公开(公告)号：US20240410030A1

公开(公告)日：2024-12-12

申请号：US18701814

申请日：2022-12-19

Applicant: POSCO CO., LTD

Inventor： Dae-Woo KIM ,  Hong-ju LEE ,  Dae-Woo BAEK

IPC: C21D9/00 ,  C21D1/18 ,  C21D6/00 ,  C21D8/00 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/42 ,  C22C38/44 ,  C22C38/46 ,  C22C38/48 ,  C22C38/50 ,  C22C38/58

Abstract: Provided is an ultrathick steel material for a flange having excellent strength and low temperature impact toughness, and a manufacturing method therefor. The steel material of the present disclosure comprises, in weight %, C: 0.05-0.2%, Si: 0.05-0.5%, Mn: 1.0-2.0%, Al: 0.005-0.1%, P: 0.01% or less, S: 0.015% or less, Nb: 0.005-0.07%, V: 0.001-0.3%, Ti: 0.001-0.05%, Cr: 0.01-0.3%, Mo: 0.01-0.12%, Cu: 0.01-0.6%, Ni: 0.05-4.0%, Ca: 0.0005-0.004%, and the balance being Fe and other unavoidable impurities, wherein the steel material has a microstructure having a prior austenite crystallite grain size of 35 μm or less and including 90 area % or more of at least one of bainite and martensite, and the remainder of ferrite or pearlite.