bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Thermodynamic Model for Inclusion Control in Steelmaking to Improve the Machinability of Low Carbon Free Cutting Steels
Authors: Zhang Xiaobing , Roelofs Hans , Lemgen Stephan , Urlau Uli , Subramanian S.V.
Published: December 2016

Oxide inclusions formed during steelmaking processes influence the machinability of steel products. At moderate and high cutting speeds, the tool life is dominated by chemical wear. However this wear can be suppressed by engineering exogenous and indigenous glassy oxide inclusions in steel. The present work demonstrates a method to engineer glassy oxide inclusions in a low carbon free cutting steel applying a new thermodynamic model for deoxidation control of steel based on slag‐melt as well as melt‐oxide inclusion equilibration. The model is used online in an industrial production line for the controlled production of glassy inclusions. These inclusions are shown to improve machinability by lubricating the tool‐chip interface during machining of the steel at high cutting speeds. Using an inclusion engineered work piece, the crater wear of an uncoated P10 tool is significantly improved and the tool life is tripled at cutting speeds in the range between 200 and 400 m/min. The industrial results show that thermodynamic modelling is a powerful tool to produce free cutting steels with consistently good machinability behaviour.
Deformation Behaviour of Iron‐Rich Iron‐Aluminium Alloys with Ternary Transition Metal Additions
Authors: Herrmann Jutta , Inden Gerhard , Sauthoff Gerhard
Published: December 2016

The hardness and yield stress at room temperature and the brittle‐to‐ductile transition temperature of Fe‐Al alloys with 16 at.% Al, which is in the range of the so‐called K‐state with possible short‐range ordering reactions, and ternary additions of 0.5 and 4 at.% of the transition metals Cr, Mo, Mn, V, Ti and Ni were studied with respect to possible hardening effects of the ternary additions. The addition of Cr, Mo and Mn to the Fe‐Al alloys produce solid‐solution hardening which corresponds to the hardening effect of Al. Only Ti, V and Ni produce extra hardening effects which cannot be related to solid‐solution hardening. This extra hardening is attributed to possible fine NiAl precipitates in the Fe‐Al‐Ni case and to possible enhanced short‐range ordering and/or fine carbide precipitates in the cases of Fe‐Al‐V and Fe‐Al‐Ti.
Structural Morphologies and Deformaiton Characteristics of Semi‐solid Type 304 Stainless Steel during Solidificaiton and Remelting
Authors: Yanagimoto Jun , Li Jing‐Yuan
Published: December 2016

Microstructural evolutions of type 304 stainless steel and the related mechanical property of flow stress in semi‐solid state are investigated. The evolutions of microstructure during solidification, partial remelting of a hot‐rolled billet and partial remelting of a cast billet are compared with respect to structural morphologies in the semi‐solid state. Various structural morphologies, such as the linear and multilayered liquid/austenite/δ‐ferrite structure, globular liquid/δ‐ferrite structure and dendrite structure, are characterized using optical micrographs and an EPMA (electron probe microanalyzer). The various structural morphologies in the semi‐solid state are influenced not only by the phase transformation but also by the previous treatment of type 304 steel, such as hot rolling and casting. Furthermore, a series of hot compression tests are conducted for various combinations of deformation rate and deformation temperature in the semi‐solid state, to measure the flow stress and the change in microstructure resulting from plastic deformation. Flow stress, phase segregation, microfracture and distortion of solid particles during and after the hot compression test are strongly affected by the structural morphology in the semi‐solid state, such as the dendrite structure, nonglobular structure and globular structure. Semi‐solid type 304 stainless steel with dendrite structure exhibits the highest flow stress, which is about three times that of steel with globular structure, although the testing temperature and deformation rate are controlled to be the same. This is a result of the higher bonding force between solid particles and lower fluidity of the liquid phase of the dendrite structure than those of the globular structure, which exhibits excellent fluidity of the liquid phase and rotation of solid particles.
Optimum Temper Rolling Degree: Pre‐Set and Influencing Effects of Bending Deformations
Authors: Stelzer Reiner , Pütz Paul‐Dieter , Diegelmann Volker , Gorgels Frank , Piesack Ditmar
Published: December 2016

The present article describes a research project concerning the influence of bending deformations on strip mechanical properties imparted by temper rolling and a strategy for mill pre‐set to achieve the selected temper rolling degree in as short a time as possible. Research results show that, during strip temper rolling, rolls involved in the process, for example deflector rolls and anti‐sticking rolls, introduce plastic bending deformations into the strip which can amount to more than 30% of the temper rolling reduction, depending on the effective bending radii.

Bending tests involving strips made of low‐carbon steel in a tension roller system with an integrated bending unit demonstrate that bending deformations influence the mechanical properties of the strip in a manner similar to the temper rolling process itself. It appears necessary to take account of the bending effects when selecting the optimum temper rolling degree.

The most accurate roll force pre‐calculation possible and its application at the mill stand are of major importance for pre‐setting the required temper rolling degree. Existing analytical methods have been unable to yield the necessary calculation accuracy. Combination of an optimised analytical approach with a data‐based model to create a hybrid model has led to significant improvements. The accuracy achieved in the pre‐calculation of the required roll force has helped to improve mill pre‐set of the investigated temper mill and to reduce strip head‐end scrap on average by around 6 m per strip. Based on the annual outputs stated by the plant operator, this makes it possible to achieve a cost saving of more than 200,000 € per year.
Incremental Forming of Hollow Shapes
Authors: Neugebauer Reimund , Glaß Roland , Hoffmann Michael , Putz Matthias
Published: December 2016

Hollow shapes, particularly the shafts of road vehicle power trains, are a major potential for technical innovation since these components have to be especially strong while component weight and unit costs are highly restrictive. This strategy for innovation requires focusing on a wide range of disciplines of product and technology development and demands intensive and advanced interdisciplinary development of the required production technology. Hollow shapes can be produced with the spin extrusion process. Spin extrusion is a flexible rotatory pressure forming process which can be applied in dimensional ranges that cannot be attained by comparable processes, not in a cost‐effective fashion or for very expensive materials. Spin extrusion is an incremental technique, meaning there are also the known difficulties standing in the way of analytically describing processes and targeted process control. The energetic approach has proved to be the most practicable because it makes it possible to differentiate between a wide range of factors and parameters having an impact on the process while applying them to machine and process control. The results of process development was a new processing principle for manufacturing hollow shaft components by forming for specific needs of the automobile industry and other industries with major accuracy and safety requirements.
Peter Groche
Authors: v. Breitenbach Gerrit , Steinheimer Rainer
Published: December 2016

Tube hydroforming (THF) is a relatively new but established technology among metal tube forming processes. It is the technology of forming closed sections, hollow parts with different cross‐sections by applying an internal hydraulic pressure and sometimes additional axial compressive loads to force a tubular blank to conform to the shape of a given die cavity. Material properties have a significant influence on the process stability. Often roll‐formed, non‐heat treated tubular materials made of steel with longitudinally oriented welding lines are used in tube hydroforming. Different production processes involve a change of the material properties from the initial flat sheet to the hydroformable tube. Testing methods such as tensile tests and conventional forming limit diagrams do not accurately reflect the state of stress and strain conditions seen in the tubular blank during the hydroforming process. Thus, inaccuracies in FEA predictions and design failures occur. Test methods were developed to characterize the relevant geometrical and mechanical properties of tubular semi‐finished products.
Controlling the Surface Quality of a Steel Sheet by Monitoring the Lubricant Layer
Authors: Fischer Niko , Oberhausen Michael , Bley Helmut
Published: December 2016

This paper focuses on the influences on surface quality of a steel sheet by controlling the application of forming compounds. To date forming compounds have been applied empirically by rolling or spraying the lubricant onto the surface of the sheet metal. But there is no possibility to control the distribution of the lubricant on the metal surface. Especially in areas of high abrasion and degree of deformation, there is a need to increase the layer of lubricant, whereas material flow has to be prevented in other areas. So the distribution of forming compounds in the different application areas must be controlled by using a monitoring system. With this process control it is possible to stabilize the surface quality of the workpieces and the amount of lubricant can be optimized.
Process Modeling for Precision Forming of Discrete Parts – State of the Technology and Critical Issues
Authors: Altan Taylan , Palaniswamy Hariharasudhan , Cho Hyunjoong
Published: December 2016

This paper presents an overview on the application of FE simulation as a virtual manufacturing tool in designing manufacturing processes for precision parts. The processes discussed include forging, sheet metal forming and hydroforming. Determination of reliable input parameters to simulate a process is a key element in successful application of process simulation for process design in all the mentioned areas. These issues are discussed in detail. Practical examples of application of FE simulation are presented for improvement of the existing metal forming process and/or designing new metal forming process for manufacturing discrete precision parts in forging, sheet metal forming and hydroforming.
Theoretical and Experimental Damage Prediction in Cold and Semi‐Hot Bulk Forming of Ductile Steels
Authors: Behrens Arno , Just Hendrik
Published: December 2016

Bulk forging is among the most important manufacturing methods in metal forming, due to its wide applicability from some ounces to several tons of steel in a high diversity of shapes and forming conditions. Economical constraints demand for further optimisation and cost‐effective production. This requires the application of suitable finite elements simulation software, in order to support the already digitalised construction processes. Ductile damage is one of the most severe problems to arise during the production sequences, not only in cold but also in semi‐hot forging operations. Mathematical approaches exist for the modelling and simulation of ductile fracture in steel. In this paper some widespread used damage models are introduced and discussed. Their damage prediction quality has been verified by experiments, the tensile test and the collar specimen upsetting with several different steels under cold and semi‐hot forging conditions. The methods for the experimental fracture detection are introduced as well. In cold forging the passive ultrasonic testing with integrated statistical filtering algorithms is used. As this method is not applicable to semi‐hot forging experiments, optical fracture detection by means of a high‐speed camera is used instead. A very interesting material behaviour of the steels tested has been identified in the semi‐hot upsetting of collar specimen. For every steel a distinct temperature crossover interval exists, in which the forging process abruptly changes from damaged to undamaged state. This interval amounts to some degrees Celsius only for each of the seven materials investigated. Among the damage models proposed, the Model of Effective Stresses by Lemaitre is chosen for the application to a cold and a semi‐hot forging operation. These industrial processes of an axle end (cold) and a journal bearing (semi‐hot) are susceptible to damage for reasons to be discussed in this paper. It will be shown that the internal fracture of the axle end (chevrons) and the surface fissures of the journal bearing can be predicted with high accuracy. Moreover, the application of the damage model in the finite element software MSC.SuperForm 2004 offers a promising approach for process optimisation. Several possibilities could be tested for their suitability of reducing the calculated damage: geometry variation of the forming tools, process annealing, different materials. The use of damage models in finite element simulation can be regarded as a further step towards an optimal process design.
Laser Beam Joining of Dissimilar Thin Sheet Materials
Authors: Vollertsen Frank , Grupp Michael
Published: December 2016

Joining of dissimilar materials is in the focus of many research activities, due to the ability of creating assemblies with advanced functionalities. The functionality can arise either from the physical properties of the interface such as electrical or heat conductivity, or the advantages of weight reduction in light weight constructions. By thermal joining like welding and brazing many metal combinations tend to form intermetallic phases. These phases have a negative influence on the properties of the joint by forming hard and brittle layers. This paper presents a study on laser beam joining of stainless steel to titanium alloy on thin materials for micro‐applications. Two joining technologies are investigated and an optimized process technology for brazing is presented. The results are evaluated with regard to the intermetallic phase formation and the mechanical strength.
Pulsed‐Magnetic Hot Joining ‐ New Solutions for Modern Lightweight Structures
Authors: Uhlmann Eckart , Hahn Robert , Jurgasch Dirk
Published: December 2016

To further significantly reduce the car weight, new and innovative production technologies are necessary which allow to join aluminium and – in the future – magnesium profiles. Then it will be possible to connect components made of aluminium or magnesium base alloy with steel parts to one group. Such a new technology is pulsed‐magnetic joining. In order to lower the process forces necessary for pulsed‐magnetic joining of high strength aluminium alloys and in order to establish a technologically useful forming of magnesium alloys, joining at increased temperatures appears to be a viable solution.

As part of the research a tool for pulsed‐magnetic hot joining has been developed that combines the processes of heating by induction and pulsed‐magnetic joining. The applicability and the potentials of the tool have been demonstrated with hot joining of aluminium and magnesium profiles. The combination of the techniques allows for the first time to join magnesium profiles with forming by using pulsed‐magnetic forming at high temperatures. Regarding aluminium the combination of the techniques allows a significant reduction of the magnetic pressure that is necessary for the forming process; it thereby increases the operating life of the tools.
Thermodynamics of Cobalt Aluminate Formation in Molten Cobalt
Authors: Soltanieh Mansour , McLean Alexander
Published: December 2016

The oxygen concentration of liquid cobalt in equilibrium with cobalt aluminate and alumina was measured by suction sampling at temperatures in the range of 1783 to 1873 K. Experiments were made with cobalt of high and low initial oxygen content and with the addition of cobalt aluminate. The Gibbs free energy of the formation of cobalt aluminate in equilibrium with cobalt containing dissolved oxygen and alumina is:

Co (l) + (1+x) Al2O3 + [O]1 wt% in Co = CoO·(1+x)Al2O3 with ΔG° = ‐(226400 ± 8730) + (93.04 ± 4.74) T [J/mol].

The oxygen partial pressure in equilibrium with the dissolved oxygen in molten cobalt was determined by zirconia stabilized with magnesia oxygen sensors. The Gibbs standard free energy of dissolution of oxygen in molten cobalt in the range of 1783 to 1873 K is:

1/2 O2 = [O]1 wt% in Co with ΔG° = ‐76410 – 2.16 T [J/g·atom].
Flow and Thermal Analysis during Hot Extrusion of Two Kinds of Stainless Steel: AISI 316Ti and AISI 329A
Authors: Mapelli Carlo , Tagliabue Chiara
Published: December 2016

A mathematical model was developed to describe the mechanical and thermal behaviour of stainless steels during hot extrusion. The reference point for the study was the experimental data of the extrusion process performed on two stainless steels in order to take into account the most significant features of the process: temperature, velocities, extrusion ratio and the shape of the extrusion die. The developed simulation approach is based on the Navier‐Stokes equations which were used to compute the speed field in the steel during its passage in the die; this formalism allows to reach the resolution of the structural problem from the data easily measured during the industrial practice, i.e. press velocity and velocity of the extruded material at the exit from the die. The behaviour of the steel can be calculated through its constitutive law at high temperature from the fields of velocity, strain rate, strain and stress. The structural model is coupled with a thermal one based on the Fourier equation which provides the thermal field that plays a fundamental role in the microstructural features of the final product. The validation of the computational approach has been realized by an analysis of the obtained velocity distribution in the material and by a comparison between the calculated temperature field, the metallographic structure and the measured micro‐hardness values.
A Study of Friction in Non‐Lubricated High Temperature Steel Processing
Authors: Jupp Simon P. , Beynon John H.
Published: December 2016

The effect of friction on the cost of steel rolling and the overall quality of the strip has been overlooked in favour of more controllable aspects, such as temperature and microstructure. When friction is considered, predominantly empirical relationships are employed that have been developed in smaller scale experiments and are not necessarily applicable to the industrial scale. An advancement to the adhesion theory of friction has been developed by Straffelini that links friction with material properties, which compares well with pin‐on‐disk experiments at room temperature using metallic tribo‐pairs. For the purposes of creating conditions analogous to hot rolling of steel, a tool steel (100Cr6) dowel and an oxidised steel sample have been used in a reciprocating friction tester to create a relatively controlled environment in which to study friction at high temperature. The simplified adhesive theory was found to agree well with these experimental results, demonstrating that this theory can be applied to a broader range of conditions than previously tested against.
The MIDAS Technique for Detection of Macroscopic Inclusions in CC‐Material: Fundamentals and Practical Applications
Authors: Jacobi Hatto F.
Published: December 2016

In this paper twelve years of experience with MIDAS (Mannesmann Inclusion Detection by Analysing Surfboards) testing for macroscopic cleanness of continuously cast steel is reviewed. MIDAS has replaced the previous slime extraction method, which was technically competitive, but too time‐consuming and costly. MIDAS is indispensible for operational trials in the steelworks. The results correlate with quality demands of the final product. The main feature of MIDAS is the flat cross‐rolling procedure transverse to the casting direction. The microstructure of the steel is grain refined by recrystallization. The inclusions are rolled flat, which is advantageous for the ultrasonic inspection. The ultrasonic frequency is 10 MHz and the scanning steps are Δx = Δy = 1 mm. A test plate of dimensions 400 mm x 300 mm is thus scanned within 15 min.

MIDAS‐test results in combination with metallographic and EDX‐analysis of the macro‐inclusions enabled a deeper understanding of the fundamentals of ladle metallurgy, metal‐slag reactions, emulsification, agglomeration and coagulation, reoxidation, fluid flow pattern, precipitation and separation. On the basis of MIDAS results CC machines have been revamped and ladle metallurgical facilities and processes optimized. Steel grades with high cleanness demands, e.g. mechanical tubing, HIC line pipe, roller bearing steel, as well as automotive sheet can be produced at lower cost and higher yield to the satisfaction of the customers.
Determination and Modelling of the Influence of Cooling in the Coil on the Mechanical Properties of Hot Strip Steels with Bainite
Authors: Siodlak Dorota , Lotter Ulrich , Kawalla Rudolf , Paul Georg
Published: December 2016

The phenomenon of bainite formation in the hot strip mill for unalloyed steels and the influence of the complex cooling process have hardly been dealt with in literature. Only two useful model equations were found, namely according to Suehiro et al. [4] for the determination of the strength parameters Rp0.2 and Rm of annealed bainite, and according to Umemoto et al. [2] for the calculation of the tensile strength Rm of bainite formed during the isothermal holding temperature. These equations could be optimized by structural complements and modification of the coefficients by adjusting them to the own measured values. For building up the necessary data base, experimental methods were developed, involving the use of a computerized deformation dilatometer. The results thus obtained can be applied to the industrial practice.
Characteristics of Metal Droplets in Slag Tapped from the Blast Furnace
Authors: Gustavsson Joel , Shoyeb Mohammed , Sarma Darbha S. , Jönsson Pär G.
Published: December 2016

Slag samples, hot‐metal samples and hot‐metal temperatures were obtained during tapping of two blast furnaces. Sampling was carried out at different time points during tapping of three separate heats. The size distribution and composition of metal droplets found in the slag were determined using scanning electron microscopy. Only metal droplets above 0.75 μm could be counted and analysed. All droplets were below 8 μm in diameter and the great majority of these droplets were found to be between 0.75 and 2 μm. The size distribution did not differ significantly for different slag samples. Iron was the main droplet component. Electron probe microanalysis showed that the droplets contained small amounts of carbon. The percentage of the area in a studied cross‐section that was covered with metal droplets varied between 0.01 and 0.07%. Calculations based on Stoke's law showed that the distance droplets travel in the slag is in the micron range. Slag samples taken in the beginning of slag tapping contained more droplets than those taken in the middle of slag tapping, an indication that most droplets can be found in the area near the furnace wall. Some droplets were determined to have magnesium enrichment at the external surface.
Sulphide Capacities of CaO‐SiO2‐Al2O3‐MgO Slags
Authors: Hayakawa Hikaru , Hasegawa Masakatsu , Oh‐nuki Kazuo , Sawai Takashi , Iwase Masanori
Published: December 2016

In Japanese steelworks, hot metal is now being produced by a scrap melting process. With this process, removals of sulphur is very much handicapped because of very high sulphur levels (0.04‐ to 0.09‐ pct by weight) and relatively low tapping temperatures (1623 to 1723 K). In order to overcome such handicaps, the authors explored on the respective phase diagrams. These explorations revealed that {CaO‐SiO2‐Al2O3‐MgO} slags with Al2O3 contents of 30‐ to 35‐pct by weight would be good candidates as reagents for sulphur removal from high sulphur hot metal at relatively low temperatures. For better understanding of the thermodynamic properties of the candidate slags, in this study, sulphide capacities were determined through gas/slag equilibrium technique. The experimental results suggest that there would be, at least, a “window” to remove sulphur from high sulphur hot metal as relatively low temperatures.
Effect of Nozzle Base Material on the Rate of Clogging during the Continuous Casting of Aluminum‐Killed Steels
Authors: Trueba Luis , Peaslee Kent D. , Smith Jeffrey D. , Karakus Musa
Published: December 2016

One approach to solving the problem of nozzle clogging during the continuous casting of aluminum‐killed steels is through careful selection of nozzle materials. In this study, the rate of clogging was measured while casting steel through simulated nozzles produced from alumina, zirconia, magnesia, zirconia‐graphite, and alumina‐graphite ‐ three common base materials and two common carbon‐containing nozzle materials. Spent nozzles were characterized using optical and cathodoluminescence microscopy. Interactions between the nozzles and steel were not observed in the alumina, zirconia, and zirconia‐graphite nozzles. Slight interactions were observed in the magnesia nozzles as alumina inclusions within the steel interacted with the nozzle to produce alumina‐magnesia spinel. Greater amounts of interaction were observed with alumina‐graphite nozzles. No statistical differences in the mean rate of clogging were observed between all of the pure oxide nozzles and zirconia‐graphite nozzles. However, the alumina‐graphite nozzles clogged at a much higher rate than the other nozzles. The higher rate of clogging is thought to be due to refractory‐steel interactions.
A Study of Microstructure and Performance of Quenching Fe‐V‐W‐Mo Alloy
Authors: Fu Hanguang , Xiao Qiang , Xing Jiandong
Published: December 2016

The critical points and time temperature transformation (TTT) curves of Fe‐5%V‐5%W‐5%Mo‐5%Cr‐3%Nb‐2%Co (Fe‐V‐W‐Mo) were measured, and the effects of quenching temperature and cooling modes on the microstructure and performance of Fe‐V‐W‐Mo alloy were investigated. The results showed that the hardness of Fe‐V‐W‐Mo alloy increased until the quenching temperature reached 1025°C and dropped down as the quenching temperature exceeded 1050°C in oil cooling. The hardness obtained in air cooling and spray cooling exhibited a similar tendency as that in oil cooling, but the temperature at which the highest hardness was obtained in these slower cooling processes changed to a higher range. The hot hardness and toughness of Fe‐V‐W‐Mo alloy increased with rising quenching temperature until it reached 1150°C, and from then on the toughness began to drop. The main reasons why the structures and properties of Fe‐V‐W‐Mo alloy obviously change under different quenching conditions are particularly analysed at last.
Comparative Study of Oxide Speciation in Steel by Inert Gas Fusion Technique
Authors: Krasovskii Pavel V. , Gruner Wolfgang , Grigorovitch Konstantin V.
Published: December 2016

The paper presents the application of an improved procedure for oxide speciation in steels by temperature ramped inert gas fusion technique on commercially available instruments. Main steps of analysis, data processing and interpretation of the results are described. The effects of instrumentation and auxiliary materials on the evolution kinetics of oxygen during an analysis are emphasised. The procedure is applied to determine the content of alumina and spinel species in high‐carbon steels, attested as reference materials. The results of the gas fusion technique are correlated to those of the chemical analysis and scanning electron microscopy equipped with energy dispersive X‐ray detector.
Effect of Cr and N on the Martensitic Transformation in Fe‐8%Mn Alloys
Authors: Cabañas Neus , Verbeken Kim , De Cooman Bruno C.
Published: December 2016

The influence of Cr and N on the transformation temperatures of a Fe‐8%Mn alloy has been investigated by means of equilibrium thermodynamics and dilatometry. The addition of Cr and N resulted in the presence of ferrite or α'‐martensite at room temperature, with the microstructure transforming to a single phase austenitic microstructure with increasing temperature. Only high amounts of Cr or N in excess of 0.2% prevented the transformation to a single phase austenitic microstructure. The addition of alloying elements resulted in a decrease of the martensite start temperature Ms. The effect on the austenite start temperature As was smaller. The effect of thermal cycling resulted in a stabilization of the transformation temperatures. More cycles were required to reach stable phase transformation temperatures when N was added to Fe‐Mn‐Cr alloys.
Reduction Behaviour of BOF Slags by Carbon in Iron
Authors: Jung Sung‐Mo , Do Young‐Ju
Published: December 2016

Experiments were carried out in a system with BOF slags from industrial operations in order to optimize the conditions of recycling BOF slags produced in the steelmaking process. Reduction reactions of FeO and P2O5 proceeded steadily and the FeO reduction rate was almost identical to that of P2O5. The reduction reaction of FeO and P2O5 in BOF slag at the slag/gas interface is the rate‐controlling step. The reaction rates of FeO and P2O5 by dissolved carbon in molten iron are of first order with respect to their respective concentrations. The reduction reactions of FeO and P2O5 by dissolved carbon in iron are much closer to the equilibrium state compared with the reduction by solid carbon. It is necessary to control the portion of phosphorus vaporization during reduction treatment in order to obtain efficient operational conditions for BOF slag reduction.
Discussion of Theoretical Methods to Predict Scale Thickness in Hot Rolling of Steel Strips
Authors: Zhou Shunxin , Liu Guanglian , Cao Yuanfeng
Published: December 2016

Oxidation of iron during hot rolling is inevitable and scale layers are formed on the strip. There are different rate laws of oxidation of iron to predict the scale thickness, in which parabolic rate law and mixed rate law are usually used in hot rolling of strips. As the strip passes through the roll gap, the scale layer can plastically be deformed. Due to limited plasticity of the oxide, cracks through the scale layer can be formed in every roll gap. They open and form new free metallic surfaces which are then oxidized in the interstand. By means of numerical simulations different rate laws of oxidation are compared and the scale deformation with different cases is taken into account. Sensitivity of some rolling parameters to prediction of the scale thickness is discussed in the present paper. Numerical results show that the parabolic rate law overestimates the scale thickness as compared with the mixed rate law and the mixed rate law is not sensitive to the deformation extent of scale.
Electrode Erosion due to High‐Current Electric Arcs in Silicon and Ferrosilicon Furnaces
Authors: Sævarsdóttir Gudrun , Pálsson Halldor , Jónsson Magnus , Bakken Jon Arne
Published: December 2016

The role of the electric arc in the consumption of electrodes in submerged arc furnaces has long been discussed. The environment does not make direct measurement possible, so simulation has been used to evaluate the arcs contribution to the erosion. Magnetofluiddynamic (MFD) electric arc simulations and a cathode / anode sub‐model developed in order to provide boundary conditions to the arc model have been used for this purpose. In the case of high‐current industrial AC arcs, arc currents are typically ~100 kA, phase voltages ~100 V and total furnace power ~10 ‐ 60 MW. The results show that although enormous amounts of material is evaporated, due to recondensation of vapour, less than half of the total electrode consumption in an industrial furnace can be attributed to the arc. The largest contributor is chemical corrosion. Results from this analysis indicated that there are probably more than one arc present in the crater.
Maximum Copper and Tin Contents in LC‐steel Thin Strip ‐ Hot Shortness Model Calculations
Authors: Pötschke Stephan , Büchner Achim R.
Published: December 2016

For conventional casting processes low copper and tin contents have to be ensured in LC‐steel to avoid hot shortness. It is expected that higher cooling rates, e.g. in thin strip casting, permit higher copper and tin limits. Hot shortness occurs because of selective oxidation of the iron whereby the more noble copper is enriched at the steel‐oxide interface. A liquid metallic copper phase which wets the grain boundaries supports cracking during hot deformation. The enrichment of the liquid copper phase depends on the oxidation temperature: At low temperatures copper is solid, cannot wet the steel surface and is incorporated into the growing oxide layer. At mid temperatures (1083‐1177 °C) the copper phase is liquid, wets the grain boundaries of the steel surface and causes hot shortness. At high temperatures a liquid fayalitic slag is formed in the oxide layer if the steel contains silicon. The fayalitic phase occludes parts of the steel surface and removes copper from the steel surface; then hot shortness is reduced or even avoided. Other mechanisms to remove copper from the steel surface need the presence of Fe3O4 and Fe2O3 in the oxide layer. These iron oxides are not formed for short oxidation times where linear oxidation takes place. Diffusion of copper into the steel is too slow to reduce hot shortness if copper has an elevated concentration in the steel, e.g. 0.5 wt.‐%. Therefore, only the occlusion mechanism is of importance during linear oxidation. A model is established on the basis of these observations in order to predict an upper copper limit in dependence of the steel strip thickness (cooling behaviour) and the oxygen content in the cooling atmosphere (nitrogen‐oxygen mixture). The model is compared to experimental results from KIMAB which are presented in this issue. It is demonstrated that a copper layer thickness of 0.098 μm at the steel‐oxide interface is sufficient to cause cracks of a depth of more than 0.2 mm. For strip thicknesses below 5 mm a simple approximation can be used to predict the maximum copper content in LC‐steel to avoid hot shortness. For example, thin strip of a thickness of 2 mm will have no cracks (above 0.2 mm) even if 0.7 wt.‐% of copper is contained in the LC‐steel. For atmospheres with a reduced oxygen partial pressure even higher copper contents are possible.

Tin is with short oxidation times not a problem concerning hot shortness, as shown by the KIMAB results. This may be explained by the much higher diffusivity of tin in iron compared to copper.
A New Transducer for Local Load Measurements of Friction and Roll Pressure in Cold Flat Rolling
Authors: Lagergren Jonas , Wanheim Tarras , Precz Woijtech , Henningsen Poul , Arentoft Mogens , Jonsson Nils‐Göran
Published: December 2016

The only way to establish the true rolling pressure and the true friction condition in cold rolling is to conduct measurements in the roll bite. A new transducer design is therefore proposed, in order to overcome problems in previous measurements in the past 70 years. The new idea is to increase the contact surface of the transducer, to be larger than the arc of contact. This is in contrast to the smaller and smaller contact pin design that has been prevailing. The measurements were conducted during cold dry rolling of both copper strips and stainless steel strips in a pilot mill. The recordings were selected from a steady state with no disturbance from the material flow. The transducer was able to simultaneously measure both the normal pressure and the friction stress. An estimation of the coefficient of friction was accordingly performed. The new transducer works very well, it was seen to be robust and able to avoid signal disturbance. The pressure and friction stress distribution results was as expected by the authors and showed good reproducibility, together with a proven agreement between recorded and simulated signals.
Comparison of Hot Rolled Textures in Different Grades of High Formable Steels
Authors: Humane M.M. , Vaish A.K. , Swaminathan J. , Kumar B. Ravi , De P.K. , Peshwe D.R. , Paretkar R.K.
Published: December 2016

During hot rolling of steels phase transformation takes place. Hot band texture and hot band grain size largely influence the texture formation of cold rolled and annealed steels. Generally, a strong crystallographic relationship exists between the parent austenite phase and the product ferrite phase. The present investigation incorporates a comparative study of hot band texture formation in austenitic zone in extra deep drawing (EDD), interstitial free (IF) and interstitial free‐ high strength (IF‐HS) steels. The intensities of hot band texture in IF‐HS steel [f(g) = 19.6] were found to be much stronger in comparison to EDD [f(g) = 3.9] and IF [f(g) = 1.4] steels.
Mechanical Properties and Bake Hardening Behaviour of two Cold Rolled Multiphase Sheet Steels subjected to CGL Heat Treatment Simulation
Authors: Krieger Markus , Estrin Yuri , Janeček Miloš , Niemeyer Matthias , Paul Silke
Published: December 2016

In recent years, multiphase steels have become a material of choice for use in the car manufacturing industry owing to their excellent mechanical properties. It is anticipated that in the years to come these steels will show the highest increase in usage. A particular aspect of their potential is that multiphase steels often show good bake hardening (BH) properties. The main factors that govern the microstructures and the properties of these steels are the chemical composition and the production process parameters.

In this work two commercial cold rolled sheet steels with different carbon content were investigated. In order to produce dual phase (DP) steels with a ferrite‐martensite microstructure, the as‐received material was subjected to heat treatment simulating continuous galvanising line (CGL) cycles with an overageing zone before the zinc pot. After a first CGL cycle predominantly ferritic microstructures with small amounts of martensite, pearlite and retained austenite were obtained, which resulted in deviations from typical DP properties, e.g. in the occurrence of discontinuous yielding. A higher line speed led to improved mechanical properties. BH prestrain was varied between 0 and 10%. While only very little bake hardening was observed without prestrain, with increasing prestrain the amount of BH was evolving quickly towards larger values of more than 60 MPa. Generally, the BH values were somewhat larger for higher carbon content. Finally, an optimised CGL cycle was simulated at laboratory scale with changes in the process parameters. Thus, characteristic DP microstructures resulting in desired mechanical properties were obtained. For these optimised conditions, BH2 values in excess of 60 MPa were achieved for both steels investigated.
Bake Hardening of Hot Rolled Multiphase Steels under Biaxial Pre‐strained Conditions
Authors: Palkowski Heinz , Anke Thorsten
Published: December 2016

Multiphase steels show a strong bake hardening effect being of importance for shaping of car body structural parts. The raised yield strength is exploited for improved crash resistance. Especially the automotive industry has a growing interest in using this effect. Normally the bake hardening effect is examined in tensile tests whereas under industrial conditions shaping of structural parts shows a wide spread of stress strain behaviour, from uniaxial conditions over plain strain to biaxial ones. So it is obvious that the bake hardening behaviour of a material cannot be described with results of the uniaxial tension test only. To give a first answer to this question, the dependence of the bake hardening effect on different biaxial prestrains was investigated for several hot rolled multiphase steels using various baking temperatures and holding times whereas the bake hardening effect under uniaxial prestrain had already been examined in [5]. Considering the choices to generate biaxial strain, a Marciniak forming tool with a diameter of 250 mm mounted on a 2500 kN hydraulic press was chosen. For control of plastic deformation and adjustment the non‐contact measuring system ARGUS, was used. To reduce the quantity of experiments “Design of Experiments” and statistical methods were applied for a martensitic steel, a dual phase steel, a complex phase steel, a ferrite‐bainite steel, and a retained austenite steel known as TRIP, all in hot rolled condition. As a result, a formula for yield stress, tensile strength and residual deformability was developed. Furthermore, a method was found to predict easily whether a steel under investigation is qualified for additional experiments in regard to bake hardening or more exactly its response to different baking temperatures and holding times.
Air Bending Process for Load Optimised Profiles
Authors: Abratis Cornel , Hirt Gerhard , Kopp Reiner
Published: December 2016

In this paper the air bending of Tailor Rolled Blanks (TRB) to load optimised profiles is investigated. A new flexible modular tool system has been developed in order to locally adapt the die height to the spring back which is more pronounced in thinner areas in comparison to thicker areas of the TRB. With the new tool system the dies can be modulated according to the thickness distribution of the Tailor Rolled Blank, whereas the amount of die lifting depends on the thickness difference and the corresponding variance of mechanical properties. In bending tests with several specimens having a constant thickness a linear relation between the increasing part angle and a stepwise increased die lifting was observed. With this linear dependency the amount of die lifting can be calculated and thus applied on bending of TRB. Special consideration is required for the die adjustment in the area of the linear thickness transition, therefore three different die arrangements have been investigated. The results of different bending tests are compared and evaluated in order to apply the new technique to form a new car body floor structure in profile intensive construction. By using load optimised profiles in combination with a steel 22MnB5 which has been heat‐treated at defined sections the survival space of a car passenger in a side pole impact has been enormously increased by more than 40 %.
Studies on Graphitisation of Blast Furnace Coke by X‐ray Diffraction Analysis and Thermal Diffusivity Measurements
Authors: Abas R. Abdul , Jakobsson A. , Hayashi M. , Seetharaman S.
Published: December 2016

High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X‐ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser‐flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X‐ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.
Activity of MnO in MnO‐CaO‐MgO‐SiO2‐Al2O3 Slags at 1500 °C
Authors: Cengizler Hakan , Eric R. Hürman
Published: December 2016

A thermodynamic study was made on the MnO‐CaO‐MgO‐SiO2‐Al2O3 slags that are typical of the production of ferromanganese in submerged arc furnaces. The Al2O3 content of the slags was kept constant at 5 per cent by mass. The activity‐composition relationship in Pt‐Mn binary alloys were re‐determined for calibration purposes at 1300, 1400 and 1500°C and po2 values between 5.40×10−6 and 4.54×10−13 atm. A linear regression equation was derived to predict the activity coefficients of manganese, in Pt‐Mn alloys at 1500°C. The effect of concentration, basicity ratio and CaO‐to‐MgO ratio on MnO activities in above mentioned complex slags was investigated at 1500 °C and at two different po2 values of 4.76×10−7 and 5.80×10−8 atm. It was found that aMno values increase with increasing MnO, and tend to increase with an increasing CaO‐to‐MgO ratio. The aMnO values also increase with increasing basicity ratio. The activity coefficient of MnO increases with an increase in its mole fraction in the slag. Quadratic multivariable regression model equations which represent the activity data successfully and which can be used to predict the MnO activities in the compositional range of this study were developed. The MnO activity data was interpreted in terms of a slag model which describes the thermodynamic properties of the slag successfully.
A Fractographical Investigation of Weld Toe Imperfections in Tandem Gas Metal Arc Welding
Authors: Farajian‐Sohi Majid , Järvstråt Niklas
Published: December 2016

Prediction and control of flaws in welds play important roles in design of complex structures against fatigue and fracture failure. Cold laps ‐ outer lack of fusion ‐ are small geometrical imperfections at weld toes, which act as fatigue crack initiation sites and reduce the life of welded structures drastically. The aim of this work is to characterize and categorize different types of such imperfections in the tandem gas metal arc welding process and find the mechanisms of their formation. Tandem welding process with different welding parameters was used to produce bead‐on‐plate coupons. These coupons were then sliced to smaller specimens for further investigations. For studying the weld toes, all the specimens were hit in an impact test machine and then the fracture surfaces of welds and base materials were analysed by scanning electron microscopy (SEM). Two types of cold laps were observed at weld toes, namely overlap and spatter. Observation and measurement showed that these imperfections are in the form of micro cracks with depth between 0.1 to 1.5mm and length between 0.1 to 4 mm.