Patent ID: 9534270
Date: 2017-01-03
CPC Classifications: C09D,C21D,C22C,C23C,C23F

Claim:
1. A method for manufacturing high strength steel sheets, comprising continuous annealing of a steel sheet which includes, in terms of mass %, C at 0.01 to 0.18%, Si at 0.4 to 2.0%, Mn at 1.0 to 3.0%, Al at 0.001 to 1.0%, P at 0.005 to 0.060% and S at ≦0.01%, the balance being represented by Fe and inevitable impurities, controlling the dew point of the annealing atmosphere with respect to an annealing furnace inside temperature including setting the dew point greater than −40° C. when the annealing furnace inside temperature is less than 750° C., and setting the dew point of the annealing atmosphere less than or equal to −40° C. when the annealing furnace inside temperature is greater than or equal to 750° C.