Nb-Ti-IF钢平衡析出相的热力学计算与分析

Thermodynamic calculation and analysis on equilibrium precipitate in Nb-Ti-IF steel

采用Thermo-Calc热力学计算软件对Nb-Ti-IF钢在0～1600℃存在的平衡析出相进行了热力学计算,讨论了合金元素Nb和Ti含量对含Nb、Ti平衡析出相的影响。此外,对Fe Ti P相的平衡析出进行了热力学计算,并将计算与显微分析结果进行对比。结果表明,Nb-Ti-IF钢中平衡析出相主要有：FCC_A1#1、FCC_A1#2、LAVES_PHASE_C14、Ti4C2S2、Mn S及M3P。Ti含量对各含Ti析出相的影响规律如下：≥0.045%Ti,Ti含量变化对FCC_A1#1相的析出几乎没有影响;〈0.045%Ti,Ti含量变化对FCC_A1#1相的析出开始产生较明显的影响。≥0.05%Ti,Ti含量变化对Ti4C2S2相的析出影响较小,而当〈0.05%Ti时,Ti含量对Ti4C2S2相的析出影响十分明显。合金元素Nb、Ti的最佳添加量分别为0.02%和0.05%。

Equilibrium precipitates in Nb-Ti-IF steel in the temperature range from 0 to 1600 ℃ were calculated based on thermodynamic software Thermo-Calc. The effects of microalloying elements Nb and Ti on Nb precipitates and Ti precipitates were studied,respectively. In addition,the comparison of thermodynamic equilibrium calculation and microscopic observation for Fe Ti P precipitates was carried out. The results show that the main equilibrium precipitates in Nb-Ti-IF steel at temperatures from 0 to 1600 ℃ are FCC_ A1 #1,FCC_ A1 #2,LAVES_PHASE_C14,Ti4C2S2,Mn S and M3 P. When Ti content is more than 0. 045%,the Ti content change almost has non effect on the FCC_A1#1 precipitates,but when Ti content is less than 0. 045%,the Ti content change has effect on the FCC_A1#1 precipitates; when Ti content is more than 0. 05%,the Ti content change almost has smaller effect on the Ti4C2S2precipitates; when Ti content is less than0. 05%,the Ti content change has marked effect on the Ti4C2S2 precipitates. The optimum contents of micro-alloying elements Nb and Ti are0. 02% and 0. 05%,respectively.