Influence of Microstructure and Precipitates on the Mechanical Properties of High Strength Hot Strip
The relation between the microstructure, precipitates and the longitudinal mechanical properties of high strength hot strip was studied by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the yield strengths of the coil outer and middle parts were higher than that of inner part by 65MPa, and the tensile strength of the coil outer part was higher than that of middle part and inner part by about 50MPa. The number of subgrain with small size and that of dispersion distribution precipitates less than 30nm in outer part and middle part were more than that in inner part, which resulted that subgrain and precipitation strengthening were larger than that of inner part. For the coil inner part, the strengthening effects were made of fine-grained strengthening and M/A islands strengthening. The contribution of subgrain and precipitation strengthening to intensity is larger than that of fine-grained strengthening, which is the main reason causing the outer and middle parts having higher yield strength. The least tensile strength of middle part is related to the many blocky ferrites.