Effect Mechanism of Curling Temperature on the Toughness of Titanium Microalloyed High-strength Steel GCL700

The effect of curling temperature on the mechanical properties of Ti microalloyed high-strength steels was investigated using electron backscatter diffraction， transmission electron microscopy， scanning electron microscopy and mechanical experiments.The results show that with the increase of curling temperature， the grain size and the proportion of small-angle grain boundaries of steel increase， while the large-angle grain boundaries and dislocation density decrease. When the curling temperature increases from 595 ℃ to 625 ℃， the tensile strength of the steel decreases by 4%， the elongation increases by 32%， and the low temperature impact toughness decreases by 53%. The migration and elimination of large-angle grain boundaries and the increase of grain size ， the reinforcement of fine grain strengthening is weakened thus reducing the strength and low temperature toughness of steel. The increase of the proportion of small-angle grain boundaries in steel and the decrease of dislocation density effectively prevents the propagation of cracks and the occurrence of brittle fracture， thus improving the plasticity of steel.When the curling temperature is 610 °C， the tensile strength and low-temperature impact toughness of the steel do not decrease significantly， and the steel has a high elongation. With the ongoing increase in the coiling temperature， there is a substantial reduction in the strength and low-temperature impact resilience of the steel.