Influence of chemical composition on heat resistance of structural steel

Abstract

It is based of process analysis of structural steel operation at elevated temperatures and stresses, it is established that their workability depends with the chemical composition of steels and operation stress, time, temperature. The heat-resistant structural steels alloying is aimed for reducing the intensity of softening processes, that is, the redistribution of the alloying elements between the solid solution and the separation phases, their coagulation and changes of the crystal structure defects. The results of the study of chemical composition effect, temperature, stress and operation time on the creep and durability of structural steels are presented in the article. Analytical dependences of the relative elongation in the creep process and time at which the destruction of the chemical composition of heat-resistant structural steels and such operational factors as temperature, stress and holding are calculated. It is established that the creep and durability of heat-resistant structural steels, in the experiment conditions, are determined by their chemical composition in quantity 61–64 %, temperature 7–18 %, holding time 11 %, stress state 18–21 %. Nitrogen and vanadium alloying have been shown to more effectively reduce the softening degree heat-resistant steel during creep process than the molybdenum alloy, since the coagulation process of carbides and nitrides in steels with nitrogen and vanadium receives less development than carbides in steels alloyed by molybdenum.