Papers by Keyword: Inclusion

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Authors: Zhi Liang Zhu, Guo Jun Ma, Chen Fan Yu
Abstract: In this study, a confocal scanning laser microscopy was used to in situ observe the collision and aggregation behavior of inclusions in molten state and the pushing/engulfing behavior in the solidifying interface of tire cord steel. The results show that the inclusion particles will be captured into the grains in the solidification front for the inclusions with a diameter are larger than 53.4μm at a cooling rate of 1 K/s. Moreover, the attraction force of inclusion particles in molten state is in the order of 10-16N~10-14 N in tire cord steel.
Authors: David J. Burnard, William D. Griffiths
Abstract: Inclusions in castings are particularly damaging as crack initiators, causing failure in service. It is therefore desirable to attempt to remove them prior to their entry into the casting. In this work the behaviour of inclusions was studied using a computer simulation to predict the movement of particles in flowing liquid metal. The computer simulation was created by a combination of Computational Fluid Dynamics (CFD) and Discrete Element Modelling (DEM), to try to predict the agglomeration characteristics of inclusions in liquid Al alloy in a launder system. The model was tailored to simulate dispersed particles in a fluid, where particle collisions with each other and with side walls are significant. The launder model had a wall or baffle placed along its length to investigate its effect on trapping inclusions, results from the model showing particle distribution.
Authors: Shujun Zhang, Zhen Xiang Cheng, Huan Chu Chen
Authors: Osvaldo Comineli
Abstract: A novel concept of hot shortness control on copper containing weathering steels is proposed. The weathering effect of copper addition in steels and its improvement in the mechanical and impact properties by age hardening are well known. Again, it is also very well know the problem of cracks on hot processing of those steels, caused by liquid copper segregation, the “hot shortness”. Hot shortness is the main problem of commercial producing of copper containing steels because of the increase of cost production caused by cracks the Ni addition to prevent them. Recent research found that copper segregates surrounding MnS inclusions in the steel, worsening the copper segregation caused by the preferential oxidation of iron on the hot processing of copper containing steels, which is the traditional cause of the “hot shortness”. The same results also show that copper additionally precipitates as CuS in the bulk of the steel. This work points that the “hot shortness” can then be prevented by reducing the Mn in the steel, rather than by the expensive Ni addition. Reducing Mn means reduction of inclusions of MnS sites for copper segregation in the steel. Residual sulphur can therefore be trapped by the copper as finer CuS precipitates, so copper is then dissolved in the bulk of the steel rather than segregated. This paper introduces an alternative solution for the problem of the “hot shortness” by partially or fully replacing the Mn by Cu in those steels. It is then proposed a novel concept of low Mn, or Mn free, Cu containing weathering steels in which Cu replaces Mn in trapping the S. That new steel opens the possibility to a cheaper and easier controls of the “hot shortness” so the copper contamination from scraps become a technological benefit because of its age hardening and weathering effect on steels. The recycling of highly copper contaminated scraps is another important environmental advantage. The conclusion of this work is that the current results introduces a new technology of cheaper copper containing low Mn, or Mn free, high strength, environmentally-friendly weathering steels with high potential market for different welded on shore and offshore specifications.
Authors: D.J. Burnard, A.J. Caden, J. Gargiuli, T. Leadbeater, D.J. Parker, William D. Griffiths
Abstract: Inclusions have a detrimental effect upon casting properties but it is known empirically that a slow liquid metal flow has a beneficial effect by reducing the number of inclusions entering the casting. Positron Emission Particle Tracking (PEPT) is a method that can be used to track the path taken by radioactive particles, and can be used to follow the behaviour of inclusions as they make their way from a furnace, along the launder and into the casting. A new PEPT camera geometry was developed and used to track radioactively labelled γ-alumina particles, in the region of 600 μm size. The camera detectors were arranged radially around a launder, into which was poured 150 kg of liquid Al alloy, the radioactive particles being released at intervals during the pour. The positron camera was 0.7 m in length and 0.1 m2 in cross-sectional area, and this matched the dimensions of an industrial launder. A model of inclusion behaviour in a flowing liquid Al alloy was also developed, and the Positron Imaging system described was used to validate this model.
Authors: Linamaría Gallegos Mayorga, Stéphane Sire, Sylvain Calloch, Suzhe Yang, Luc Dieleman, Jean Luc Martin
Abstract: The puddled iron is known for its extended use in monumental construction during the second half of the nineteenth century; among the structures built with such material are about half of French railway metallic bridges, most of them with over a century of service life. This scenario rises several concerns about the resistance of this material to cyclic loadings and therefore its fatigue behaviour. However, the puddled iron possesses several properties that make its mechanical characterization particularly difficult. Due to the puddling process this metal contains an important number of non-metallic inclusions that not only will turn out in a heterogeneous material but also (due to the rolling process) into an anisotropic one. In this paper a fast characterization of fatigue properties is proposed by using the self-heating method. The experimental self-heating curves obtained from specimens of the bridge of Toles (Chaumont, France) showed a scatter that was not observed in homogeneous materials (modern steel for example), this phenomenon is explained by the lack of determination of the representative elementary volume of the puddled iron. However, this data gives us important information such as the minimum and maximum boundaries of the mean fatigue limit for several orientations. An anisotropic two-scale probabilistic model for high cycle fatigue is also used to represent the orientation dependency of the results and the scatter found on the experimental data by using Hills elasto-plastic law and Weibulls distribution law to describe several characteristics of each site where the microplasticity occurs. The influence of such parameters and the limitations of the model are also discussed.
Authors: J. Zhou, Winston O. Soboyejo
Authors: M. Díaz-Fuentes, Inaki Madariaga, Isabel Gutiérrez
Authors: Chong Lin Wang, Chun Guang Zhang
Abstract: X-ray analysis on iron ores and reduced iron powders revealed that around 60% acidinsoluble substances were hexagonal and tetragonal quartz, another 40% substances were sillimanite, alumina-silicate, an unnamed zeolite, all contained Si and Al. SEM images displayed that the particle size of them was in the range of 3~7 μm, which may be the initial source of the cracking in the sintered body. Statistics analysis showed that the Acid-Insoluble Content (AIC) for high-grade magnetite powder was (0.130±0.010) % during the latest five months. The predicting value for reduced iron powder from ore powders should be 0.179 %. However, the testing value for reduced iron powder was (0.192±0.014) %. The limited difference of 0.013% might imply rare pollution coming from the reduction and milling processes. The most important step for control AIC should be the separation process of iron ore powders.
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