Control of Cast Iron Mechanical Properties Using Microimpact Indentation Method

Instrumental indentation is one of the effective methods for measuring the physical and mechanical properties of various materials. This paper discusses the features of testing cast iron with various forms of graphite inclusions: flake-like structure, spherical, vermicular, etc., and models that allow, based on the data of the micro-impact loading diagram of the material, to calculate the Brinell hardness HBW, the elastic modulus E and the tensile strength σ of cast iron of various grades. It is shown that the use of a set of different parameters in the calculations allows eliminating gross errors in assessing HBW caused by the influence of the graphite structure on the values of the elastic modulus and dynamic hardness. Based on experimental data, it is demonstrated that measuring the hardness of cast iron using the values of the restitution coefficient leads to a measurement error of up to 75 units. In this connection, such testing using standard dynamic hardness testers is unreliable. A stable relationship between the tensile strength and the product of hardness and elastic modulus is also confirmed. The possibility of establishing the cast iron grade (grey or spheroidal graphite iron) based on a single measurement is shown. The proposed method makes it possible the nondestructive testing of parts at industrial enterprises producing iron castings. The carried out studies prove that the developed algorithms can be used for express diagnostics of cast iron hardness using dynamic portable hardness testers with their certain modernization.

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