The paper refers to previous publications of the author, focused on criteria of casting feeding, including the thermal criterion proposed by Niyama. On the basis of this criterion, present in the post-processing of practically all the simulation codes, danger of casting compactness (in the sense of soundness) in form of a microporosity, caused by the shrinkage phenomena, is predicted. The vast majority of publications in this field concerns shrinkage and feeding phenomena in the cast steel castings – these are the alloys, in which parallel expansion phenomenon does not occur as in the cast irons (graphite crystallization). The paper, basing on the simulation-experimental studies, presents problems of usability of a classic, definition-based approach to the Niyama criterion for the cast iron castings, especially of greater massiveness, for prediction of presence of zones of dispersed porosity, with relation to predictions of the shrinkage type defects. The graphite expansion and its influence on shrinkage compensation during solidification of eutectic is also discussed.
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The simulation codes using from many years by foundry industry such e.g. Magmasoft, NovaFlow&Solid and ProCast, contain also the thermo-mechanical modules permitting the estimation of mechanical stresses/deformations in casting during its cooling. It is also known that these modules are rarely used because of the very limited thermo-mechanical database especially for ceramic materials such as foundry sand mould. These technologies – castings pouring in non-permanent sand moulds, particularly iron alloys are most often applied in foundry. In our study the method of evaluating the algorithms quality applied in thermo-mechanical phenomena models based on parameters sensitivity testing from the proper database of the simulation system was used [1]. The comparative analyses of both experimental and virtual results were realized (by stress estimation). Methodology of experimental research was resemble to that described in provided that the applied gray cast iron casting of stress bars (grid) were casted in sand mould bonded by organic resins. Also the usefulness of author's method called Hot Distortion Plus® consisting in acquisition of temperature/distortion curves of heated sample of sand mould material and correlation with curves of their dilatation and also the inverse solution method are signalized as new proposition to estimate the chosen mechanical moulds parameters.
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Praca przedstawia analizę rozkładu wielkości wydzieleń grafitu na przekroju grubego odlewu żeliwnego. Dokonano opisu funkcyjnego rozkładu wielkości wydzieleń grafitu w warstwach pomiarowych odległych od siebie o 5 mm. Określono jak zmieniają się na przekroju walca parametry funkcji opisującej rozkład wielkości wydzieleń grafitu. W badaniach nie stwierdzono wyraźnej zależności miedzy odległością od powierzchni (szybkością krzepnięcia) a wielkością wydzieleń grafitu, a potwierdzono wpływ na udział objętościowy grafitu.
EN
In the work analysis of graphite size distribution on cross section of thick cast iron casting has been presented. Functional description of graphite size distribution in measurement layers each 5 mm distant has been done. How change parameters of function describing graphite size distribution on cross section of cast iron roll has been determined. In researches has not been affirmed clear dependence between distance from surface (solidification rate) and size of graphite grain, however its influence on graphite volume fraction has been confirmed.
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Sformułowane w literaturze hipotezy opisujące wpływ dodatków węglotwórczych na kształtowanie powierzchni odlewów żeliwnych nie udzielają jednoznacznych odpowiedzi. Zaproponowane w referacie rozważania kompleksowego występowania zjawisk na granicy metal - forma w funkcji temperatury porządkuje i wyjaśnia rolę i znaczenie dodatków węglotwórczych w kształtowaniu powierzchni odlewów.
EN
Literature theories which describe the effect of carbon-forming additives in shaping of cast iron castings surface do not explain synonymously the processes occuring at metal-mould interface. The considerations presented in the paper, regarding these phenomena completely as a function of temperature, explain the role and the influence of carbon-forming additives on shaping of castings surface.
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