ANALYSIS OF THE GRAPHITE PHASE IN CENTRIFUGED BILLIONS MADE OF HIGH-QUALITY CAST IRON

Abstract

Purpose. To determine the characteristic geometric parameters of spherical graphite inclusions in the cross-section of a cast iron billet for piston rings.
 Research methods. A cylindrical blank for piston rings was obtained by the centrifugal method. The chemical composition of the blank according to the ВЧ 500-2 brand (DSTU 3925-99). To obtain spherical graphite, nickel-magnesium ligature (15 % Mg) and secondary graphitizing modification with ferrosilicobarium ФС65Ба4 were used. The amount of each additive was 1.0 % of the metal mass. Spherical graphite was evaluated according to GOST 3443 and several characteristic geometric parameters. A computer image analyzer based on a “ZEISS Epityp-2” microscope with a digital video camera “Baumer” was used.
 Results. The geometric parameters of graphite inclusions in the cross-section of a centrifugal billet made of high-strength cast iron are examined. A significant difference in the geometric parameters of spherical inclusions of graphite according to several size groups formed in different layers of the cast iron billet obtained by centrifugal casting was established.
 Scientific novelty. Spherical graphite inclusions in the oil billet are classified according to 6 size groups of GOST 3443 and 11 size groups built in arithmetic progression. Significant differences between the outer and central layers of the casting were established: 2.14 times – by the number of small (5...10 μm) inclusions; 1.59 times – by the number of inclusions with a size of 10...15 μm, 1.4 times – by the number of inclusions with a size of 20...25 μm; 3.9 times – by the number of large (more than 35 μm inclusions).
 Practical value. A comparative assessment of the morphology of spherical graphite in the outer, central and inner layers of the centered workpiece will allow to improve the technological parameters of the production of cast piston rings in order to ensure a high resource of engines or compressors.