Influences of heating and coiling temperatures on recrystallization during hot-rolling process in Ti added high-purity ferritic stainless steel

The influence of heating and coiling temperatures on recrystallization of Ti added high purity ferritic stainless steels (17Cr-0.1Ti-ultra low C, N) was investigated to claryfy the conditions of accelerating recrystallization in the coiling processes. The recrystallization during coiling significantly retarded when the heating temperature before rolling was higher than 1423 K or coiling temperature was lower than 1023 K. The effect of heating temperature was explained by the precipitation of Ti₄C₂S₂. At heating temperature higher than 1423K, Ti₄C₂S₂ dissolved and they finely re-precipitated during finishing rolling. These fine precipitates significantly retarded the recrystallization. At low coiling temperature, retardation of recrystallization was caused by the precipitation of FeTiP. At the coiling temperature below 1023 K, FeTiP finely precipitated during coiling before recrystallization and retarded recrystallization. When P content decreases, precipitation temperature of FeTiP becomes lower and recrystallization at 1023 K was accelerated. Two important conditions to accelerate recrystallization were confirmed. One is low heating temperature less than 1423K to prevent the dissolution of Ti₄C₂S₂. The other is coiling temperature higher than 1023 K to prevent the precipitation of FeTiP. In the latter case, the decrease of P content is also effective.