Method of manufacturing dual phase strip steel and steel strip manufactured by the method.

摘要

In a method of manufacturing a dual phase steel a strip of thickness 0.1 to 0.5 mm from an unalloyed low C, low Mn steel composition of 0.02 - 0.15% C and 0.15 - 0.60% Mn, which method includes continuous annealing, a flat product can be obtained without strip fracture if
(a) the strip is heated to not above 770°C in the A1-A3 region of the iron-carbon diagram region and thereafter(b) the strip is cooled sufficiently rapidly that austenite is at least partly converted to martensite and/or bainite, the cooling rate is such that the value P = d.V where d is strip thickness in mm and V is average cooling rate in °C/sec from 700°C to 300°C, is in the range 20 to 900 and the time interval between the end of step (a) and the beginning of step (b) is less than 4 seconds.