Effects of Titanium Microalloying on Microstructure and Properties of Rephosphorized Steel Sheet

The effects of 0.015% titanium microalloying on the microstructure and properties of rephosphorized steel sheet were investigated by analyzing its microstructure and properties as hot-rolled and as annealed as well as its recrystallization dynamic behavior during annealing under different coiling temperatures (600,650 and 700℃ separately).The results showed that the microstructure and properties of the rephosphorized steel sheet were little affected by the hot-rolling coiling temperature whereas its recrystallization dynamics was prohibited after titanium microalloying,especially coiling at 600℃.It was also found that not only the strength of as hot-rolled or as annealed was increased after titanium microalloying,but also the mechanical properties became more sensitive to coiling temperature and annealing temperature.As a result,both the as hot-rolled and the as annealed strength of the Ti treated rephosphorized steel sheet were increased as the coiling temperature or the annealing temperature was lowered. The effect of titanium on the microstructure and properties of the rephosphorized steel was related to the coarsening of titanium precipitates.