不同初始状态中碳钢双向温轧组织的退火稳定性

Annealing stability of bidirectional warm rolled medium carbon steel with different initial microstructure

通过扫描电镜(SEM)和电子背散射衍射技术(EBSD)研究了不同初始组织对中碳钢双向温轧退火后的组织演变以及稳定性变化的影响规律。结果表明,轧后铁素体-珠光体钢的平均晶粒尺寸为1.11μm,小角度晶界占比81%;而马氏体钢平均晶粒尺寸为0.99μm,小角度晶界占比65.3%。随退火时间的延长,铁素体晶粒发生回复再结晶后,铁素体-珠光体钢发生二次再结晶,平均晶粒尺寸不断增大,小角度晶界占比逐渐减小最终趋于平稳,退火8 h后分别为1.89μm和54.9%;而马氏体钢仅发生晶粒的均匀长大,晶粒尺寸稍有增加,小角度晶界比例降低较少,保温8 h后分别为1.43μm和58.1%。因此,马氏体钢轧后显微组织的退火稳定性要高于铁素体-珠光体钢。

Effect of different initial microstructure on microstructural evolution and stability on the bidirectional warm rolled medium carbon steel after annealing was investigated by SEM and EBSD. The results show that after rolling, the average ferrite grain size of ferrite-pearlite steel is 1.11 μm, and small angle grain boundaries accounte for 81% , whereas the average grain size of quenched martensite is 0.99 μm, low angle grain boundaries accounte for 65. 3%. With the increase of annealing time, ferrite-pearlite steel continues secondary recrystallization after the recovery and recrystallization of ferrite grains. The average grain size of ferrite increases, the proportion of small angle grain boundaries gradually decreases and eventually tends to stabilize, the values are 1.89 μm and 54.9% respectively after annealing 8 hours ; however martensite steel only occurs the uniform growth of equiaxed grains, the average grain size increases a small amount and the proportion of small angle grain boundaries decreases slightly. When holding 8 hours, the grain size and the proportion are 1.43 gna and 58.1%, respectively. Thus, the thermal stability of the rolled microstructure of martensite steel is higher than that of ferrite and pearlite steel.