987 resultados para Cast-iron pipe


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"A list of authors quoted in the alphabetical table, with the titles of the works from which the datea have been quoted": on verson of p.223.

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DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

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A review of the literature pertaining to the mechanical properties, solidification and segregation effects in nodular cast iron has been made. A series of investigations concerning the influence of microsegregation on mechanical properties of :pearlitic, ferritic and austenitic nodular cast iron have then been reported. The influence of section size on the tensile and impact properties of cornmercial purity and refined ferritic nodular cast iron has been studied. It has been shown. that an increase in section caused a decrease in impact transition temperature of the commercial purity material without greatly affecting the impact transition temperature of the purer material. This effect has been related to increased amounts of segregation effects such as cell boundary carbides in heavier sections of the commercial purity material. Microsegregation studies on the materials used in this thesis have been carried out using an electron probe microanalyser. This technique has shown that concentrations of chromium and manganese and depletions of nickel and silicon occurred at eutectic cell boundaries in nodular cast iron and were often associated with brittle carbides in these areas. These effects have been shown to be more prevalent in heavier sections. The nature of segregation during the solidification of nodular cast iron has been studied by quenching samples of nodular iron during the solidification process. Micro-analysis of such samples has shown that segregation of manganese and chromium occurs by a gradual build-up of these elements at the solid/liquid interface. The microstructures of the quenched specimens revealed carbide filaments connecting graphite nodules and areas of quenched liquid. These filaments have been used as evidence for a revised hypothesis for the solidification of nodular cast iron by a liquid diffusion mechanism. A similar series of experiments has been carried out on two high nickel austenitic irons containing 0.5 per cent manganese and 4 per cent manganese respectively. In both these materials a decrease in elongation was experienced with increasing section. This effect was more drastic in the 4 per cent manganese material which also contained much greater amounts of cell boundary carbide in heavy sections. Micro-analysis of samples of the 4 per cent manganese material quenched during solidification revealed that manganese concentrated in the liquid and that nickel concentrated in the solid during solidification. No segregation of silicon occurred in this material. Carbide filaments appeared in the microstructures of these specimens. A discussion of all the above effects in terms of current concepts is included.

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Shrinkage porosity as a volume change related casting defect in lamellar cast iron was reported in theliterature to form during solidification in connection to the dendrite coherency. The present work includesan experimental study on dendrite coherency – also called columnar-to-equiaxed transition in lamellar castiron using thermal analysis and expansion force measurements. Investigation was carried out in order tostudy the mechanism of dendrite coherency formation. Cylindrical test bars were cast from the same alloywith different pouring temperature, amount of inoculant and time between the addition of inoculant andstart of pouring the samples. Cooling rate and expansion force was recorded as a function of time. Anumerical algorithm based on temperature differences measured under solidification was used to inter-pret the solidification process. Three different methods have been compared to determine the columnarto equiaxed transition. The compared methods were based on registered temperature differences, basedon registered expansion forces during the volume change of the solidifying samples and based on the cal-culated released latent heat of crystallization. The obtained results indicate a considerable influence on theformation and progress of coherency due to variation of casting parameters. It has been shown that thecoherency is not a single event at a defined time moment rather a process progressing during a timeinterval.

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Titanium and grey cast iron powders were blended and deposited by plasma transferred arc onto mild steel substrates. The powders were injected directly into the arc by a stream of inert gas. The grey cast iron provided the iron matrix and the excess carbon content for reaction and precipitation of titanium carbides. The microstructure of the overlay was analysed by optical microscopy and scanning electron microscopy, and the respective phases were identified by X-ray diffraction. Microhardness measurements were taken from representative areas and the wear behaviour was assessed under low-stress abrasion conditions. The results show that the addition of titanium produced a significant change in the microstructure of the overlays, increased surface hardness and enhanced wear resistance compared to overlays produced without titanium.

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The loss of valuable water resources due to pipe failure has become a major problem in Australia, especially in areas under high level of water restrictions. Generally pipe failure occurs due to a combination of physical and environmental factors. Stresses induced by shrinking and swelling of reactive soils are one of the major factors affecting the performance of buried pipes. This paper presents the details of a field instrumentation undertaken to monitor the performance of an in-service water reticulation pipe buried in a reactive soil and subjected to seasonal climatic changes.