ALEXANDRIA, Va., Aug. 20 -- United States Patent no. 12,392,020, issued on Aug. 19, was assigned to NIPPON STEEL Corp. (Tokyo).
"Hot-rolled steel sheet" was invented by Kazumasa Tsutsui (Tokyo), Hiroshi Shuto (Tokyo) and Koutarou Hayashi (Tokyo).
According to the abstract* released by the U.S. Patent & Trademark Office: "This hot-rolled steel sheet has a predetermined chemical composition, in which a metallographic structure contains, by area %, more than 92.0% and 100.0% or less of martensite and tempered martensite in total, less than 3.0% of residual austenite, and less than 5.0% of ferrite, has a ratio S60/S7, which is a ratio of a density S60 of a length of a grain boundary having a crystal misorientation of 60deg to a density S7 of ...