高铌超纯铁素体不锈钢中铌的偏析行为及机理分析  

Segregation behavior and mechanism of Nb in high-Nb and ultra-purified ferritic stainless steel

作　　者：武敏[1,2] 付金柱 刘春来 李国平[1,2] WU Min;FU Jinzhu;LIU Chunlai;LI Guoping(State Key Laboratory of Advanced Stainless Steel,Taiyuan Iron and Steel(Group)Co.,Ltd.,Taiyuan 030003,Shanxi,China;Technical Center,Shanxi Taigang Stainless Steel Co.,Ltd.,Taiyuan 030003,Shanxi,China)

机构地区：[1]太原钢铁(集团)有限公司先进不锈钢材料国家重点实验室,山西太原030003 [2]山西太钢不锈钢股份有限公司技术中心,山西太原030003

出　　处：《中国冶金》2024年第7期51-57,共7页China Metallurgy

基　　金：山西省基础研究资助计划(202203021212024)。

摘　　要：超纯铁素体不锈钢是汽车排气系统领域的主流材料,铌(Nb)元素合金化能有效提高铁素体不锈钢的高温性能。以441高铌超纯铁素体不锈钢为研究对象,利用扫描电镜(SEM)、透射电镜(TEM)和电子探针(EPMA)表征了冷轧退火板中带状组织的形貌、成分和结构,并依次对连铸坯、热轧板以及热轧退火板进行全流程分析,结合热力学软件Thermo-Calc模拟,阐明铌元素的偏析行为、形成机理和影响因素。结果表明,铌元素偏析在连铸坯凝固环节形成,连铸坯等轴晶比例为主要影响因素;铌元素偏析从连铸坯中遗传至热轧退火板以及冷轧退火板中形成带状组织,带状组织由铌元素偏聚导致Laves相聚集析出并钉扎晶界形成。研究结果可为高铌超纯铁素体不锈钢的工艺优化控制提供理论基础。Ultra-purified ferritic stainless steels are the dominate materials in the field of automotive exhaust system.Alloying with niobium(Nb)element can effectively improve the high-temperature performance of ferritic stainless steels.Focusing on the research of high-Nb and ultra-purified ferritic stainless steel 441,the morphology,composition and structure of the banded structure in the cold-rolled annealed sheet were characterized using scanning electron microscopy(SEM),transmission electron microscopy(TEM),and electron probe microanalysis(EPMA).The entire process analysis was then performed on the continuous casting slab,hot-rolled plate,and hot-rolled annealed plate,combined with thermodynamic software Thermo-Calc for simulation,to elucidate the segregation behavior,formation mechanism and influencing factors of niobium elements.The results show that niobium segregation occurs during the solidification stage of the slab,and the equiaxed crystal ratio is the main influencing factor.Niobium segregation is inherited from the slab and forms a banded structure in the hot-rolled annealed plate and cold-rolled annealed sheet.The banded structure is caused by the aggregation and precipitation of Nb element leading to the formation of Laves phases and pinning at grain boundaries.The results provide a theoretical basis for the optimal control of the process for high-Nb and ultra-purified ferritic stainless steel.

关 键 词：高铌超纯铁素体不锈钢 带状组织 偏析 LAVES相 等轴晶比例 

分 类 号：TG142.71[一般工业技术—材料科学与工程]