INFLUENCE OF MODIFYING OF CAST IRON SCH25 (RUSSIAN GRADE) WITH ULTRAFINE POWDERS OF REFRACTORY METAL OXIDE AND CRYOLITE ON STRUCTURE, MECHANICAL PROPERTIES AND FRACTURE

The comparative study of the influence of the modifying oxide ultrafine powders of refractory metals and cryolite on the structure and deformation behavior of cast gray iron SCH25 (Russian grade) was carried out. It was shown that the modification of cast iron by ultrafine particles of titanium oxide, zirconium oxide (containing impurities Nb, Hf, Mg, Fe, Cr, Sr, Mo not more than 5 %) and cryo-lite lead to significant changes of the distribution of flake graphite in the matrix and its sizes. The distribution of flake graphite was in form of the colonies of the directed dendritic structure with length of the flake graphite, decreased in 2 times, was observed. Dispersion of perlite was increased from 0.57 to 0.32. The changes of morphological characteristics of phosphide eutectic were observed. Modification of cast iron leads to increasing of the tensile strength by 90 MPa. Ductility of 0.17 –  0.18 % and hardness of 207 HB was changed insignificantly. 

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