Compacted Cast Iron Research Articles

EFFECT OF MAGNESIUM TREATMENT PROCESS ON THE PRODUCING COMPACTED GRAPHITECAST IRON WITH DIFFERENT CASTING THICKNESS

Strength, toughness, machinability and damping capacity are properties of compacted graphite iron that distinguish the properties between flake graphite cast iron and spheroidal cast iron. The formation of compacted graphite can be set to achieve the required specification. The formation of compacted graphite is started from spheroidal to compacted cast iron. The residual magnesium after magnesium treatment and the solidification ratehave a significant role in the formation of compacted graphite. The high content of residual magnesium can obstruct the graphite plane to grow during the transformation from spheroidal to compacted shape. In addition, the cooling rate of the casting can be controlled by varying the casting thickness. The compacted graphite in the cast iron are characterized according to shape, size ai`nd distribution. The optimum compacted graphite in the cast iron that can be produced has 30 mm of casting thickness with 0.017 % of residual magnesium.

The effect of graphite number per area on tribological behavior of high-strength compacted cast irons in lubricated tests

The effect of graphite number per area on tribological behavior of high-strength compacted cast irons in lubricated tests

EFFECT OF MAGNESIUM TREATMENT PROCESS ON THE PRODUCING COMPACTED GRAPHITE CAST IRON WITH DIFFERENT CASTING THICKNESS

Strength, toughness, machinability and damping capacity are properties of compacted graphite iron that distinguish the properties between flake graphite cast iron and spheroidal cast iron. The formation of compacted graphite can be set to achieve the required specification. The formation of compacted graphite is started from spheroidal to compacted cast iron. The residual magnesium after magnesium treatment and the solidification rate have a significant role in the formation of compacted graphite. The high content of residual magnesium can obstruct the graphite plane to grow during the transformation from spheroidal to compacted shape. In addition, the cooling rate of the casting can be controlled by varying the casting thickness. The compacted graphite in the cast iron are characterized according to shape, size and distribution. The optimum compacted graphite in the cast iron that can be produced has 30 mm of casting thickness with 0.017 % of residual magnesium. 

Comparison of solidification kinetics of compacted and lamellar cast irons

Thermal analysis is largely used in cast-iron foundry shops as a means to check melt preparation before casting. It has been suggested that the shape of the cooling curves could be related to graphite form, either spheroidal, lamellar or else compacted. The present work is part of a larger study intended to improve melt control for compacted graphite castings by using controlled additions of sulfur and magnesium. Experiments showing lamellar graphite and their counterpart with compacted graphite have been selected for analysis and simulation of the thermal analysis records. Simulation makes use of the fact that compacted graphite differs from lamellar graphite by the limitation of graphite branching in the former. Solidification of both types of irons may thus be simulated using the same basic growth law for irregular eutectics, though changing the parameters describing the branching capability of the faceted graphite phase. The increase of the undercooling of the eutectic plateau during solidification of compacted cast iron when compared to that of lamellar cast iron could be verified and reproduced by simulation. The limitations of the present approach which assumes the temperature in thermal cups is homogeneous at any time are also pointed out.

Effect of graphite on folded metal occurrence in honed surfaces of grey and compacted cast irons

Grey cast iron (GCI) and compacted graphite iron (CGI) are the most employed materials to manufacture cylinder liners. The use of diamond tools to hone the surfaces resulted in an increase of the so-called folded metal occurrence. This irregularity can reduce the performance of engines and investigations to understand it have been made. In this sense, the current study aims to correlate the variation of graphite and the folded metal occurrence. Different samples of GCI and CGI were extracted directly of engine blocks, resulting in four metallurgical conditions. Topographical analysis was conducted in an optical interferometer and a dedicated routine to count the folded metal was developed using 3D images. Folded metal occurrence can be associated to a specific region of topography and to an increase in the graphite area fraction. Experimental evidences were provided revealing cross-sectional images of grooves using a scanning electron microscope. In addition, the present investigation shows that a larger amount of folded metal was related to the microstructure of thicker walls of compact graphite 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.

Microstructure and Mechanical Properties of Austenitic Compacted Cast Iron with Additive Manganese

High composition of austenitic matrix in microstructure is contributed to its special characteristic in reducing cracking and distortion. This special alloy will be in austenitic matrix when high temperature and also at room temperature which make it successful avoid matrix volume changes. In this study, austenitic compacted iron with minimum nickel contain of 12wt% is produced by using in-mould magnesium treatment. Magnesium Ferro Silicon (MgFeSi) used in determining the graphite form. Some of nickel replace by manganese in range of 9wt% to 12wt% Mn while Nickel remain at 12wt% Ni at all parameter. This research focuses on to investigate the effect of alloying elements on microstructure and mechanical properties. The outcome compared to standard of unmodified austenitic cast iron as in ASTM standard. The matrix obtained was all in austenitic matrix with the presence of compacted graphite distribution throughout the matrix. It is appeared that result shows increment of manganese at the centre region between graphite in the microstructure. It is occurred when percentage of manganese addition was increased. There are increases in hardness compared to unmodified austenitic iron. Tensile strength decreases when the manganese content increases in alloy.

Simulation of Cylinder Deformations during Honing of Thermally Coated Running Surfaces in Crankcases

The internal combustion engine of the future has to cope with increasing high requirements. A large potential is seen in reducing friction in the piston group. For this purpose a coating technology for cylinder running surfaces, including mechanical machining processes was developed. By substituting the compact cast iron liners (4 mm wall thickness) for the thin coating layer (0.1 mm) the normal forces become more important in the honing process. Due to the different stiffness of the crankcase roundness deviations occur caused by the machining forces as a result of elastic deformation. Content of this paper is the calculation of the elastic deformations using the finite element method. Based on a honing tool model, the effective normal forces are calculated, which afterwards are used as input variables for the crankcase model.

Graphite Morphology's Influence on Shot Peening Results in Cast Irons

The different shot peening responds of a grey cast iron (GI) with its flake graphite and a compacted cast iron (CGI) with its vermicular graphite was analyzed and compared in this paper. For peening using identical parameters, CGI showed a larger plastic deformation zone with higher subsurface compressive stresses than GI. Electron backscatter diffraction (EBSD) mapping and backscatter electron imaging revealed that plastic deformation of the matrix near graphite inclusions is affected by the size and geometry of the graphite. The different behaviors of graphite are explained by their capability to damp mechanical force but at the same time to cause stress concentration in the matrix. The better shot peening results for CGI may be attributed to a lower damping effect of its graphite inclusions and capability of the matrix for larger plastic deformation.

Effect of graphite morphologies on the tribological behavior of austempered cast iron

Three different cast irons, gray, nodular and compact iron, with different chemical compositions were subjected to austempering to investigate the effects of graphite morphology, composition and austempering on tribological behavior. The austempering process was carried out at 375 °C for different periods to achieve optimum mechanical properties. The austempered cast iron specimens with optimum mechanical properties were used for wear tests. For comparison, wear tests were also carried out on a pearlitic gray iron specimen made from railway brake shoes. Sliding wear tests were performed in a block-on-ring wear tester with the test materials rubbing under dry atmospheric condition against a ring made from a railway wheel at speeds of 250 and 950 rpm with nominal stress of 2 MPa. A non-contacting capacitance transducer with a computer interface was used to measure the coefficient of friction of the specimens. The impact test results show that austempered nodular iron with 105 J/cm 2 has the highest impact energy while austempered gray iron with 7–9 J/cm 2 shows the lowest. The optimum impact energy of the austempered compact cast iron was 14–22 J/cm 2 as a function of chemical composition. The wear test results indicate that austempered cast iron shows superior wear resistance than pearlitic gray iron, particularly at the lower speed. For austempered cast iron specimens, compact iron shows the highest wear resistance while gray and nodular cast iron have lower wear resistance.

Thermal shock resistance test for cast iron used in casting environments

The thermal shock resistance test was conducted for grey cast iron and a compacted cast iron for use in casting environment. The test consisted of a specimen partially immersed in a molten salt bath of 55% Na2C03 and 45% CaC03 at 1000 ° C for 4.5 min, followed by plunging into water. The test results from laboratory and field indicated that the grey cast iron is superior to the compacted cast iron. In the laboratory test, the thermal shock resistance of the cast iron can be judged from the summation of crack length and crack patterns in the specimen after a certain number of thermal shock cycles. The inferior thermal shock resistance of the compacted cast iron is mainly attributed to the more extensive martensite formation after the thermal shock cycling compared with the grey cast iron.

The urea nitrocarburizing of cast irons with various graphite morphologies

The urea nitrocarburizing of nodular and compacted graphite cast irons has been investigated. Optical microscopy, EDAX analysis and hardness measurements have shown that a thick compound layer with high contents of nitrogen and silicon is formed, and a greater hardness in the area around the graphite beneath the surface is observed. The compacted cast iron with interconnected graphite has been found to exhibit a smaller effective diffusion zone, and formed Si3N4 precipitates within the hardened area. The nitrided nodular cast iron exhibited a higher fatigue strength increment and a smaller elongation decrement than that of compacted cast iron. Most fracture surfaces of compacted cast iron were found to be granular whereas the nodular cast iron was characterized as transgranular cleavage.

Effect of several physical and mechanical variables on the relation between COD and J

The influence of several variables on the relation between COD and J is experimentally studied. These variables are temperature, geometry, strain-hardening exponent, slow stable crack growth, toughness value for each material and rolling direction. Four steels and a compacted cast iron were tested. From the experimental results, this relationship would be a function of the strainhardening exponent and rolling direction.