Study on Continuous Annealing Process of Ti-IF Steel on a Continuous-annealing/Hot-dip Galvanizing Dual Purpose Line

According to the characteristics of a Continuous-annealing/Hot-dip Galvanizing Dual Purpose Line,a series of Ti-IF steels with different carbon content were used to investigate the effect of continuous annealing temperature and annealing time,cold-rolling reduction and prestretching deformation on the microstructure and properties.The results showed that ferrite grain size of the experimental steels almost remained unchanged when annealing temperature increased from 780℃ to 880℃,and the steel with higher carbon produced finer ferrite grains.As annealing temperature increased,yield strength and tensile strength increased,but ultimate elongation and n₉₀ value decreased,however,r₉₀ value remained almost unchanged.As the annealing time increased from 30 s to 45 s,yield strength and tensile strength change little,the ultimate elongation,the n₉₀ value and the r₉₀ value increase.As the annealing time further increased up to 60 s,mechanical properties are independent of annealing time.As the cold-rolling reduction increases,the yield strength,the tensile strength,the ultimate elongation and the r₉₀ value tend to increase,but the n₉₀ value tends to decrease.The r₉₀ value reaches peak value when the cold-rolling reduction is 80%.As the prestretching deformation increases,the yield strength increases obviously,the n₉₀ value and the ultimate elongation decrease markedly,the tensile strength remains almost unchanged,and the r₉₀ value tends to decrease.The continuous annealing Process of Ti-IF steel on a Continuous-annealing/Hot-dip Galvanizing Dual Purpose Line was analyzed.