含Ti铁素体不锈钢连铸坯表层TiN夹杂物的分布  

Distribution of TiN inclusions at subsurface of Ti-stabilized ferritic stainless steel slabs

作　　者：李实 段豪剑 张立峰 LI Shi;DUAN Haojian;ZHANG Lifeng(School of Mechanical Engineering,Yanshan University,Qinhuangdao 066004,Hebei,China;Stainless Steel Research and Development Center,Central Research and Development Institute,Baoshan Iron and Steel Co.,Ltd.,Shanghai 201999,China;School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China;School of Mechanical and Materials Engineering,North China University of Technology,Beijing 100144,China)

机构地区：[1]燕山大学机械工程学院,河北秦皇岛066004 [2]宝钢股份中央研究院不锈钢研发中心,上海201999 [3]北京科技大学冶金与生态工程学院,北京100083 [4]北方工业大学机械与材料工程学院,北京100144

出　　处：《钢铁》2025年第1期100-108,共9页Iron and Steel

基　　金：国家重点研发计划资助项目(2023YFB3709900);国家自然科学基金资助项目(U22A20171)。

摘　　要：连铸坯表层的TiN夹杂物是导致含Ti铁素体不锈钢冷轧板表面条纹缺陷产生的主要原因。通过自动扫描电镜分析了TiN夹杂物在含Ti铁素体不锈钢连铸坯表层的分布情况。结果表明,在连铸坯表层,TiN夹杂物的数密度由连铸坯表面向内呈减小的趋势,而TiN夹杂物的平均尺寸由外向内呈增大的趋势。在连铸坯宽度方向1/2处距离连铸坯表面5 mm以内和连铸坯宽度方向1/4处距离连铸坯表面6 mm以内,TiN夹杂物的数密度大于650个/mm^(2)而平均尺寸小于1.1μm。通过综合考虑热力学平衡和微观偏析,分析了含Ti铁素体不锈钢凝固过程中TiN夹杂物形核的过饱和度,并基于经典形核理论估算了TiN夹杂物的临界形核半径。随着凝固的进行,TiN夹杂物形核的过饱和度增大而临界形核半径减小;此外,随着冷却速率的增加,TiN夹杂物的临界形核半径减小,表明TiN夹杂物更容易在连铸坯表面形核生成。最后,采用扩散控速模型分析了TiN夹杂物在钢液凝固过程中的尺寸演变行为。结果表明,TiN夹杂物的尺寸随着冷却速率的降低而增大,从而阐明了TiN夹杂物尺寸在连铸坯表层由外向内增加的原因。Titanium nitride(TiN)inclusions at the subsurface of slabs were mainly responsible for the sliver defects in Ti-stabilized ferritic stainless steel cold rolled sheets.By using the automatic SEM/EDS inclusion analysis,the distribution of TiN inclusions at the subsurface of the slabs was investigated.It was found that the number density of TiN inclusions decreased while the average size increased along the slab thickness from the surface toward the interior.The number density of TiN inclusions is greater than 650/mm^(2) while the average size is smaller than 1.1μm within 5 mm below the slab surface at the 1/2 width of the slab and 6 mm below the slab surface at the 1/4 width.The supersaturation for TiN nucleation in the liquid Ti-stabilized ferritic stainless steel was studied by considering the thermodynamics equilibrium and the microsegregation during solidification.Furthermore,the critical radius for TiN nucleation was estimates according to the classical nucleation theory.With the solidification proceeding,the supersaturation increased and the critical radius for TiN nucleation became smaller.Meanwhile,it was found that the critical radius for TiN nucleation was smaller for the higher cooling rate indicating TiN inclusions were more easily generated closer to the slab surface.Finally,the size evolution of TiN inclusions during solidification was analyzed by the diffusion-controlled growth model.It was shown that the size of TiN inclusions increased with the decrease of cooling rate,revealing the size of TiN inclusions increased from the slab surface toward the interior.

关 键 词：TiN夹杂物 含Ti铁素体不锈钢 连铸坯 表层 形核与长大 凝固过程 冷轧板 冷却速率 

分 类 号：TF777[冶金工程—钢铁冶金]