Fire resistant steel plate for 490 MPa grade building structure with low cost and manufacture method thereof

The invention discloses fire resistant steel plate for 490 MPa grade building structure with low cost and manufacture method thereof. The chemical components of the steel comprise C 0.03-0.09%, Si 0.10-0.38%, Mn 0.55-1.50%, Nb 0.011-0.039%, Ti 0.012-0.050%, Als 0.007-0.045%, Cr 0.12-0.49%, Cu 0.10-0.40%, B 0.0008-0.0020%, and Fe and unavoidable impurity in balance; wherein impurity element P is controlled less than or equal to 0.016%, S is controlled less than or equal to 0.006%, [N] is controlled less than or equal to 0.0040%, and [O] is controlled less than or equal to 0.0030%. The steel blanks are heated to 1,150-1,270 DEG C., and heating time is controlled to 60-110 s/cm according to steel plate thickness; a first-stage rolling begins after steel plate surface dephosphorization is performed, and final rolling temperature is controlled greater than or equal to 960 DEG C.; a second-stage rolling initial temperature is controlled at 960-840 DEG C., recrystallization zone accumulated deformation amount is greater than 55%, and final rolling temperature is controlled at 720-880 DEG C.; holding for 20-100 s between final rolling and cooling; initial cooling temperature is controlled at 680-840 DEG C., and final cooling temperature is controlled at 650-420 DEG C.; and rapid stacking slow cooling thermal insulation is performed, with stacking temperature of 600-300 DEG C., and holding time of 8-16 h.