Al对稀土处理C-Mn钢连续冷却组织转变的影响

Effect of Al on continuous cooling transformation in rare earth treated C-Mn steel

研究Al预脱氧对Ce处理钢夹杂物和显微组织的影响,利用热力学计算、带能谱的扫描电镜和DIL805A热膨胀仪检测进行了对比研究。得到如下结论:Ce处理后钢中的主要夹杂物从MnS转变为Ce2O2S+MnS,Al脱氧能使Ce处理钢中夹杂物转变为CeAlO3+Ce2S3+MnS。Ce处理C-Mn钢连续冷却过程有利于获得晶内铁素体的冷速为2~8℃/s。Al脱氧能改变诱导晶内铁素体形核的核心夹杂物种类,诱导铁素体形核的能力降低,且Al能够使Ce处理钢连续冷却组织转变(CCT)曲线向左上方移动,促进铁素体在晶界形核,不利于Ce处理后晶内铁素体的形成。Al脱氧Ce处理C-Mn钢在冷速为2~5℃/s时,由于夹杂物核心成分的改变与Al合金化作用导致晶内铁素体含量较未用Al脱氧Ce处理钢少。

To make clear the effect of aluminum pre-deoxidization on inclusion formation and microstructure variation in the rare earth Ce treated C-Mn steel,the thermodynamic calculation,scanning electron microscope（SEM）with energy dispersive spectrometer（EDS）,and thermal expansion instrument DIL805 A were used.The results show that the main inclusions in steel changed from MnS to Ce2O2S＋MnS after rare earth treatment,aluminum deoxidation technology can make the inclusions in rare earth treated steel into CeAlO3＋Ce2S3＋MnS.It is helpful to obtain the intragranular ferrite at the cold speed of 2-8℃/s in rare earth treated C-Mn steel during continuous cooling process.The aluminum deoxidation technology changes the composition of the nucleus which can induced intragranular ferrite nucleation,as the ability to induce intragranular ferrite decreased.In addition,aluminum can make the continuous cooling transformation curve（CCT curve）of C-Mn steel treated by rare earth move to the left upper side,which enhanced ferrite nucleation at the grain boundary,not conducive to the formation of intragranular ferrite.The content of intragranular ferrite formed in aluminum deoxidizing rare earth treated C-Mn steel is less than that of not Al-deoxidized one as the result of composition changed of nucleus and adverse effect of Al alloying when the cooling speed is 2-5℃/s.