Influence of Stresses on Structural Changes in Gray Cast Iron
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INFLUENCE OF STRESSES ON STRUCTURAL CHANGES IN GRAY CAST IRON T. S. Skoblo,1, 2 O. I. Sidashenko,1, 3 O. V. Saichuk,1 O. Yu. Klochko,1 and D. A. Levkin1
UDC 621.74
According to the results of simulation of stressed states, it is shown that coarse graphite inclusions formed in the walls of case-shaped parts of transient in thickness are the sites of initiation of defects due to the changes in the dislocation structure and diffusion of carbon from graphite. The cavities formed in graphite also promote the development of oxidation. Keywords: stress, structure formation, carbon diffusion, dislocation structure, formation of defects, energy parameters.
Introduction In the course of operation, articles made of high-carbon alloys in the machine-building industry and metallurgy suffer the influence of various loads, including cyclic, tensile, compressive, and temperature. This leads to the development of structural inhomogeneities and defects. It is known that an important role in the degradation of steels and alloys is played by graphite, carbide, and other types of nonmetallic inclusions. In the course of manufacturing and operation, these inclusions may lead to the formation of local stresses, which is accompanied by the development of diffusion processes and defects in the crystal structure [1, 2]. At present, for the evaluation of stresses, it is customary to use the so-called optical-mathematical methods of processing of the experimental data [3, 4]. In what follows, we focus our attention on the analysis of the influence of the graphite phase on local deformations in gray cast iron used to produce cast case-shaped parts in the machine-building industry. Under the conditions of specialized enterprise (“Kharkiv Tractor Plant” PJSC), by the methods of statistical analysis of the quality of products, it was discovered that the zones with transient thicknesses of the walls are characterized by the highest degrees of damage. Those zones were discovered according to the results of measurements of the coercive force H c . We study the influence of the morphology of graphite inclusions on the local stresses and crack initiation in the course of crystallization and operation of case-shaped cast products with walls of variable thickness made of gray cast iron. Testing Methods We studied products chosen according to the results of nondestructive magnetic testing and characterized by significant deviations of the values of coercive force H c in the transient zones with variable thicknesses of the walls. The measurements were carried out by using a KRMTs-K2M device. 1 2 3
Vasylenko Kharkiv National University of Agriculture, Kharkiv, Ukraine. Corresponding author; e-mail: [email protected]. Deceased.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 56, No. 3, pp. 57–65, May–June, 2020. Original article submitted June 5, 2018. 1068-820X/20/5603–0347
© 2020
Springer Science+Business Media, LLC
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T. S. SKOBLO, O. I. SIDASHENKO, O. V. SAICHUK, O. YU. KLOCHKO,
AND
D. A. LEVKIN
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