Joint effect of the first and the second kind of modifiers on the constructional steels structure and properties

The influence of modifying horophilic and refractory elements injected at the main smelting stages into structural steels on their structural mechanical properties has been analyzed. The solid crust building-up rate in castings that makes it possible to evaluate the thermal characteristics of steel hardening has been experimentally determined. It has been found that increase of the amount of solid additives into molten steel before melting results in a significant increase of the thickness of the hardened layer during the same period of time. The microstructure of the 09G2S and St3 steels after modifying the melt with a solid additive, with titanium nitride and a joint modifying with calcium and titanium nitride has been studied. As a result of the combined effect of the modifiers of the first and second kind the cast steel macrostructure improves. The mechanical tests of the 09G2S steel and St3 deformed steel specimens, modified by calcium and titanium nitride, after the ingots were forged and rolled with subsequent normalization showed that the strength increased by 15÷25%, the elongation increased by 10÷25%, while impact strength increased by 0,5 MJ/m2 at room temperature. The results can be applied to improve and manage the process of structuring during steel smelting and casting, as well as to improve their quality