Improvement of the properties of gray cast iron by silicon dioxide and carbon nanostructures

Abstract

Increasing requirements in terms of performance in modern industry forced to use materials that can operate at higher loads. For metallurgical industry production increasingly require the casting of gray cast iron (GI) high marks. Improving the properties of cast iron and steel is achieved only through the effective doping and modification, allowing to eliminate defects, to grind grain. Currently, the industry uses over 500 existing types of modifiers, most of them are multicomponent. Amount of various additives vary from 2 to 15 components. Very often the main component of additives is silicon – effective graphitizer and deoxidizer. Additives remaining components serve to enhance the effect of modification, increase “survivability” of modifiers, and to change the shape of inclusions of graphite in the iron. Frequently alloying additives are rare earth metals, and other components, considerably raising the price of the final product. At present, the highly competitive component requires an efficiency modifiers, considering the economic component. For this purpose, this paper investigated the effect of nano-additives with high chemical reactivity of carbon and silicon. The theoretical aspects of the modification and the main difficulties that do not fit into the framework of the theory of nucleation are explored. Cast iron modification process made by three different formulations of modifiers, including: Composition 1 – Replaced 50 % of standard metallurgical graphite particulate graphitic carbon with a content of 0.20 % by weight. carbon multiwalled nanotubes. Composition 2 – nanograins silica (89-90 %) + amorphous carbon in different concentrations. Composition 3 – blend compositions 1 and 2 in the proportion of 30 to 70 %. Smelting of gray iron took place in standard mode according to the current smelting technology instruction. Casting the melt in two ways: 1) Fill the melt on top of the modifier 2) “sandwich” process. Evaluation of modifier performed using test strength at break the modified samples. Modifiers all formulations showed a temporary increase in resistance (HB). The tested samples were subjected to the study by scanning electron microscopy (SEM). The theoretical justification of efficiency of dispersed mixed modifiers