摘要
316L奥氏体不锈钢耐腐蚀性能优秀,但由于镍元素的价格昂贵,为降低冶炼成本,将镍质量分数控制在10.00%~10.30%。这种镍含量处于GB/T 20878—2024标准下限的316L不锈钢被称为节镍型316L不锈钢。研究了节镍型316L奥氏体不锈钢板坯中铁素体形貌和分布特征。通过微观组织表征、元素偏析分析和热力学计算,揭示板坯不同位置铁素体含量及形貌的变化规律,并且通过熔炼试验研究冷却速率对铁素体的影响规律。从节镍型316L板坯沿厚度方向依次取样,结合金相观察、电子背散射衍射(Electron backscatter diffraction,EBSD)和电子探针显微分析(Electron probe micro-analyzer,EPMA)技术,研究了板坯铁素体形貌演变、铁素体含量、冷却速率及元素分布特征;通过重熔试验结合不同冷却条件,分析冷却速率对铁素体含量的影响;结合Thermo-Calc热力学计算解析凝固模式。结果表明,板坯中沿着厚度方向铁素体含量呈现“M”型分布,表面至50 mm处铁素体面积分数从7.52%升至11.20%,随后向中心递减至6.98%。随着表面到中心距离增加,铁素体形貌呈现规律性演变,从表面的骨骼状/板条状逐渐变为块状、网状,在中心呈现短棒状;二次枝晶臂间距由表面21.37μm增加至中心63.67μm,对应冷却速率从6.69℃/s降低至0.38℃/s。热力学计算表明,凝固模式为铁素体先凝固的FA(铁素体-奥氏体)模式。元素偏析分析表明,铬、钼在铁素体中富集,镍在奥氏体富集。重熔试验铸锭水冷、炉冷试样的铁素体面积分数为22.40%、2.71%;水冷试样中铁素体呈枝晶状结构,炉冷试样中为短棒状和条状铁素体,此外在炉冷试样中还发现少量Chi相。板坯铁素体“M”型分布是由冷却速率对初始凝固枝晶间距和固态相变的综合作用的结果。
316L austenitic stainless steel has excellent corrosion resistance,but due to the high price of Ni,in order to reduce smelting costs,the Ni mass fraction is controlled at 10.00%-10.30%.This 316L stainless steel with a Ni content at the lower limit of GB/T 20878—2024 is called low-nickel 316L.The morphology and distribution characteristics of ferrite in low-nickel 316L austenitic stainless steel continuous casting slabs was investigated.The variation in ferrite content and morphology across different slab positions was analyzed through microstructure characterization,element segregation analysis,and thermodynamic calculations.The influence of cooling rate on ferrite was further examined via remelting experiments.Samples were sequentially extracted along the slab thickness direction.Ferrite morphology evolution,content,cooling rate,and element distribution were studied using metallographic observation,electron backscatter diffraction(EBSD),and electron probe microanalysis(EPMA).The effect of cooling rate on ferrite content was assessed through remelting experiments under different cooling conditions.The solidification mode was determined using Thermo-Calc thermodynamic calculations.Results reveal an"M"-type distribution of ferrite content along the slab thickness.Ferrite content increases from 7.52%at the surface to 11.20%at 50 mm depth,then decreases to 6.98%toward the center.The ferrite morphology evolves systematically with increasing distance from the surface,transitioning from skeletal/lath-like to block-like and mesh-like,finally forming short rod-like shapes at the center.Secondary dendrite arm spacing increases from 21.37μm(surface)to 63.67μm(center),corresponding to a cooling rate decrease from 6.69°C/s to 0.38°C/s.Thermodynamic calculations confirm an FA(Ferrite-Austenite)solidification mode,where ferrite forms first.Element segregation analysis indicates Cr and Mo enrichment in ferrite,while Ni concentrates in austenite.In remelting experiments,water-cooled samples exhibit 22.40%dendritic ferrite,whereas furnace-cooled samples contain 2.71%short rod-like and strip-like ferrite.A small amount of Chi phase is also observed in the furnace-cooled sample.The"M"-type ferrite distribution results from the combined effects of cooling rate on initial dendrite spacing and solid-state phase transformation.
作者
张政睿
陈超
王洋
周丰
马辉
孙鑫
李亚峰
牟望重
ZHANG Zhengrui;CHEN Chao;WANG Yang;ZHOU Feng;MA Hui;SUN Xin;LI Yafeng;MU Wangzhong(College of Materials Science and Engineering,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;No.2 Steelmaking Plant,Shanxi Taigang Stainless Steel Co.,Ltd.,Taiyuan 030030,Shanxi,China;Tianjin Customs Mineral and Metal Material Testing Center,Tianjin 300456,China;Xinzhou Comprehensive Inspection and Testing Center,Xinzhou 034000,Shanxi,China;Department of Materials Science and Engineering,KTH Royal Institute of Technology,Stockholm SE-10044,Sweden)
出处
《钢铁》
北大核心
2025年第10期156-166,共11页
Iron and Steel
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(202303021221036)。
关键词
节镍型316L奥氏体不锈钢
铁素体
“M”型分布
析出相
冷却速率
微观组织
连铸板坯
凝固模式
low-nickel 316L austenitic stainless steel
ferrite
"M-shaped"distribution
precipitates
cooling rate
microstructure
continuous casting slab
solidification mode
