Though it is usually neglected, and in spite of its detrimental effects, the expulsion phenomenon is very commonly observed in spot welding practice. Here, it is better emphasized through an experimental study, which brings to light the importance of the expulsion diameter. But some work has still to be done in order to better understand this phenomenon, its triggering mechanisms and its consequences.

This paper presents the experience that EKO Stahl has gained with the blast furnace injection of plastics and animal fats as alternative reducing agents since 1993. The specific pieces of equipment that have been designed and implemented for handling, storing and injecting these substances into the blast furnace tuyeres are described. The parameters that allow line stability and the overall effects on blast furnace operation are reported.

The results observed during ferritic rolling campaigns have highlighted a significant improvement of the behaviour of rolls. This improvement concerns the roll wear, the roughness and the roll surface evolution, as well as the friction coefficient, furthermore the strip surface quality. These results enabled us to validate that for ferritic rolling, the usage cost of HSS rolls is significantly lower than the one of high chromium rolls.

The residual stress field in a titanium nitride coating was determined using the X-ray diffraction method based on grazing incident angle geometry. The first order stress components were determined in TiN coating on WC and on steel substrates. The diffraction elastic constants calculated by the self-consistent method were used for the interpretation of the results. The advantages of the grazing incidence geometry are pointed out in the case of the examination of heterogeneous residual stresses in thin layers.

In order to improve the productivity and quality results of tandem - cold rolling mills and coupled pickling - tandem lines, VOEST-ALPINE Industrieanlagenbau (VAI) offers a complete range of innovative solutions, which concern as well mechanical equipments as operation and control systems. This paper describes some of these innovations and illustrates them by project examples where these solutions were implemented.

Mechanical properties models and the development of new control tools and methods induce radical changes in the activity of metallurgy quality technicians with regards to product qualification and allocation on the production lines. The conclusion of these projects enables the metallurgists to summarize on a work-friendly and interactive interface all the data required for qualifying the product with the greatest reliability in terms of surface finish, mechanical properties, product and process critical parameters, special instructions, and thus to take the best quality decision possible.The development of these skills leads to an important reduction in the number of off-line tests, and a faster product release, which improves lead times and limits the stock levels. Finally and above all, the warnings on product and process increase our reactivity on the whole production process and contribute to the improvement of our internal and customer quality results.

A thermodynamic approach has been used to progress in the understanding of the chemical processes taking place in the casting furnaces. The ceramic mould materials used for the casting of superalloys vaporize at high temperature under vacuum and the vapors condense then in the colder zones of the furnace. In addition, the graphite of the furnace resistor perturbs the vaporization regime of the moulds and is at the origin of other vaporization and condensation processes. The deposition regime of impurities leading to inclusions formation during the casting of the metal is modified. The thermodynamic analysis is confirmed by observations made on the superalloy casting furnaces. The deposits observed and characterized correspond to those predicted by the thermodynamic analysis, but the mass losses of the moulds producing these deposits are 60 times smaller than predicted.

A phenomenological relation is proposed for the description of the mechanical behaviour of Zr 702α polycrystalline samples deformed in channel die compression at room temperature. The identification of the parameters of the model from macroscopic stress-strain curves shows a good description of the anisotropy of the material. The analysis of the identified parameters shows the role of the activated deformation modes in the different samples.

The possibility to produce deep drawing quality - bake hardenable steel grades, by introducing carbon into the strip after its recrystallization, was shown few years ago at the laboratory scale. A closed reactive zone with high contents of CO and H2 was implemented on the CRM's pilot line of continuous annealing and hot-dip galvanizing. The 0.7 mm-thick strip is carburized in less than 15 seconds with C pick-up between 10 and 70 ppm. Developments performed to isolate atmospheres could also benefit to other reactive treatments (nitriding, oxidation-reduction, etc.) aiming to improve the response of high strength steel grades to hot-dip galvanizing. The reactor design, process feasibility demonstration and product potentialities are presented.

Due to their outstanding properties, high strength steels (HSS) are ever more required by the automotive industry. Indeed, high strength steels make it possible to reduce the overall weight of the vehicles. However, manufacturing of industrial parts may be hindered by the higher hardenability of these steels. The laser weldability of different HSS joints and the beneficial effects of on-line pre- and post-heat treatments on the mechanical properties of the welds are presented.

In multiphase materials, X-Ray Elasticity Constants (XEC) depend on the nature and volume fraction of each phase constituting the polycrystal. These XEC play a leading role during X-Ray diffraction stress analysis. Self-consistent scale transition models have been developed in order to simulate the XEC characteristics of several two-phase alloys. This work makes possible the quantitative study of the influence of the second phase on the results of X-Ray stress analysis.

The development of a new type of stopper rod, Argorod, makes it possible to improve the steel quality during continuous casting. The main results that have been obtained concern the tightness of the joint : the new Argorod system, of second generation, has a better tightness, the assembling operation is simplified and more reliable; the optimization of the system for argon introduction: sized tube, more accurate adjustment of the couple argon flow rate / back pressure ; the accurate control of steel throughput: choice of the nozzle shape factor “material strength / stopper rod weight”: weight saving for the same or for a higher transverse strength.

The hot tearing of aluminium-copper alloys is a serious defect for the foundrymen. The grain refinement of these alloys allows to decrease their hot tearing susceptibility. The aim of this work is to better understand the hot tearing mechanism and the grain refinement action. So, hot tearing tests and tensile tests in the mushy state have been performed. Moreover, a hot tearing model, based on the nucleation and growth of a cavity in a liquid film and taking into account the mushy zone rheology, has been developed.

ACB was the first thin slab casting and coiling plant in Europe, using CSP technology and up to now is the only CSP that uses steel from an electric arc furnace. The evolution of process and products in these facilities are presented from the start up in 1996 to the present situation. Particular attention is paid to the development of microalloyed, electrical and weather resistant steels, the improvements of surface and internal quality and the modifications introduced in the plant to improve productivity. Furthermore, geometrical aspects and thin gauge rolling are discussed with a view to develop 1 mm hot rolled coils.

Using recent and more accurate data, the thermodynamic model of Ma and Janke has been extended to a five element system. The content of non-metallic inclusions has been investigated for two grades of duplex stainless steels after solidification. The chemical and morphological features of the inclusions were determined by SEM observations and EDS analysis for different cooling rates. The results are interpreted on the basis of the chemical-physical interactions in the Fe-Cr-Ni-Si-Mn-O system. They can be used to define the optimal oxygen potential pattern for the casting of this type of steel in foundries.

The low energy loss spectroscopy interpretes the signal resulting from the excitation of the valence or conduction electrons of a material under the impact with an electron beam. The analysis of this signal in terms of plasmon energy, low-loss function or dielectric function gives a lot of informations about the electronic structure and the chemical bonding of the sample. When this spectroscopy is connected with a field emission gun scanning transmission electron microscope (STEM-VG HB5O1) it constitutes a very relevant tool to solve material problems for which nanoanalytical investigations are of prime importance. These performances are illustrated by three examples.

The energy stored in grains during cold rolling has been evaluated in a Fe-53%Ni alloy and in a duplex stainless steel using neutron diffraction. The measurements of diffraction peak broadening were undertaken to study the influence of stored energy on mechanisms that govern the development of the cube texture in a heavily cold rolled Fe-Ni alloy. The results suggest that the energy difference between the cube and the other main orientations increases with reduction and thus promotes the cube growth during recrystallization. It appears that such a method is relevant for a two-phase material. Furthermore, the energy levels found in the two phases are in good agreement with the strain measurements found in the literature. The austenite phase stores more energy than the ferrite one.

The results achieved with the COREX plants presently in operation show that this technology is a true alternative to the conventional blast furnace. With the experience gained from these plants, continuing developments have been made for the COREX process itself (recycling of steel plant wastes and use of other raw materials), for the equipment design and in the area of investment costs and profitability.

European standardization related to steel construction covers several aspects: design, materials and execution rules. The paper sums up the state of progress concerning materials (steels, bolting, welding consumables) and execution rules. It explains the connection with the Construction Product Directive and develops implications. It specifies the time schedule and consequences for existing French standardization.

The impregnation of a fibrous preform by a liquid metal is one of the techniques used to prepare metal matrix composites (MMC). The preparation by impregnation may however lead to defects like microporosity. The micropores present in MMC result from the superposition of two processes: the trapping of gas by capillarity during the infiltration phase and the formation of additional porosity related to solidification shrinkage. These two processes are analyzed in this paper and physical models are proposed for their description. It is then shown how the formation of microporosities can be simulated numerically using these models. Finally, prospects for a better numerical simulation of the preparation of MMC by impregnation are discussed.