| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength hot-dip galvanized steel sheet having a high yield ratio, which has excellent workability, i.e., ductility and hole expandability. <P>SOLUTION: The composition of chemical components of the steel sheet includes, in mass%, 0.05-0.15% of C, 0.10-0.90% of Si, 1.0-1.9% of Mn, 0.005-0.10% of P, 0.0050% or less of S, 0.01-0.10% of Al, 0.0050% or less of N, and 0.010-0.100% of Nb, with the remainder including Fe and inevitable impurities. The microstructure of the steel sheet has a composite structure that includes 90% or more, in volume fraction, of ferrite having an average crystal grain size of 15 μm or smaller, 0.5% or more to less than 5.0%, in volume fraction, of martensite having an average crystal grain size of 3.0 μm or smaller, and 5.0% or less, in volume fraction, of pearlite, with the remainder including a phase formed at low temperatures. <P>COPYRIGHT: (C)2013,JPO&INPIT |
