Study of Microstructural Evolutions in Thermally Processed High-Strength Pig-Iron

Abstract

The purpose of the present work is studying feature of structure and phase structure thermal processed high-strength pig-iron with spherical graphite. Re­search has been dictated by difficulty of differentiation of structural compo­nents in the normalized pig-iron, es­pecially perlite and top of bainite. It is explained, difficulties of differentiation in nickel pig-iron perlite (sor­bite, trostite) and top of bainite: a plenty austenite at the given way of heat treat­ment undergoes disintegration on evtektoide to the mechanism, and separate plates of bainite ferrite are very fine, as defines similarity of structures at etching in nit­ric acid and their super­vi­sion at small increases. Samples of the same alloy (about 2%Ni), but cooled with the big speed indus­trially, get structure needle of bainite. It is confirmed, that the quantity austenite increases with rise in temperature austenition. It is installed, that in the pig-iron, cast in the metal form trans­formation occurs to education of smaller quantity residual austenite. This effect is connected with smaller micro liquation che­mi­cal elements, first of all silicon. It is established, that in the pig-iron, cast in the metal form by virtue of specific distribution of chemical elements at crystallization and crushing evtekti­ke grains, manganese is kept in the places corresponding sites ledeburite, and on borders of grains, silicon is distributed in regular more intervals, than in the pig-iron, cast in the sandy form. All this predetermines more uniform and full course of process γ–α of transformation.