Bainite Transformation of Low-carbon and Boron-containing Steel under Continuous Cooling

The effects of deformation temperature and strain on bainitc transformation of low carbon steel and boron-containing steel were investigated under continuous cooling conditions by means of dilatometrie measurement and microstructurc observation. The results show that with decreasing the deformation temperature from 1000 to 800 °C and increasing strains, bainitc start temperature for boron-containing low carbon steel increases, whereas it decreases for low carbon steel under the same condition. The bainitc microstructurcs arc easily obtained for boron-containing steel deformed at different temperatures and different strains compared with plain low carbon steel. With increasing the continuous cooling rate, the bainitc start temperature under deformed condition is about 20 °C higher than that under undcformed condition for boron-containing steel, but it changes slightly when the cooling rate is 20 °C/s or more.