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Turowski M.,Laser Zentrum Hannover e.V. | Jupe M.,Laser Zentrum Hannover e.V. | Jupe M.,Space Time Research | Melzig T.,Fraunhofer Institute for Surface Engineering and Thin Films | And 6 more authors.
Thin Solid Films | Year: 2015

Simulation of the coating process is a very promising approach for the understanding of thin film formation. Nevertheless, this complex matter cannot be covered by a single simulation technique. To consider all mechanisms and processes influencing the optical properties of the growing thin films, various common theoretical methods have been combined to a multi-scale model approach. The simulation techniques have been selected in order to describe all processes in the coating chamber, especially the various mechanisms of thin film growth, and to enable the analysis of the resulting structural as well as optical and electronic layer properties. All methods are merged with adapted communication interfaces to achieve optimum compatibility of the different approaches and to generate physically meaningful results. The present contribution offers an approach for the full simulation of an Ion Beam Sputtering (IBS) coating process combining direct simulation Monte Carlo, classical molecular dynamics, kinetic Monte Carlo, and density functional theory. The simulation is performed exemplary for an existing IBS-coating plant to achieve a validation of the developed multi-scale approach. Finally, the modeled results are compared to experimental data. © 2015 Elsevier B.V.

Ondrouskova J.,Brno University of Technology | Pohanka M.,Brno University of Technology | Vervaet B.,Center for Research in Metallurgy
Materiali in Tehnologije | Year: 2013

Due to the long service life of work rolls it is very important to follow the thermal load, but it is very difficult to measure it. One option for computing this thermal load is to measure the temperature and to study the thermal load through the heat flux. A unique work roll was made for testing different process conditions, such as rolling velocity, roll cooling, skin cooling and reduction. This work roll was tested on a real, hot-rolling, continuous pilot line. Two types of temperature sensors were embedded in the work roll in order to measure the temperature and these gave very detailed information about the development of the temperature inside the work roll. A time-dependent heat flux was computed using an inverse heat-conduction task with a detailed numerical model. The surface-temperature history was also obtained from this computational model. These boundary conditions give detailed information about the influence of different process conditions and allow a computation of the temperature field in the work roll. The paper describes the measuring equipment, details of the used temperature sensors, the inverse heat-conduction task for computing the thermal-surface boundary conditions and the results obtained from hot-rolling conditions.

Jacobs L.,Tata Steel | Vervaet B.,Center for Research in Metallurgy | Hermann H.,TU Bergakademie Freiberg | Agostini M.,ArcelorMittal | And 5 more authors.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | Year: 2011

Strip cleanliness in the industrial cold rolling mill must be controlled by optimizing the roll, strip, lubricant and process parameters. Obtained experimental evidence in this work shows which of these parameters have a significant influence on strip cleanliness. The experiments were carried out on a plate-out tester and on cold rolling pilot mills. New findings were the influence of thickness reduction on strip cleanliness: a high reduction in the first stands of a tandem mill results in poor strip cleanliness, but in the latter stands a high reduction results in a better strip cleanliness than a low reduction. Furthermore the beneficial influence of a chrome coating on the work roll was shown to be related to the better adherence of oil to this type of work roll. This article provides a concise overview of the experimental results achieved and their interpretation. © Tata Steel Nederland Technology B.V., 2011.

Raudensky M.,Brno University of Technology | Horsky J.,Brno University of Technology | Ondrouskova J.,Brno University of Technology | Vervaet B.,Center for Research in Metallurgy
Steel Research International | Year: 2013

Work rolls in hot rolling mills are thermally and mechanically loaded; both of these loading aspects are difficult to measure. Laboratory tests can be used for the specification of the thermal load in the cooling area; however a thermal load in a roll gap is still difficult to measure. The paper describes an experimental technique developed for monitoring the work roll surface temperature by sensors embedded in the work roll. Continuous hot rolling pilot line trials were performed for different process conditions. One parameter, for example, roll cooling, rolling velocity, reduction, or skin cooling, can easily be changed during the trials, and the effect on the thermal cycle of the work roll can be directly measured. These thermal measurements give very detailed information about the temperature field. An inverse heat-conduction model has been developed to compute the surface boundary condition from the measured temperatures. The heat flux and heat transfer coefficient distribution along the roll circumference can be obtained afterwards. The results for different rolling velocities and reductions (up to 50%) are shown. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Debrabandere D.,Center for Research in Metallurgy | Eynde X.V.,Center for Research in Metallurgy | Reniers F.,Free University of Colombia
Journal of Physics: Conference Series | Year: 2011

Si-based coatings were deposited with a cold plasma jet (Plasmabrush® PB1 from Reinhausen lasma) at atmospheric pressure with nitrogen as main carrier gas and hexamethyldisilazane (HMDSN) as precursor. Effects of hydrogen addition on the plasma characteristics and the coatings compositions have been evidenced with optical emission spectroscopy (OES), power measurements and XPS in-depth analyses. The intensity evolution of the nitrogen line (at 315.9 nm) with the applied voltage has a sigmoid shape for the pure nitrogen plasma but a quite linear one with hydrogen addition (up to 3%). Based on OES spectra, the presence of the NH specie in the nitrogen-hydrogen plasmas has been evidenced (around 336.0 nm) but not in the pure nitrogen plasmas. Although the plasma power is similar for both gases, the nitrogen atomic concentrations in the films as evidenced by XPS were lower with the nitrogen-hydrogen plasmas than with the pure nitrogen plasmas indicating a chemical effect of the presence of hydrogen in the plasma.

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