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1. (WO2017155263) HOT-DIP GALVANIZED STEEL SHEET WITH SUPERIOR BAKE HARDENABILITY AND AGING RESISTANCE, AND MANUFACTURING METHOD THEREOF

Pub. No.:    WO/2017/155263    International Application No.:    PCT/KR2017/002417
Publication Date: Fri Sep 15 01:59:59 CEST 2017 International Filing Date: Wed Mar 08 00:59:59 CET 2017
IPC: C22C 38/18
C22C 38/22
C22C 38/32
C22C 38/38
C22C 38/00
C22C 38/02
C22C 38/06
C22C 38/04
C23C 2/06
Applicants: POSCO
주식회사 포스코
Inventors: HAN, Sang-Ho
한상호
AHN, Yeon-Sang
안연상
Title: HOT-DIP GALVANIZED STEEL SHEET WITH SUPERIOR BAKE HARDENABILITY AND AGING RESISTANCE, AND MANUFACTURING METHOD THEREOF
Abstract:
Disclosed are a cold-rolled steel sheet having excellent bake hardenability and aging resistance, and a manufacturing method thereof. The cold-rolled steel sheet comprises, by weight %, 0.02-0.08% of C; 1.3-2.1% of Mn; 0.3% or less (excluding 0%) of Si; 1.0% or less (excluding 0%) of Cr; 0.1% or less (excluding 0%) of P; 0.01% or less (excluding 0%) of S; 0.01% or less (excluding 0%) of N; and 0.01-0.06% of sol.Al; at least one selected from the group consisting of 0.2% or less (excluding 0%) of Mo and 0.003% or less (excluding 0%) of B; and the balance being Fe and other inevitable impurities, wherein the steel sheet contains, as a microstructure thereof, 90-99% of ferrite and 1-10% of martensite in an area fraction,wherein a ratio (a/b) of an average carbon concentration a in the martensite and an average carbon concentration b in the ferrite located in an imaginary circle having a major axis of the martensite as a diameter, at a point of the sheet thickness of 1/4 t is 1.4 or less, and a ratio (d/c) of an average manganese concentration c in the martensite and an average manganese concentration d in the ferrite located in an imaginary circle having a major axis of the martensite as a diameter, at a point of a sheet thickness of 1/4 t is 0.9 or less.