bluuebunny/crossref_metadata_2025 huggingface dataset:
Decarburization of high carbon ferromanganese melts
Authors: You Byung‐don , Han Jeong‐whan , Pak Jong‐jin
Published: December 2016

The effect of oxygen/argon mixing ratio in the bottom blowing gas on the decarburization behaviour of high carbon ferromanganese melt was investigated in the temperature range of 1350 – 1550°C. Thermodynamic analysis indicates that high melt temperature and low PCO are essential for an effective decarburization. An empirical equation for the utilization ratio of oxygen for decarburization was derived as functions of the melt temperature and the oxygen/argon mixing ratio in the refining gas. The utilization ratio of oxygen for decarburization sharply increases as the melt temperature increases and the oxygen ratio in blowing gas decreases. In oxygen refining of high carbon ferromanganese melt, it is not desirable to inject oxygen through bottom tuyères in an early stage of refining. When the melt temperature is low, the oxygen predominantly oxidizes the manganese in melt in spite of high carbon contents. The injection of oxygen/argon mixture gas is found to be an effective decarburization technique when the melt temperature is higher than 1500°C.
The oxygen pressure of dilute FexO‐CaO‐Al2O3 slag in equilibrium with liquid iron
Authors: Ichise Eiji , Fujiwara Hiroyasu , Han Qiyong
Published: December 2016

The relationship between slag composition and oxygen partial pressure of dilute FexO‐CaO‐Al2O3 slag in equilibrium with iron the activity of which is below 1 was extrapolated to give the oxygen partial pressure of a slag equilibrated with iron of the activity 1. In the process of extrapolation, the oxygen partial pressure and the activity of iron were unified to give a single thermodynamic quantity which is defined as: , where K(x) is the equilibrium constant for the formation reaction of FexO and is considered to be a function of x. The dependence of on the slag composition was obtained experimentally. On the other hand, it was found that the plot of against log aFe has the slope −1 as expected from the theoretical consideration. The relation has been employed to estimate the composition of slag in equilibrium with liquid iron. Thus, the obtained composition is used to calculate the values of and of the slag in equilibrium with liquid iron.
Reduction kinetics of manganese oxide in basic oxygen furnace type slag
Authors: Sohn Ho‐Sang , Chen Zhao‐Ping , Jung Woo‐Gwang
Published: December 2016

In order to improve manganese yield during the reduction of manganese ore, the reduction kinetics of manganese oxide in BOF type slag has been investigated on an experimental scale. The reduction rate of (MnO) was promoted for the slag of low basicity and high contents of (FeO). The maximum reduction rate of (MnO) has been found for an iron melt with carbon mass contents of 1.9 %. The silicon in metal may accelerate the reduction of manganese oxide in slag. The kinetic model for the reduction rate of (MnO) has been formulated based on the assumption that the reduction of (MnO) was controlled by the mass transfer through the metal and slag boundary layers at the metal/slag interface. The result calculated by the kinetic model showed a good agreement with the experimental one. The reduction behaviour of (MnO) can be described by the present model.
Control of inclusions in a resulphurised steel
Authors: Mapelli Carlo , Nicodemi Walter , Vedani Maurizio , Zoppi Alessio
Published: December 2016

The formation of non‐metallic endogenous inclusions in ladle‐furnace treatment of a resulphurised C‐Mn Al‐killed steel was investigated. A model based on equilibrium reactions and using as input data compositions and temperatures measured at various stages of secondary steelmaking was developed and applied to different routine and experimental heats.

Microstructural analyses were carried out on samples systematically extracted from ladle and from tundish. Detailed characterisation of inclusion morphology and composition was carried out to investigate their properties in the present resulphurised steel and to evaluate reactions taking place during different phases of ladle treatment. The experimental results were also used to validate the theoretical model. A good agreement between predicted concentrations of inclusions and experimentally measured values was obtained.
Comparison of methods for calculating the influence of asymmetry in strip and plate rolling
Authors: Pawelski Hartmut
Published: December 2016

The effect of different work roll diameters, different circumferential speeds of work rolls, and different friction for top and bottom side on roll parameters, especially on curvature of outgoing material, is investigated. Three methods, which are all based on the theorem of the upper bound of total power, are discussed. Their results are compared with experimental data of Juretzek. They differ in the kind of velocity field for the material flow in the roll gap. The first makes use of a polynomial global velocity field. The second employs bilinear quadrilateral finite elements, which are fixed to space, while the stationary rigid plastic material flow goes through (stationary FEM). The third field consists of rigid triangles which can slide along their contact lines. The last method produces a formation of shear lines, which is in good coincidence with that of the zones of high strain rate, given by stationary FEM. Results of parameter studies using stationary FEM are shown as relationship between dimensionless characteristic numbers. At last a comparative analysis of the effectiveness of the different methods is given.
Optimisation of edging amount for high accuracy plan view control in plate mill
Authors: Chun Myung‐Sik , Moon Young‐Hoon
Published: December 2016

Algorithm to optimise the edging amount for high accuracy plan view control has been developed to improve plate yield. To produce rectangular shape of rolled plate, the edging amount that can minimise the crop length and width deviation must be determined from the operational analysis of plate mill. For the plan view control, new mathematical models to predict crop length at the top and bottom ends and width deviation at side ends are developed on the basis of statistics and back propagation learning algorithm of neural network. Using new mathematical models, under given rolling conditions of broadside and finishing pass and the permissible tolerance in width deviation, optimised algorithm which can achieve high accuracy plan view pattern is proposed. The application of newly developed algorithm in actual plate mill for plan view pattern control reduced width deviation by 20%, and crop length by 30% on average with a suitable fishtail crop shape.
Surface effects and flow conditions in small volume melts with varying sulphur content
Authors: Scheller Piotr R.
Published: December 2016

The surface effects and flow behaviour in melts with a volume of a few cubic millimetres were investigated using 1 mm thick X5CrNi18‐9 (AISI 304) stainless steel strips after partial remelting by a TIG (tungsten inert gas) burner. In the industrially produced material the S mass content was varied between 20 and 100 ppm. The surface excess of sulphur indicates that the surface saturation was not achieved compared to the values in the Fe‐S system. The thickness of the layer with high sulphur enrichment depends on the S activity and varied between approximately 260 and 460 nm and achieves the bulk S content at a distance of approximately 1.2 μm from the surface. This layer is noticeably thinner than the diffusion boundary layer and considerably thinner than the flow boundary layer. The topography of the rapidly solidified liquid pool makes it possible, taking previously estimated temperature coefficients of surface tension into account, to explain the flow behaviour in the melt with regard to the S content and to the temperature gradients. The results obtained indicate that the shearing force caused by surface tension gradients (Marangoni effect) controls the flow conditions in small volume melts.
Picture analysing method of slag foaming behaviour
Authors: Juhart Matjaž , Peter Michael , Koch Klaus , Lamut Jakob
Published: December 2016

Hot tests of foaming behaviour of steelmaking slags were conducted on a laboratory scale up to 1760 °C using a Tammann furnace. The foaming behaviour of the slags was quantified on the basis of a new measuring method. The volume increase and the progress of the foaming process can be continuously observed and calculated by means of picture analysis. The gas content of foaming slags was compared with the results of the measurements performed in steel plants. The influence of the magnesia content on the foaming behaviour is investigated. The chemical composition of the slag is beside the CO evolution the decisive factor influencing slag foaming behaviour. The highest volume increase values observed lie in the region of 2500 % in relation to the initial volume.
Recycling of scrap for high quality steel products
Authors: Boom Rob , Steffen Rolf
Published: December 2016

In an ECSC project several aspects of tramp element control in steel were studied by a group of steel producers and research institutes in the European Union. Upgrading of incinerator scrap and shredded automobile and consumer durable scrap was realised through size and density separation and by pre‐dismantling and sorting of goods before shredding. Removal of tin from tinplate by pre‐treatment with reactive gases was investigated. A dezincing process was developed by dissolution of the zinc‐alloy layer in caustic soda followed by electrochemical deposition of zinc. Results of laboratory scale trials showed that generation of high mass transfer between the phases metalslag‐gas as well as vacuum distillation of the solute elements influencing the evaporation rate can remove copper and zinc from steel melts. A mass balance for the distribution of zinc and lead between metal, slag and dust during scrap melting in an EAF was established. Additional sponge iron charging is a very efficient measure to lower zinc and lead content due to the CO boiling effect during melting.
Combined blowing with three ‐ hole lance in a sidewall blowing converter
Authors: Juhani Fabritius Timo Matti , Mure Petri Tapani , Kupari Pentti Antero , Juntunen Veikko Antero , Härkki Jouko Juhani
Published: December 2016

Traditionally, in stainless steelmaking converters, oxygen has been blown by a one‐hole lance (1 HL) and sidewall tuyères. In order to reduce the tap‐to‐tap time, the multi‐hole lance has been used for oxygen blowing. The aim of this work was to develop blowing practise for a multi‐hole lance to reduce the tap‐to‐tap time and minimise metal splashing and spitting in the sidewall blowing converter (chromium converter). In the chromium converter the chemical energy of liquid ferrochrome (which contains 4 % silicon and 7 % carbon) is utilised for scrap melting by oxidising the silicon and the part of carbon.

The research has been made by a dynamically scaled water model and full‐scale converter. Used parameters were the gas flowrate from sidewall tuyères and lance, lance height, charge weight and position of multi‐hole lance. Splashing has been measured during blowing from walls (splashing) and mouth of the converter model (spitting). The model tests indicated less splashing and spitting by the three‐hole lance (3 HL) than traditional 1 HL. The 1 HL caused strong skulling of the converter cone. By 3 HL blowing the position of the lance has a remarkable effect on the direction and the amount of splashing and lance life. Because of hot metal‐slag splashes, the life time of the 3 HL was halved by position 1 (compared to 1 HL). With the lance position 2 the splashing decreased by approx. 50% in model tests and lance life time increased by ~ 50% (compared to 1 HL) in the full‐scale converter. The model agreed well with the full‐scale converter. According to the process tests, the nominal productivity of the chromium converter has increased 15 % and depending on the refining practise and the silicon content of ferrochromium the lining life has increased 20 ‐ 30 %. In the future the multi‐hole lance will be tested in the AOD vessel.
Effect of steel composition on failure of oxide scales in tension under hot rolling conditions
Authors: Tan Kim Soong , Krzyzanowski Michal , Beynon John H.
Published: December 2016

The differences in failure of oxide scales formed on mild, Si‐Mn, Mn‐Mo and stainless steels were investigated using a high‐temperature tensile test technique over the range of test parameters near to the hot rolling conditions at entry into the roll gap. Temperature, strain and strain rates were 783 – 1200 °C, 2.0 – 5.0 % and 0.2 – 4.0 s−1 respectively. The scale thickness was maintained within 5 – 250 μm. Mild steel has the highest oxidation rate throughout the temperature range. A slightly thicker scale for the Mn‐Mo steel compared with Si‐Mn steel was observed. The stainless steel has shown the highest resistance to oxidation. Although through‐thickness cracks and sliding were competitive mechanisms for oxide scale failure for the mild steel, the other steel oxides failed only by through‐thickness cracking or were delaminated over the whole temperature range 783 ‐ 1200 °C. Modelling based on the finite‐element method was applied for better understanding of the micro‐events both during uni‐axial tension and just before contact with the rolls. The part of the model related to oxide scale failure has been upgraded taking into account experimental evidence concerning differences in scale failure, due to the steel chemical content, which were observed in the hot tensile tests.
The effect of aging on the intergranular corrosion of a 24Cr‐14Ni‐0.7Si stainless steel for welding in architecture
Authors: Lin Dong‐Yih , Wu Weite , Lin Chang Herng ,   Hsin‐Hsin‐Hsieh
Published: December 2016

Stainless steel with high Cr (24 %) and Ni (14 %) contents is becoming more important for use as core material for welding wires and in burning ovens due to its excellent corrosion resistance. This 24Cr‐14Ni material, with a Cr enriched σ‐phase, can be formed in a temperature range between 600 ‐ 950°C. In contrast, the remaining matrix phase can be induced into a Cr‐depletion after the σ‐phase formation. This research studied the intergranular corrosion rate under aging temperatures that are similar to the service parameters of this material in burning ovens. The study provided evidence that the relationship between the aging time and corrosion rate is not linear. A series of metallographic studies was performed to survey this phenomenon.
Celtic steel – an evaluation of depot finds
Authors: Preßlinger Hubert , Mayr Michael
Published: December 2016

In the course of archaeological excavations on the Gründberg in Linz/Austria, several depots containing a total of 45 steel objects were discovered. These depots had been set up around 100 before Christ (BC). 25 objects were used to take samples for metallographic and microanalytical investigations.

In the exercise of his trade, the Celtic smith could resort to different steel grades: non‐alloyed, carbon alloyed, phosphorus alloyed. The technique applied was that of fire‐forging single pieces of steel ‐ which had previously been widened by hammering – to give flat bars showing a multi‐layer structure.

For workpieces with special requirements with regard both to hardness and to toughness, a number of carefully selected flat bars with differing contents of alloying metals were bonded by forge welding, which produced a compound material. Hardening by cold working as well as by torquing was already known to these Celtic craftsmen. To obtain tools with a hard edge and a tough core, cementation was used.
Ferronickel production in Kosova ‐ past performance and new opportunities
Authors: Mehmetaj Bedri , Boom Rob
Published: December 2016

The Feronikeli complex, located in Glogovc of Kosova, consists of open cast mines with estimated reserves of 24 Mt of laterite ferronickel ore with an average Ni+Co content of 1.25 %, and a large metallurgical complex with an installed capacity of 12000 t of nickel in ferronickel per year. It began operating in 1984 and was shut down in 1998 due to the armed conflict in Kosova. The installed technology was state‐of‐the‐art at the time and is described in the paper. Past performance technological problems are analysed and solutions are proposed. The main problems during the operation were due to the high sulphur contents of both the heavy oil used as a fuel in the rotary kiln as well as of the Kosova basin lignite used as a reductant in the process. The reconstruction of the plant is an ideal opportunity to upgrade the process in terms of energy efficiency and environmental control. Recommendations for revamp to this effect are formulated.
A plasma tundish heater
Authors: Bebber Hans , Kranz Alexander
Published: December 2016

The world's first industrially employed plasma system with graphite electrodes for the continuous heating of a tundish was commissioned at the end of March 2001. The system is equipped with 2 graphite electrodes so that a floor electrode is no longer needed. The process data recorded during commissioning give cause for optimism for the future applications of this technology. With an efficiency of 67 %, the system is better than the normal 55 % achieved by the metal torches. In addition, the results show that no carbon pickup takes place and the nitrogen absorption of the melt is far less than 10 ppm and thus well inside the tolerance range of the plant operator.
Metallurgical process engineering for castability‐improvement in steel with elevated sulfur contents
Authors: Bolender Thorsten , Cappel Jürgen , Wünnenberg Klaus , Pluschkell Wolfgang
Published: December 2016

Trouble‐free casting of Al deoxidized steel heats with high sulfur contents necessitates controlled addition of Ca in secondary metallurgy, in order to avoid the nozzle clogging effect. With too little Ca input on the one hand, clogging occurs as a result of the deposition of high melting point calcium aluminates, and at excessively high Ca inputs, on the other hand, precipitation of calcium sulfide occurs. Process engineering for precisely targeted Ca input is developed on the basis of thermodynamic calculations, general steelplant experience, and comprehensive operational tests. The new method reduces the failure rate from casting problems to less than one quarter. Sequence casting of Al killed grades with high sulfur contents is then no longer a problem.
Hard amorphous silicon carbonitride coatings produced by plasma enhanced chemical vapour deposition
Authors: Marx Günter , Körner Kay‐Uwe , Heger Percy
Published: December 2016

Hard amorphous silicon carbonitride coatings for wear resistance have been produced by d.c. plasma‐enhanced chemical vapour deposition on pure iron at 573 K. Compared with most plasma assisted processes work was conducted under a relatively high pressure of 130 Pa. The advantages of this technique are an amorphous film structure, high deposition rates (up to 2 μm/min), high hardness and simple equipment. Hexamethyldisilazan (HMDSN) was used as precursor and argon, hydrogen, nitrogen and ammonia as process gases. The dependence of the coatings on the process parameters (process gas and d.c. power) was investigated. The characterization of the samples was carried out mainly by Fourier transform infrared spectrometry (FTIR), electron probe microanalysis (EPMA) and hardness measurement. Samples show clearly the infrared spectra absorption bands characteristic of SiC and Si3N4, with traces of hydrogen bonding. The material structure shows a strong dependence on the process gas and the d.c. power. However, for argon and hydrogen were deposited carbon‐rich SiC films with low nitrogen content. Nitridic films with low carbon content were deposited using nitrogen and especially ammonia. The hardness of the produced coatings was about 10 ‐ 55 GPa.
Chromium vaporisation from Fe,Cr base alloys used as interconnect in fuel cells
Authors: Gindorf Christian , Singheiser Lorenz , Hilpert Klaus
Published: December 2016

Fe,Cr base alloys protected by Cr2O3 base oxidation scales are candidate materials for the metallic interconnect of solid oxide fuel cells (SOFC). The operating temperatures of such cells range between 800 and 950 °C. Cr2O3 base oxide scales are necessary since they show sufficient electrical conductivity unlike Al2O3 or SiO2 scales. It is, however, disadvantageous that Cr2O3 base oxide scales form the volatile chromium(VI) species CrO3(g) and CrO2(OH)2(g) under operating conditions at the cathode side of SOFC. The electrochemical reduction of these species forming solid Cr(III) oxides at the three‐phase boundary electrolyte/cathode/oxidant leads to a rapid degradation of the electrical properties of SOFC. The study of the chromium vaporisation of different Fe,Cr base alloys under SOFC operating conditions and its reduction by the coating of the alloy surface are, therefore, of topical interest in SOFC development. The commercial alloys Fe18Cr1Al (DIN 1.4742), Fe25Cr0.7Mn0.5Si (AISI 446), Fe20.4Cr5.7A10.3Si (DIN 1.4767) and the oxide dispersion strengthened (ODS) alloy Cr5Fe1Y2O3 as well as the model alloy FeCrMn (HNA) were investigated. These alloys form the following oxide scales under operating conditions on the cathode side: iron rich chromium oxides (DIN 1.4742), Cr,Mn spinel (AISI 446 and HNA), Al2O3 (DIN 1.4767), and Cr2O3 (Cr5Fe1Y2O3). The alloys DIN 1.4742 and Cr5Fe1Y2O3 were coated with a perovskite layer (25 to 30 μm thickness) made of La0.90Sr0.10CrO3 (LSC) and La0.8Sr0.2MnO3 (LSM) by the use of vacuum plasma spraying (VPS). The vaporisation studies were carried out under non‐equilibrium conditions using the vapour transportation method. The carrier gas consisted of synthetic air with a relative humidity of rH = 60%. Alloy plates of the dimensions 80 · 30 · 5 mm3 with rounded edges and a surface area of 48.5 cm2 were used as samples in the vaporisation experiments carried out at 850 and 950 °C. Typical time periods of the vaporisation measurements were between 20 and 350 h. Alloy Cr5Fe1Y2O3 with Cr2O3 scale showed the highest chromium vaporisation rate among the uncoated samples. The latter showed the following factors for the reduction of the chromium vaporisation rate as compared to Cr5Fe1Y2O3 at 850 °C: 23 for AISI 446, 10 for HNA, 5 for DIN 1.4767, and 2 for DIN 1.4742. The different factors are explained by the different oxide scales mentioned above. The alloys with VPS coatings showed a reduction of chromium release by up to a factor of > 100. Investigations of the microstrucure of the perovskite coating revealed its densification during the transpiration experiments which in turn reduces the chromium vaporisation. Moreover, the Cr2O3 vaporisation was re‐determined under equilibrium conditions by the vapour transportation method leading to new results.
Mechanical properties relationships in V‐ and Ti‐microalloyed steels
Authors: Eissa Mamdouh , Mattar Taha
Published: December 2016

Microalloyed steels are characterised by their mechanical properties. Nowadays, they are used in a wide range of applications. The convenience and simplicity of hardness tests permit to obtain economically and rapidly information on the structure of steels and control their treatments. This study has been carried out to derive equations for prediction of the mechanical properties of microalloyed steels by hardness measurement. With this objective, V‐ and Ti‐microalloyed plain carbon steel bars were melted, hot rolled, heat treated and machined for the measurement of their mechanical properties and to reach a correlation between both ultimate tensile strength, yield strength and uniform elongation and Vickers hardness. The obtained data were treated using different mathematical fittings. They are mathematically treated as groups according to the heat treatment processes and as one group. The derived equations show good agreement with each other and with most of the little relations found in the literature. General equations for deducing mechanical properties values from the easily measured Vickers hardness values were derived. The equations derived from one group without regarding the treatment processes are more reliable.
Thermodynamic behaviour of carbonate in CaO based slag
Authors: Song Hyo Seok , Kim Dong Sik , Rhee Peter Chang Hee , Min Dong Joon
Published: December 2016

Carbonate solubility was measured for CaO bearing slag systems at 1600 °C under different thermodynamic conditions by using equilibration techniques. Carbonate solubility increased with activity of (CaO). The reaction mechanism of the carbonate dissolution in slag can be expressed as a reaction between CO2 gaseous phase and oxygen ion to form carbonate (CO32‐). Carbonate capacities of various slags depended not only on oxygen ion but also activity coefficient of carbonate ion. The activity coefficient of carbonate ion in CaO‐SiO2 slag changed with CaO content, but that of CaO‐Al2O3 slag did not change remarkably. Substitution of MgO by CaO for solubility of carbonate had a similar effect as in the case of carbide in CaO‐SiO2‐MgO slag. The critical oxygen potential for carbide and carbonate stability was found to be 10‐10 bar.
Steel – foundation stone for the industrial development in Taiwan
Authors: Lin Dong‐Yin , Wu Weite
Published: December 2016

This paper presents the development, actual status of steel industry and research in Taiwan.
Mechanical properties of new stainless steels based on the system Fe‐30Mn‐5A1‐XCr‐0.5C
Authors: Jiménez José A. , Caruana Guillermo , Adeva Paloma , Frommeyer Georg
Published: December 2016

New stainless steels based on the system Fe‐30Mn‐5AI‐XCr‐0.5C (Cr mass contents of ≤ 9 %) were developed and evaluated as a replacement of conventional AISI 304 steel. The alloys were produced by induction melting and thermomechanically processed to obtain a fine equiaxed microstructure. A typical thermomechanical processing for AISI 300 austenitic stainless steels was used and included forging at 1200°C, rolling at 850 °C and final recrystallization at 1050 °C. A final fully austenitic microstructure with grains of about 150 μm in size was obtained in all the steels. Tensile tests at temperatures ranging from ‐196 to 400 °C showed similar results for the various alloys tested. In accordance with the values for the elongation to fracture, this temperature range was subdivided into three regions. In the temperature range of ‐196 °C to room temperature, elongation to fracture increases with decreasing temperature. At temperatures ranging from 100 to 300 °C, elongation to fracture increases with testing temperature and serrations on the stress‐strain curve were observed. Finally, higher testing temperatures were accompanied by a decrease in ductility. Examination of the microstructures after deformation led to the conclusion that mechanical twinning was the dominant mechanism of deformation at the tested temperatures.
Metallurgical characterisation of dissimilar welds between modified 9Cr‐1Mo steel and Alloy 800
Authors: Sireesha Mopati , Albert Shaju K. , Sundaresan Subramania
Published: December 2016

Dissimilar metal welds between ferritic low‐alloy and austenitic stainless steels commonly occur in power plant application. In order to overcome some of the problems encountered here, a trimetallic configuration using an intermediate piece (such as Alloy 800) between the austenitic and ferritic steels has been suggested. This paper describes some features of the joints between modified 9Cr‐1Mo steel and Alloy 800, produced with Inconel 82/182 filler material. The joints require heat‐treatment after welding and the results have shown that a treatment at 760 °C for 2 h would be optimal. Although most tensile failures occurred in the weld metal the welds were found to exhibit strength properties that are at least equal to those of Alloy 800, with a tensile elongation lying between those of the two base materials. Similarly, while the weld metals are slightly less tough than the two base materials, the weld metal toughness at 120 J is still quite adequate for the intended application.
Mathematical modelling of decarburisation and degassing during vacuum circulation refining process of molten steel: application of the model and results
Authors: Wei Ji‐He , Yu Neng‐Wen
Published: December 2016

The mathematical model for decarburisation and degassing in the vacuum circulation refining process of molten steel, proposed and presented earlier, has been applied to the refining process of molten steel in a multifunction RH degasser of 90 t capacity. The decarburisation and degassing processes in the degasser under the RH and RH‐KTB operating conditions have been modelled and analysed using this model. It was demonstrated that for the RH and RH‐KTB refining processes, the results predicted by the model are in good agreement with some plant data. The mean contributions of the three refining sites in six circulation cycles to decarburisation are 10.5 – 11.6, 37.4 – 38.0 and 50.5 – 52.1 % of the overall amount of decarburisation, respectively. The KTB operation can markedly accelerate the decarburisation of molten steel. Using the top blowing oxygen of 6 min with the flow rate of (600 ‐ 1000) m3(STP)/h, the initial carbon mass content of the liquid steel for the RH refining process may be increased to (550 ‐ 700) · 10‐4 from 400 · 10‐4 %. And the treatment time needed for reducing the carbon mass content in the steel to a level of ≤ 20 · 10‐4 % may be shortened over 3 ‐ 4 min. The effectiveness of decarburisation and degassing cannot be obviously improved by increasing the lifting argon blow rate to 900 from 600 I(STP)/min under the operating modes examined in the present work.
Optimisation of flash welding parameters for wheel rim manufacture using continuously cast steels
Authors: Raj N. Krishna , Srinivasan P. Bala
Published: December 2016

Continuously cast steels are nowadays commonly employed for the manufacture of wheel rims, and the flash welding process is generally employed for that purpose. The current work addresses the flash welding of a continuously cast material (carbon steel with carbon segregation in it), in the wheel rim manufacturing process route, with emphasis on the control of process parameters on the quality of weld joints. It has been established in this research work that the controlled post weld heat cycles, during the flash welding process, Improve the quality of joints and also eliminate or at least drastically decrease the failure susceptibility of such flash welded joints during subsequent manufacturing operations.
Detailed study of the transformation mechanisms in ferrous TRIP aided steels
Authors: Iung Thierry , Drillet Josée , Couturier Audrey , Olier Christopher
Published: December 2016

Development of TRIP aided ferrous alloys is one answer to the demand for weight decrease in the automotive industry. The microstructure of hot rolled and cold rolled TRIP steels is quite complex and the optimisation of such steel products requires a detailed understanding of the mechanisms of phase transformation, during thermomechanical treatment as well as during mechanical testing or metal forming.

We present in this paper the results obtained at Irsid concerning the study of austenite stabilisation through bainitic transformation during thermal treatment and its transformation into martensite during mechanical testing.

First of all, the characterisation methods are presented. An effort has to be put on this point due to the refinement of the microstructure of TRIP steels, especially the size of austenite and martensite islands. Carbon replicas for the observation by means of transmission electron microscopy (TEM) are used to analyse the morphological features of the microstructure ‐ nature of the constituents, size and shape ‐ and the composition of cementite particles present in the steels. The mean value for this carbon content in retained austenite is deduced from X‐ray diffraction measurements.

Then the kinetics of bainitic transformation are discussed as well as cementite precipitation. The typical composition of the steel studied is 0.5 % C, 1.5 % Mn. The use of 0.5 % C steels facilitates the study of bainitic transformation by avoiding the ferrite formation usually occurring in TRIP steels. Cementite nucleation appears at the ferrite/austenite interface without any partitionning of substitutional elements. To satisfy thermodynamic equilibrium at the interface, the silicon content on the cementite side is very low and high on the austenite side. Then, carbon diffusion towards austenite is delayed and, as a consequence, cementite growth is also delayed. As the diffusion kinetics are low at 400 °C, cementite keeps this “non partitioned” composition, even after 3 hours holding. At 500 °C, diffusion kinetics are higher and cementite composition approaches that predicted by equilibrium.

Finally, the stability of retained austenite during mechanical testing is studied. Before and after mechanical testing the morphological characteristics of the microstructure (austenite island size and elongation) are analysed by TEM replicas and image analysis. There is a high density of very small austenite islands but they represent only a small fraction of the total retained austenite. These results confirm and quantify the size effect on austenite stabilisation during deformation.
In situ observations on the austenite stability in TRIP‐steel during tensile testing
Authors: Kruijver Suzelotte , Zhao Lie , Sietsma Jilt , Offerman Erik , van Dijk Niels , Margulies Lawrence , Lauridsen Erik , Grigull Stephan , Poulsen Henning , van der Zwaag Sybrand
Published: December 2016

In‐situ deformation tests have been performed on a steel displaying the transformation‐induced plasticity (TRIP) effect, while monitoring the phase transformation by means of X‐ray diffraction. A tensile stress is applied to 0.4 mm thick samples of this steel with mass contents of 0.26 % Si, 1.5 % Mn, and 1.8 % Al in a transmission geometry for a synchrotron‐radiation beam of 25 μm · 25 μm. On the diffraction patterns every grain appears as a discrete spot. The austenite {200} reflections are analysed during this investigation. The diffraction patterns are treated like a powder pattern for five different η‐angles, with η representing the angle between the tensile direction and the normal direction of the diffracting {200} planes. The results of the analysis show that η = 0° and η = 90° are the preferential orientations for the transformation to martensite. The Ludwigson and Burger model [9] is used to gain more information about the stress dependence of the deformation induced martensite formation. The microdiffraction patterns also reveal the changes in carbon concentration in austenite at each retained austenite fraction.
Development of high strength low alloy TRIP‐aided steels with annealed martensite matrix
Authors: Sugimoto Koh‐ichi , Kikuchi Ryo , Hashimoto Shun‐ichi
Published: December 2016

Formable high‐strength low‐alloy TRIP‐aided sheet steels with annealed martensite matrix or TRIP‐aided annealed martensitic steel were developed for automotive applications. The steels possessed a large amount of plate‐like retained austenite along annealed martensite lath boundary, the stability of which against the strain‐induced transformation was higher than that of the conventional TRIP‐aided dual‐phase steel with polygonal ferrite matrix. In a tensile strength range between 600 and 1000 MPa, the TRIP‐aided annealed martensitic steels exhibited superior large elongation and reduction of area. In addition, the steels possessed the same excellent stretch‐flangeability and bendability as TRIP‐aided bainitic steel with bainitic ferrite matrix. These properties were discussed by matrix structure, a strength ratio of second phase to matrix, retained austenite stability, internal stress in matrix and so on.
Effect of alloying elements on the microstructure‐property relationship in thermomechanically processed C‐Mn‐Si TRIP steels
Authors: Timokhina Ilana B. , Hodgson Peter D. , Pereloma Elena V.
Published: December 2016

The effect of additions of Nb, Al and Mo to Fe‐C‐Mn‐Si TRIP steel on the final microstructure and mechanical properties after simulated thermomechanical processing (TMP) has been studied. The laboratory simulations of discontinuous cooling during TMP were performed using a hot rolling mill. All samples were characterised using optical microscopy and image analysis. The volume fraction of retained austenite was ascertained using a heat tinting technique and X‐ray diffraction measurements. Room temperature mechanical properties were determined by a tensile test. From this a comprehensive understanding of the structural aspect of the bainite transformation in these types of TRIP steels has been developed. The results have shown that the final microstructures of thermomechanically processed TRIP steels comprise ~ 50 % of polygonal ferrite, 7 ‐12 % of retained austenite, non‐carbide bainitic structure and martensite. All steels exhibited a good combination of ultimate tensile strength and total elongation. The microstructure‐property examination revealed the relationship between the composition of TRIP steels and their mechanical properties. It has been shown that the addition of Mo to the C‐Si‐Mn‐Nb TRIP steel increases the ultimate tensile strength up to 1020 MPa. The stability of the retained austenite of the Nb‐Mo steel was degraded, which led to a decrease in the elongation (24 %). The results have demonstrated that the addition of Al to C‐Si‐Mn‐Nb steel leads to a good combination of strength (~ 940 MPa) and elongation (~ 30 %) due to the formation of refined acicular ferrite and granular bainite structure with ~7 ‐ 8 % of stable retained austenite. Furthermore, it has been found that the addition of Al increases the volume fraction of bainitic ferrite laths. The investigations have shown an interesting result that, in the Nb‐Mo‐Al steel, Al has a more pronounced effect on the microstructure in comparison with Mo. It has been found that the bainitic structure of the Nb‐Mo‐Al steel appears to be more granular than in the Nb‐Mo steel. Moreover, the volume fraction of the retained austenite increased (12 %) with decreasing bainitic ferrite content. The results have demonstrated that this steel has the best mechanical properties (1100 MPa and 28 % elongation). It has been concluded that the combined effect of Nb, Mo, and Al addition on the dispersion of the bainite, martensite and retained austenite in the ferrite matrix and the morphology of these phases is different than effect of Nb, Mo and Al, separately.
Development and characterization of high strength impact resistant Fe‐Mn‐(Al‐, Si) TRIP/TWIP steels
Authors: Brüx Udo , Frommeyer Georg , Grässel Oliver , Meyer Lothar Werner , Weise Andrea
Published: December 2016

Iron manganese steels with Mn mass contents of 15 to 30 % exhibit microstructural related superior ductility and extraordinary strengthening behaviour during plastic deformation, which strongly depends on the Mn content. This influences the austenite stability and stacking fault energy γfcc and shows a great impact on the microstructure to be developed under certain stress state or during severe plastic deformation. At medium Mn mass contents (15 to 20 %) the martensitic γ‐ε‐ά phase transformation plays an important role in the deformation mechanisms of the TRIP effect in addition to dislocation glide. With Increasing Mn mass content large elongation is favoured by intensive twinning formation. The mechanical properties of plain iron manganese alloys are strongly influenced by the alloying elements, Al and Si. Alloying with Al Increases the stacking fault energy and therefore strongly suppresses the martensitic γ‐ε transformation, while Si sustains the γ‐ε transformation by decreasing the stacking fault energy γfcc. The γ‐ε phase transformation takes place in Fe‐Mn‐X alloys with γfcc ≤ 20 mJm−2.

The developed light weight high manganese TRIP and TWIP (twinning induced plasticity) steels exhibit high ultimate tensile strength (600 to 1100 MPa) and extremely large elongation of 60 to 95 % even at high strain rates of έ = 103 s−1.

Particularly due to the advanced specific energy absorption of TRIP and TWIP steels compared to conventional deep drawing steels high dynamic tensile and compression tests were carried out in order to investigate the change in the microstructure under near crash conditions. Tensile and compression tests of iron manganese alloys with varying Mn content were performed at different temperatures and strain rates. The resulting formation of γ twins, ά‐ and ε martensite by plastic deformation was analysed by optical microscopy and X‐ray diffraction. The deep drawing and stretch forming behaviour at varying deformation rates were determined by performing cupping tests and digitalised stress‐strain‐analysis.
Constitutive model of the TWIP effect in a polycrystalline high manganese content austenitic steel
Authors: Allain Sébastien , Chateau Jean‐Philippe , Bouaziz Olivier
Published: December 2016

The TEM study of our steel with a high manganese content reveals that mechanical twining (TWIP effect) occurs during the deformation at room temperature. Microtwins are organised into parallel stacks and two systems are sequentially activated in each grain. They participate to the deformation and they are strong obstacles for the dislocations and for other twins, leading to the decrease of the effective grain size. Thus, TWIP provides our alloy a very good ductility and a high hardening rate.

Our constitutive modelling deduced from a model proposed by Bouaziz and Guelton [4] integrates this typical organisation of microtwins. Twinning is quantified in each grain by the partial volume fraction of twins in each system. A nucleation law for the microtwins is introduced which depends on the local stress and the stress relaxation due to pre‐existing twins. The flow stress is deduced from the dislocation density, which evolves with the dynamical recovery and the decrease of the mean free path (MFP). The MFP takes into account the grain and twin boundaries and the forest dislocations. The strain is calculated by adding the contributions of dislocation glide and twinning accounting the orientation of the grain. To treat the polycristal, the behaviours of different grain orientations are mixed by assuming at each strain step that the increment of elastic energy stored is the same in each grain.

The model was successfully applied to describe the mechanical properties of our alloy, for two different grain sizes. Some microstructural parameters are yet fitted. This leads to an insufficient prediction of the evolution of the microstructure. In further developments, we expect to introduce numerical simulation results on local characteristics of microtwins (thickness, critical resolved shear stress for twinning) and experimental results on the rate of twin nucleation.
Bubble Entrapment on Solidified Shell caused by Unsteady Steel Flow in Mold
Authors: Miki Yuji , Takeuchi Shuji
Published: December 2016

The molten steel flow in the continuous casting mold and entrapment of inclusions and bubbles on the inner surface of the solidified shell are examined to clarify the mechanism of internal defects in steel products. Defects on steel sheets are caused by bubbles and inclusions entrapped on the solidified shell during casting. It was found that bubbles penetrate deeply due to an unbalanced time‐dependent flow. This phenomenon can be explained by the Large Eddy Simulation model, which can predict the time‐dependent flow.

The number of inclusions increases as the bubble diameter and the distance of the position of entrapment from the top free surface increase. This indicates that bubbles collect inclusions while traveling in the molten steel in the continuous caster. A simple mathematical model is presented to explain the mechanism by which inclusions become attached to bubbles.
Motion of Fine Particles under Interfacial Tension Gradient in Relation to Continuous Casting Process
Authors: Mukai Kusuhiro , Zeze Masafumi
Published: December 2016

In front of the solidifying interface of a water solution, in the case of NaCl water solution, fine bubbles (10~100 μm in diameter) were just moving upward, no matter how close they were from the solidifying interface. However, in front of the solidifying interface of C8H17SO3Na water solution, once the distance between the bubbles and the solidifying interface became less than 90~100 μm, rising bubbles were found to move horizontally toward the solidifying interface quickly, and then to be engulfed by the interface. This effect can be attributed to the surface tension gradient around the bubbles induced by the concentration gradient in the boundary layer formed in front of the solidifying interface. The phenomenon is taken as a kind of the Marangoni effect in a broad sense. The movement of fine particles driven by the interfacial tension gradient is found to have a close relationship to certain phenomena in continuous casting processes, such as the occurrence of bubble or inclusion‐related defects in steel and nozzle clogging.
Effects of Solute Elements on Primary and Secondary Dendrite Arm Spacings in Fe‐based Alloys
Authors: Kudoh Masayuki , Wo Bo
Published: December 2016

There have been many experiments and theoretical studies of primary dendrites, and most of which have focused on the effects of extrinsic factors such as solidification rate and temperature gradient. However, intrinsic factors such as the kind of solute element and initial solute concentration are also considered to be important for controlling the spacing of primary dendrites.

In this study, the effects of intrinsic factors on primary and secondary arm spacings of dendrites were investigated, and changes in a microsegregation index with changes in primary arm spacings and equilibrium distribution coefficient of each solute element were also examined. Fe‐Cr‐C, Fe‐C‐Cr, Fe‐C‐Cr‐Mo, Fe‐C‐Cr‐Mo‐V and Fe‐C‐Cr‐Mo‐V‐W alloys were solidified unidirectionally and water‐quenched. The primary arm spacing increased with increase in initial solute concentration in all alloys because the range of solidification temperature increased with increase in solute concentration. On the other hand, the secondary arm spacing in all alloys decreased with increase in initial solute concentration, and it was proportional to about the one‐third root of local solidification time. The microsegregation index increased with increasing primary arm spacing and with decreasing equilibrium distribution coefficient.
Towards modelling elastic‐plastic deformation of a tube‐shaped work‐piece under axisymmetric load
Authors: van Putten Koos , van der Werff Klaas , Steinhoff Kurt , Fontijne Jaap
Published: December 2016

The complex mechanisms occurring during the expansion of a tube‐shaped work‐piece are of particular interest for many industrial production processes. In case of the expansion of the outer end of a tube, so‐called flare forming, most of the process‐design parameters are mainly based on experience and empirical knowledge. To improve the methodological basis of process design and consequently to increase the technological efficiency of the process itself, two different types of models are developed and compared in this paper. The first one is a continuum‐mechanics based analytical model, the second one is a numerical model based on finite‐element simulation. Both models are able to describe the elastic and plastic behaviour during flare forming. For the analytical model classical theories are applied. Such theories are on the one hand those of Timoshenko, which are applied for the description of the elastic behaviour, and on the other hand a limit analysis for the characterization of the plastic behaviour. For the numerical model a non‐linear elastic‐plastic finite‐element simulation is carried out with the commercially available FEM‐software MARC‐Autoforge. Both models are validated and verified with experimental data and evaluated regarding their applicability under real industrial process conditions. Finally, it is not only concluded that flare forming can be modelled sufficiently by both approaches, but beyond that, tools for an optimised process design can be derived. These design tools can directly be integrated in a CAD‐system.