The effect of hydrogenation of the melt of blast furnace iron on its coefficient of linear expansion

The article is devoted to the study of the effect of treatment of blast furnace iron melt with hydrogen on its coefficient of linear expansion. Currently, there is a change of views on the nature of graphite inclusions in cast iron. The monograph by V. K. Afanasyev “Progressive methods of improving the properties of blast furnace” notes the influence of gases on the formation of the structure and properties of cast iron. Special attention is paid to the influence of gases (hydrogen, nitrogen and oxygen) on the change in the coefficient of linear expansion. There are considered two methods of hydrogenation - electrolytic charge hydrogenation and placing on the mirror of wet asbestos melt, there are made conclusions about their influence on the coefficient of linear expansion of blast furnace iron after treatment. It is shown that the electrolytic hydrogenation of the charge leads to a decrease in the coefficient of linear expansion: to the values of 6.2∙10-6 deg-1 in the temperature range of 100-150 °С. Hydrogenation of the melt with wet asbestos showed a decrease in the coefficient of linear expansion to 6.5∙10-6 deg-1 and the test temperature range of 100-150 °С. The study of the microstructure of blast furnace iron before and after treatment with the proposed methods leads to the elimination of graphite inclusions and the production of ledeburite structure. The values of the coefficient of linear expansion of blast furnace iron are compared with values of the coefficient of grey cast iron, rapid steel. Currently, much attention is paid to materials having stable dimensions throughout the operating temperature range. A classic example of such alloys are invars; to reduce the coefficient of linear expansion, they may contain in their composition such expensive elements as platinum and palladium. An urgent task is to replace expensive materials with materials that do not have expensive additives in their composition and have a low coefficient of linear expansion in the range of operating temperatures. This material can be blast furnace iron.