Effect of Annealing Processes on Microstructures and Textures of a Nb-Ti-IF Steel

According to the processes of continuous hot-dip galvanizing lines,an industrially hot rolled and cold rolled Nb-Ti-IF steel was used to study the effect of annealing processes on the microstructures and recrystallization textures.The results showed that the steel was fully recrystallised above an annealing temperature of 720℃. When the annealing temperature is between 720℃and 840℃,the grain size is measured to be about ASTM grade 10.0 and it tended to grow to be ASTM grade 9.0 as the annealing temperature was increased to 880℃.When the annealing temperature was increased,the hardness of the experimental steel was decreased.However,although the grain was coarsened when the annealing temperature was 920℃,the hardness was increased when non polygonal microstructure was obtained due to water cooling after annealing.The change of holding time at 840℃from 30 s to 60 s had little effect on grain size.However,the hardness tended to reduce remarkably when the holding time was increased from 30 s to 45 s and remain almost constant when the holding time was further increased from 45 s to 60 s.Strong {223} <110>and {114} <110> texture components were fotmd after annealing,the intensity of them was little affected by the annealing processes while the intensity of {554} <225>,{111} <112> and {111} <110 > recrystallization texture tended to increase when the annealing temperature was increased.