SYSTEM ANALYSIS OF POROSITY FORMATION PROCESSES IN STEEL CASTINGS AND THEIR MATHEMATICAL MODELS
DOI:
https://doi.org/10.34185/1562-9945-6-125-2019-09Keywords:
shrinkage, defects, porosity, castings, steel, casting properties, fluidity, impact, melt, Siverts law, gas concentration, pressure, Niyama criterion, complex mathematical modelAbstract
The analysis of scientific and technical information about the hardening features of steel castings, which lead to the formation of shrinkage defects is presented. The mechanisms of the relationship of the casting properties of alloys are shown. The analysis of factors that determine fluidity is carried out. The technological parameters of casting are determined, which lead to the formation of pores in steel castings. The mechanisms of porosity formation of endogenous and exogenous nature are considered. Siverts law is given, that describes the dependence of gas concentration on pressure. Graphs of changes in the concentration of nitrogen and hydrogen in the pressure range 1 - 4 atm are given for medium alloyed steel, open-hearth steel, cast iron. The mechanism of the influence of temperature and gas pressure on the process of gas evolution in the melt is analyzed. Technological methods for influencing the solubility of gases during the solidification of the casting are described. The microporosity model of Advanced Porosity Module, the Niyama criterion are analyzed. The need for further studies to develop a general model for the formation of shrinkage defects, which will take into account, inter alia, the dependence of the concentration of gases dissolved in the metal on pressure temperature, is noted.
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