摘要
结合热力学计算、X射线衍射、扫描电镜和显微硬度测试,分析了0.3C-9Mn-3Al(mass%)热轧淬火钢临界退火过程中的微观组织演变。结果表明:热轧淬火态显微组织呈现明显的带状偏析特征,残留奥氏体含量(VγR)为35.0 vol%,形态以带状和条块为主,其间分布着细针或板条状马氏体;当退火温度为650℃时,细小渗碳体颗粒从原马氏体内析出并长大,而后不断溶解,板条奥氏体从马氏体界处形核长大,VγR逐渐增加至65.9 vol%(90 min);退火温度为700℃时,粒状和板条奥氏体分别从临界铁素体和马氏体界处形核长大,VγR增至65.2 vol%(10 min)后趋于稳定;退火温度为750℃时,VγR在初期(10 min)时即达到峰值(68.6 vol%),而后在60.4 vol%~65.1 vol%之间波动,奥氏体存在带状、条块、板条和颗粒等多种形态,保温时间超过60 min,逆转变粒状与板条奥氏体趋于合并,晶粒明显粗化和均匀化,初始奥氏体(富锰偏析带)因C、Mn扩散导致初始奥氏体的稳定性下降,在淬火过程中热诱发转变为马氏体。
Microstructure evolution of 0.3 C-9 Mn-3 Al(in mass%) hot-rolled and quenched steel during intercritical annealing(IA) were investigated by means of thermal-dynamic calculation, X-ray diffraction, scanning electron microscopy and micro-hardness test. The results show that the microstructure of the hot-rolled and quenched steel shows apparent characteristics of segregation band, the volume fraction of the retained austenite(VγR) is 35 vol%, and the morphology is mainly strip and relatively short block, with the fine acicular or lath martensite distributed in it. When the intercritical annealing temperature is 650 ℃, the fine cementite particles precipitate and grow from the primary martensite and then dissolve continuously, the lath reversed austenite nucleates from the martensite boundary and grows, and the VγR gradually increases to 65.9 vol% when the annealing time is 90 min. When the intercritical annealing temperature is 700 ℃, the granular and lath austenite nucleate and grow up from the intercritical ferrite and primary martensite grain boundary, respectively, the VγR rapidly increases to 65.2 vol%(10 min) and then keeps stable. When the intercritical annealing temperature is 750 ℃, the VγR reaches peak value(68.6 vol%) at the initial stage(10 min) and then fluctuates between 60.4 vol% and 65.1 vol%. The austenite presents different morphology, such as band, block, lath and granule. When the annealing time is more than 60 min, the granular and lath reversed austenite grains tend to merge and grow up, leading to apparent size coarsening and distribution homogenization. Due to the diffusion of C and Mn atoms, the stability of the primary band-like austenite decreases and is transformed into martensite during quenching.
作者
朱延山
廖岳太
张继明
曲锦波
ZHU Yan-shan;LIAO Yue-tai;ZHANG Ji-ming;QU Jin-bo(Institute of Research of Iron and Steel(IRIS),Sha-steel,Zhangjiagang 215625,China)
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2020年第7期134-143,共10页
Transactions of Materials and Heat Treatment
关键词
中锰钢
临界退火
偏析带
组织演变
medium-manganese steel
intercritical annealing
segregation band
microstructure evolution
