High strength, hot rolled steel plate providing high level of bore
expandability and high level of ductility. Also, method of manufacturing
same. In first aspect, steel plate comprises steel having, by mass,
C:0.01-0.15%; Si:0.30-2.00%; Mn:0.50-3.00%; P.ltoreq.0.03%;
S.ltoreq.0.005%; Ti:0.01-0.50%; and/or Ni:0.01-0.05%, with balance Fe and
unavoidable impurities. In this steel, .gtoreq.80% of all grains have
ratio of minor axis to major axis of .gtoreq.0.1. This steel plate has
steel structure comprising .gtoreq.80% ferrite and balance bainite. In
second aspect, steel plate has above composition, and ferrite-bainite
duplex steel structure in which proportion of ferrite having grain
diameter .ltoreq.2 .mu.m is .gtoreq.80%. In third aspect, steel plate has
above composition. wherein contents of C, Si, Mn, Ti, and Nb satisfy
requirement represented by formula: 115 .ltoreq.(917-480[C %]+100[Si
%]-100[Mn %])-(790.times.([Ti %]+[Nb %]/2).sup.0.05).ltoreq.235. This
steel plate has steel structure comprising .gtoreq.80% ferrite and
balance bainite.