Showing papers on "Gray iron published in 2007"

Influences of the Graphite Growth Direction on the Thermal Conductivity of Cast Iron

Abstract: The thermal conductivity of ferritic spheroidal graphite iron samples containing various amounts of chunky or spheroidal graphite was investigated by means of the laser flash method. Scanning electron microscopy studies were performed to investigate the graphite morphology. Although chunky graphite is believed to grow in large interconnected eutectic cells, no beneficial effects on the thermal transport properties can be established for spheroidal graphite irons containing considerable amounts of chunky graphite. The results can be explained by the growth mode of chunky graphite with the c-axis of the hexagonal crystal as the dominating growth direction. This produces less favorable paths for the propagation of heat throughout the material as compared to lamellar and compacted graphite, owing to the low thermal conductivity of graphite along the prism planes. The crystallographic orientation of the hexagonal unit cells within lamellar, compacted, spheroidal, and chunky graphite was analyzed by means of electron backscatter diffraction (EBSD) and related to the thermal transport properties.

Mechanical Behavior of Spun-Cast Gray Iron Pipe

Abstract: Past work has made little differentiation between the mechanical properties of pit and spun cast gray iron water pipes. Mechanical tests on coupons from spun and pit cast samples presented here show that spun cast gray iron has mechanical properties that fall between those of pit cast gray iron and ductile iron pipes, often with marked similarities to ductile iron. The properties determined from the mechanical tests were used to examine whether linear elastic analysis can be successfully used to approximate the mechanical behavior of a pipe loaded in bending. Linear elastic analysis was found to produce reasonable approximations to the behavior of undamaged pipes. The effect of corrosion pitting was included in the analysis by determining stress concentration factors for pits of varying depths at different stress levels. Multiplying the stress concentration factors by the results of the linear elastic analysis produced results with an error of no more than 6% from the values produced by a full cast iron p...

Eutectic Cell and Nodule Count in Cast Iron : Part II. Experimental Verification

Abstract: In this work the predictions of a proposed theoretical analysis aimed at elucidating eutectic cell counts, N in gray iron cast and nodule counts, Nn in ductile iron were experimentally verified. The work was focused on processing flake graphite and ductile cast iron under various inoculation conditions in order to achieve various physicochemical states in the experimental melts. In addition, plates of various wall thicknesses were cast and the resultant eutectic cell N and nodule Nn count were established. Moreover, thermal analysis was employed for determinations of the maximum degree of graphite eutectic undercooling, ΔTm. A comparison was made between the theoretical predictions and the experimental determinations of eutectic cells, N, nodule counts, Nn and ΔTm. It was found that N and Nn can be related to the casting modulus, M and as a consequence to the wall thickness, s in plate shaped castings. In particular, the outcome of this work indicates that the predictions of the theoretical analysis are in good agreement with the experimental outcome.

Cylinder bush or cylinder liner made of gray iron- or aluminum alloy for casting in a light metal alloy on the basis of aluminum or aluminum/magnesium, comprises a conditioning coating for casting

Abstract: The cylinder bush or cylinder liner made of gray iron- or aluminum alloy for casting in a light metal alloy on the basis of aluminum or aluminum/magnesium, comprises a conditioning coating for casting. The surface of the conditioning coating has a thickness of 0.5-5 mu m, a surface roughness of 2-60 mu m, and a porosity of 5-20 vol.%. The cylinder bush or cylinder liner is constructed in a multilayered manner and has cylinder running surfaces and cylinder body of different consistency. The conditioning coating comprises a joining layer. Independent claims are included for: (1) method for the production of a composite casting part; and (2) a light metal cylinder crankcase.

Influence of Melting Process on Oxygen Content in Gray Iron

Abstract: The presence of defects is of major concern in the production of grey iron castings. Some defects are merely an aesthetic problem while others can be detrimental for the performance of the component. Among the several possible defects, shrinkage porosity is one of the more challenging to understand and avoid. This type of defect can penetrate through the casting as a three-dimensional network. The purpose of this work has been to develop knowledge and understanding about the foundry process in order to increase product quality by eliminating or at least minimising the presence of shrinkage porosity in the production of vital engine components. This was done by developing fundamental knowledge concerning factors known to influence the presence of shrinkage porosity. Initially, an investigation was carried out in order to characterize shrinkage porosity commonly occurring in cylinder heads. Factors found to be important and contributing to the formation of shrinkage porosity were identified. It was found that this type of defect is formed at hot spots that have migrated during solidification. Knowledge of the migrating hot spot was used as a design criterion in the development of a geometry with the purpose of deliberately generating porosity. Based on this geometry a mechanism for the formation of this type of shrinkage porosity was proposed. The formation of shrinkage porosity depends on gases dissolved in the melt. In this work, their levels and variations in the melting process were investigated. It was shown how the solubility of oxygen depends on the temperature but not on the method used to produce the iron. On the other hand, the total amount of oxygen depends on the process but not on temperature. The discussion about gases also included hydrogen and nitrogen. The solidification of grey cast iron is complex. It is during the solidification that not only the final properties of the component but also the conditions for defect formation are established. Shrinkage porosity is formed due to volumetric changes followed by an inability to supply material to the contracting areas. The solidification of grey iron starts with nucleation and growth of the primary austenite followed by nucleation of eutectic cells. It was found that the microstructural constituents are interconnected. The importance of the macrostructure was also discussed and it was shown that shrinkage porosity can be found not only between eutectic cells but also between equiaxed crystals.

Application of ultrasound in testing of heat-treated cast iron

Abstract: The first papers concerning ultrasonic diagnosis of the mechanical properties of cast iron were published in the 1950-ties [1,2]. From this time on many works that concerned the relationships between structure, mechanical properties and the acoustic parameters of material were carried out and published. Most research was devoted to gray iron [2-13]. These researches concerned mainly the as-cast material. For technical reasons is it easiest to assess the speed of longitudinal ultrasonic waves, cL. Therefore, most of the works relate to this acoustic parameter of cast iron.

Influence of Melting Process on Hydrogen and Nitrogen Content in Gray Iron

Abstract: High concentrations of hydrogen and nitrogen in molten gray iron increase the risk of porosity in castings. Therefore, equilibrium variations of these gases at different stages in the process chain ...

Investigation of the Effect of Microstructures on CGI Machining

Abstract: The aim of this investigation is to evaluate the effect of microstructures on CGI machining and to compare to gray iron reference material Special designed workpieces, to reproduce real situations

Research on a New Type of Inoculant of High Strength Gray Iron

Abstract: The effect of adding different contents of 75SiFe and FeSiRe27 alloy into molten iron on the properties of high strength gray iron is studied. The experimental results show that the addition of a inoculant containing rare earth element could reduce the undercooling, the chilling tendency, hardness and blowhole formation tendency of the cast iron, and increase its tensile strength. Based on the research findings, a new type Fe-Si-Re alloy inoculant is prepared for molten iron. The machine tool castings treated with such inoculant obtain predicted effect.

Effect of chemical composition on the strength of large castings from gray iron

Abstract: The effect of C, Si, Mn, V, Cu, Mo, and joint additives of Cr + Cu and Cu + Ni + Mo on the static and cyclic strength of iron in large castings is considered.

Method for enamelling cast parts of standard hypoeutectic gray iron

Abstract: The present invention refers to a method for enamelling cast parts made of standard hypoeutectic gray iron, comprising following steps: - preparing a cast part of standard hypoeutectic gray iron; - pre-treating said cast part in order to promote mechanical bond and adherence of the enamel substances to the surface of the part to be enamelled; - applying porcelain-enamel powders onto the thus pre-treated part by dry electrostatic spray technique; - vitrifying the enamel powders by exposing the part to a heating and cooling sequence occurring according to such a heating and cooling pattern versus time as to cause the part to dwell at a temperature between 700°C and 780°C for 480 seconds ± 5%.

Method of improving mechanical properties of gray iron

Abstract: A method of forming gray iron components includes applying a substantially uniform magnetic field to gray iron. The method also includes heat-treating the gray iron while the gray iron is within the magnetic field.

Inoculating Influence of Re-Carburizers in Grey Cast Iron

Abstract: In laboratory experiments Thermal Analysis data were recorded and different solidification parameters were identified to characterize the inoculation effect of the carbon materials (amorphous and crystalline structure) in low sulphur (