Impact of hot-rolling cooling pattern and cold-rolling reduction on properties of low-carbon annealed steel

Aiming at the low-carbon cold-rolled annealed sheets produced by domestic equipment, the influence mechanisms of hot rolling cooling processes and cold rolling reduction ratios on the texture and mechanical properties of the material were systematically investigated. A comparison between the early-stage and late-stage hot rolling cooling processes revealed that the late-stage cooling process prolonged the austenite holding time at high temperature, which promoted grain coarsening, reduced the yield/tensile strength by approximately 10 MPa after annealing, and increased the R-value by 0.17 simultaneously. Microstructural analysis indicated that the late-stage cooling process could significantly improve the uniformity of the transverse properties of the steel sheet and suppress the strength difference between the edge and central regions. In addition, when the cold rolling reduction ratio was increased to more than 62.5%, the abnormal points of mechanical properties at the edge disappeared, the mixed grain phenomenon was reduced, the proportion of 111 texture increased, and the distribution was more uniform along the thickness direction. EBSD analysis showed that the high reduction ratio(66.7%) could promote the evolution of γ-fiber texture(111//ND), and the competitive growth of 111<112> oriented grains during recrystallization dominated the optimization of deep drawing performance. The research results demonstrated that the combined process of late-stage hot rolling cooling and high cold rolling reduction ratio(≥62.5%) effectively coordinated the strength, plasticity and anisotropy through strain energy homogenization and grain refinement(Hall-Petch effect), reducing the yield strength ratio to below 0.7 and significantly improving the stability of transverse properties. This process verified the production feasibility of cold-rolled steel with high formability on domestic equipment, and provided a theoretical and practical basis for the optimization of deep drawing performance of low-carbon steel.