Papers by Keyword: Spheroidal Graphite Iron

Abstract: Due to the combination of its numerous excellent mechanical qualities, the flexible iron has been used more and more since its invention in 1948. To develop significantly improved characteristics, the unnecessary investigation is being done. The most recent development in the field of flexible iron, or SG iron, is Austempererd malleable iron. At four different temperatures, two different types of spheroidal graphite (SG) cast iron samples with varying copper weight levels were austempered. The temperatures used for austempering were 200°C, 300°C, 350°C, and 400°C. As a component of the austempering time and temperature, the effect of the austempering process (i.e. time and temperature) on the mechanical characteristics of spheroidal graphite iron was investigated. The progress of spheroidal graphite iron's properties was significantly influenced by the pace of cooling and the extinguishing process. The organisation of different stages during isothermal change under varied austempering settings has also been the focus of XRD analysis. By using SEM, graphite morphology has been focused on. For this investigation, samples were obtained from the castings' focal point for XRD analysis. It was discovered that virtually always, it is possible to discriminate between the ferrite (110) and austenite (111) lines. The ferrite (110) line is growing with expanding austempering time and declining with increasing austempering temperature, whereas the highest power of the austenite (111) line is expanding with expanding temperature. Thus, very precise control of the interaction components (austempering duration and temperature) is required for austempering. The results showed that, when compared to other grades (N1) through the various austempering processes used in this evaluation, ADI containing the alloying component copper (grade N2) achieved crucial mechanical qualities.

Abstract: The main objective of this paper is to identify the thermo-mechanical behaviour of the spheroidal graphite (SG) iron EN-GJS-700. In the first instance, compression tests are carried out using Gleeble 3500 system enabling a precise control on testing temperature and strain rate. The effects of these testing parameters on the SG iron behaviour are studied. Through this, the occurrence of dynamic recrystallization phenomenon is highlighted. Specific rheological models based on metallurgy are introduced. Finally, shear tests on hat shaped specimens are performed to reach higher strain rates.

Abstract: This work is a trial to reach the optimum composition and structure of cast iron used for anode fixation in the aluminum electrolytic cells. Grey iron with low- and high-phosphorus contents, spheroidal graphite irons with compositions typical of ferritic and pearlitic grades as well as grey iron with different carbon equivalent values were compared. A bench-scale experimental set up was used to simulate the operating conditions at the steel stub/cast iron collar/carbon anode connection. The change in microstructure and electrical resistance was measured at temperatures up to 850°C for 30 days, which correspond to the electrolytic cell operating conditions. The thermal expansion properties of irons were measured using a high precision automatic dilatometer. The electrical resistance at the connection was found to decrease with spheroidal graphite irons. In flake graphite irons the resistance decreases with lower phosphorus content as well as higher CE values due to the enhanced graphitization potential during solidification, which increases the contact pressure at the connection. Decomposition of ledeburitic carbides in the structure plays – to lower extent – some role in increasing the contact pressure. This contact pressure rather than the resistivity of the cast iron seems to play the dominant role in determining the electrical resistance of the connection.

Abstract: The mathematical model for microstructure formation and porosity prediction during solidification process of SG iron casting was established and applied to a practical brake housing casting. Quantitative microstructure analysis of specimens machined from the castings was compared with the simulation, and the two results are in acceptable agreement on nodule counts and size, pearlite fractions and hardness. It is indicated that the model can calculate the fraction of ferrite and pearlite more accurately, and specially can reflect the effect of both under-cooling during solidification and the nodules formed in eutectic period on the pearlite content. The present porosity prediction was compared with those of a former method and commercial software, which leads to that the current methods used for porosity prediction should be investigated and improved further.

Abstract: The thermal conductivity of five predominately pearlitic grades of lamellar, compacted and spheroidal graphite iron have been modelled by means of existing models based on average field approximations. The model is based on the area fraction of different constituents and the width to length ratio of the graphite. The thermal conductivity of graphite in cast iron is derived by inverse modelling. These data are used in combination with experimental thermal conductivity values for a pearlitic matrix in order to model the thermal conductivity of various cast iron grades with good agreement. The calculations are executed for cast iron from room temperature up to 500°C.

Abstract: The thermal conductivity of various grades of pearlitic cast iron has been modelled with good results by means of regression analysis. The experimental thermal conductivity data, which the modelling is based on, were obtained by the laser flash method. The microstructure was investigated by digital image analysis combined with a colour etching technique. The model developed takes the carbon content, the silicon content, the nodularity as well as the fraction of cementite into consideration. The graphite morphologies of the samples investigated were lamellar, compacted and spheroidal.