The fire resistance of structures is one of the main brakes concerning the development of steel in buildings. This handicap of steel is in order to disappear due to the results of recent researches that permit to dimension the steel structures by considering the natural fire and the active fire fighting measures. In the frame of an ECSC financed research, an interactive calculation software has been developed with the aim of enabling engineering offices to perform easily calculations under natural fire conditions. This paper describes this new tool that should contribute to the promotion of steel by making the dimensioning under fire conditions easier and more competitive.

Several parts of degraded organ pipes belonging to some organs produced in different periods (from the 18th to 20th century) and from different Italian geographical areas have been examined and investigated in order to identify the possible causes of the degradation phenomena. An analysis through DSC-DTA measurements has been performed to define the crystallographic transformation of the studied alloys and a metallographic analysis has been realized to point out the microstructural characteristics. The morphological analysis has been improved by SEM equipped with an EDS device which permits a quantitative chemical characterization of the intact zones and of the degraded ones. The presence of chlorides has been identified as the starting factor of the degradation phenomena.

Good stability of the steel strip is essential in galvanizinglines, especially in the rapid cooling section before the zincbath, where the strip is cooled and excited by high-speedgas jets.
The process parameters and the design have beeninvestigated in order to characterize the strip vibrationsphenomena and to define optimized solutions for improvingthe cooling performances of present and future galvanizinglines while reducing the strip fluttering in the rapid coolingzone as well as in the cooling tower.

La première étape de ce travail est le calcul ab initio des énergies de mise en solution et de mélange du chrome et du fer. Nous confirmons les résultats ab initio proposés précédemment. Nous utilisons cette même méthodologie afin de calculer les énergies de surface du fer et du chrome dans les orientations (100), (110), (111) et (211). Contrairement aux extrapolations depuis les mesures expérimentales aux hautes températures, ces calculs montrent que les énergies de surface du chrome sont supérieures à celles du fer. Nous calculons également l’énergie de ségrégation d’impureté du chrome dans le fer (100) qui est endothermique. Enfin, nous proposons un modèle énergétique ajusté sur les calculs ab initio. À partir de ce modèle, nous calculons des isothermes de ségrégation et montrons que les surfaces de l’alliage sont toujours appauvries en chrome du fait de la grande différence d’énergie de surface entre les deux éléments qui a été révélée par les calculs ab initio.

The main purpose of ArcelorMittal Tubarao skin pass is to improvethe flatness in thin gauges hot rolled strips. Since the start-up in2002 several actions have been implemented and a consistentevolution of quality and process control has been reached:
The philosophy of production scheduling along the rolls campaignto minimize the effect of roll wear;
The definition of optimum target elongations to keep as constantas possible the roll forces and avoid roll bending changes;
The automation of bending forces control according tocharacteristics of the strip and the rolls.

To optimize the process and improve the degree of reduction, a two-stage experiment wasdesigned. It was carried out in a micro-fluidized bed. It is operated as a differentialreactor to ensure every particle in the micro-fluidized bed is at equal temperature,concentration and residence time. The experiment used iron ore powder from Yangdi. Thereducing gas and temperature in the pre-reduction stage were, respectively, pure CO and625 °C. In the final reduction stage, the temperature and reducing gas were, respectively,800 °C and pure CO. The residence time was between 10 min and 60 min. In addition to theexperiment, a microscopic technique was also carried out. The test shows a significantinfluence of the temperature and residence time of the two-step experiment on the finalreduction degree.

A physical limit to the galvanizing speed exists over which the liquid film explodes completely and prevents any further wiping. This limit is presently estimated around 180-200 m/min. A dimensionless approach including the Weber and Reynolds numbers is proposed to be able to predict the occurrence of the phenomenon. Practically it comes out that nozzles tilted by 30° down to the pot can pushback the limit by 30 %. A maximal line speed around 220 m/min could thus be reached.

Le comportement atypique des fissures courtes peut être, pour une large part, expliquépar l’effet de la fermeture. Toutefois, la détection du niveau de contrainte correspondantà l’ouverture s’avère généralement difficile sinon impossible pour les fissures de petitedimension. Cette étude porte sur la fermeture des fissures courtes 2D dans un acierinoxydable 304L. Pour optimiser la détection des variations de complaisance, une méthodeautomatique a été développée pour analyser les signaux numériques grâce à des méthodes defiltrage. Il est montré que cet outil permet d’obtenir une mesure précise de la charged’ouverture même pour des fissures ayant une profondeur de l’ordre de 0,1 mm. Lesrésultats obtenus permettent de définir l’évolution de la contribution de la fermeture enfonction de la profondeur de la fissure.

The paper introduces a slop detection algorithm, based on imagestaken by a CMOS camera aimed at the converter mouth. Theproposed algorithm, with an accuracy and selectivity of 74%and 94% respectively, is relatively simple and can therefore easilybe used in on-line applications.

To maximize furnace campaigns and to minimize production downtimesthrough short lining times, the entire integral blast furnacearea, including the auxiliary units, has to be theoretically partitioned.The evolution of measures for extending furnace life is in conjunctionwith the investigation and understanding of the in some respectsvery complicated wear mechanisms and their causes. Of mostimportance are the constructional, material and process engineeringmeasures to reduce wear and the measuring instrumentation forearly detection and progress monitoring of wear.

In regard to the sustainability of future cities, an increase in sustainable energysources needs to be managed. Therefore, the German government decided on increasing theratio of green energy up to 20% by 2020. In accordance with this, offshore wind energyparks will be constructed, as they provide the advantage of lasting air cleanliness andpreserving natural resources. To ensure construction safety, wind energy mills areconstructed using ductile steels of large thickness. Here, an application of high-strengthsteels provides the possibility of reducing the amount of material while constructionsafety is still ensured. Considering the long life cycle of wind energy mills’ foundationstructures and the recyclability of the steel grades used, their construction becomes arelevant factor in reducing CO2 emissions. Furthermore, the use of less material reducesCO2 emissions.Due to existing safety concepts, however, the application of high-strength steels is onlyconditionally allowed. Thus, the current study concerns the development of a safetyconcept based on the existing concepts to allow the application of high-strength steels.Furthermore, as the structural steel parts need to be joined, an energy-efficient weldingprocess is utilised: electron beam welding. The structural steel parts and weld joints areinvestigated with respect to their mechanical properties by analysing their loadability incombination with safety concepts. The load on the material is evaluated to ensureconstruction safety. In addition to the investigation of safety requirements, the suppliedmechanical properties are investigated. As the weld joints show different properties fromthe base material, the joints are considered the critical part. The joints areinvestigated concerning strength and toughness. Afterwards the mechanical properties arecorrelated with the wind energy structures. The prevention of failure is fulfilled whenthe mechanical properties of the weld joints exceed the required mechanicalproperties.

We studied, in steady and in unsteady state, the gas-solid reaction of gas nitriding(NH3-H2) of steel, in order to control the atomic nitrogentransfer in α-iron as a function of the inlet flow rates. We obtained the simultaneoussimulation of the gas phase variations, and the nitrogen transfer in the sample. Theevolution of the nitrogen concentration at the surface and inside of the α-iron, as afunction of the time, is presented. The results are in good agreement with the experimentand with previous work. We also established a correlation between the gas compositionaround the sample and the inlet conditions, in order to obtain an optimal nitrogentransfer at the sample’s surface, and thus control the nitride layer growth.

Accretion on the lining of the blast furnace results in a harmful effect on burdendescent, which also has a negative effect on energy balance. This eventually leads toincreased CO2emission. We examined which blast furnace zones were significantly affected by thethickness of the accretion layer and how this affects the blast furnace gas streamrelations. Using a heat transfer model, the samples taken from the accretion andstatistical analysis of the typical operating parameters of the blast furnace, amathematical model was created in order to determine the thickness of blast furnace shaftaccretion and its effect on gas utilization.

Steel rolling technology has achieved such fantastic progress in the 20th century that it might be considered to have come to maturity.Actually, it remains nowadays the object of intense development thataffords further impressive improvements. The progress of rollingtechnology is fostered by a drastic global growth of the number ofrolling equipments on the order of 40% over the last 15 years. Itbenefits from a dedicated R&D effort based upon a large scope ofscientific knowledge. The 9th Steel Rolling Conference illustrates thispotent innovative approach and it offers a unique opportunity forfruitful exchanges between steel producers, equipment suppliersand steel users.

Fe-Al alloys containing 25 and 31.5 at. % Al have been studied by internal friction, X-ray diffraction and dilatometric analyses. These techniques show for the first time that two internal friction peaks appear during the change in long range order type which occurs during the precipitation at 300°C of the metastable phase B2(FeAl). These peaks correspond to the formation of two phases: the equilibrium phase Fe3Al and a new intermediate tetragonal phase θ.

At the end of 2008 and in response to the economic crisis, the EU launched a Recovery Plan supported by technology initiatives, one of them being the European Green Car Initiative (EGCI) to help the car industry design next-generation passenger vehicles, which address fuel efficiency and carbon footprint issues at the level of the challenges of the 21st century. The European steel sector, which supplies material to the European car industry, which builds 1/3 of all passenger cars in the world, has launched an extensive, bold and imaginative series of projects to address lightweight design, cost, safety, sustainability, availability, recycling, electric applications and Life Cycle Assessment (LCA), which are the main technical topics, as steel retains an essential role in the design of these future green vehicles. Highlights of these are presented here, such as the development of new steel grades, either new advanced high-strength steels or low-loss steels for electric cores, the co-design of steel solutions with OEMs and the importance of LCA in vehicle conception.

In view of the weight reduction strategies required and increasingly implemented by the automobile industry, growing importance is being attached not only to the materials but also the forming methods used. Forming processes using hydraulic media in particular offer the potential to produce more complex parts economically while optimizing component properties. The tube hydroforming (IHU) and hydromechanical sheet forming (AHU) processes are ideally suited for the production of automotive components in line with these requirements.

The properties of the well known enhanced steel 12 Cr Mo9-10 are compared with those of the most recent generation of modified CrMoV steels who are characterized by the addition of vanadium. The comparison concerns the base material properties before and after heat treatment, as well as the influence of hot forming and welding with and without step cooling. Creep data are also reported.

An approach is proposed for the evaluation of surface fatiguedamage of hot forming tools that undergo severe thermomechanical loading. Fatigue crack propagation in a hot worktool steel X38CrMoV5-47HRC is investigated using singleedgecracked tension specimens with 3 different thicknesses(2.5, 1, 0.6 mm) and two R-values. The stress intensity factoris evaluated with ABAQUS®. Paris curves are established forthe crack propagation experiments.

Over the past few years several technical efforts have been focused on continuous improvement of quench and tempered product at ArcelorMittal Burns Harbor plate mill facility with particular attention being given to optimization of the flatness of quenched product. Incremental improvement in quench line equipment and practices is being aided by computer-based modelling tools and specialized instrumentation. The paper describes the development of different tools used to control flatness after quench and tempering units. The detailed description of a 3D model designed to predict distortion such as edge waves, center buckles, longbows and crossbows during quenching is presented. The model developed with Abaqus is able to predict the evolution of plate temperature, thermal stresses, strains, and distortions during cooling. The water cooling system is represented by top and bottom movable surfaces where a heat flux depending on width, length and temperature is applied. The effect of phase transformation is approximated by a variation of the plate thermal expansion coefficient.