THERMODYNAMIC ANALYSIS OF NITROGEN DISSOLUTION PROCESSES IN IRON-CARBON MELT AT DIFFERENT CONCENTRATIONS OF IMPURITIES

Abstract

In modern conditions, the requirements for the service properties of metal products, and in particular for the steels from which they are made, are significantly increased. The effectiveness of nitrogen dissolution in the iron-carbon melt was evaluated by means of thermodynamic calculations with the additional introduction of titanium, chromium and aluminum. Additional introduction of chromium into the melt in the amount of 0.25-0.05% by weight. has a positive effect on the solubility of nitrogen in the iron-carbon melt regardless of the carbon content, allowing to increase the nitrogen content by 32-46 times compared to standard conditions. At the same time, the lower the carbon content in the melt, the higher the calculated dissolved nitrogen content in the melt and the better the increase in the amount of chromium added to the melt is manifested. The effect of additionally introduced aluminum in the melt on the nitrogen content showed that aluminum negatively affects the solubility of nitrogen, even in small amounts. This is especially evident when the carbon content in the melt increases. The analysis of the possible effect of additional introduction of titanium into the melt on the solubility of nitrogen showed that the most positive effect is manifested at a low carbon content (an increase in solubility by 1.0-1.33 times at a titanium content of 0.05 to 0.25% by weight, respectively). When the carbon content is increased to 0.45% by mass, the addition of titanium has a positive effect only when the amount is greater than 0.1% by mass (by 1.0-0-1.27 times). At a higher carbon content, the solubility of nitrogen when titanium is introduced increases only at its amount of 0.25% by mass. At a lower concentration, the dissolution decreases by an amount of up to 1.5%, ie, only the effect of carbon on the reduction of nitrogen solubility is manifested. According to the performed studies, it was established that the best element that can increase the degree of assimilation of nitrogen by iron-carbon melt is chromium; titanium can be used in certain cases for a specific range of steels. In addition, it should be taken into account that in order to evaluate the influence of one or another component on the dissolution of nitrogen in the metal melt, it is necessary to consider not the influence of a single component on the melt, but a combination of several components, the mutual manifestation of which can be quite important.