Abstract: In order to accelerate the development and application of the domestic dual phase steel， the effects of the heating speed， intercritical annealing temperature， overaging temperature， and the time of overaging on the microstructure and properties of DP590 dual phase steels were studied by a CAS300Ⅱannealing simulator. The results showed that the yield strength and tensile strength both increased and the elongation and product of strength and ductility both decreased with the increase of the heating speeds between 5 and 60℃/s. The yield strength and tensile strength both decreased first， then increased， the elongation and product of strength and ductility both increased with the increase of intercritical annealing temperatures between 780 and 850℃， The yield strength increased， the tensile strength decreased， the elongation increased generally， the yield ratio increased apparently with the increase of the overaging temperature between 260 and 400℃. When the overaging temperature was 280℃， the yield strength and tensile strength both decreased， the elongation and product of strength and ductility decreased first， then increased with the increase of the over aging time within the range of 240~480s.

Key words: coldrolled sheets, dual phase steels, heat treatment, microstructure, mechanical properties