STRENGTH CONTROL OF GREY CAST IRON BY ELECTROGRAPHIC METHOD

The experimental procedure carried out on a test installation to determine the electrical resistance value in the process of crystallization of cast iron is presented. A scheme of a test installation using a measuring circuit based on the Wheatstone bridge circuit to determine the electrical resistance value of crystallized cast iron is given. Recording measured data over time allowed constructing a graphical dependence of the change in the values of specific electrical resistance during the crystallization of gray cast iron. Experimental data on changes in the values of the specific electrical conductivity of a sample of gray cast iron during crystallization and their relationship to the amount of supercooling of the melt of this alloy are presented. The obtained dependence made it possible to identify on the curve of specific electrical resistivity change under supercooling of cast-iron test sample those areas, which were exposed to the cast-iron melt supercooling. The ratio of the initial and final values of the electrical resistivity under supercooling of cast iron allowed calculating the values of the relative electrical resistivity. Measurements of cast iron strength have shown that they are functionally related to the value of the relative electrical resistivity of gray cast iron, determined by the degree of supercooling of the cast iron melt. The use of this method will make it possible to predict gray cast iron strength and will allow reducing the amount of castings defective in terms of mechanical properties and at the same time increasing foundry production profitability.

technological process, grey cast iron, crystallization, electrical resistance, supercooling value, relative electrical resistivity, elec-trographic method, cast iron strength