公开(公告)号：US20250066891A1

公开(公告)日：2025-02-27

申请号：US18724764

申请日：2023-02-16

Applicant: NIPPON STEEL CORPORATION

Inventor： Hiroki KAMITANI ,  Yuji ARAI ,  Jin KAWASAKI ,  Keiichi KONDO

IPC: C22C38/32 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/22 ,  C22C38/26 ,  C22C38/28

Abstract: A steel material according to the present disclosure consists of, in mass %, C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.05 to 0.30%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr: 0.30 to 1.10%, Mo: 0.40 to 2.00%, Ti: 0.002 to 0.020%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, and O: less than 0.0040%, with the balance being Fe and impurities, and has a yield strength of 862 MPa or more. In the steel material, a number density of Si oxides which have a major axis of 5.0 μm or more is 5/100 mm2 or less, and in a case where the yield strength is 931 MPa or more, the number density of the Si oxides is 5/200 mm2 or less.