Nb-Ti微合金钢中第二相析出的热力学计算

分析了Nb-Ti微合金钢在液相、凝固过程、奥氏体以及铁素体相中氮化物、碳化物和碳氮化物等第二相析出的热力学条件,计算了钛和铌的碳化物和氮化物在不同温度下的溶度积,由此得出微合金钢在不同相阶段的析出规律。计算结果表明,在该微合金钢中,氮化物、碳化物和碳氮化物不可能在液相中析出;TiC0.03N0.97和TiN在凝固过程中具备析出的热力学条件;在奥氏体相中,随着温度的降低,氮化物、碳化物及碳氮化物的析出顺序为:NbC0.75N0.25、NbC、TiC、NbN。

Thermodynamic calculations of the second-phase precipitation in Nb-Ti microalloyed steel

The thermodynamic conditions of the second phases precipitation（carbides,nitrides and carbonitrides）in liquid,semi-solid,austenite and ferrite phases for Nb-Ti microalloyed steel were analyzed.The solubility product of the steel＇s carbides and nitrides at different temperatures was calculated.On the basis of all these,the precipitation sequence of the microalloyed steel in different phases was acquired.The calculation results show that for the microalloyed steel,carbides,nitrides and carbonitrides cannot precipitate in its liquid;the precipitation of TiC0.03N0.97 and TiN has the thermodynamic conditions during solidification;and in its austenite phase,with the decrease of temperature,the precipitation sequence is as follows： NbC0.75N0.25,NbC,TiC and NbN.