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Switzerland
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Guo L.,University of Cambridge | Roelofs H.,Swiss Steel AG | Lembke M.I.,Steeltec AG | Bhadeshia H.K.D.H.,University of Cambridge
Materials Science and Technology (United Kingdom) | Year: 2017

A model for recalescence has been established by integrating a model for the decomposition of austenite and one dealing with heat transfer with latent heat release taken into account. The effects of recalescence on each individual austenite transformation product have been studied. It was found that Widmanstätten ferrite and pearlite reactions are most affected. The calculated cooling curve, as affected by the recalescence, has also been verified with a commercial steel subjected to two different environment conditions. © 2017 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute


Chabbi L.,Swiss Steel AG | Hasler S.,Swiss Steel AG | Roelofs H.,Swiss Steel AG | Haupt-Peter H.,Swiss Steel AG
Materials Science Forum | Year: 2017

Products and manufacturing processes of long-product producers are subject to constantly changing requirements, characterized by increasing demands on product quality and the efficient use of resources in production, combined with permanent cost pressures. For these reasons steel wire producers must constantly improve their innovation capacity to be able to meet increasing customer demands more flexibly and more efficiently. This awareness has been anchored at Swiss Steel AG, part of the Schmolz + Bickenbach Group, for many years and leads to more and new solutions in all corporate divisions. This article focuses on practical examples from the areas of process and product innovation. It discusses options for and the potentials and challenges of meeting current and future market needs. The successful implementation of new solutions requires an in-depth understanding as well as the application of knowledge throughout the entire process chain from development, production, sales to further processing and actual use of a product. The technical challenges are addressed as well as the opportunities presented when new approaches are sought. © 2017 Trans Tech Publications, Switzerland.


Guo L.,University of Cambridge | Bhadeshia H.K.D.H.,University of Cambridge | Roelofs H.,Swiss Steel AG | Lembke M.I.,Steeltec AG
Materials Science and Technology (United Kingdom) | Year: 2017

The bainite transformation in a low-carbon Si-containing steel has been studied in situ by synchrotron X-rays. While the austenite is homogeneous prior to transformation, the carbon distribution becomes nonuniform as bainite plates form. This is because of the different degrees of physical isolation of films and blocks of residual austenite. The method for converting dilatational strain into bainite volume fraction, using lattice strain as a reference, during isothermal transformation was found to overestimate it. The bainitic and martensitic ferrite did not exhibit a tetragonal unit cell due to the low-carbon content of the steel and the high transformation temperature. © 2017 Institute of Materials, Minerals and Mining


Guo L.,University of Cambridge | Roelofs H.,Swiss Steel AG | Lembke M.I.,Steeltec AG | Bhadeshia H.K.D.H.,University of Cambridge
Materials Science and Technology (United Kingdom) | Year: 2017

A model for estimating the blocky retained austenite size distribution in Si-containing steels has been developed for the first time, based on the geometric partitioning of prior austenite grains by bainite sheaves. A random volume allocation method for the two new compartments formed by the formation of one bainite sheaf is adopted for reasons detailed in the text. Random selection of the compartment for subdivision is also employed at each step. The model has been verified experimentally using Si-containing bainitic steels. © 2017 Institute of Materials, Minerals and Mining


Patent
Swiss Steel AG, ArcelorMittal and Instytut Metalurgii Zelaza | Date: 2010-06-23

A rolled steel wire or rod suitable for the production of cold headed products without the application of heat treating operations has a chemical composition, by weight, of:0.04% C 0.1%1.8% Mn 2.0%0.15% Si 0.30%S 0.025%P 0.025%Cr 0.50%Mo 0.08%Ni+Cu 0.30%0.01% Al 0.05%V 0.05%10 ppm B 30 ppmN 100 ppmTi 0.06%the remainder being iron and impurities resulting from the production process. The steel has a cementite-free microstructure comprising a predominant phase, a minor phase and MX-precipitations distributed within the predominant phase, the predominant phase consisting of bainitic ferrite, the minor phase comprising retained austenite and optionally martensite with a size of 2 to 3 m, the relative amount of the minor phase amounting to < 20% by volume.


Guo L.,Charles University | Roelofs H.,Swiss Steel AG | Lembke M.I.,Steeltec AG | Bhadeshia H.K.D.H.,Charles University
Materials Science and Technology (United Kingdom) | Year: 2016

A model for estimating the upper to lower bainite transition has been developed for the iron–carbon–manganese–chromium–silicon alloy system by comparing the time required to decarburise a supersaturated bainitic ferrite platelet and that needed for the start of cementite precipitation in the ferrite. The problem is treated as a competition between the decarburisation time and the kinetics of cementite precipitation. Lower bainite is induced when the latter process is faster. The time for forming a volume fraction of 0.01 of the equilibrium amount of cementite is taken as the precipitation start time. The model was calibrated using experimental data from the iron–carbon system, and verified with the iron–carbon–manganese–molybdenum system and an experimental steel currently being developed for high-strength applications. © 2016 Institute of Materials, Minerals and Mining


Caballero F.G.,CSIC - National Center for Metallurgical Research | Roelofs H.,Swiss Steel AG | Hasler St.,Swiss Steel AG | Capdevila C.,CSIC - National Center for Metallurgical Research | And 3 more authors.
Materials Science and Technology | Year: 2012

The influence of bainite morphology on the impact toughness behaviour of continuously cooled cementite free low carbon bainitic steels has been examined. In these steels, bainitic microstructures formed mainly by lath-like upper bainite, consisting of thin and long parallel ferrite laths, were shown to exhibit higher impact toughness values than those with a granular bainite, consisting of equiaxed ferrite structure and discrete island of martensite/austenite constituent. Results suggest that the mechanism of brittle fracture of cementite free bainitic steels involves the nucleation of microcracks in martensite/austenite islands but is controlled by the bainite packet size. © 2012 Institute of Materials, Minerals and Mining.


Smolenicki D.,ETH Zurich | Boos J.,ETH Zurich | Kuster F.,ETH Zurich | Roelofs H.,Swiss Steel AG | Wyen C.F.,Rieter Machine Works Ltd.
CIRP Annals - Manufacturing Technology | Year: 2014

In order to represent actual cutting process conditions, an in-process tribometer is examined to measure friction during orthogonal turning process at cutting speeds up to 300 m/min. The tribometer consists of a spring preloaded tungsten carbide pin with spherical tip mounted behind the cutting edge and rubbing on the freshly generated workpiece surface. The pin preload is set according to feed force. A 3D-force measuring device in the fixation of the pin allows evaluating friction coefficient from tangential and normal forces. Experiments show strongly different results when contacting fresh and oxidized surfaces and decreasing friction coefficient with increasing cutting speed. © 2014 CIRP.


In order to achieve the goals for a sustainable development, concrete with recycled aggregates (concrete and mixtures from concrete and masonry, e.g. clay bricks and calcium silicate blocks etc.) is going to be used more and more in the future. Due to its thermal insulating properties, the demand for concrete with light-weight aggregates (e.g. foam glass) will also increase. As an essential element of this development, an increasing amount of cements with a reduced clinker factor as well as of mineral additions such as fly ash and ground granulated blast furnace slag is used for concrete production. Therefore, as a general tendency, the carbonation resistance of concrete mixes decreases while the risk of corrosion damages increases. The goal of the investigations described in this paper was to evaluate and to assess the corrosion resistance of a stainless rebar (Top12, composition corresponds approx. to steel grade 1.4003) in various carbonated concrete mixes and to compare the results with common rebars. The results lead to the conclusion that, in contrast to common rebars, Top12 is durable in all investigated concrete mixes, including strongly carbonated recycling concretes. Copyright © 2010 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Stucklin S.,Swiss Steel AG
Praktische Metallographie/Practical Metallography | Year: 2016

Accredited metallography laboratories are required to estimate the uncertainty ot the result of every test carried out. This presents a particular challenge in evaluating the cleanliness of a metal as usually a particle distribution - log-normal at best and represented by a tiny sample size - is truncated and split into discrete classes. Therefore, neither indirect (top-down) nor direct (bottom-up) methods succeed in estimating the uncertainty of cleanliness evaluations. For these reasons, such evaluations should be viewed through a process surveillance lens, particularly when discussing results or setting acceptance thresholds. © Carl Hanser Verlag, München.

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