摘要
为了满足核电和手机等领域对316L奥氏体不锈钢无磁性的要求,必须严格控制316L不锈钢铸坯中残余铁素体的含量。本文以某厂生产的高镍高氮316L奥氏体不锈钢板坯为研究对象,采用金相观察、EBSD等方法研究了的板坯宽度中心厚度方向铁素体的形貌、含量及板坯析出相,使用热力学计算铸坯的平衡凝固过程,对比不同经验模型对凝固模式和铁素体含量的预测准确性。研究表明:高镍高氮含量316L板坯铁素体形貌从板坯表面到中心依次为:颗粒状→短棒状→半网状,大部分位于奥氏体晶界处。铁素体体积分数在0.14%~1.47%内变化,在板坯中心铁素体体积分数最高为1.47%,铁素体含量基本符合无磁要求。板坯二次析出相主要为Chi相和Sigma相。板坯表层铁素体在奥氏体晶界以颗粒状析出,部分铁素体转变为Chi相,表层冷却速率较高Chi相转变驱动力不足,保留下来形成铁素体和Chi相的耦合组织。板坯中心在奥氏体晶界处的半网状铁素体已基本转化为Sigma相。热力学计算结果显示本研究的316L板坯以奥氏体单相凝固即A模式,但实际观察结果显示铸坯凝固模式为AF模式。结合5种铬镍当量公式与WRC-1988铁素体含量预测图对本研究316L板坯凝固模式和铁素体含量进行预测,仅有Hull提出的铬镍当量公式预测的铁素体体积分数在1%~2%和实验观察一致,其余公式预测结果为纯奥氏体、3%或7%~10%。
To meet the stringent non-magnetic requirements for 316L austenitic stainless steel in applications such as nuclear power and mobile devices,it is essential to precisely control the residual ferrite content in the cast slab.This study investigates a high-nickel,high-nitrogen 316L austenitic stainless steel slab produced industrially.Using metallographic examination and electron backscatter diffraction(EBSD),the morphology,distribution,and content of ferrite across the thickness direction at the slab centerline were characterized,along with the identification of secondary precipitated phases.Thermodynamic simulations were employed to analyze the equilibrium solidification process,and the predictive accuracy of various empirical models for solidification mode and ferrite content was evaluated.The results indicate that the ferrite morphology varies from granular near the surface to short rod-like and finally to a semi-network morphology toward the center,predominantly along austenite grain boundaries.The ferrite content(volume fraction)ranges from 0.14%to 1.47%,with the highest value observed at the center,meeting the non-magnetic criteria.The main secondary precipitates were identified as chi-phase and sigma-phase.Near the surface,ferrite precipitates as discrete particles at austenite grain boundaries,with partial transformation into chi-phase.The high cooling rate at the surface inhibits complete transformation,resulting in a coupled ferrite/chi-phase microstructure.In contrast,the semi-network ferrite in the central region has largely transformed into sigma-phase.Although thermodynamic calculations predict single-phase austenitic solidification(A-mode),experimental observations confirm austenite-ferrite(AF-mode)solidification.Among five chromium/nickel equivalent formulas and the WRC-1992 diagram evaluated,only the Hull formula accurately predicts the ferrite content(1%-2%),consistent with measured results.Other models either overpredict(3%or 7%-10%)or incorrectly predict fully austenitic solidification.
作者
薛智轩
张政睿
陈超
王洋
陈兴润
李亚峰
杨琨
牟望重
XUE Zhixuan;ZHANG Zhengrui;CHEN Chao;WANG Yang;CHEN Xingrun;LI Yafeng;YANG Kun;MU Wangzhong(College of Materials Science and Engineering,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;Hongxing Iron&Steel Co.,Ltd.,Jiuquan Iron and Steel Group Corporation,Jiayuguan 735100,Gansu,China;Xinzhou Comprehensive Inspection and Testing Center,Xinzhou 034000,Shanxi,China;College of Mechanical Engineering,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;Department of Materials Science and Engineering,KTH Royal Institute of Technology,Stockholm SE10044,Sweden)
出处
《连铸》
北大核心
2025年第5期74-81,共8页
Continuous Casting
基金
教育部“春晖计划”合作科研资助项目(HZKY20220507)
山西省回国留学人员科研资助项目(2022-040)
山西省应用基础研究计划面上资助项目(202301D111108)
山西省研究生创新资助项目(2025XS228)。
关键词
高镍高氮316L不锈钢
铁素体形貌
铁素体含量
凝固模式
析出相
high-nickel and high-nitrogen 316L austenitic stainless steel
ferrite morphology
ferrite content
solidification mode
precipitation phases
