超纯铁素体不锈钢中TiN夹杂析出的热力学分析

TiN inclusion and its precipitation regularity in ultra-clean ferritic stainless steel

为了控制TiN夹杂对材料性能的不利影响,对TiN在超纯铁素体不锈钢冶炼和凝固过程中析出的热力学条件进行分析。结果表明,在Cr含量为16%～23%的条件下,超纯铁素体不锈钢的最佳钛含量为0.1%～0.3%;当w(Ti)=0.3%时,将w(N)控制在0.004 6%以下才能避免在液相区中生成TiN夹杂;超纯铁素体不锈钢凝固过程中钛的富集程度稍低于氮;凝固末期残余液相中[Ti]和[N]的浓度分别提高到其初始浓度的2.5倍和3.2倍;随着钢液的逐渐凝固,凝固前沿温度和凝固前沿钛氮平衡浓度积下降,凝固前沿钛氮实际浓度积升高;降低钢中氮含量能推迟TiN析出时间,使TiN夹杂在凝固末期形成,可减小TiN夹杂尺寸,减少其析出数量。

In order to control the adverse effect of TiN in ultra-clean ferritic stainless steel,the thermo-dynamic precipitation condition in smelting and solidification process was studied.The results showthat,the best content of[Ti]in the ultra-clean ferritic stainless steel which contains[Cr]16%～23%is 0.1%to 0.3%;and when[Ti]=0.3mass%,controlling[N]to less than 46×10-4 mass%can a-void TiN formation in liquid steel.The segregation degree of Ti is less than that of N,and at the endof solidification,the content of [Ti ]and [N] in residual liquid increase to 2.5times and 3.2times oftheir initial contents,respectively.Along with gradual solidification of liquid steel,in the solidifica-tion frontier the temperature and equilibrium of [%Ti] [%N ]go down,and the real equilibrium of [%Ti] [%N] rises.To reduce [%Ti] and [%N] can limit TiN precipitation at the end of solidifica-tion and reduce the size and quantity of TiN inclusion.