Investigation of the Influence of Nanomodifiers on the Microstructure and Mechanical Properties of P265GH/HII Steel

摘要

New method of modifying of metals and alloys by means of exogenous nanometric modifiers is proposed. They represent nanoparticles of high melting compounds usually carbides, nitrides, carbo-nitrides. The quantity of these modifiers is a tenth or a hundredth part of the percentage and the size is 10-50 nm. Nanoparticles are obtained by means of plasma-chemical method. The nanomodifiers introduced in the melt form a self organizing dispersed system. The nucleus of every one of its parts represents solid phase surrounded by amassed atoms and changing the chemical composition of the molten metal. As a consequence, concentration undercooling is occurred in the adsorbed layer, which causes essential change in the process of microstructure formation. Some laboratory experimental results concerning carbon steel castings modified by TiCN, TiN and TiC are given. It is established that modified castings have up to 42% smaller grain size, up to 18 % higher microhardness and up to 27% higher plastic characteristics than unmodified ones.