Abstract: 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.

Key words: B250P steel, continuous annealing, grain size, precipitate, rvalue