Effect of Cooling Rate and Coiling Temperature on Precipitate in Ferrite of a Nb-V-Ti Microalloyed Strip Steel

The effect of cooling rate (1 −30°C/s) and coiling temperature (650 −550°C) on the fine precipitate in ferrite was studied on Gleeble simulator with a commercial Nb-V-Ti complex microalloyed strip steel. The result show that the interphase precipitations appear at the cooling rate of 1°C/sand 5°C/s. The volume fraction of general precipitation under 10nm will decrease with the increasing cooling rate at the coiling temperature of 650°C and 600°C. At 550°C, the volume fraction of general precipitation was apparently reduced at cooling rate of 30°C/s. This may be related to the slow kinetic of the precipitation at lower temperature. The lower coiling temperature at the same cooling rate after hot rolling will lead to more general precipitation. This was contributed to the higher thermodynamic driving force of the precipitation at lower coiling temperature.