Thermodynamics Analysis and Control of TiN Precipitation During Solidification of Q345EN Steel

摘要

The formation of Ti and N as a secondary inclusion precipitated during solidification is of great interest because it has an important impact on the quality of final products. In the present study the formation reaction of TiN was discussed based on the thermodynamic calculation in Q345EN steel. The activity coefficient values of titanium and nitrogen at 1873 K were obtained and the relational expression of their activity coefficients with temperature was calculated. The results show that TiN inclusions only form in solid phase, but under the chemical composition of this Q345EN steel, TiN inclusions can't be formed in solid phase zone. Only in a solidification front, the formation reaction of TiN can take place owing to the enrichment of Ti and N elements. It is considered the best way to reduce TiN's precipitation is to go through the mushy zone rapidly, and control titanium and nitrogen contents in steel simultaneously.