奥氏体化温度对Ti–Zr处理钢中针状铁素体转变的影响  

Effect of austenite grain size on the acicular ferrite transformation in Ti–Zr treated steel

作　　者：姚浩 刘承军 张立峰 YAO Hao;LIU Cheng-jun;ZHANG Li-feng(School of Metallurgy,Northeastern University,Shenyang 110819,China;School of Mechanical and Materials Engineering,North China University of Technology,Beijing 100144,China)

机构地区：[1]东北大学冶金学院,沈阳110819 [2]北方工业大学机械与材料工程学院,北京100144

出　　处：《工程科学学报》2023年第6期907-914,共8页Chinese Journal of Engineering

基　　金：河北省省级科技计划(20311004D,20591001D)。

摘　　要：Ti、Zr的复合氧化物可以有效诱导针状铁素体形核,从而细化晶粒.为了研究Ti–Zr处理钢中针状铁素体转变机理,使用25 kg真空感应炉中熔炼试验所需钢种,向低合金钢中添加了质量分数为0.038%钛和0.008%锆.利用高温激光共聚焦显微镜原位观察了奥氏体化温度对针状铁素体转变行为的变化,使用扫描电镜观察了Ti–Zr处理钢种的夹杂物成分和针状铁素体在夹杂物表面形核,使用光学显微镜观察不同奥氏体化温度下的微观组织变化差异.结果表明,随着奥氏体化温度从1250℃增加至1400℃,奥氏体晶粒尺寸从125.6μm增加至279.8μm,针状铁素体开始转变温度和侧板条铁素体开始转变温度先增加,在1350℃条件下达到最大值,后又降低,针状铁素体的体积分数由39.6%增加至83.6%;Ti–Zr处理钢中核心为Zr–Ti–O,外部为Al–Ti–Zr–O的氧化物为核心表面析出MnS的复合氧化物主要集中在1.5~3μm,可以有效促进针状铁素体形核,贫Mn区和夹杂物与铁素体之间的良好晶格关系为该型夹杂物能够促进针状铁素体形核机理.奥氏体晶粒尺寸的增加导致多边形铁素形核位点的减少和针状铁素体的形核空间的增加,钛锆复合处理形成大量的有效诱发针状铁素体形核的夹杂物,这共同导致了针状铁素体体积分数增加.The composite oxides of Ti and Zr can effectively induce acicular ferrite nucleation and refine austenite grain size. To study the transformation mechanism of acicular ferrite in Ti –Zr treated steel, the mass fraction of 0.038% titanium and 0.008%zirconium were added to low alloy steel by melting in a 25 kg vacuum induction furnace. The effect of austenitizing temperature on acicular ferrite transformation behavior was observed in-situ using a high-temperature laser confocal microscope: the samples were heated to 1250, 1300, 1350, and 1400 ℃ at a heating rate of 5 ℃·s^(-1) and then cooled to 400 ℃ at a cooling rate of 3 ℃·s-1 after holding for 300 s. The ferrite transformation behavior of samples during the above process was observed using a high-temperature confocal microscope. The inclusion composition of Ti –Zr treated steel and the nucleation of acicular ferrite on the inclusion surface were observed using a scanning electron microscope. The variation in microstructure at different austenitizing temperatures was observed using an optical microscope. The austenite grain size was found to increase from 125.6 to 279.8 μm with increasing austenitizing temperature from 1250 to 1400 ℃. The initial transformation temperature of acicular ferrite and side-plate ferrite increased, reached a maximum at 1350 ℃, and then decreased. The volume fraction of acicular ferrite increased from 39.6% to 83.6%. In Ti–Zr treated steel, the size of complex inclusion with Zr–Ti–O in core and Al–Ti–Zr–O in exterior and MnS precipitated on the surface was mainly concentrated in 1–3 μm. It could effectively promote acicular ferrite nucleation. The Mn-poor region and the good lattice relationship between complex inclusions and ferrite were the mechanisms by which the type of inclusions in the steel could promote acicular ferrite nucleation. Using classical nucleation theory, the nucleation potential of acicular ferrite under different conditions was calculated. The results showed that when the austenitiz

关 键 词：Ti–Zr处理钢 奥氏体晶粒尺寸 针状铁素体 原位观察 转变温度 夹杂物 

分 类 号：TG142.1[一般工业技术—材料科学与工程]