Patent ID: 7503984
Filing Date: 2009-03-17
Classification: C21D,C22C,C23C

Abstract:
1. A high-burring and high-strength thin steel sheet drawable having a particular shape fixation property and high burring workability, characterized in that the steel sheet and is composed in mass essentially of: C: 0.01 to 0.035%, Si: 0.01 to 2%, Mn: 0.05 to 3%, P: 0.1% or less, S: 0.03% or less, and Al: 0.005 to 1%, N: 0.005% or less, Ti: 0.05 to 0.5%, satisfying the expression Ti−(48/12)C−(48/14)N−(48/32)S>0%, and Cu-free, with the balance consisting of Fe and unavoidable impurities, wherein the steel sheet at least on a plane at a center of the thickness of at least a section has: a. a first average ratio of an X-ray strength in an orientation component group of {100}<011> to {223}<110> to a random X-ray diffraction strength is at least 3, and b. a second average ratio of the X-ray strength in three orientation components of {554}<225>, {111}<112> and {111}<110> to the random X-ray diffraction strength is at most 3.5, and wherein the steel sheet has a microstructure composed of single phase bainitic ferrite or bainitic ferrite and less than 10% volume bainite, with unavoidable other phase, so that the steel sheet has a particular shape fixation property.