Papers by Keyword: Cast Iron

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Authors: Davi Munhoz Benati, Kazuhiro Ito, Kazuyuki Kohama, Hajime Yamamoto, Eugênio José Zoqui
Abstract: Fe-2.5C-1.5Si gray cast iron evaluated in previous works exhibited promising potential as semisolid raw material presenting low levels of maximum stress and viscosity, similar to Al-Si alloys. This work is intended to investigate phase transformations and liquid phase formation for the Fe-2.5C-1.5Si gray cast iron in order to understand the performance of the alloy during the semisolid processing. Thus in situ heating experiments via high temperature laser scanning confocal microscopy were performed to analyze the solid-to-liquid transition. At room temperature alloy presented a matrix of pearlite and ferrite with type D flake graphite. During the heating process the main transformations observed were graphite precipitation on the austenite grain boundaries, graphite precipitates and flakes graphite growing and coarsening with the increasing of temperature and the beginning of melt around 1140°C. Coarsened flakes at high temperatures resulted in a liquid continuous network after melting, thereby the liquid phase was formed surrounding and wetting homogeneously the solid phase. This favors the detachment of grains from each other and leads to the intended solid globules immersed in liquid.
Authors: Doru Michael Ştefănescu
Abstract: This paper is a review of the marvelous development of mathematical and computer models that describe the fundamentals of microstructure evolution during the solidification of cast alloys, from the 1966 seminal paper by Oldfield, the first to attempt computational modeling of microstructure evolution during solidification, to the current prediction of mechanical properties. The latest analytical models for irregular eutectics such as cast iron, as well as numerical models with microstructure output, to include cellular automaton, will be discussed. Phase field models will not be discussed because of their inapplicability to casting solidification at the present time.
Authors: Susumu Takamori, Yoshiaki Osawa, Hideki Kakisawa, Kazumi Minagawa, Kohmei Halada
Authors: Torsten Sjögren, Per Eric Persson, Peter Vomacka
Abstract: During the last years the use of digital image correlation techniques (DIC) has become wide spread within different areas of research. One area in which these techniques are used is in the analysis of deformation of engineering materials. By the analysis of a set of successive images taken during a tensile test DIC makes it possible to determine how the deformation is localized. The observed local strains are often several times higher than the global strain measured by standard strain gauges. In this study, a set of compacted graphite cast irons (CGI) with different ratios of pearlite to ferrite have been examined by the use of DIC. In contrast to the normal use of DIC, where a pattern is sprayed on the tensile test sample as a reference for the determination of deformation taking place between successive images, the materials natural microstructural pattern has been used in this study. The use of the natural microstructural pattern makes it possible to study how the macroscopic deformation is accommodated within the different phases in the CGI studied. It is shown that the graphite phase accommodates a large portion of the strain and that the soft ferrite is strained more than the stronger, less ductile pearlite. The local strain of the observed area might be up to ten times higher than the global strain measured. The use of DIC improves the understanding of the deformation behaviour of compacted graphite cast irons and will be a useful tool when validating future finite element analyses of the micro-mechanical properties of cast irons.
Authors: Wen Bang Gong, Yun Zhang, Gang Yu Xiang
Abstract: In this paper, a formula for the calculation of carbon content during austenitizing of cast iron was deduced, considering the effect of silicon content on the heat treatment parameter. According to this formula, the carbon content of the austenite in a certain austenization temperature for a cast iron with given components can be easily calculated, and the austenization temperature for getting the expected carbon content in the austenite can also be determined. Besides, according to the relationship between austenization temperature Tx and the according carbon content Cax, and considering the effect of silicon content, the diagram of Cax, Tx and silicon content during the austenitizing process of cast iron was made.
Authors: Pål Schmidt, Lin Peng Ru, Vadim Davydov, Mattias Lundberg, Maqsood Ahmad, Taina Vuoristo, Daniel Bäckström, Sten Johansson
Abstract: Stress harps with bars of different size were used to study residual stresses due to different cooling rate during casting of a grey iron. Finite element (FE) simulations were performed to predict residual stresses from the casting process and the effect of a stress relieving heat treatment. Intended for validating the simulations, neutron diffraction (ND) and hole drilling methods were used to measure the residual stress distribution through the thickness and in a thin surface layer, respectively. Good agreement between the FE simulations and ND measurements is observed for the annealed harp and the normal and transverse directions of the as cast harp. Discrepancy occurs in the axial direction and especially in the side bars of the as cast harp for which the simulation shows much higher compressive residual stresses. The observed difference between the different techniques was discussed with respect to the characteristics of the different methods.
Authors: Wen Wei Li, Qing Du, Wei Zhong Li
Abstract: The existing researches only put forward the stress concentration portion and design improvements from the perspective of stress analysis, or conducts safety assessment on dryers with the methodology of fracture mechanics, without non-destructive testing methods. Based on over 3,400 tests on cast iron dryers in Hangzhou, an ultrasonic testing technology with longitudinal wave double crystal probe is developed in the present investigation. This study illustrates how to identify the volume defects through testing on the air holes, shrinkage cavities and inclusions in the dryer cylinder and small R transition zone with longitudinal wave double crystal probe at a small angle (5°), as well as plane defects with deep cracks through testing on the dryer cylinder and small R transition zone with longitudinal wave double crystal probe at a large angle (42°). It addresses the issues of how to measure the thickness in regular online testing for cast iron dryers, to calculate the intensity or compare with the design value, to identify low hardness value, to determine the key parts in online testing, and how to conduct safety assessment on the cast iron dryers with small cracks. This technique may resolve various problems in cast iron dryer testing.
Authors: Sung Yong Shim, Hwan Goo Seong, Jin Ho Jeong, Su Gun Lim
Abstract: The influence of angles of inclined cooling plate on cast structure and mechanical properties of cast iron was investigated experimentally in 3.1 wt.% C containing hypoeutectic semisolid cast irons fabricated by flowing the molten melt over the inclined cooling plate and pouring into a preheated permanent mold. The variables used in this study were angles of the cooling plate (5 ~ 15 deg) and the mold temperatures (500~700 deg). The microstructure of resultant specimens were characterized by measuring grain sizes of primary austenite and its solid fraction, using an optical microscope equipped with a digital image analyzer. It was shown that the spherical-like austenite (1.4 aspect ratio) was formed at the cast iron specimens prepared in employing a 10 deg angle of the inclined cooling plate. This was ascribed to the relative extent of duration time of the flowing melt which determine the solidification rate of the melt. The peak hardness and impact values were achieved in the semi-solid cast iron specimen with relatively more spherical austenite. The measured values were approximately 44HRC and 1.71 J/cm2.
Authors: P.K. Mehrotra
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