ALEXANDRIA, Va., June 4 -- United States Patent no. 12,319,977, issued on June 3, was assigned to NIPPON STEEL Corp. (Tokyo).
"Hot rolled steel sheet and production method thereof" was invented by Masaharu Oka (Tokyo), Nobusato Kojima (Tokyo) and Mitsuru Yoshida (Tokyo).
According to the abstract* released by the U.S. Patent & Trademark Office: "A hot-rolled steel sheet has a predetermined chemical composition in which a microstructure includes 99% or more of martensite by volume fraction and a remainder in microstructure including residual austenite and ferrite, in a cross section parallel to a rolling direction, an average aspect ratio of prior austenite grains is less than 3.0, a proportion of sulfides having an aspect ratio of more th...