*Programme subject to change
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11:45 |
Registration open |
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| 13:00 |
Welcome Address Didier Farrugia
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Session 1: Oxidation Mechanisms, Properties, Morphology & Control |
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| 13:30 |
Keynote: Model-based assessment of the mechanical parameters for oxide scale fracture Michael SchützeAbstractDescaling processes can be based on the effect of mechanical stresses to remove the unwanted oxide scale independent of how these stresses are applied, e. g. in reverse bending. For a better adjustment of the parameters in the descaling process a (semi-) quantitative knowledge of the stress situation during the descaling process is required as well as knowledge on the oxide scale structure and on the parameters for fracture of the oxide. The latter has been a subject of research in high temperature materials science since the early work of U. R. Evans in the middle of the last century who came up with a first quantitative description of scale fracture as a function of scale thickness. Meanwhile there is a more profound understanding of mechanical scale failure based on a number of well-elaborated equations taking into account the relevant material parameters. These equations can be used for assessing and optimizing the parameters for the descaling process of oxides on steels. In the paper the different models and equations will be presented and evaluated together with experimental data from the literature and from own measurements. It will also be described how new oxide data can be measured with the respective laboratory equipment. Besides more complex approaches a pragmatic concept using data from metallographic investigations can provide a useful tool for assessing the mechanical parameters needed for scale removal, the -c – concept. This approach will be described in some detail including data from the literature for different oxides but first of all with data on iron oxides. The approach offers a significant industrial potential for the adjustment of oxide descaling processes in steel industries.
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| 14:00 | |||
| 14:25 | |||
| 14:50 |
Study of internal oxides formed during hot coil cooling and their evolution during pickling Wanda MelfoAbstractGrain boundary oxides are formed during strip coil cooling of alloyed steels. The tertiary scale gets reduced due to the formation of alloy oxides in grain boundaries and bulk of the steel near surface. When pickled, the iron oxides are removed in the first seconds while after longer pickling times the grain boundaries are etched. We will show the results of experiments on both predicting the depth of internal oxides in coils and the determination of optimum pickling times to remove them before cold rolling.
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| 15:15 | |||
| 15:40 | Refreshments, exhibition & networking | ||
| 16:10 |
Oxidation of a dual phase steel during rapid alloy prototyping Lauren O'Donnell-McLeanAbstractThe growth of oxide scale during high temperature processing routes such as reheating and rolling has a large influence on the surface quality of steels and can result in large quantities of metal loss during steelmaking. Within recent years, research focussed on rapid product development has resulted in the simulation of the integrated steelmaking route, allowing representative steel samples to be generated and processed on a laboratory-scale. This study explores the effects of oxidation behaviour on a dual phase steel, DP800, using small-scale samples produced through Rapid Alloy Prototyping. In terms of oxidation, the limitations and opportunities of Rapid Alloy Prototyping are not yet fully understood. Experimental interrupted oxidation investigations have been conducted on both Rapid Alloy Prototyping and plant-generated samples to understand the scale growth evolution in DP800, with the intention of determining whether the laboratory route can be comparable and representative of processes taking place on an industrial scale, and to determine if Rapid Alloy Prototyping is suitable for oxidation studies.
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| 16:35 |
Oxidation behaviour and oxide/metal interface characteristics in a low-carbon steel containing impurities Jiaqi DuanAbstractResidual elements have been added to a low carbon steel to simulate the scenario of scrap recycling during steel production. Five alloys were studied (in wt pct): Base, 0.15 Cu-0.15Ni- 0.03Sn, 0.30Cu-0.30Ni-0.06Sn, 0.60Cu-0.15Ni-0.06Sn, and 0.60Cu-0.30Ni-0.06Sn. The samples were oxidized in air at 1180°C for 3 hours using thermogravimetry analysis (TGA) to simulate reheating stage. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were employed to characterize the oxides/metal interface. The effect of residual elements on oxidation rate and interface characteristics has been studied. TGA results showed that the oxidation rates increased and then decreased as the contents of residual elements increased under current experiment condition. FactStage software was used to predict the equilibrium phases at the interface, and agreements between the predication and experimental results were obtained.
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| 17:00 | |||
| 17:25 |
Importance of roll oxide formation to improve hot rolling campaigns with high quality strip surface Sebastien FlamentAbstractAuthors: The importance of the roll oxidation has already been observed in the 90’s when implementing the Rollscope in industrial rolling mills. Roll oxidation is a complex process combining thermal, chemical and mechanical actuators. The formation of an adequate oxide layer strongly determine the performance of work rolls in a rolling stand with respect to roll friction and its degradation. Within the RFCS European project “Mastering Rolls II”, new developments like a full non-destructive roll oxide thickness measurement by XRF and roll pre-oxidation have been further assessed. This paper will give a complete overview on the complex phenomenon of roll oxidation and its benefits for the hot strip mills. |
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| 17:50 |
The impact of oxidised powder particles on the microstructure and mechanical properties of Ti-6Al-4V processed by laser powder bed fusion Robert WilliamsAbstractIn selective laser melting (SLM) heat diffusing from the melt pool promotes the growth of surface oxide layers on powder particles surrounding the built part, and material ejected from the melt pool oxidises rapidly before landing on the powder bed, creating local variability in the oxygen content of any used powder. Although large particles are removed when recycling, smaller oxidised particles (the size of the specified powder for the machine) and oxide residue (<10 µm) are not removed and become incorporated into subsequent builds on powder reuse. This paper considers the effect these oxidised particles may have on part integrity and how they affect mechanical failure. In this research, grade 23 Ti-6Al-4 V metal powder was artificially oxidised to produce a range of interference colours that correspond to specific oxide thicknesses. Powder characterisation established the oxygen wt% of each coloured powder. Yellow and blue powder were chosen for further investigation as in the context of this study, they represent low (0.4 wt%) and high (0.7 wt%) oxygen levels respectively. Tensile builds were produced using SLM with a known feedstock layer, part way up the build, formed of a blend of oxidised and virgin particles. Tensile tests were performed for each build to evaluate the failure modes. Microscopy techniques were used to examine the material near the fractured region, including chemical composition and semi-quantification of the oxygen levels, allowing any microstructural and chemical changes to be investigated. It was shown that the region doped with oxidised particles negatively affected the mechanical properties of the final build, as they produce mechanical (oxide films/residue) and chemical flaws (interstitial elements). Unless these particles can be removed from recycled feedstock their effects will limit the reuse of powder, especially in safety critical industries, significantly increasing the costs of components produced by this route.
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| 18:15-19:45 | Drinks & canapés | ||
