Explanation of the description of scientific, technical, technological principles and approaches to the implementation of the project “Creation of a foundry using nanomodifiers of auto components of block, piston, crankcase groups” project number ID 2069
The volume of cast iron currently produced by domestic industry is estimated at millions of tons. The problems associated with improving the quality of castings are becoming especially acute.
Their successful solution will contribute to the creation of large material reserves, increasing the durability and reliability of machines in general, and the automotive industry in particular.
The most important quality criteria for casting include the physical and mechanical properties of the metal. In high-carbon iron alloys, these properties are determined in the vast majority of cases by the shape, quantity, size and nature of the distribution of graphite inclusions. These processes are regulated by introducing special materials – modifiers – into the liquid melt.
Modification of cast iron
Modification is one of the most effective methods of influencing crystallization in order to obtain a favorable structure of graphite and a metal matrix, and, consequently, high properties of castings. The modifiers used are usually classified as graphitizing, stabilizing (or perlitizing), vermicularizing and spheroidizing. But to ensure the course of the modification process, the aspect of the nucleation of the graphite phase is very important, i.e. the creation of conditions for the formation of substrates on which graphite is formed during crystallization of the alloy. [1,2]
Modern ideas about the process of nucleation of substrates or crystals in alloys are based on the views of Gibbs and Volmer, according to which the formation of crystallization centers (substrates) during solidification of liquids (alloys) is possible only after supercooling of the liquid (alloy) relative to the equilibrium temperature with the solid phase.[3] In a supercooled melt or liquid solution, the free energy of the solid phase is lower than the free energy of the liquid, which creates the necessary thermodynamic conditions for the emergence of crystallization centers. However, the appearance of a phase boundary surface increases the free energy of the system.
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