HOT-STAMP-MOLDED ARTICLE, PROCESS FOR PRODUCTION OF STEEL SHEET FOR HOT STAMPING, AND PROCESS FOR PRODUCTION OF HOT-STAMP-MOLDED ARTICLE

摘要

A hot-stamped steel according to the present invention includes, by mass%, C: 0.20% to 0.3 5%, Si: 0.1% to 0.5%, the total of at least one selected from Mn and Cr: 1% to 3%, Al: 0.005% to 0.06%, Ti: 0.002% to 0.1 %, Nb: 0.002% to 0.1 1 %, O: 0.003% to 0.007%, and a balance of iron and inevitable impurities, wherein P is limited to 0.015% or less, S is limited to 0.01% or less, N is limited to 0.004% or less, the dimensional ratio of the lengths of prior austenite grains in a rolling direction to the lengths of the prior austenite grains in the sheet thickness direction is 1.3 to 2.5, the average grain size of the prior austenite grains is 6 µm or less, the microstructure includes 98% or more of martensite, and the tensile strength is 1470 MPa or more.