bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation between formability and precipitates in Ti‐IF enamelling steels
Authors: Cauter An Van , Hörzenberger Franz , De Cooman Bruno C.
Published: December 2016

The influence of steel composition and processing conditions on the nature of precipitates in Ti interstitial free (IF) steels for enamelling were investigated in detail. Steels designed for enamelling applications require a higher amount of precipitates than conventional deep drawing IF steels, e.g. for automotive applications. Formable IF grades for enamelling applications have high Ti, S and C contents and the properties have hitherto not been investigated in detail. This work focused on the correlation between precipitate nature, texture development and deep drawability. It was found that a low reheating temperature, a high coiling temperature and a C/S ratio in the range of 0.4–0.5, favoured the beneficial precipitation of Ti4C2S2. Furthermore, it is shown that for a steel with a given C/S ratio, a high Ti4C2S2/Ti4S5‐ratio resulted in improved deep drawability. The deep drawability decreases with increasing C/S ratio. This is due to the decrease in γ‐fibre intensity, caused by an increased amount of TiC‐precipitates.
New cold‐rolled deep‐drawing grades
Authors: Herman Jean‐Claude , Durme Christophe Van , Neutjens Joeri
Published: December 2016

An unstabilised ultra low carbon steel (12 ppm of C) offers an attractive combination of formability properties like yield strength, elongation, mean r‐value and BH‐index. The major drawback is its large planar anisotropy. This is attributed to the large grain‐size of the hot‐rolled product. An increase in the cooling rate (using ultra fast cooling technology) or a decrease in the coiling temperature do not refine the hot‐band grain size. However, an optimisation of the cold‐rolling and the annealing sequences result in a better balance of the drawing properties. Alloying elements like Cr, B, V, Al. Si or reduction of Mn content exert only a minor influence on the final properties. An addition of Nb (mass contents of 0.01 %) improves the drawability but decreases the BH‐index when conventional continuous annealing temperatures are applied.
Steel research in Europe – today and tomorrow
Authors: Ameling Dieter
Published: December 2016

The exchange of technological information is an important pre‐requisite for effective joint research. The joint research model has proven itself in Germany. The European steel research network with 13 executive committees, 4 circles of experts assured the highly efficient steel research within the European Community The German Technology Road Map &„Steel research … and the future is light&” and the &„European Technology Road Map to Determine the Research Priorities of the European Steel Industry&” clearly define the focal points of future steel research. The assurance of ECSC research funds even beyond 2002 look promising. Maintaining the network for European steel research remains an important goal keeping European steel research in the future at the same level. Phasing‐in to the 5th European frame work programme is absolutely a must despite the much more complicated organisational rules of the 5th EU frame work programme.
Activities of carbon and nitrogen in Fe‐Cr and Fe‐Cr‐Ni melts
Authors: Ma Zhongting , Janke Dieter
Published: December 2016

Carbon and nitrogen in steel are the original sources of carbides, nitrides and carbonitrides which exert a strong effect on the production process and the service properties of steel. The knowledge of the activities and contents of carbon and nitrogen in Fe‐Cr and Fe‐Cr‐Ni melts under atmospheric and vacuum conditions is indispensable to optimize existing processes and to create new ones. With the help of computer based modelling and simulation programs, the thermodynamic behaviour of carbon and nitrogen was analyzed. The calculated results are supported by the available experimental ones. They provide a basis to better understand metallurgical reactions occurring in steelmaking and enable an improved control of the steelmaking process.
Cold model investigations of fluid flows and mixing within top and combined blowing in metallurgical processes
Authors: Roth Christian , Peter Michael , Juhart Matjaz , Koch Klaus
Published: December 2016

Cold model investigations were performed during top and combined blowing in metallurgical processes. The investigations include 2‐ and 3‐phase systems with gas, water and oil phase. The results of top blowing tests can be used to arrange and optimise the fluid flow. Further, conclusions can be drawn for the spraying and emulsification process, if the slag thickness is known. Under combined blowing conditions a small amount of stirring gas injected from the bottom has a great influence on mixing. According to the slag thickness, in combination with the power of the top blowing momentum, the fluid flow is dominated by top or bottom blowing. If bottom blowing is added as a stirring mechanism, a better mixing can not be guaranteed by this means. The bottom blowing conditions have to be adapted to the top blowing conditions and to the reactor geometry.
Heterogeneous phase equilibria as a basis for crevice corrosion modelling
Authors: Hoffmeister Hans
Published: December 2016

The presented crevice corrosion model is intended to provide basic understanding of formation and dissolution of passivating layers during time dependent metal dissolution in an already deoxygenated crevice. It operates along a constant cathodic polarization curve in subsequent time steps with time dependent anodic polarization curves and corrosion currents. The anodic polarization curves are determined by dissoluted ionic chromium and respective Nernst potentials as well as by the mass of precipitated passivating chromiumhydroxide layers. All chemical reactions including diffusion of chloride into the model crevice configuration are assumed to be at equilibrium during the respective time steps. The amounts of passivating chromiumhydroxide masses are determined by lever‐rule application at increasing chromium and chloride contents in aquaeous solution of the quaternary water‐chromium‐hydrogen‐chloride phase diagram at various Nernst potentials. For this purpose, the established water–chromium Pourbaix diagram had to be redrawn in terms of ternary water‐chromium‐hydrogen phase diagrams for constant potentials. It was tentatively extended to the quaternary chloride including diagram based on literature results. This included solubility of chromiumchloride in hydrochloric acid and most probable effects of chloride ions on chromiumhydroxide solubility at saturation with chromium metal. The results of the interactive corrosion process are based on a crevice geometry drawn from previous publications and given initial solution concentrations as well as assumed polarization curves for time steps of one second. It is shown, how the process starts with concentration changes of chromium, chloride and hydrogen in the crevice, the subsequent formation of the passive layer and the corresponding decrease in the corrosion current and increase in the mixed potentials. In the presence of the chromiumhydroxide phase, however, chromium and hydrogen remain at low levels in the equilibrium aqaeous solution while chloride is increasing. The saturated solution reaches the four phase equilibrium concentration including saturation by chromium, chromiumhydroxide and chromiumchloride at corresponding Nernst potentials. The further increase in total chromium and chloride concentrations of the crevice then leads to initiation and propagation of crevice corrosion by formation of non‐passivating chromiumchloride at the expence and finally, the total dissolution of passivating chromiumhydroxide, at decreasing mixed potentials and increasing currents. Due to the low solubility of chromiumchloride in hydrochloric acid, the latter is finally formed with the result of the well‐known increase in crevice acidity. Thus, it is demonstrated that the acidification itself is not a requirement for crevice corrosion but rather a consequence of it.
Influence of a solution treatment on the evolution of through‐thickness texture gradients in dry cold rolled and recrystallized low carbon steel
Authors: Huh Moo‐Young , Kim Hyun‐Chul , Engler Olaf
Published: December 2016

The influence of a solution treatment on the evolution of through‐thickness texture gradients in a low carbon steel was studied. In order to intensify through‐thickness variations of the strain state, the samples were cold rolled dry, i.e. without lubrication. The evolution of the texture and the microstructure during rolling and recrystallization was tracked by X‐ray texture analysis and TEM microstructure investigations. The strain distribution during rolling was simulated for several layers of the rolled sheets by the finite element method. After the rolling deformation, a specimen taken directly from the hot band showed pronounced through‐thickness texture gradients, whereas the solution treated specimen showed a rather uniform rolling texture in all layers analyzed. Analysis of the friction behaviour between the different specimens and the roll material points to a much higher friction between the softer hot band and the rolls. This leads to stronger through‐thickness variations in the strain state and, thus, to the pronounced texture gradients observed. The texture gradients in the recrystallized samples reflected those of the as‐rolled sheets. In the center layer of the hot band specimen and in all layers of the solution treated specimen characteristic though notably weakened typical plane strain recrystallization textures formed; the textures in outer layers of the hot band sample were even almost random. These weak recrystallization textures could be attributed to the highly inhomogeneous as‐deformed microstructure.
Ferritic rolling with additional annealing to produce a deep‐drawable ultra‐thin‐gauge hot strip
Authors: Tomitz Andreas , Kaspar Radko
Published: December 2016

In order to produce ultra‐thin hot strips by ferritic rolling, that exhibit a good deep‐drawability, finishing temperatures must be reduced, so that an additional recrystallization annealing of hot strips after coiling becomes necessary. In the present work laboratory investigations were carried out on a commercial IF and ELC steel by using the hot deformation simulator Wumsi. By means of texture measurement and the calculation of r‐values the process parameters of the ferritic rolling and of a subsequent annealing were optimized. Additionally to a conventional annealing of cold coils a new energy saving processing route with direct charging of warm coils was tested by the laboratory simulation. Particularly good deep‐drawabilty were achieved by this technology.
The bake hardening behaviour of electro‐galvanized cold rolled CMnSi and CMnAlSi TRIP steels
Authors: De Meyer Marijke , De Wit Katrien , De Cooman Bruno
Published: December 2016

Cold rolled, intercritically annealed TRIP steels will very likely be used as electrogalvanized sheet steel for passenger safety‐related automotive body parts. This implies that their properties during and after manufacturing, i.e. in the deformed and paint‐baked state, must be known to evaluate their actual in‐service properties. The ageing behaviour of electrogalvanized TRIP steels and the effect of controlled ageing of the complex microstructure by paint baking on the mechanical properties was therefore investigated. Electroplating tests showed that the H uptake during pretreatment and electrogalvanization is limited and that the paintability of the electroplated sheet steel is unaffected even after deformation induced transformation of the austenite. In addition, a strong bake hardening effect was found in the case of the CMnAlSi TRIP steel. Internal friction measurements indicated that a damping peak for interstitial C could be obtained but that the free C content was less than 1 ppm prior to paint baking. A BH mechanism for TRIP steels is proposed.
Modelling steel flow in a three‐strand billet tundish using a turbulence inhibitor
Authors: Morales Rodolfo D. , Díaz‐Cruz Manuela , Palfox‐Ramos Jorge , López‐Ramírez Simón , de Jesús Barreto‐Sandoval José
Published: December 2016

A three‐strand tundish belonging to a billet caster was water modelled and plant trials were performed to compare the performance of a pouring box and a turbulence inhibitor in terms of melt flow parameters and steel cleanliness.

A tailor made turbulence inhibitor for this tundish is useful to accomplish with flow control of fluid turbulence and even melt redirection to all strands. The turbulence inhibitor helps to decrease nitrogen pickup during ladle changes and to float out inclusions towards the covering slag. As a consequence, rod operations to take of alumina deposits from nozzle walls are considerably decreased using a turbulence inhibitor.
Influence of TiN particles distribution on static recrystallisation in structural steels at reheating temperature
Authors: Medina Sebastián F. , Vega María Isabel , Quispe Alberto
Published: December 2016

Results of investigations concerning the influence of Ti and N contents on static recrystallisation kinetics are presented. By means of torsion tests, and applying the back extrapolation method, the statically recrystallised fraction has been determined for four structural steels with different Ti and N contents, at different temperatures, equivalent strain of 0.35 and strain rate of 3.63 s−1. Two reheating temperatures have been used to obtain different austenite grain sizes and different precipitate mean size in steels containing Ti. The results show that a low precipitated volume and a relatively large size of precipitates, at reheating temperature, did not impede grain boundary self‐diffusion during the static recrystallisation, the main mechanism governing static recrystallisation. Nevertheless, the smaller size of the precipitates acted as an obstacle to grain boundary self‐diffusion. These effects were measured by calculation of the activation energy for static recrystallisation. On the other hand, the influence of austenite grain size in steels containing Ti can not be correctly determined, as at each reheating temperature, in addition to a different austenite grain, the distribution of precipitates is also different, affecting the activation energy and making it impossible to clearly appreciate the influence of austenite grain size.
Microstructural investigations in the semi‐solid state of the steel X210CrW12
Authors: Meuser Heike , Bleck Wolfgang
Published: December 2016

Thixoforming is an emerging young technology to produce complex structural parts and near net shape components. Thixoforming stands for the forming of materials in the semi‐solid state. One precondition for the thixoformability of materials is the minimum temperature range for the solidus‐liquidus interval and the globulitic formation of the solid phase during the thixoforming process. Besides this other parameters like shape factor, contiguity, matrix character, melting interval, and phase distribution are important process parameters. Aluminium and magnesium alloys are the objectives of numerous investigations, but research activities concerning the thixoformability of steel alloys have been commenced recently. This article provides metallographic information on the relevant parameters of the steel X210CrW12, taking into account the microstructural evolution and the establishment of a parameter field for forming this material in the semi‐solid state.
Thermodynamic evaluation of surface tension of liquid metal‐oxygen systems
Authors: Tanaka Toshihiro , Hara Shigeta
Published: December 2016

Thermodynamic equations have been derived to evaluate the surface tension of liquid metal‐oxygen systems. On the basis of these equations, the effect of the oxygen on the surface tension of liquid metals has been evaluated by using the fundamental information on the oxygen solubility in the metals, the surface tension and the molar volume of pure liquid metals and oxides. The calculated results from these equations agree with the literature values of the surface tension of liquid Fe‐O, Co‐O, Ni‐O, Cu‐O and Si‐O systems.
Thermodynamic and kinetic aspects of the desulphurisation reaction in secondary metallurgy
Authors: Lachmund Helmut , Xie Yongkun , Harste Klaus
Published: December 2016

The desulphurisation of liquid steels with a refining ladle top slag is one of the most important processes of secondary metallurgy. But the process control is even now based on empirical rules. Deviations from the sulphur contents aimed at can often be observed in practice. An improvement of the process control supported by knowledge of the thermodynamics and kinetics of the desulphurisation reaction is of great importance, especially for the production of steels with very low sulphur contents.

To investigate the removal of sulphur, operational trials were carried out in 185 t steel ladles. In the trials the stirring gas flow rate, the pressure on the bath surface and the steel composition were varied as process parameters. The obtained results show that ladle slags saturated with lime have a high sulphide capacity. The desulphurisation rate of steel melts increases if the specific stirring energy is enhanced by increasing the gas flow rate or reducing the pressure on the bath surface. In the case of production of Al/Si‐killed steel melts, a desulphurisation degree above 90 % can be obtained by a vacuum treatment within 10 minutes.
Thermodynamics of Hägg carbide (Fe5C2) formation
Authors: Schneider André , Inden Gerhard
Published: December 2016

Gas carburisation experiments on iron samples were conducted in CO‐H2‐H2O‐H2S atmospheres with different carbon activities at 500 °C. Carbon activities well above aC = 1 (equilibrium iron/graphite) were used in order to form iron carbides such as cementite (Fe3C) and Hägg carbide (Fe5C2). The Gibbs energy of formation ΔG for Fe5C2 was determined at 500 °C. This result combined with thermodynamic properties at other temperatures taken from literature strongly supports the existence of the three phase equilibrium α‐Fe+Fe3C+Fe5C2 at about 350°C in the binary Fe‐C system.
In‐situ investigation on the oxidation behaviour of low alloyed steels annealed under N2‐5%H2 protective atmospheres
Authors: Martínez Carlos , Cremer Rainer , Loison Didier , Servais Jean P.
Published: December 2016

The oxidation behaviour of low alloyed steels, Fe‐0.6%Mn and Fe‐1.5%Mn, under different annealing conditions was studied. Due to the crucial importance of the surface state of the sample, the experiments were performed in an in‐situ device to avoid any contact with air after the annealings. The annealing experiments were carried out under different conditions: high vacuum (~10−6 mbar), N2/H2 protective atmospheres with traces of water (dew point ‐30 °C) and temperatures ranging from 873 to 1073 K. Under this variety of heat treatments, the reconstruction of the Fe surface and the formation of different oxides was observed and characterised, paying special attention to the selective oxidation of manganese. The surface structure and composition was investigated by means of the combined use of reflection high‐energy electron diffraction (RHEED) and X‐ray photoelectron spectroscopy (XPS). The analyses show that the use of RHEED is a good alternative for determining the crystallographic structure of the outermost layers of the surface. With this technique the structures of iron and manganese oxides can be distinguished despite the similar structures and lattice parameters. It is also possible to identify the crystallographic textures present on the oxidation products and to give qualitative information about the surface reconstruction of the grains.
Prediction of the size distribution of precipitates
Authors: Prikhodovsky Andrey
Published: December 2016

Modelling has proven to be an efficient way of cutting the time and costs associated with the investigation of materials properties. A new mathematical model for the prediction of the particle size distribution of precipitates has been developed. The model allows the description of all stages of the precipitation process: nucleation, growth and Ostwald ripening of particles. The incorporation of existing thermodynamic databases allows the simulation of a formation of dispersed phases in commercial multicomponent alloys.

The influence of the model parameters on the final particle size distribution was investigated with the example of NbC formation in austenite. It was shown that the interfacial energy of a particle‐matrix interface has the most significant effect on the final particle arrangement. A pre‐exponential factor, which is the subject of nucleation theories, plays a less significant role in the final particle arrangement.
Influence of nitrogen addition on the microstructure and mechanical properties of duplex stainless steel weld metals
Authors: Muthupandi Veerappan , Srinivasan Parthasarathy Bala , Sundaresan Subramanian
Published: December 2016

Duplex stainless steels find extensive applications in off‐shore, paper/pulp, refineries and petrochemical industries owing to their excellent combination of properties. Because of the thermal cycle experienced during the manufacturing/processing operations like welding, the weldment developed in this material is generally inferior in properties (mechanical and corrosion) when compared to the base material. The problem is more severe when the welding is done in the autogenous condition. The current work correlates the microstructure and property of UNS 31803 duplex stainless steel (material no. 1.4462) welded by autogenous GTA process with and without nitrogen in the shielding gas. It has been found that the nitrogen addition to the weld metal through the shielding gas mixture not only helps in achieving the proper phase balance but also improves the impact toughness of the resultant weld metal.
EAF Process Monitoring at OneSteel's Sydney Steel Mill
Authors: Prestidge John , Lee Mark , Wibberley Louis
Published: December 2016

Monitoring was conducted at OneSteel's Sydney Steel Mill electric arc furnace to study the effect of hot briquetted iron (HBI) upon furnace performance. Results from this study have been previously published by Trotter [1]. These studies were then continued for zero HBI operation to investigate the effects of a new, more reliable coke injection system into the slag and the change from two consumable oxygen pipes to a water‐cooled oxygen lance and the installation of a spray‐cooled roof. The investigations were comprised of an energy balance across the furnace, foaming slag investigations with regard to thermal efficiency and acoustic noise, effect of equipment modifications on the primary fume analysis, harmonic measurement for slag foam indicator, triboelectric system for measuring off‐gas dust loading. Each of these investigations is detailed in this report.
Improvement of surface quality on peritectic steel slabs
Authors: Weisgerber Bernadette , Hecht Michael , Harste Klaus , Morand Hervé , Kandel Matthieu , Lamant Jean‐Yves
Published: December 2016

Peritectic steel grades are very sensitive to microcracking along austenitic grain boundaries in continuous casting. Irsid and Aktiengesellschaft der Dillinger Hüttenwerke (DH) have combined laboratory studies and industrial trials to improve surface quality on these sensitive grades. Laboratory studies at Irsid confirmed the hypothesis that a very thin layer of ferrite along austenitic grain boundaries is detrimental for cracking and indicate that the risk of cracking decreases as soon as ferrite ratio is above 10 %. Dilatometric investigations demonstrate that there is a strong shift between thermodynamic equilibrium and beginning of γ→α phase transformation under casting conditions. Furthermore, at the slab surface, there is no cyclic transformation γ→α→γ induced by thermal cycling in front of spray nozzles and supporting rolls. DH performed trials with various cooling strategies on its new vertical caster No. 5. No cracks appear with intensive cooling whereas microcracks are present with soft cooling. These results are in agreement with laboratory studies. Intensive cooling is the standard condition at DH. With this process, microcracking is avoided for all slab formats.
The properties and production of iron‐coated burnt lime
Authors: Lee Mark , Barr Peter
Published: December 2016

Ferruginous lime is the name given to burnt lime (CaO) coated with di‐calcium ferrite (2CaO·Fe2O3). Its high degradation strength, its resistance to hydration and its capacity for fast and complete solution of fluxes in the BOF and EAF make it extremely attractive as a steelmaking flux.

The objectives of the present work were to assess the feasibility of producing ferruginous lime in a rotary‐kiln‐type reactor and to determine the operating conditions favourable both for the formation of a hydration resistant product and the minimisation of problems such as accretions and agglomerations within the reactor.

With respect to processing conditions, the trials suggest that ferruginous lime should be generated using a peak reaction temperature of 1260 °C and allowing 45 min at greater than 1200 °C. The optimal oxide addition is 10 % (referring to mass contents) of the limestone charge to the rotary lime kiln.

When subjected to short duration hydrating conditions i.e. 30 min in contact with steam at 100 °C (as per ASTM specification X6) the ferruginous lime product exhibited good resistance to hydration (relative to pure CaO) and moderate physical degradation. Laboratory tests demonstrated the significantly enhanced rate and degree of dissolution of ferruginous lime (cf. uncoated lime) in a steelmaking slag.
A computerised kinetic database system for metallurgy and materials processing
Authors: Zhang Jiayun , Liu Jianhua , Luo Shiyong , Shi Dongpe
Published: December 2016

An integrated and computerised kinetic database system, intellectualised database management system on kinetics of metallurgy (IDMSKM) is described in this report. IDMSKM has been designed using MS Windows and a Visual C++ and Foxpro hybrid coding technique. It consists of two packages. The ThermoPhysData package has been established for physical property data retrieval and prediction, and presented in a previous publication in steel research. The emphasis in the present paper is placed on the KineticApp package. KineticApp involves G/S, S/S' and G/L' modules for the kinetic prediction, evaluation and analysis of gas/solid, solid/solid and gas/liquid reactions respectively. The key consideration in the module design is to establish the links of the kinetic model and parameters of a reaction system with the system characterisation. Assessed kinetic parameters stored in the database files in KineticApp include the activation energies for some reduction and decomposition reactions, as well as the diffusion in solid oxide systems.

Those data are necessary while dealing with the reaction kinetic prediction problems. Several examples regarding the reduction of wustite pellet, the decomposition of CaCO3 and the synthesis of SrTiO3 are illustrated to show the features and functions of G/S and S/S modules.
Towards an austenite decomposition model for TRIP steels
Authors: Fazeli Fateh , Militzer Matthias
Published: December 2016

The current status of developing a fundamental model for describing the overall austenite decomposition kinetics to ferrite and carbide‐free bainite in low carbon TRIP steels alloyed with Mn and Si is reviewed. For ferrite growth, a model is proposed where both interface and carbon diffusion‐controlled ferrite formation are considered in a mixed‐mode approach. The kinetic model is coupled with Thermocalc to obtain necessary thermodynamic information. Spherical geometry with an outer ferrite shell is assumed to capture in a simple way the topological conditions for growth. The mixed‐mode modelling philosophy has been identified to permit a rigorous incorporation of the solute drag effect of substitutional alloying elements, in particular Mn. The Purdy‐Brechet solute drag theory is adopted to characterize the interaction of Mn with the moving austenite‐ferrite interface. The challenges of quantifying the required solute drag parameters are discussed with an emphasis on a potential solute drag interaction of Mn and Si. The model is extended to non‐isothermal processing paths to account for continuous and stepped cooling occurring on the run‐out table of a hot strip mill or on a continuous annealing line. The transformation start temperature during cooling is predicted with a model combining nucleation and early growth which had previously been validated for conventional low carbon steels. The overall model is evaluated by comparing the predictions with experimental data for the ferrite growth kinetics during continuous cooling of a classical TRIP steel with mass contents of 0.19 % C, 1.49 % Mn and 1.95 % Si. Extension of the model to include bainite formation remains a challenge. Both diffusional and displacive model approaches are discussed for the formation of carbide‐free bainite. It is suggested to develop a combined nucleation and growth model which would enable to capture a potential transition from a diffusional to a displacive transformation mode with decreasing temperature.
Influence of Al, Si and P on the kinetics of intercritical annealing of TRIP‐aided steels: thermodynamical prediction and experimental verification
Authors: Mahieu Jan , Van Dooren Danny , Barbé Liesbeth , De Cooman Bruno C.
Published: December 2016

TRIP‐aided steels offer an excellent combination of strength and formability, which makes them particularly interesting for use in automotive applications. Recent investigations have shown that while the typical high CMnSi TRIP‐aided steel composition offers good mechanical properties, alloying with other elements or a modification of the processing are required to make this steel readily galvanizable without loss of the TRIP properties. Al‐alloying seems especially promising to realize this goal and P could also be an alternative. Due to the very specific thermal processing needed to obtain a TRIP microstructure, it is important to know the influence of these alloying elements on the re‐austenitization kinetics during the annealing. This paper aims at identifying the differences in the influence of Si, Al and P on the intercritical annealing of TRIP‐aided steels. The equilibrium thermodynamics calculations and diffusion‐controlled transformation simulations were used in order to predict the transformation behaviour, and experimental verification was done based on dilatometric experiments.
Effect of hot‐rolling conditions on the tensile properties of multiphase steels exhibiting a TRIP effect
Authors: Godet Stéphane , Harlet Philippe , Delannay Francis , Jacques Pascal J.
Published: December 2016

TRIP‐assisted multiphase steels have been thoroughly studied in the cold‐rolled and annealed state. The effects of hot‐rolling conditions on these steels are much less studied even though these are of major importance for industrial practice. This study was carried out in order to understand the effect of the hot deformation of austenite on the tensile properties of TRIP‐assisted multiphase steels. Two different compositions and microstructures are investigated. The first one is a low‐carbon steel (mass content of 0.15 %) with a microstructure consisting of an intercritical ferritic matrix, bainite and retained austenite. The second one is a medium‐carbon steel (mass content of 0.4 %) that consists of bainite and retained austenite. Both steels were deformed to various strain levels below the non‐recrystallisation temperature of austenite. The medium carbon steel was deformed in the fully austenitic temperature range whereas the low‐carbon steel was deformed in the intercritical temperature range. In both cases, the prior hot deformation of austenite brings about a large enhancement of the work‐hardening capabilities. In the case of the medium‐carbon steel, this effect can be attributed to a much larger TRIP effect taking place during straining. In the case of the low‐carbon steel, the improvement of the work‐hardening behaviour was attributed to an Interaction between the martensitic transformation and the dislocations already present within the surrounding ferrite matrix.
Properties and application of TRIP‐steel in sheet metal forming
Authors: Doege Eckart , Kulp Steffen , Sunderkötter Christina
Published: December 2016

A further development of dual‐phase‐steels are represented by TRIP (transformation induced plasticity) ‐steels. TRIP‐steels contain austenite, which is metastable at room temperature. It transforms to martensite during straining (TRIP effect). This process improves the strength‐ductility balance of these steels. Two types of TRIP‐steels, low alloyed (L‐TRIP) and high alloyed (H‐TRIP), can be applied in sheet forming processes and exhibit different forming characteristics. Basing on results of uniaxial tensile tests and the evaluation of Young's modulus the forming limits in deep drawing processes and the component properties of deep drawn parts are discussed. The Young's modulus decreases significantly with increasing pre‐strain, especially demonstrated for the L‐TRIP material TRIP700. Forming limit curves determined at different forming temperatures indicate its influence on the forming limits. Martensite transformation is suppressed at a temperature of approximately T = 200 °C and therefore the major strain ϕ1 decreases significantly. For the investigated stainless steel AISI304 (H‐TRIP) different lubricant types in comparison to chlorinated paraffins have been tested. Lubricants consisting of sulphur additives led to good forming conditions in forming processes, even better than lubricants based on chlorinated paraffins. The evaluation of component properties, compared between L‐TRIP and H‐TRIP, was done based on the analysis of springback and dent resistance. The L‐TRIP material TRIP700 shows higher springback angles than AISI304 resulting from higher yield strength and decreased Young's modulus, resulting from the forming process. The dent resistance of TRIP‐steel was exemplarily demonstrated for AISI304. Uniaxial pre‐strained sheet specimen were analysed to show the dent resistance depending on dent depth. During elastic denting pre‐strain has no influence on dent resistance. Further increasing dent depth lead to increased dent forces for pre‐strained specimens.
Control of Ejections Caused by Bubble Bursting in Steelmaking Processes
Authors: Müller Klaus T. , Holappa Lauri , Neuschütz Dieter
Published: December 2016

To investigate the ejection of liquid steel and slag from gas‐stirred melts in view of minimum formation of dusts and accretions, studies were performed combining laboratory experiments on single bubble/melt interactions with bench‐scale tests on 150 kg heats and with observations in metallurgical production facilities. Fine droplets are created when single bubbles burst on the melt surface or on the surface of bigger drops to form film (< 20 mm) and jet (0.1‐2 mm) droplets. At gas exit velocities of ≥ 0.1 m/s, gas flow tends to become turbulent leading to the ejection of splashes > 2 mm. In secondary metallurgy, the gas throughput is relatively small keeping the amount of small droplets (dust) low. On the other hand, the conditions for splashing are frequently met, and splashing is in fact observed in practice. An explanation model for the mechanisms of dust generation in the BOF process is derived from the lab results.
Investigations of Unsteady and Asymmetric Flow Phenomena in Continuous Casting Moulds by Advanced Simulation Techniques
Authors: Pütz Oliver , Rödl Sigurd
Published: December 2016

For further improvement of the continuous casting process a more detailed insight into the unsteady flow conditions in the mould is of great importance. Due to the difficulties to obtain this information directly in an operational plant, simulation techniques can be successfully used to extend the relevant knowledge. Therefore, simultaneously measurements of both, unsteady flow velocity using particle‐image‐velocimetry and mould level fluctuations using ultrasonic sensors, were carried out in physical models providing correlation between casting parameters and asymmetric flow behaviour. The numerical simulation of unsteady multiphase flow conditions shows time‐dependent varying local mould level fluctuations indicating an asymmetrical distribution across the mould. Both simulation approaches provide important information for increase in process stability, productivity and product quality.
Prediction of Metallic Materials Relaxation at Elevated Temperature
Authors: Batsoulas Nikolaos D.
Published: December 2016

A simple stress relaxation function is presented for metallic materials at elevated temperature. The function is derived from a more general physical‐phenomenological model describing the mechanical behaviour of metallic materials under creep conditions. The physical‐phenomenological model is represented by a simple Theological diagram with the minimum possible number of rheological elements. The creep function has only three fitting parameters whose dependencies on stress are presented by simple functions. The resulting stress relaxation curves agree with the experiments, not only the ones carried out in the laboratory but also the ones taken from literature.
Manganese Distribution between FeO‐MnO‐SiO2–CaO–MgO‐Al2O3 Slags and Molten Iron
Authors: El‐Faramawy Hoda , Fathy Ayman , Ewais Emad , Eissa Mamdouh , Ahmed Azza M.
Published: December 2016

Pretreatment of high manganese hot metal is suggested to produce hot metal suitable for further processing to steel in conventional LD converter and rich manganese slags satisfy the requirements for the production of silicomanganese alloys. Manganese distribution between slag and iron represents the efficiency of manganese oxidation from hot metal. The present study has been done to investigate the effect of temperature, slag basicity and composition of oxidizer mixture on the distribution coefficient of manganese between slag and iron. Ferrous oxide activity was determined in molten synthetic slag mixtures of FeO‐MnO‐SiO2–CaO–MgO‐Al2O3. The investigated slags had chemical compositions similar to either oxidizer mixture or slags expected to result from the treatment of high manganese hot metal. The technique used to measure the ferrous oxide activity in the investigated slag systems was the well established one of gas‐slag‐metal equilibration in which molten slags contained in armco iron crucibles are exposed to a flowing gas mixture with a known oxygen potential until equilibrium has been attained. After equilibration, the final chemical analysis of the slags gave compositions having a particular ferrous oxide activity corresponding to the oxygen potential of the gas mixture. The determined values of ferrous oxide activity were used to calculate the equilibrium distribution of manganese between slag and iron. Higher manganese distribution between slag and iron was found to be obtained by using oxidizer containing high active iron oxide under acidic slag and relatively low temperature of about 1350°C.
Online Calculation and Prediction of the Strip Temperature in a Hot Strip Finishing Mill
Authors: Kurz Matthias , Metzger Michael
Published: December 2016

The paper deals with a physical model for the calculation of the strip temperature in a hot rolling mill. Beside the heat transfer from the strip to the environment in the different mill sections a sub‐model for the material properties of steel including phase transitions is introduced. For the application in a process automation system an online adaptation of the model to the current state of the mill is indispensable. The adaptation is explained in detail.
Overview on Basic Types of Hot Rolling Textures of Steels
Authors: Raabe Dierk
Published: December 2016

The present study gives a review on basic types of crystallographic textures developing during hot rolling of polycrystalline steels. The results are grouped into three fundamental classes of textures. The first group comprises pure Fe, some weakly bonded B2 and DO3 structured intermetallics, as well as closely related alloys such as ferritic low carbon and microalloyed interstitial free steels. The second group includes highly alloyed corrosion‐resistant ferritic stainless and Fe‐Si transformer steels. Typical examples are steels with about 10 wt.%‐17 wt.% Cr, with about 3 wt.% Si, as well as body centered cubic transition metals such as Ta, Mo, and Nb which do not undergo any phase transformation during hot rolling. The third group comprises stable and instable austenitic stainless steels for instance on the basis of larger amounts of Cr and Ni or on Mn as well as duplex steels. Most L12 structured intermetallic alloys can also be assigned to this group. The suggested classification scheme is discussed in terms of different processing parameters, thermodynamics, microstructure, and crystallographic aspects.
Structural Superplasticity at High Strain Rates of Super Duplex Stainless Steel Fe‐25Cr‐7Ni‐3Mo‐0.3N
Authors: Frommeyer Georg , Hofmann Harald , Löhr Jens
Published: December 2016

The fine‐grained super duplex stainless steel Fe‐25Cr‐7Ni‐3Mo‐0.3N consisting of two phases (δ‐ferrite/austenite) exhibits structural super‐plasticity at higher strain rates of έ ≈ 10−2s−1 in the temperature range between 975 and 1100°C. The equiaxed microstructure with an average grain size of was produced by thermomechanical processing. Maximum strain‐rate‐sensitivity exponents of m ≈ 0.5 and elongations to failure of more than 500% were achieved. From thermal activation analysis an activation energy for superplastic flow of Q = 310 ± 20 kJ/mole was derived.

The superplastic behaviour at higher strain rates is quantitatively described by a deformation model where grain or interphase boundary sliding is accommodated by sequential steps of dislocation glide and climb. The high strain‐rate‐sensitivity exponent and the observed dislocation density indicate that dislocation climb in the slightly solid solution strengthened austenite is the rate controlling step for superplastic flow. The deformation mechanism reveals that the investigated super duplex stainless steel exhibits superplastic behaviour that is typical for class II solid solution alloys.
Microstructural Evolution and Crystallographic Texture Formation of Cold Rolled Austenitic Fe‐30Mn‐3Al‐3Si TWIP‐Steel
Authors: Vercammen Steven , De Cooman Bruno C. , Akdut Nuri , Blanpain Bart , Wollants Patrick
Published: December 2016

The microstructural and texture evolution of cold rolled low stacking fault energy fcc Fe‐30Mn‐3Al‐3Si alloy was investigated as a function of the cold rolling strain. The alloy was melted and cast in a vacuum induction furnace, hot rolled and annealed before being cold rolled at three different strains: ε = 0.035, e = 0.2 and ε = 1.2. During the cold rolling process different deformation mechanisms became active depending on the strain. At low strain levels, ε = 0.035 and ε = 0.2, slip traces were observed whereas at higher strains shear bands appeared. The brass orientation {110}<112> spreading towards the Goss orientation {110}<001> was dominant at every strain level. The intensity of these texture components increased with increasing rolling strain. The increase of the brass component was more pronounced when e varied from 0.035 to 0.2, whereas the increase of the Goss component was more pronounced when ε varied from 0.2 to 1.2. Additional texture components developed: the E orientation {111}<110> lying on the γ‐fibre and the S orientation {123}<634> lying on the ß‐fibre. This evolution is comparable to other low SFE fcc materials exhibiting the brass‐type texture.
Contraction of high strength Invar steel during creep test
Authors: Myslowicki Thomas , Weirich Thomas E. , Bleck Wolfgang
Published: December 2016

Modern large size Cathode Ray Tubes are equipped with so called “true flat” shadowmasks made of Invar steel. The mask is stretched onto a solid frame and both are submitted to a final heat treatment (blackening treatment). Elevated temperatures and pretension make the mask material prone to creep, resulting in disutility of the unit for the application. In order to reduce creep elongation of the mask material to a minimum, Mo added high strength Invar steels have been considered to provide the required specifications. Depending on prior processing this type of Invar steel shows an inexplicable contraction during the creep test. Even though this effect can be perfectly used to fulfil the creep requirements, the mechanisms involved were not understood. Focus of the present work was the examination of the effect of precipitations on the “negative creep” behaviour of the investigated Invar steel using carbon extraction replicae, transmission electron microscopy as well as SAED. Information about the chemical composition, morphology, size and number of the precipitations in the different states could be gained. The observations revealed that during the creep test, depending on the prior annealing temperature, the chemical composition of the precipitates changed. The Nb content decreased while simultaneously the Mo content increased. Due to the volume difference caused by Mo in solid solution and in precipitated form respectively, the precipitation of Mo during the creep test is supposed to cause the observed sample contraction. The results can be confirmed by calculating the effect of Mo on the distortion of the FeNi lattice.
Desilicating Zircon with Plasma Heating and Phase Equilibrium Analyses
Authors: Yuan Zhangfu , Pan Yifang , Luo Min , Liu Jishen
Published: December 2016

Desilicated zirconia has a great variety of applications. The maximum SiO2 content in desilicated zirconia is <7 mass%. The present techniques to produce zirconia are always accompanied by many drawbacks. So the authors have developed a new plasma process. Desilicated zirconia (88.6 ~ 96.9 mass% ZrO2) and magnesia‐stabilized zirconia (> 91.54 mass% ZrO2, < 5.39 mass% MgO) were produced successfully from zircon using a 150 kW plasma rotating furnace. The effects of time and carbon content on the desilication degree were investigated. The mixture treated in the plasma furnace included condensed phases Zr, ZrC, ZrN, ZrO2, C, Si, SiC, SiO2 and gaseous phases SiO, O2, N2, CO. The established phase equilibrium diagrams of the Si‐C‐N‐O and Zr‐C‐N‐O systems suggest that the formation of Si3N4 is thermodynamically impossible, and the formation of ZrC and ZrN is thermodynamically possible in the central high‐temperature region of the plasma furnace. Experimental results supported the analyses.
Theoretical Analysis of “Slow Hot Rolling” in Direct Linkage with Thin Slab and Strip Continuous Casting
Authors: Zhou Shunxin , Schwerdtfeger Klaus , Plociennik Christian
Published: December 2016

The present investigation was undertaken in context with the development of the single‐belt strip casting process. In this new process the casting is directly connected to hot rolling which must be carried out at lower speed than in conventional hot rolling to match the casting rate. We have used an integrated thermal/mechanical finite element model to theoretically study the effect of rolling speed on rolling parameters. Since the model is general and the question of “slow hot rolling” is of general interest, the computations were carried out for a wide range of volumetric flow rate extending from that in thin slab casting to that in conventional finishing rolling. The results are given on the influence of rolling speed on roll force, torque, power, temperature change of stock and roll, and roll life. The most important effect of slow hot rolling seems to be the increased heat up of the rolls. This causes an increase of plastic strain in the near surface region of the rolls that will intensify the formation of fatigue cracks.