Transformation Behavior of Low Carbon Steels Containing Two Different Si Contents

Continuous cooling transformation behaviors of low carbon steels with two Si contents (0.50% and 1.35%) were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on gamma transformation start temperature (A(r3)), phase microstructures, and hardness were studied. The results show that, in the case of the deformation with the true strain of 0.4, the length of bainitic ferrite laths is Significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the A(r3) greatly. The steel with higher level of Si exhibits higher A(r3), and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on A(r3) is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.