Graphite Cast Iron Research Articles

Understanding compacted graphite iron solidification through interrupted solidification experiments

While the manufacture of compacted graphite (CG) iron castings has seen significant expansion over the recent years, the growth of CG during iron solidification is still not fully understood. In this work, effort was expanded to experimentally reveal the evolution of graphite shape during early solidification and its relationship to the solid fraction. To this purpose, interrupted solidification experiments were carried out on hypereutectic irons with three magnesium levels. The graphite shape factors were measured and analysed as a function of chemical composition and solid fraction. Scanning electron microscopy was carried out to establish the fraction of solid at which the transition from spheroidal graphite (SG) to CG occurs. It was confirmed that solidification started with the development of SG for all CG irons. The SG-to-CG transition was considered to occur when the SG developed a tail (tadpole graphite). The findings were integrated in previous knowledge to attempt an understanding of the solidification of CG iron.

Effect of cooling rate and of titanium additions on the microstructure of thin-walled compacted iron castings

This article addresses the effect of cooling rate and of titanium additions on the exhibited microstructure of thin-walled compacted graphite iron (TWCI) castings as determined by changing moulding media, section size and ferrotitanium. Various moulding materials were employed (silica sand and insulating sand ‘‘LDASC’’) to achieve different cooling rates. This study shows that the cooling rates exhibited in the TWCI castings varies widely (70–14 °C/s) when the wall thickness is changed from 2 to 5 mm. In turn, this is accompanied by a significant variation in the compacted graphite fraction. The resultant cooling rates were effectively reduced by applying an insulating sand in order to obtain the desired graphite compactness. Ti additions in combination with LDASC sand moulds were highly effective in promoting the development of over 80% compacted graphite in castings with wall thicknesses of 2–3 mm as evidenced by quantitative metallographic analyses.

Financing for Plants, Equipment and Operations for the Establishment of a Plant for the Manufacturing of Spheroidal Graphite Iron Castings for Automobile Industries

The Steel sector must be developed to meet up with challenges posed by auto parts replacement by developing auto parts production industries such as Inner and outer panels of automotive bodies, wheel housings and peripheral components, fuel tanks automotive exhaust systems, automatic fuel tanks and radiators, Steel cord for reinforcement radials tyres. Steel sector is the backbone of any economic or industrial development of any nation. The industrial revolution of the Government should aim at boosting the steel industry .To is able to produce car components, the establishment of small plants must be encouraged .The raw materials to produce car parts must come from our indigenous steel industry. In the situation of the Country where spare parts and components are not readily available therefore local production and local content must be encouraged. The research paper therefore carried out an Investment analysis to analysis the establishment of a plant for the manufacturing of Spheroidal Graphite iron for the manufacturing of spare parts, components for automobile industry. The analyzed investment proved that the amount to be invested in this plant could be recouped within the stipulated period of three years. Time value of money was considered throughout the implementation of the project. The describe investment analysis present a unique way in handling the establishment of plants of this nature. The work further looked into some areas like market potential of Spheroidal Graphite Iron, its characteristics and its vital role in engineering applications, implementation schedule, technical aspects that include all the necessary details for project execution, quality control and standard, pollution and protection within the plant, the production capacity of the plant were highlighted this shows that the plant can produce about 450 metric tonnes of finished castings in a year. The financial aspects and analysis were discussed in details, revealing the amount that could be involved in floating the plant for meeting the needs and demands that may arise from automobile industry. The overall aim of the project was achieved, this indicated that within a year of the establishment of the plant, a lot of revenue could be generated as shown from the rate of return on investment and the form break – even point. Some recommendations were given to encourage the establishment for such plants in any part of the country, which will continue to meet the demand of our local industries.

Structure and Properties of Cast Iron DESIGNATED for Working Layer of Rolls

<p class="1Body">The formation of the structure and properties of cast irons designated for the working layer during solidification and subsequent tempering of Indefinite Chill Double Poured Centrifugal Casting Rolls (ICDP) has been studied.</p><p class="1Body">Graphitization of cast irons designated for the working layer of rolls occurs under isothermal conditions at high temperatures, which vary over the cross section and resulted from casting the roll core. At subsequent slow cooling, secondary carbides precipitate and austenite partially transforms into martensite; the resulting end structure consists of martensite and austenite metallic base (primary austenite dendrites) with 11.4 per cent of retained austenite, 26 per cent of eutectic and secondary carbides, and 2.6 per cent of flake graphite.<em> </em></p><p class="1Body">The amount of retained austenite in the metallic base of the cast structure of cast iron designated for the working layer, heated to 430 °C, decreases<strong> </strong>from 11.4 per cent to 3.2 per cent due to the partial transformation into bainite. The martensite tetragonality decreases due to the carbide precipitation; the existing excess phases grow and the new ones are formed; the total volume fraction of the carbide phase increases to 29.8 per cent and graphite to 3.7 per cent.</p>

Multiple inoculations of ductile iron and the effects on properties

Multiple inoculation of ductile iron and the effects on the structure and mechanical properties have being investigated. Samples of ductile iron were produced with inoculation carried out either once or twice and with different materials as inoculants. Ferrosilicon was used for the primary inoculation and either ferrosilicon or nickel-ferrosilicon for the secondary inoculation. It is observed that the nodules produced are more and finer with multiple inoculations and the effect is more pronounced with nickel-ferrosilicon as the secondary inoculant. Multiple inoculations produce an increase in the hardness of ductile iron when ferrosilicon is used as the secondary inoculant while a decrease in the hardness is observed with nickel-ferrosilicon despite the finer nodules. This is explained by the fact that nickel enhances graphitization in cast iron thereby depleting carbon in the matrix and making the cast iron weaker but with more nodules.

Graphite Phase Characteristics in Compacted/Vermicular Graphite Cast Iron Inoculated in the Mould

The objective of this research paper is to examine the effects of adding an oxy-sulphide inoculant enhancer alloy [OS-IE = S,O,Al,Mg-CaSi alloy] to a conventional CaBa-FeSi alloy and to examine the graphite phase characteristics in these irons, as affected by different in the mould inoculants, for resin sand mould castings. The surface layer of all the Mg,RE-FeSi treated compacted / vermicular graphite cast iron samples with 0.018 – 0.023% Mgresis influenced by S diffusion from Furan Resin–P-Toluol Sulphonic Acid (PTSA). The graphite phase is strongly influenced in this surface layer. Inoculation has a visible, beneficial effect in both the surface layer and the body of casting. Even with the highest solidification rate, at the surface layer of the 25mm round bar samples, the structure has the lowest graphite nodularity (15-20%), due to the sulphur content in the mould binder, in contrast with 40-50% nodularity in the casting body. Adding two inoculant type alloys Ca,Ba-FeSi + [OS-IE], led to the highest compacted / vermicular graphite formation. Inoculation with [OS-IE] only appears to encourage the formation of a high number of small graphite nodules that also display higher nodularity. This is represented by the second highest levels for circularity and sphericity shape factors at a much smaller inoculant addition, compared with a conventional Ca,Ba-FeSi inoculant addition. Inoculation with oxide-forming elements or pairing oxy-sulphide inoculant enhancer with commercial inoculants appears to be an economical alternative to rare earth (RE) based inoculants in compacted / vermicular graphite iron casting production.

INCREASING OF MECHANICAL PROPERTIES OF CAST GRAPHITIZED STEEL

Purpose. Due to the presence of many essential properties (low prime cost, high manufacturability and damping ability, heat conductivity, fluidity and others),the graphitized cast irons are widely applied for parts operating under the conditions of static and cyclic loads, wear at dry friction and aggressive media at elevated temperatures. At the same time because of significant content of the graphite phase in the structure, the cast irons possess relatively low mechanical properties. Thereby the attention is drawn to graphitized steels, the peculiarity of which consists in the presence of graphite inclusions in the structure, which appoints specific cast iron's properties to these materials. But unlike cast irons, the graphite content in them is in 2…3 times lower and it affects positively on mechanical and service properties indices. This work deals with the optimization of the composition of cast graphitized steel, which has high mechanical properties indices. Methodology. The experimental design technique was used in this work. Alloys prototypes were smelted and their mechanical properties were investigated on the basis of these techniques. Findings were exposed to regression processing, and the dependences of the alloys components influence on its properties were obtained. By means of graphical optimization the optimal composition of steel with high mechanical properties indices has been determined. Findings.Ithasbeenestablishedthat carbon and silicon have the most significant influence on the strength and cyclic endurance of graphitized steels. The chemical composition of the cast graphitized steel with high static and cyclic strength indices was suggested in this work. Originality. With the use of mathematical experimental design techniques the dependences describing the influence of carbon, silicon and copper on the static and cyclic strength indices were obtained. They allow optimizing compositions of graphitized steels. Practical value. Using the graphitized steels with optimized composition in mechanical engineering will allow expanding their application areas along with providing reliability and durability of the parts operating under the conditions of static and cyclic loads.

Thermal Conductivity of Thin Walled Compacted Graphite Iron Castings

This study addresses the effect of the cooling rate and of titanium additions on the exhibited microstructure and thermophysical parameters of thin-walled compacted graphite iron (TWCI) castings as determined by changing the moulding materials (silica sand and insulating sand LDASC), and Ferro Titanium. The research was conducted for thin-walled iron castings with a 3-mm wall thickness. The tested material represents the occurrence of graphite in the shape of nodules, flakes (C and D types, according to ISO Standard) and compacted graphite with a different shape factor and percent of nodularity. Thermal conductivity has been evaluated by the laser flash technique in a temperature range of 22–600°C. The results show that the cooling rates together with the titanium content largely influence the microstructure, graphite morphology and finally thermal conductivity of thin walled castings. Finally mechanism for thermal conductivity profile as a function of temperature for thin wall castings with different graphite morphology is provided.

Nano-scale orientation mapping of graphite in cast irons

A diametrical section of a graphite spheroid from a ductile iron sample was prepared using the focused ion beam-lift out technique. Characterization of this section was carried out through automated crystal orientation mapping in a transmission electron microscope. This new technique automatically collects electron diffraction patterns and matches them with precalculated templates. The results of this investigation are crystal orientation and phase maps of the specimen, which bring new light to the understanding of growth mechanisms of this peculiar graphite morphology. This article shows that mapping the orientation of carbon-based materials such as graphite, which is difficult to achieve with conventional techniques, can be performed automatically and at high spatial resolution using automated crystal orientation mapping in a transmission electron microscope.

The Effect of Aluminium on Graphitization of Cast Iron Treated with Cerium Mixture

Abstract The work determined the influence of aluminium in the amount from about 0.6% to about 8% on graphitization of cast iron with relatively high silicon content (3.4%-3.9%) and low manganese content (about 0.1%). The cast iron was spheroidized with cerium mixture and graphitized with ferrosilicon. It was found that the degree of graphitization increases with an increase in aluminium content in cast iron up to 2.8%, then decreases. Nodular and vermicular graphite precipitates were found after the applied treatment in cast iron containing aluminium in the amount from about 1.9% to about 8%. The Fe3AlCx carbides, increasing brittleness and deteriorating the machinability of cast iron, were not found in cast iron containing up to about 6.8% Al. These carbides were revealed only in cast iron containing about 8% Al.

Graphitized Cast Irons

An analytical review of data on general-purpose grayed cast iron with different forms of graphite (lamellar, vermicular, globular, flaked) is presented. Grades of cast iron, their compositions, special features of structure of the graphite, and properties of gray, high-strength and malleable irons are described. The data on the kinds of iron considered are compared with those stipulated in international and some national standards.

Shot Peening Induced Plastic Deformation in Cast Iron – Influence of Graphite Morphology*

Abstract Graphite morphology in cast iron strongly affects the mechanical properties such as: Young's modulus, tensile/compressive strength and cyclic mechanical behaviour. In this study, pearlitic compact graphite iron (CGI) and grey cast iron (GI) have been studied in a scanning electron microscope (SEM) before and after shot peening under different conditions. The plastic deformation behaviour of CGI and GI under different shot peening conditions has been analysed using electron backscattering diffraction (EBSD) and electron contrast channelling imaging (ECCI). EBSD and ECCI revealed that plastic deformation around graphite inclusions depends on the size and shape of the graphite. The different response of CGI and GI to shot peening is explained by the different damping properties of the graphite and the matrix capability for plastic deformation. n

Structure of fullerene-containing deformed powder steels

The effect of dynamic hot compaction (DHC) and intensive plastic torsional deformation (IPTD) on the structure and properties fullerene-containing powdered compositions of Fe graphite and Fe cast iron has been investigated. It is found that sintering Fe graphite samples results in the synthesis of fullerenes in their surface layer and a fullerene-containing phase is observed in their body after DHC as well. DHC results in an increase in the wear resistance of the Fe graphite composition. It is shown that a 6.16 A line appears on diffractograms of all examined samples (both Fe graphite and Fe cast iron) as a result of IPTD. Scanning probe microscopy found that the elasticity modulus of samples of iron graphite increases from 50–58 to 67–91 GPa and local hardness increases from 10–19 to 137–155 GPa because of IPTD. The elasticity modulus of iron-pig-iron samples also increases from 63 GPa before IPTD to 55–109 GPa afterwards. A wide scatter in values of this index testifies to the inhomogeneity of the structure formed in the course of deformation.

Thermo-mechanical behavior and fatigue strength of a grey cast iron for automotive brake discs considering graphite flakes debonding

This paper aims at developing an approach for thermo-mechanical fatigue design of automotive brake discs made of lamellar graphite (grey) cast-iron. The first step consists of modelling the nonlinear cyclic behavior and tension/compression strong dissymmetry of grey cast iron. The proposed model is based on the introduction of a second-order induced damage tensor. From the analysis of the damage mechanisms, a fatigue criterion based on the dissipated energy per cycle is proposed.

Effect of Cooling Rate and Titanium Additions on Microstructure of Thin-Walled Compacted Graphite Iron Castings

Effect of Cooling Rate and Titanium Additions on Microstructure of Thin-Walled Compacted Graphite Iron Castings

Grain count in castings: theoretical background and experimental verification

In this work, a theoretical model is proposed for heterogeneous nucleation on substrates whose size distributions can be described by the Weibull statistics. In particular, the proposed model suggests that the size distribution for the various nucleation sites is exponential in nature. Measurements of grain count were carried out on experimental Al–1·3Si and Al–5·0Cu single phase alloys inoculated using an Al–5Ti–1B master alloy. In addition, experimental nodular and flake graphite iron castings were processed under various metallurgical conditions. In single phase alloys, the area of the equiaxed dendritic grain count was estimated from the electron backscattering diffraction analysis, whereas the graphite nodule and graphite eutectic cell count were estimated on polished cast iron surface sections by stereological means. In addition, maximum undercoolings were determined by thermal analysis. The experimental outcome indicates that the grain count can be properly described by a proposed exponential function of the maximum undercooling at the onset of alloy solidification. Finally, the magnitudes of the nucleation parameters were experimentally determined in this work.

Distribution of Stress around the Graphitic Particles in Cast Iron Microstructure

The given work is focused on the analysis of the distribution of stress around graphitic particles in microstructure of the ductile cast iron with the spheroidal shape of graphite (SGCI) and grey cast iron with the lamellar shape of graphite (LGCI). The analysis was made with help of finite element method in the software system ADINA.v.8.6.2. On the basis of the real structure, the finite element method was used for creation of the model which was subsequently used for calculation of the distribution of stress in the material structure. The input data for numerical analysis were obtained on the basis of evaluation of the structure by help of image analysis. The numerical analysis proved that the graphitic particles in the matrix cause the accumulation of the stress and the distribution of the given stress depends on the shape of the graphitic particles.

Role of Titanium in Thin Wall Vermicular Graphite Iron Castings Production

Abstract In this paper the effects of titanium addition in an amount up to 0.13 wt.% have been investigated to determine their effect on the microstructure and mechanical properties of Thin Wall Vermicular Graphite Iron Castings (TWVGI). The study was performed for thinwalled iron castings with 3-5 mm wall thickness and for the reference casting with 13 mm. Microstructural changes were evaluated by analyzing quantitative data sets obtained by image analyzer and also using scanning electron microscope (SEM). Metallographic examinations show that in thin-walled castings there is a significant impact of titanium addition to vermicular graphite formation. Thinwalled castings with vermicular graphite have a homogeneous structure, free of chills, and good mechanical properties. It may predispose them as a potential use as substitutes for aluminum alloy castings in diverse applications.

Redistribution and Effect of Various Elements on the Morphology of Primary Graphite in Cast Iron

It has been shown repeatedly that many elements present as traces or at low level can affect graphite shape in cast irons. As part of a long term project aimed at clarifying the growth and the alteration of spheroidal graphite, a study on the effect of a few elements (Cu, Sn, Sb, and Ti) on primary graphite growth was undertaken and analysed with reference to an alloy without any such additions. This work was performed by remelting alloys in graphite crucibles thus saturating the melt in carbon and enabling primary graphite to grow by controlled cooling of the melt above the eutectic temperature. Primary graphite growth in the reference alloy was observed to be lamellar, while the added elements were found to affect bulk graphite and to modify its outer shape, with Sb leading eventually to rounded agglomerates together with wavy lamellae. Secondary ion mass spectrometry was used to analyze the distribution of elements, and no build-up of trace elements at the graphite surface could be observed. Instead, it is established that the perturbation of bulk graphite is associated with inhomogeneous distribution of metallic elements inside graphite precipitates.

Effects of Titanium Addition on Microstructure and Mechanical Properties of Thin-Walled Compacted Graphite Iron Castings

This research studies the effects of titanium added in an amount up to 0.13 wt.% on the microstructure and mechanical properties. The research was conducted for thin-walled iron castings with 3-5 mm wall thickness and for the reference casting with 13 mm wall thickness to achieve various cooling rates. Microstructural changes were evaluated by analyzing quantitative data sets obtained by image analyzer and also using scanning electron microscope. Metallographic examination revealed in thin-walled castings a significant effect of the addition of Ti to compacted graphite, much stronger in comparison with castings with thicker sections. Moreover, thin-walled castings with high degrees of inoculation and which have been solidified under high cooling rates have a homogeneous structure, free of chills, and good mechanical properties, which may predispose them for potential use as substitutes for aluminum alloy castings in diverse applications.