快速冷却前停留时间对微合金钢相变的作用  

Effect of delay time before rapid cooling on transformation of micro-alloyed steel

作　　者：郭锦[1] 史佳新 陈雨来[1] GUO Jin;SHI Jia-xin;CHEN Yu-lai(National Engineering Research Center of Advanced Rolling, University of Science and Technology Beijing, Beijing 100083, China)

机构地区：[1]北京科技大学高效轧制国家工程研究中心

出　　处：《钢铁》2018年第5期62-67,共6页Iron and Steel

基　　金：国家自然科学基金资助项目(51274036)

摘　　要：高温加工硬化和软化会影响钢相变形核,进而改变材料的组织与性能,而变形后至超快冷前停留期间软化不可避免。试验采用0.055C-1.47Mn-0.17Mo-0.054Nb-0.012Ti微合金低碳钢组织,通过热模拟试验研究了830℃终止变形后至80℃/s超快冷前,停留时间对铁素体和马奥岛（M/A）相的影响。分别采用SEM和图像分析方法测量晶粒尺寸与相变比例。结果表明,在2~7 s的范围内,随着快冷前停留时间的增加,铁素体晶粒尺寸呈现先增大后减小的趋势,5 s时晶粒尺寸最大,7 s时最小。马奥岛（M/A）相所占的体积分数呈先减小后增大的趋势,M/A相形状从点状向块状改变,5 s时M/A相所占体积分数最小。综合考虑超快冷前停留时间对铁素体和M/A相晶粒尺寸和M/A相所占体积分数的影响,缩短超快冷前停留时间对同时提高韧性和强度性能有利。Hardening and softening at high temperature can improve the microstructure and properties of the materials by enhancing the transformation nucleation of the steel. However,it is inevitable to soften between finishing deformation and ultra-fast cooling. The influence of delay time on ferrite and M/A（martensite/anstenite）phase in micro-alloyed low carbon steel（0.055C-1.47Mn-0.17Mo-0.054Nb-0.012Ti）was investigated through the Gleeble thermal simulation experiment,and the delay time is the time from the finishing deformation at 830 ℃ to ultra-fast cooling at the ratio of 80 ℃/s.The phase transformation ratio of M/A phase and the grain size were analyzed and measured by the scanning electron microscope and image analysis respectively. The results showed that in the time range of 2-7 s,the ferrite grain size increased firstly and then decreased with the increase of the delay time before the ultra-fast cooling. The maximum grain size was obtained at the delay time of 5 s while the minimum was 7 s. The volume ratio of M/A phase also showed a trend of decreasing first and then increasing with the delay time prolonging,the shape of M/A phase changed from point to block. Moreover the minimum M/A phase ratio was obtained at 5 s. Considering the influence of delay time on the ferrite and M/A grain size and the ratio of M/A phase,shortening the delay time was favorable to improve the toughness and strength of micro-alloy steel.

关 键 词：变形 软化时间 超快冷 组织细化 M/A组织 

分 类 号：TG142.1[一般工业技术—材料科学与工程]