连续退火工艺对B250P钢组织性能的影响

Effect of Continuous Annealing Process on Microstructure and Properties of B250P Steel

对含磷高强B250P钢板的连续退火工艺进行了模拟实验,通过光学金相、透射电子显微技术及拉伸实验,研究了连退工艺中加热速度、退火温度、保温时间及冷却速度对B250P钢微观组织及力学性能的影响.结果表明,B250P钢晶粒尺寸随着加热速度的增加、退火温度的升高及冷却速度的增大而增大;随着保温时间的增加,晶粒尺寸呈现出先减小后增大的趋势.退火过程中B250P钢析出相主要为纳米级的NbC和TiC,具有钉扎位错和大角度晶界及细化晶粒的作用.B250P钢的r值随着加热速度的升高而增大,随着冷却速度的增加而减小;提高退火温度和保温时间,r值先增大后减小.

The continuous annealing process of B250P steel was simulated, and the effects of continuous annealing process parameters （heating rate, annealing temperature, holding time and cooling rate ） on the microstructure and properties of B250P steel were investigated by using optical microscopy, transmission electron microscopy and tensile test. The results showed that the grain size of B250P steel increases with heating rate, annealing temperature and cooling rate. While the grain size firstly increases and then decreases with increasing the holding time. The dominant precipitates during the annealing process are nano-scale NbC and TiC, which can pin the dislocations and high angle boundaries as well as refine the grains. The r-value of B250P steel increases with increasing the heating rate and decreases with increasing the cooling rate. The r- value increases and then decreases with increasing annealing temperature and holding time.