D0I:10.13374.issn1001-053x2012.07.009 第34卷第7期 北京科技大学学报 Vol.34 No.7 2012年7月 Journal of University of Science and Technology Beijing Jul.2012 低碳Nb一Ti二元微合金钢析出过程的演变 罗衍昭1,2)✉ 张炯明》肖超2》赵新宇，》 刘志明2 吴炼2》 1)北京科技大学钢铁治金新技术国家重点实验室，北京1000832)北京科技大学治金与生态工程学院，北京100083 ☒通信作者，E-mail:luoyanzhao(@yahoo.cn 摘要建立规则溶液亚点阵模型计算了不同温度(1073~1523K)下低碳Nb-T二元微合金钢(Nb质量分数为0.023%，Ti 质量分数为0.012%)中碳氮化物析出相的平衡摩尔分数、化学驱动力和各组元摩尔分数，对微合金钢中析出粒子演变规律进 行研究，并利用透射电镜观察及能谱分析验证这种析出模式.计算结果表明，1523K下析出粒子化学式组成为(Nh。5Tas) (C。6Na4),由富Ti的析出物逐渐过渡至Nb-Ti均匀析出，析出粒子演变顺序为(Na5 Tia.ss)(Ca6Na.)、(Nb,Ti-.) (C,N-,)和(haTi.)(Ca6Naa),与实验结果符合较好.随着温度降低，T/N质量比逐渐减小，得到的TiC比NbC更难 溶.对均匀形核及位错处形核的临界核心尺寸和相对形核速率进行计算，得到最大形核率即可获得最细小第二相尺寸的 温度. 关键词合金钢：析出：热力学：位错形核 分类号TG142.33 Evolution of precipitates in Nb-Ti binary low-carbon microalloyed steels LUO Yan-hao,ZHANG Jiong-ming?,XIAO Chao,ZHAO Xin-yu,LIU Zhi-ming,WU Lian 1)State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,Beijing 100083,China 2)School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China X Corresponding author,E-mail:luoyanzhao@yahoo.cn ABSTRACT A thermodynamic model of binary low-earbon microalloved steel with 0.023%Nb and 0.012%Ti additions was estab- lished to calculate the equilibrium molar fraction and chemical driving force of carbonitride precipitation as well as the molar fraction of each element in austenite at temperatures from 1073 to 1523 K.The evolution of precipitation in the microalloyed steel was studied, and the precipitation pattern was verified by transmission electron microscopy (TEM)and energy dispersive spectroscopy (EDS).The calculating results show that the chemical formula of precipitation particles is (Nbos Tis)(CaN)at 1523K,Ti-rich precipitates gradually transit to Nb-Ti uniform precipitates.The evolution order of precipitation particles is (Nba s Tioss)(Ca Nos), (Nb,Ti)(C,N)and (NbasTias)(CasN),which accord with the experimental results.The Ti/Nb mass ratio decreases gradually with decreasing temperature,and TiC is more insoluble than NbC.The critical core size and the relative nucleation rate were computed under two nucleation conditions,and the temperatures at which the size of the second phase is the smallest,i.e.the nuclea- tion rate is maximum are 1 198 K and 1 123 K for homogeneous nucleation and dislocation nucleation,respectively. KEY WORDS alloy steel:precipitation:thermodynamics:dislocation nucleation 微合金化与控轧控冷技术的有机结合是近年来 程中应变诱导析出的微合金碳氮化物可通过质点钉 用于高强高韧钢发展的一大趋势.在这类钢中微合 扎晶界和亚晶界的作用，相当显著地抑制形变奥氏 金元素在变形奥氏体中的析出行为对钢的组织与性 体的再结晶和再结晶晶粒的长大，为形变细化晶粒 能有至关重要的影响.均热态未溶的微合金碳氮化 打下坚实的基础- 物通过质点钉扎晶界可以明显抑制奥氏体晶粒的粗 Dutta和Sellars最早提出了Nb微合金钢开始 化，从而确保获得细小的均热态奥氏体晶粒：轧制过 析出的时间模型，即析出体积分数5%的半定量模 收稿日期：2011-0504 基金项目：国家自然科学基金资助项目(51074022)第 34 卷 第 7 期 2012 年 7 月 北京科技大学学报 Journal of University of Science and Technology Beijing Vol． 34 No． 7 Jul． 2012 低碳 Nb--Ti 二元微合金钢析出过程的演变 罗衍昭1，2) 张炯明2) 肖 超1，2) 赵新宇1，2) 刘志明2) 吴 炼1，2) 1) 北京科技大学钢铁冶金新技术国家重点实验室，北京 100083 2) 北京科技大学冶金与生态工程学院，北京 100083 通信作者，E-mail: luoyanzhao@ yahoo． cn 摘 要 建立规则溶液亚点阵模型计算了不同温度( 1 073 ～ 1 523 K) 下低碳 Nb--Ti 二元微合金钢( Nb 质量分数为 0. 023% ，Ti 质量分数为 0. 012% ) 中碳氮化物析出相的平衡摩尔分数、化学驱动力和各组元摩尔分数，对微合金钢中析出粒子演变规律进 行研究，并利用透射电镜观察及能谱分析验证这种析出模式． 计算结果表明，1 523 K 下析出粒子化学式组成为( Nb0. 15 Ti0. 85 ) ( C0. 16N0. 84 ) ，由富 Ti 的析出物逐渐过渡至 Nb--Ti 均匀析出，析出粒子演变顺序为( Nb0. 15 Ti0. 85 ) ( C0. 16 N0. 84 ) 、( Nbx Ti1 － x ) ( CyN1 － y ) 和( Nb0. 5Ti0. 5 ) ( C0. 56N0. 44 ) ，与实验结果符合较好． 随着温度降低，Ti /Nb 质量比逐渐减小，得到的 TiC 比 NbC 更难 溶． 对均匀形核及位错处形核的临界核心尺寸和相对形核速率进行计算，得到最大形核率即可获得最细小第二相尺寸的 温度． 关键词 合金钢; 析出; 热力学; 位错形核 分类号 TG142. 33 Evolution of precipitates in Nb-Ti binary low-carbon microalloyed steels LUO Yan-zhao 1，2) ，ZHANG Jiong-ming2) ，XIAO Chao 1，2) ，ZHAO Xin-yu1，2) ，LIU Zhi-ming2) ，WU Lian1，2) 1) State Key Laboratory of Advanced Metallurgy，University of Science and Technology Beijing，Beijing 100083，China 2) School of Metallurgical and Ecological Engineering，University of Science and Technology Beijing，Beijing 100083，China Corresponding author，E-mail: luoyanzhao@ yahoo． cn ABSTRACT A thermodynamic model of binary low-carbon microalloyed steel with 0. 023% Nb and 0. 012% Ti additions was estab￾lished to calculate the equilibrium molar fraction and chemical driving force of carbonitride precipitation as well as the molar fraction of each element in austenite at temperatures from 1 073 to 1 523 K． The evolution of precipitation in the microalloyed steel was studied， and the precipitation pattern was verified by transmission electron microscopy ( TEM) and energy dispersive spectroscopy ( EDS) ． The calculating results show that the chemical formula of precipitation particles is ( Nb0. 15Ti0. 85 ) ( C0. 16N0. 84 ) at 1523K，Ti-rich precipitates gradually transit to Nb-Ti uniform precipitates． The evolution order of precipitation particles is ( Nb0. 15 Ti0. 85 ) ( C0. 16 N0. 84 ) ， ( NbxTi1 － x ) ( CyN1 － y ) and ( Nb0. 5 Ti0. 5 ) ( C0. 56 N0. 44 ) ，which accord with the experimental results． The Ti /Nb mass ratio decreases gradually with decreasing temperature，and TiC is more insoluble than NbC． The critical core size and the relative nucleation rate were computed under two nucleation conditions，and the temperatures at which the size of the second phase is the smallest，i． e． the nuclea￾tion rate is maximum are 1 198 K and 1 123 K for homogeneous nucleation and dislocation nucleation，respectively． KEY WORDS alloy steel; precipitation; thermodynamics; dislocation nucleation 收稿日期: 2011--05--04 基金项目: 国家自然科学基金资助项目( 51074022) 微合金化与控轧控冷技术的有机结合是近年来 用于高强高韧钢发展的一大趋势． 在这类钢中微合 金元素在变形奥氏体中的析出行为对钢的组织与性 能有至关重要的影响． 均热态未溶的微合金碳氮化 物通过质点钉扎晶界可以明显抑制奥氏体晶粒的粗 化，从而确保获得细小的均热态奥氏体晶粒; 轧制过 程中应变诱导析出的微合金碳氮化物可通过质点钉 扎晶界和亚晶界的作用，相当显著地抑制形变奥氏 体的再结晶和再结晶晶粒的长大，为形变细化晶粒 打下坚实的基础［1--3］． Dutta 和 Sellars ［4］最早提出了 Nb 微合金钢开始 析出的时间模型，即析出体积分数 5% 的半定量模 DOI:10.13374/j.issn1001-053x.2012.07.009