Centro Sviluppo Materiali (Italy)

Abstract The prediction accuracy of ductile damage models is subject to a sound calibration strategy, which normally involves the execution of complex multiaxial tests and requires dedicated facilities. In addition, finite element (FE) analysis is mandatory to retrieve the stress and strain states at the critical point, which cannot be directly measured from experiments. To overcome this complexity, a minimal set of simple multiaxial tests is selected, and an analytical‐numerical approach is proposed to evaluate, without resorting to FE, both the stress evolution with plastic deformation and the fracture strain, under any different loading condition of each test. This is achieved from the sole knowledge of the material bilinear stress–strain relation and of the applied test displacement at fracture. The obtained results are compared with a traditional testing and calibration methodology, and the robustness of the approach is proved on a 17‐4PH steel, an X65 steel, and a Ti6Al4V alloy.

Abstract The current digital and technological transformation affecting the European steel industry is carried out through the continuous and progressive application of Key Enabling Technologies (KETs) according to the Industry 4.0 paradigm. Among these technologies, robotic systems and autonomous vehicles (UAV/UGV), are increasingly applied in steel plants with the aim of improving health and safety in workplaces. Dangerous operations related to monitoring, maintenance and safety are often performed by using such systems in order to avoid workers’ exposure to accidents and injuries. Therefore, robotic applications and autonomous vehicles, which are suitably equipped with artificial vision and innovative sensors, are integrated in the daily operations by supporting humans and interacting with them according to well defined procedures, in order to minimise potential and dangerous events. The present chapter assesses the state-of-art for this technology, by analysing both the literature and European-funded projects, and investigates two specific use-cases related to different applications in steel plants with specific focus on the workforce impact in terms of implications in work organisation and operational procedure. Moreover, changed work patterns (e.g., behaviours, tasks, decision-making, training, skills, etc.) are also discussed considering human experience as a fundamental aspect.

Monitoring of parameters of electric traction systems plays a crucial role to enable an efficient operation of railway infrastructure. This paper describes the features of a flexible measurement system developed to equip 3 kV DC traction power substations in order to provide continuous monitoring as well as automatic event recording. Data recording is useful as a support tool for network operation and for fault analysis. The paper shows the results of laboratory and field tests conducted on a measurement system prototype and points out some examples of key indicators for network analysis based on real data.

Summary Crude fired heater furnaces in refineries are adopting P5 and P9 steel grades, depending on temperature and feed characteristics. Process conditions, however, are characterised by temperatures up to 600°C, well above the conventional creep threshold, which eventually cause a considerable over-tempering of the material. At the same time, crudes being processed have become more‘critical’ in terms of sulphur content and TAN (total acid number). THOR®115 steel grade designed by Tenaris already showed very good corrosion resistance against oxidation and sulphidation. In the present work, THOR®115 and P9 have been analysed and compared, considering their static and creep resistance, together with oxidation and corrosion rate occurring on the external and internal surfaces. The output of the benchmark, resulting in a better performance of THOR®115 rather than P9, has been used to develop an economical comparison between the two materials and quantify the advantage to adopt THOR®115 in furnace applications.

The boron-free S700MC steel is usually produced by exploiting the properties of a ferrite-bainite mixed microstructure formed by coiling the strips at a temperature of about 450?C, i.e.below the bainite starting temperature. With the aim of further enhancing the mechanical properties of 6 to 10 mm thick strips, industrial tests were carried out at a coiling temperature of 600?C to promote the formation of a structure of ferrite and carbides, which is also acceptable for this type of steel. Unexpectedly, a microstructure composed of ferrite and martensite was obtained. Compared to the ferritic-bainitic grade, the new structure is characterized by a slight decrease of the yield point but by an increase of the ultimate tensile strength by no less than 80 MPa, with a transition from a quasi-discontinuous to a clearly continuous yielding behaviour. Accordingly, the ratio of yield strength to tensile strength decreases from 0.90 to 0.75 and the impact energy decreases by 35 J and 60 J for the two gauge levels, respectively. The mechanical behaviour of the strips coiled at high temperature is explained as a direct consequence of the dual phase structure with a hard phase interspersed in a soft ferrite matrix. The presence of martensite is explained by the so-called incomplete bainite reaction. The partial transformation into ferrite after coiling and the long time required for the coil to cool down stabilize the untransformed austenite due to the carbon enrichment making bainite formation at lower temperatures impossible.

Abstract Materials selection for oil and gas fields is challenged by the dual requirements of ensuring well integrity and affordability. This can be a demanding task for any field, but is particularly problematic for reservoirs with relatively high temperature, pressure and produced water salinity. Over the last decade, there have been advances in the assessment of environment aggressiveness (including pH and the quantity of H2S present) and from continued assurance of material performance (gained from multiple qualifications, routine validations and deep technical relationships with one or more mills). The materials selection for a mildly sour, multi-well gas field is presented, demonstrating how non-ideal gas behaviors were used in the well environment predictions to permit selection of a more economic casing grade. The environmental modelling and extensive ambient and high-pressure sour service validation testing is described with testing approaches optimized to increase confidence in the results. Additional work is presented in defining H2S limits for the selected completion materials, demonstrating that both the casing and completion are robust to excursion events. Recommendations are made for materials selection assessments in mildly sour wells, emphasizing that as conservatism is removed from the modelling approach, additional testing is required in qualification and validation.

A discrete multi-particle model of Ostwald ripening based on direct pairwise interactions between precipitates with incoherent interfaces is presented. Although based on the mean field concept, it is a valid alternative to the classical LSW theory. The main differences with respect to the classical approach can be summarized as follows: i) Particles interact the one another; ii) The first Fick’s law is considered to evaluate the fluxes of matter instead of the quasi stationary solution of the concentration field around particles; iii) The rate of matter exchange depends on the average surface-to-surface interparticle distance, a characteristic feature of the system which naturally incorporates the effect of volume fraction of second phase; iv) The multi-particle diffusion is described through the definition of an interaction volume containing all the particles involved in the exchange of solute. The model is in excellent agreement with the experimental data available in the literature. The shape of the quasi-stationary 3D particle size distribution of solid-solid and solid-liquid systems is well predicted from volume fractions of 0.07, 0.30, 0.52 and 0.74. Similarly, a very good prediction of the dependence of the kinetic constant of the coarsening process on the volume fraction of precipitates is obtained with reference to literature data on solid-liquid mixtures in the volume fraction range from 0.20 to about 0.75. For volume fractions below about 0.1 the model predicts broad and right-skewed stationary size distributions resembling a lognormal function. Above this value, a transition to sharper, more symmetrical but still right-skewed shapes occurs.

Digitalization represents a paramount process started some decades ago, but which received a strong acceleration by Industry 4.0 and now directly impacts all the process and manufacturing sectors. It is expected to allow the European industry to increase its production efficiency and its sustainability. In particular, in the energy-intensive industries, such as the steel industry, digitalization concerns the application of the related technologies to the production processes, focusing on two main often overlapping directions: Advanced tools for the optimization of the production chain and specific technologies for low-carbon and sustainable production. Furthermore, the rapid evolution of the technologies in the steel sector require the continuous update of the skills of the industrial workforce. The present review paper, resulting from a recent study developed inside a Blueprint European project, introduces the context of digitalization and some important definitions in both the European industry and the European iron and steel sector. The current technological transformation is depicted, and the main developments funded by European Research Programs are analyzed. Moreover, the impact of digitalization on the steel industry workforce are considered together with the foreseen economic developments.