Abstract: Microstructure and mechanical properties of the T4003 high strength ferritic stainless steel annealed at 640-850 ℃ by using a box furnace in laboratory were analyzed by means of optical microscope, scanning electron microscope and tensile test. The results show that after annealing, the matrix is mainly composed of ferrite and a few fine carbide particles. When the annealing temperature is 640 ℃, the uneven grain size is obvious. When annealed at 680-780 ℃, the grain size is still uneven, but the number of fine grains increases with the increase of annealing temperature. When the annealing temperature is 830 ℃ and 850 ℃, the austenite transformation occurs and fine recrystallized grains are obtained. The as-hot-rolled tested steel has high strength and low plasticity, while with the increase of annealing temperature, the strength shows a trend of first decreasing and then increasing, and the elongation after fracture shows a trend of first increasing and then decreasing. The yield strength of the tested steel annealed at 640 ℃ is slightly lower than the requirement of high strength stainless steel(R_p0.2≥350 MPa), but that at other annealing temperatures meets the requirement. The reasonable annealing temperature can be selected according to the requirements of the strength level.

Key words: ferritic stainless steel, annealing, microstructure, mechanical properties