2SiO4 could be demonstrated. At high dew point of +10°C, less oxides were present at the steel surface. There was no effect of the annealing temperature on the coatability.
Effect on Manufacturing Conditions on Mechanical Properties of Super Formable IF High Strength Steels
Authors: Han Sangho , Lee Ohyeon
Published: December 2016

There have been increasing demands for improving safety, fuel economy and dent resistance in the automotive industry. To meet these demands, a super‐formable high strength steel with excellent formability was investigated. The mechanical properties and precipitation behaviour of Ti‐Nb bearing Interstitial Free (IF) steels with various contents of Ti and P were studied. In addition, the effect of processing conditions such as the cold reduction ratio and the annealing temperature on the formability was analysed. Improved mean r‐value was obtained in Ti‐0.01Nb steels with Ti content ranging from 0.015% to 0.025%. This improvement was due to non‐scanvenging effect and FeTiP precipitates. Furthermore, with an increase in P content, the mean r‐value was increased because of grain refinement in the hot rolled strip.
Effects of Ca and B on the Strip Deformation of Cold Rolled Duplex Stainless Steel Type 2205 during Continuous Annealing
Authors: Lee Soo Chan , Kim Young Hwan , Lee Yong Deuk
Published: December 2016

The effects of Ca and B on the strip deformation of duplex stainless steel Type 2205 under continuous annealing conditions were investigated. For the creep test, the stresses were calculated from the line tension applied to hot rolled and cold rolled Type 2205 strip during continuous annealing. It was found that the cold rolled Type 2205 steel showed more prominent superplasticity as compared with the hot rolled steel, which could be attributed to the fine grain size of the cold rolled steel. The creep rate of cold rolled Type 2205 steel decreased with the Ca and B additions due to the grain boundary segregation of B. It is suggested that the rate controlling mechanism for the strip deformation of cold rolled Type 2205 steel seems to be grain boundary diffusion in γ phase.
Effects of Mn ore on the Dephosphorization and Desulphurization in Hot Metal Pretreatment
Authors: Kim Seong‐Woo , Jung Sung‐Mo , Rhee Chang‐Hee , Shim Sang‐Chul
Published: December 2016

In order to examine the possibility of utilizing Mn ore in the pretreatment process of liquid iron, experiments were carried out in a system with liquid iron and CaO‐SiO2‐MgO‐Al2O3‐FeO slag with additives (Mn ore and Fe2O3+MnO2) in a magnesia crucible at 1673K. When Mn ore was added to the pretreatment slag, decarburization, desiliconization, dephosphorization and desulphurization proceeded simultaneously with the reduction of Mn ore. The reduction rate of MnO and the Mn concentration in the melt increased with increasing initial Si content. The maximum dephosphorization was obtained when the additive consisted of 66.6 mass% Fe2O3 and 33.4 mass% MnO2. The desulphurization ratio increased with increasing the relative amount of MnO2 in the additives. The amount of additives comprising Fe2O3 and MnO2 required for a targeted manganese content could be predicted using the mass balance. Effects of the additives on dephosphorization were also estimated.
Formability of High‐Alloy Dual‐Phase Cr‐Ni Steels
Authors: Elfmark Jiri
Published: December 2016

The formability of dual‐phase high‐alloy Cr‐Ni steel within the temperature range from 900 to 1250°C was studied using laboratory tensile and torsion tests. The dual‐phase steels on 24% Cr basis are characterized by poor hot formability due to very low stable deformation values and slow recrystallization. Mathematical description of deformation stability exhaustion was derived, as well as a model of formability control based on analysis of the gradual diffuse deformation stability from the stability limit to the moment when the deformation starts to concentrate in a small volume of the test piece. Rolling simulation of dual‐phase steel strip was used as an example demonstrating the draught scheme optimization technique which avoids the danger of crack occurrence during the rolling of dual‐phase steel strip.
Atomized Spray Quenching as an Alternative Quenching Method for Defined Adjustment of Heat Transfer
Authors: Puschmann Frank , Specht Eckehard
Published: December 2016

In Atomized Spray Quenching, water is atomized to a fine spray by compressed air and sprayed onto the hot metallic surface. On the surface, the single drops partially evaporate. Afterwards they are taken away by the superposed airflow. Thus a water film cannot form. By quenching one edge, it is shown that an undefined water film collapses at the edges and corners; roughness, as known from Water Spray Quenching, does not occur. In this way a defined adjustment of heat transfer including quality improvement is possible. The influence of impingement density, spray characteristics, drop velocity, drop diameter and surface temperature on heat transfer was investigated. The heat transfer was measured with infrared thermography. The spray characteristics were measured with a combination of 2D‐Phase‐Doppler‐Anemometer and Patternator. Heat transfer coefficients up to 3000 W/(m2 K) were measured.
Recent Advances in the Modelling of Solid Flows in the Blast Furnace
Authors: Zaïmi Sami‐Alex , Sert Dominique , Guillot Jean‐Bernard , Biausser Hervé
Published: December 2016

The solid flow inside a blast furnace is modelled using a standalone finite element program and a constitutive equation called hypo‐plastic, in order to better simulate the granular material behaviour. The parameters of this constitutive equation are calibrated using data obtained from simple soil mechanics tests on coke and sinter materials, such as triaxial and oedometric devices. Steady velocity, stress and void fraction fields are obtained after several iterations of the code. Knowledge of the solids velocity field makes it possible to determine the dead man profile, as well as its renewal kinetics. Burden trajectories and time lines are also computed. Knowledge of the stress field makes it possible to compute pressures acting on the burden as well as on the walls. Finally, knowledge of void fraction field makes it possible to determine gas paths. The solid flow model was validated on 2D and 3D small‐scale cold blast furnaces, but the simulations never required any tuning parameter. This code is in fact an invaluable tool to determine the effect of blast furnace profile on solid flow conditions, and reciprocally.
Modelling the Temperature Distribution along the Length of Strip during Hot Rolling Process
Authors: Sha Xiaochun , Li Dianzhong , Lan Yongjun , Zhang Xiaogang , Li Yiyi
Published: December 2016

Hot strip rolling process includes four main stages, which are reheating process, roughing and finishing process, laminar‐cooling process, and coiling process respectively. Temperature is the most sensitive parameter and has direct effect on the microstructural evolution and further the mechanical properties, and the accurate control of temperature guarantees the quality of products and homogeneity of properties along the strip length. However, for the conventional hot strip rolling process, thermal history along the strip length is very complex, the related temperature variation concerns air cooling, water cooling, heat transmission by roll contact, heat generation by deformation and friction. Based on the actual hot strip mill, the thermal models are established in this paper to simulate the temperature distribution along the whole strip length from the reheating furnace exit to the down coiler. Different interface heat transmission coefficients are selected for the scale breaking and spray water‐cooling process, and a self‐learning algorithm is thus employed to improve the calculation accuracy. This model is characterized as simple and fast, and convenient for on‐line/off‐line prediction of temperature. Finally the simulated results are verified by the on‐line temperature detection at typical points such as roughing exit (RT2), finishing exit (FT7) and coiling position (CT).
The Development of Ring Rolling Technology
Authors: Allwood Julian M. , Tekkaya A. Erman , Stanistreet Timothy F.
Published: December 2016

A thorough survey of work on ring rolling published in the English and German languages by 2004 is presented. The process is briefly introduced and a set of ideals are stated, as the target for all developments in the area. The main challenges which inhibit attainment of these ideals are given, and the process is compared with alternatives. The main body of the review is organised in four parts: the evolution of the design of ring rolling equipment is described, including detailed discussion of the design and manufacture of preforms; the methods used to investigate the process are reviewed, separated into experimental and theoretical categories; the insights gained from these investigations are organised according to the challenges identified at the outset; developments in the control and operation of the process are described. Having given a set of ideal targets for the process, the state of current knowledge about ring rolling is assessed in order to predict likely developments: process modelling capability is nearly able to predict rolling behaviour for a complete cycle with sufficient accuracy to allow effective use of models for design of rolling schedules and preforms; analysis of material behaviour is relatively mature for steel rings, but has scope for significant extension for titanium and aluminium alloys and composites; design choices that seek to extend the flexibility of the process have had some exploration, but could be extended. Finally, the seminal contribution of Professor Kopp is briefly described.
Micro‐scale Strain Distribution in Hot‐worked Duplex Stainless Steel
Authors: Hernandez‐Castillo Luis E. , Beynon John H. , Pinna Christophe , van der Zwaag Sybrand
Published: December 2016

A modified microgrid technique has been applied to a laboratory‐made duplex stainless steel, to experimentally simulate the local state of deformation of the austenite‐ferrite microstructure of low‐alloy steels subject to intercritical deformation. A sample containing such a microgrid was deformed by plane strain compression at high temperature under conditions representative of hot rolling processes. The distortion of the microgrid after hot deformation revealed, in a quantifiable manner, the plastic flow of both phases and different deformation features. The micro‐strain distributions measured can be used to validate the models predicting the hot deformation of low alloyed C‐Mn steels during intercritical rolling.
Deformation Inhomogeneity and Texture Development brought about in Steel Strip by Multi‐Step Cold Rolling
Authors: Lehnert Wolfgang , Kawalla Rudolf
Published: December 2016

Predicting the microstructure obtained in cold‐rolled strips is of major importance with regard to optimizing the production of deep‐drawing steels with high and defined mechanical and technological properties. By using the hydrodynamic rolling theory of A. Kneschke, it has been possible to determine the effects of the most important rolling parameters and also of the rolling strategy on the velocity field and on the in‐homogeneous distribution of deformation over the strip thickness. Rolling on experimental laboratory facilities has provided the opportunity to observe the texture evolution. The tests were carried out on two deep‐drawing steel grades IF and ULC. The initial thickness of the strip samples was 3.0 mm. The textures were determined at 3 locations over the strip thickness by means of pole figure measurements according to the X‐ray diffraction method.
Calculability of the Bake Hardening Effect of Hot Rolled Multiphase Steels
Authors: Palkowski Heinz , Anke Thorsten
Published: December 2016

In recent years high strength hot rolled multiphase steels with a thickness of less than 2 mm have become available. These multiphase steels show a good Bake Hardening effect, which makes them important for automotive constructions, because an increase of yield strength may lead to a weight optimised body structure and/or a better crash resistance. In this investigation five different hot rolled multiphase steels were examined. The steels were exposed to different prestrains, temperatures and holding times. Design of Experiments and statistical methods were used to reduce the quantity of experiments. After evaluation of the results it was possible to develop a formula to predict the yield strength for a given prestrain, temperature and time for each steel. Furthermore, a method was found to decide easily if a steel is qualified for further investigation of the Bake Hardening effect, or more exactly, of its response to different annealing temperatures and times.
Innovative Flexible Metal Forming Processes based on Hybrid Thermo‐Mechanical Interaction
Authors: Steinhoff Kurt , Weidig Ursula , Scholtes Berthold , Zinn Wolfgang
Published: December 2016

A new approach towards functional gradation of structural parts is presented. This approach is based on the utilization of locally varying thermo‐mechanically coupled effects applied to different initial workpiece geometries. The possible degree of freedom for the gradation of material properties and geometrical shape for sheet metal forming applications as well as for parts produced by bulk metal forming is characterized by the results of metallographic investigations, by mechanical testing and by an indication of the remaining residual stress state. On the basis of experimental results and process simulations, it could be revealed that the ability to exactly control the dynamic microstructural evolution by thermal and mechanical process parameters combined with predefined material design parameters constitutes a key towards the adjustment of flexible material property profiles even for parts with complex three‐dimensional geometry. Beyond that, the integrative aspect of thermal and mechanical treatment already implies the high level of obtainable efficiency resulting from shortening of process chains. However, it is not only the ability to integrate shape generation and property gradation, but also the automatically included positive effect of tailoring process behaviour by a gradation of formability finally allowing to improve process efficiency e.g. by a reduction of forming steps or reduction of (local) tool load.
Numerical Simulation using Finite Elements to Develop and Optimize Forging Processes
Authors: Schaeffer Lirio , Brito Alberto M. G. , Geier Martin
Published: December 2016

Forging is one of the main processes used to manufacture metal components for a broad range of applications. This occurs mainly because forged products are highly reliable and present superior mechanical properties. However, lately the competitiveness of forged products has been threatened, since the difference between their superior performance and the performance resulting from other processes has lessened continuously. This has obliged the forging industry to invest in optimizing its processes, saving in raw materials and energy. In this context, the use of numerical simulation of the forging process has become an increasingly reliable tool in seeking this optimization. This study uses the commercial software QForm 3D, version 3.2.1.1, to analyse two forging processes, one by hot forging and one by cold. In the case of hot forging, work on a component with axial symmetry is looked at from which a gear is machined. Currently the part is forged in three stages based on an initial billet with a 7.0 kg mass. Forging is performed in a 40 NM mechanical press with an initial temperature of 1200°C. The hot forging process is optimized and this results in a saving of about 5% in material. In the cold forging case it is shown that the process, as designed, results in laps in the final part, and in possible tool failure due to excess load. In both cases, the material used is DIN 1.7131 (16MnCr5) steel.
Towards Large Area MAX Phase Coatings on Steel
Authors: Walter Claudia , Martinez Carlos , El‐Raghy Tamer , Schneider Jochen M.
Published: December 2016

MAX phases are promising materials for protective coatings on steel due to their unique combination of properties like corrosion and oxidation resistance, good electrical conductivity, low friction coefficient, damage tolerance, and high temperature stability. Here the deposition of large area MAX phase coatings on steel was investigated by magnetron sputtering of a Ti2AlC compound target. It was found that the chemical composition of the produced films was different from the composition of the target. The deposited films contained about half as much Ti as the target. Consequently the dependence of the film composition on temperature and pressure was investigated. The film composition prooved to be independent of pressure but the lack of Ti increased with increasing temperature. The stoichiometry of the films was then adjusted by adding Ti to the growing coating from a separate plasma source. This method provides a pathway to stoichiometric Ti2AlC coatings with an equilibrium volume that is in excellent agreement with our ab initio calculations.
Fundamentals of the Deep Rolling of Compressor Blades for Turbo Aircraft Engines
Authors: Klocke Fritz , Mader Sebastian
Published: December 2016

The weakening of the fatigue strength of turbine blades due to local impact damage caused by foreign objects (Foreign Object Damage ‐ FOD) represents a significant safety risk in modern civil and military aviation. It is possible to employ deep rolling to counteract such component weakening in a particularly effective way. Although deep rolling has long been used on rotationally symmetric components, the underlying deformation processes are largely unknown. The deep rolling of thin‐walled free‐form surfaces, such as those on turbine blades, represents a new, demanding production challenge. For this reason, this paper describes the implementation of a deep‐rolling process for machining thin‐walled turbine blades and, by combining practical and numerical test results, outlines some of the underlying deformation processes.
One Modified FE‐model to Simulate the Process Chain of Forming and Welding
Authors: Zaeh Michael F. , Roeren Sven
Published: December 2016

This paper presents a possibility of creating a virtual process chain consisting of forming and welding. Independent of any manufacturing process, a variable Finite Element model is introduced. This model can be an input for more than one simulation by means of the Finite Element Method (FEM). The process chain forming and welding is chosen to demonstrate the need and the importance to simulate a process chain in comparison to a single process simulation.

Each simulation has its own specifications and intentions. Therefore, an FE‐model for a forming simulation is different from a model for a welding simulation. In this paper a way is shown how to keep the model and the results of a forming simulation for the succeeding simulation of welding. The results of the forming simulation remain as an initial state in the welding simulation. Thereby, a spring‐back behaviour can be modelled. A few adjustments have to be done to satisfy the specifications of the welding simulation. The used material for the integrated simulation is a DC 04 steel. Therefore, metallurgical phases must be considered to achieve sufficient results. For reasons of further industrial applications commercial FE‐solvers are used for calculations.

The method of integration is applied to different examples. The verified results are presented and discussed. The simulated transient distortional behaviour of a formed and welded part is presented and compared to a mere welding simulation. A significant improvement of the distortion as a result of the welding simulation is reached by consideration of a previous forming simulation.
Viscosities of Slags ‐ an Overview
Authors: Seetharaman Seshadri , Mukai Kusuhiro , Sichen Du
Published: December 2016

Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well‐known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network.

The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out.

A number of semi‐empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., (2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH‐model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two‐phase mixtures are also taken up in the presentation.