Papers by Keyword: Cast Iron

Abstract: Ultrasonic inspection is a well-known method in non-destructive testing. Based on the changes in the ultrasonic sound speed, tested materials are evaluated in terms of internal defects. In addition to flaw detection, ultrasonic testing is used in the material characterization of ductile cast iron. Graphite shape detection has been widely investigated by ultrasonic inspection in literature. However, most of the measurements has been conducted at single frequencies. In this work, three different nodulizer included casting operations were carried out to produce ductile cast irons having various graphite morphologies. A wide frequency range of 1.25-10 MHz was selected in the ultrasonic inspection. In addition to graphite morphology analyses, the relationship between ultrasonic sound speed and mechanical properties was studied. In the mechanical analyses, hardness and tensile testing properties were investigated for the specimens. From the results, ultrasonic sound speed exhibits a considerable dependency to the graphite morphology. In addition to a good graphite detection capability, ultrasonic inspection exhibits promising results for predicting the mechanical properties such as hardness, elastic modulus, yield strength and tensile strength. It is also found that there is a slight increase in the ultrasonic sound speed by increasing the frequency, although sound speed is independent from this parameter.

Abstract: The paper presents the results of the development of a special group of cast composite materials based on nodular cast irons. The alloys were based on alloying cast iron with copper in amounts that exceed its solubility in liquid Fe-C-Si systems (Cu>6 wt.%). A new component is obtained in the structure of castings in the form of a complex mixture based on the Cu-phase. Inclusions are relatively large (up to 200 μm) and globular in shape, with a uniform allocation in the volume of the castings. This favorably distinguishes the obtained alloys from the known cast irons and gives them high antifriction properties. With isothermal hardening, it is possible to obtain the lowest values of wear for structures of lower bainite. Developed cast composite materials are recommended to be used as tribotechnical materials working in conditions of poor lubrication and corrosion.

Abstract: Modern metal melting includes of cast iron production in different types furnaces with specific characteristics. Furnaces usually adopted are cupola and induction furnaces. Casting cast iron is a manufacturing process characterized by its energy-intensive nature (ie, the use of large amounts of energy per unit of product for main activities) and a long tradition. An example of the energy balance in a foundry is the design of procedures to reduce energy consumption. The most important is the consumption of energy in the production of hot metals (52%), therefore reducing the cost of preparing hot metal is especially important by reducing the energy consumption of metal melting. The most important energy cost practices are the consumption of hot metal to produce 1mt of high quality castings (often 1700 kg) and reduce the energy consumption of hot metal production that varies over a wide range (from 500 to 1300 kWh/mt). Although scientific and technological aspects are now well established, new studies seem to be needed to describe "foundry of the future", where energy and material efficiency is of great importance to ensure competitiveness alongside environmental protection. The paper presents specific procedures for reducing both economically important indicators in cupola and electric induction furnaces.

Abstract: A new surface texturing technique, based on liquid plasma discharging in an aqueous electrolyte, is proposed to modify the surface morphology of grey cast iron. During the process, a grey cast iron sample serves as a cathode where the reduction of hydrogen from the aqueous electrolyte occurs and consequently plasma discharging is generated on the sample surface under applied high voltages (up to 480V). The formed hydrogen bubbles are exploded during the electrical discharging, leaving an irregular array of craters on the sample surface due to the high temperature and shockwaves of the plasma micro-arc discharging. After polishing the crater-like textured surface, surface roughness and oil retention are measured by a profilometer. Reciprocating tribotests are utilized to determine the coefficients of friction. The surface morphology of the polished and tested surface is studied by SEM. The same tests are also conducted for the cast iron with a cross-hatched surface. These two set of results are compared to determine the effects of the texturing and polishing on friction. The results show that the polishing of textured surface can decrease the roughness and coefficients of friction significantly at starved lubricating conditions. This method has potential to be applied on the cylinder bore surface of a cast iron liner for the internal combustion engine (ICE). By honing the textured bore surface, the friction between piston and cylinder bore is expected to decrease and the ICE efficiency to increase for environmental benefits.

Abstract: In this work, the corrosion behavior of different grades of cast iron in 3.5% and 5% of NaClsolution was evaluated. The samples used in this work are; Grey cast iron (GI), ductile cast iron(DI), austempered ductile cast iron (ADI), intercritically austempered cast iron (IADI) and Ni-Resist cast iron. The study was carried out using the Open- Circuit technique (OPC),Potentiodynamic polarization (PP), and electrochemical impedance spectroscopy (EIS)measurements and complemented by Scanning electron microscopy (SEM) and Energydispersive X-ray analysis (EDAX). The results obtained showed that the austempering heattreatment and nickel addition improves the corrosion resistance of cast iron. The order ofcorrosion resistance in NaCl solution is as follows: Ni-Resist > ADI > IADI > DI > GI.

Abstract: The paper considers the possibility of improving the quality of gray cast iron castings by controlling the cooling rate of castings in a mold. It is shown that the use of differentiated cooling can increase tensile strength of cast iron by 12-16%

Abstract: Focusing on heritage structures, various non-destructive tests (NDT) or minor-destructive techniques (MDT) can be applied while the application of destructive testing is limited. The probabilistic models for tensile and compressive strengths of historic cast iron are developed on the basis of destructive tests (DTs) and MDTs, respectively. NDT results are critically compared with DTs. It appears that numerous uncertainties affecting estimated resistance can be treated by statistical approaches along with the semi-probabilistic verification method. Non-destructive hardness tests can hardly be used to estimate strength of cast iron and must be supplemented by destructive tests.

Abstract: Principle, significance and history of cast iron surface hardening. Benefit of high-energy heat sources. Cast iron resistance against thermal shock. Production of large surface hardening. Measurement of its depth and hardness - hardening depth definition of cast iron. Practical results and experience with large castings for machine tools. Research of diagnostics of magnetic spot method application. Optimization of diagnostics of layer depth and hardness using special developed non-destructive structuroscope DOMENA ZL.

Abstract: The article deals with technologies of refining and inoculating casting alloys with the use of nanostructured diamond powder, as well as stimulation technique on molten metal including processing of the liquid alloy with nanosecond electromagnetic pulses. The developed method of cast iron inoculation allows to eliminate the flare and to increase the physical and mechanical properties of the castings through the grain refining and the decrease of chilling tendency during crystallization of the liquid alloy. Inoculating of aluminium alloys by high-melting particles of a nanostructured diamond powder leads to the grinding of structural constituents, including conditions for dispersing hardening intermetallics during postbaking of such castings. As a result, foundry and physicomechanical properties of castings are significantly improved.

Abstract: The term “street furniture” includes numerous elements (e.g. street lamps, benches, fountains, gazebos) easing city life, complementing architecture and contributing to decorate urban areas. Despite the massive presence of street furniture in the urban environment, the knowledge about its evolution through the centuries is frequently ignored or neglected. This study analyses the main metallurgical features of twenty cast iron metalworks dating back to the 19^th and early 20^th centuries manufactured in cast iron foundries mainly located in Italy, France and England. The experimental activity was carried out in collaboration with “Fondazione Neri – Museo Italiano della Ghisa” (Longiano, FC, Italy).The microstructure was determined by means of optical microscopy (OM), whereas the semi-quantitative chemical composition was evaluated through scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS).The experimental results highlight the lack of a shared metallurgical culture in steel industry over the last one hundred and fifty years, since non-uniform microstructural features were observed among the specimens produced in that period in the geographical areas under study.