The present invention provides a method for manufacturing an ultra high
strength cold-rolled steel sheet, comprising the step of continuously
annealing a cold-rolled steel sheet consisting essentially of, in terms
of weight percentages, 0.07 to 0.15% C, 0.7 to 2% Si, 1.8 to 3% Mn, 0.02%
or less P, 0.01% or less S, 0.01 to 0.1% Sol. Al, 0.005% or less N,
0.0003 to 0.003% B, and the balance being Fe, in which such continuous
annealing comprises the steps of: heating the cold-rolled steel sheet at
from 800.degree. C. to 870.degree. C. for 10 seconds or more; slowly
cooling the heated steel sheet down to from 650.degree. C. to 750.degree.
C.; rapidly cooling the slowly cooled steel sheet down to 100.degree. C.
or less at a cooling speed of over 500.degree. C./sec; reheating the
rapidly cooled steel sheet at from 325.degree. C. to 425.degree. C. for
from 5 minutes to 20 minutes; cooling the reheated steel sheet down to
room temperature; and coiling the cooled steel sheet. According to the
invention, the ultra high strength cold-rolled steel sheet, for use in a
structural member of automobile, which has a tensile strength of 980 MPa
or more and is excellent in stretch-flangeability, ductility, and
spot-weldability can be obtained.