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.
The paper presents the effect of manganese on the crystallization process, microstructure and selected properties: cast iron hardness as well as ferrite and pearlite microhardness. The compacted graphite was obtained by Inmold technology. The lack of significant effect on the temperature of the eutectic transformation was demonstrated. On the other hand, a significant reduction in the eutectoid transformation temperature with increasing manganese concentration has been shown. The effect of manganese on microstructure of cast iron with compacted graphite considering casting wall thickness was investigated and described. The nomograms describing the microstructure of compacted graphite iron versus manganese concentration were developed. The effect of manganese on the hardness of cast iron and microhardness of ferrite and pearlite were given.
Chunky graphite has been recognized for a long time as one of the major problems in production of heavy section nodular cast iron. A great number of studies have been conducted to describe the chunky graphite formation, but a clear understanding of its appearance and a safe mastering of the melt preparation to avoid chunky graphite are not yet available. In the present work the cooling curves were recorded in large cone blocks and standard TA cup. According to measured data from the cone block, melt characteristics and heat transfer coefficient between casting and mould were adjusted in the ProCAST® simulation software. For a near-eutectic nodular cast iron test melt with 0.7 wt. % Ni, relationship between the area of the cone block affected by chunky graphite and simulation software results has been observed, i.e., thermal modulus and time to solidus.
The paper presents the effect of tin on the crystallization process, microstructure and hardness of cast iron with compacted (vermicular) graphite. The compacted graphite was obtained with the use of magnesium treatment process (Inmold technology). The lack of significant effect of tin on the temperature of the eutectic transformation has been demonstrated. On the other hand, a significant decrease in the eutectoid transformation temperature with increasing tin concentration has been shown. It was demonstrated that tin narrows the temperature range of the austenite transformation. The effect of tin on the microstructure of cast iron with compacted graphite considering casting wall thickness has been investigated and described. The carbide-forming effect of tin in thin-walled (3 mm) castings has been demonstrated. The nomograms describing the microstructure of compacted graphite iron versus tin concentration have been developed. The effect of tin on the hardness of cast iron was given.
In this paper the experimental results of piezoelectric and magnetostrictive ultrasonic stimulation are comparatively analyzed in the evaluation of impact damage in a graphite epoxy composite sample chosen for a round robin test. By comparing theoretical and experimental results, it is shown that the equivalent power of internal friction can reach some hundreds mill watt per a single crack.
The paper presents results of a study on the effect of passage of time on magnesium content in iron alloys and the effect of magnesium content on the number of vermicular graphite precipitations per unit surface area and value of the longitudinal ultrasonic wave velocity for two different vermicularization methods. The study was carried out with the use of inspection bar castings. For specific production conditions, it has been found that in case of application of both the cored wire injection method and the method of pouring liquid metal over magnesium master alloy on ladle bottom, the satisfactory level of magnesium content in the bottom-pour ladle, for which it was still possible to obtain castings with vermicular graphite, was 0.018% Mg. In case of the cored wire injection method, the “time window” available to a pouring station at which castings of vermicular cast iron are expected to be obtained, was about 5 minutes. This corresponds to the longitudinal ultrasonic wave velocity values exceeding 5500 m/s and the number of graphite precipitations per unit surface area above 320 mm–2. In case of the master alloy method, the respective “time window” allowing to obtain castings of vermicular cast iron was only about 3 minutes long. This corresponds to the longitudinal ultrasonic wave velocity value above 5400 m/s and the number of graphite precipitations per unit surface area above 380 mm–2.
The paper presents an analysis of a selected grade of high silicon cast iron intended for work in corrosive and abrasive conditions. The text describes its microstructure taking into account the process of crystallization, TDA analysis, EDS, XRD and the chemical composition analysis. In order to determine the phase composition, X-ray diffraction tests were carried out. The tests were executed on a Panalytical X'Pert PRO X-ray diffractometer with filtration of radiation from a lamp with copper anode and PIXcel 3D detector on the deflected beam axis. Completed tests allowed to describe the microstructure with detailed consideration of intermetallic phases present in the alloy. Results of the analysis of the examined alloy clearly show that we deal with intermetallic phases of Fe3Si, Fe5Si3 types, as well as silicon ferrite and crystals of silicon. In the examined alloy, we observed the phenomenon of segregation of carbon, which, as a result of this process, enriches the surface of silicon crystals, not creating a compound with it. Moreover, the paper demonstrates capability for crystallization of spheroidal graphite in the examined alloy despite lack of elements that contribute to balling in the charge materials.
High temperature behavior of three compacted graphite iron (CGI) alloys on polycrystalline alumina substrates (99.7%, porosity <3%) were examined by the sessile drop method combined with classical contact heating procedure in flowing Ar. High-speed high-resolution CCD camera was used for continuous recording of the CGI/Al2O3 couples during melting alloy, heating to and holding the couples at the test temperature of 1450°C for 15 min and their subsequent cooling. The comparative studies were made with conventional CGI (in wt.%: 3.70 C, 2.30 Si, 0.44 Mn, 0.054 P, 0.017 Mg, 0.015 S) and two alloys additionally containing the same amounts of 0.25 Mo, 0.1 V, 0.045 Sn and 0.032 Sb with different concentrations of Mg + Cu additions, i.e. 0.01Mg + 0.33Cu and 0.02Mg + 0.83Cu. All three CGI alloys demonstrated non-wetting behavior on the Al2O3 substrates while the contact angle values slightly decreased with increase of the Mg + Cu content in the alloy, i.e. 131° (unalloyed CGI), 130° (0.01Mg + 0.33Cu) and 125° (0.02Mg + 0.83Cu). Structural characterization of solidified couples by light microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy revealed: 1) heterogeneous nucleation of discontinuous graphite layer at the drop-side interfaces and on the surface of the drops; 2) reactively formed Mg-rich oxide layer at the substrate-side interface; 3) the formation of satellite droplets on the surface of the drops during their solidification; 4) degeneration of initially compacted graphite to lamellar graphite after remelting and subsequent solidification of the drops, particularly in their surface layer.
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