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采用扫描电镜、X射线能谱仪以及扫描电镜配置的夹杂物自动扫描统计软件(INCAFeature)表征了Fe-Mn-C(-Al)系TWIP钢中夹杂物的成分、形貌和数量,考察了Al质量分数在0.002%~1.590%的四种TWIP钢中夹杂物的特征和Al含量对AlN析出行为的影响.并在此基础上,采用了适合TWIP钢中高锰高铝特点的热力学参数对AlN夹杂物进行了系统的热力学分析.研究表明,在含有相似N质量分数(0.0078%~0.0100%)的TWIP钢中,当钢中Al质量分数升高至0.75%时,AlN夹杂物开始在钢中析出,并在MnS(Se)-Al_2O_3上局部析出形成MnS(Se)-Al_2O_3-AlN复合夹杂;当Al质量分数升高至1.07%时,热力学计算表明AlN已经可以在TWIP钢液相中形成,经不断长大后在MnS(Se)夹杂物表面局部析出形成MnS(Se)-AlN复合夹杂物;在Al质量分数为1.59%的TWIP钢中,AlN的平衡析出温度比其液相线温度高出42℃,在液相中形成的AlN可以作为异质核心,MnS(Se)夹杂在其表面包裹形成MnS(Se)-AlN复合夹杂物.另外,在Fe-18.21%Mn-0.64%C-1.59%Al体系的TWIP钢中,AlN在液相中析出所需的最低氮的质量分数仅为0.0043%.因此,在TWIP钢的冶炼过程中,应尽可能的降低钢中的氮含量,避免生成过量的AlN夹杂.
The composition, morphology and amount of inclusions in Fe-Mn-C (-Al) TWIP steels were characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy and scanning electron microscopy (INCAFeature) Based on the characteristics of inclusions and the content of Al in four kinds of TWIP steels with Al mass fraction of 0.002% ~ 1.590%, the effects of AlN Inclusions were systematically investigated.The results show that in the TWIP steels with similar N content (0.0078% ~ 0.0100%), the AlN inclusions begin to appear in the steel when the mass fraction of Al in steel increases to 0.75% (Se) -Al_2O_3-AlN composite inclusions were precipitated locally on MnS (Se) -Al_2O_3. When the mass fraction of Al was increased to 1.07%, the thermodynamic calculation showed that AlN was already formed in the liquid phase of TWIP steel. The MnS (Se) -AlN compound inclusions were locally precipitated on the surface of MnS (Se) inclusions after growing up. The equilibrium precipitation temperature of AlN was higher than the liquidus temperature in TWIP steels with Al mass fraction of 1.59% Out of 42 ° C, AlN formed in the liquid phase can be used as a heterogeneous core, MnS (Se) inclusions in its surface (Se) -AlN composite inclusions.In addition, the mass fraction of the lowest nitrogen required for precipitation of AlN in the liquid phase in the TWIP steels with Fe-18.21% Mn-0.64% C-1.59% Al is only 0.0043% .Therefore, during the smelting of TWIP steel, the nitrogen content in the steel should be reduced as much as possible to avoid excessive AlN inclusions.