Patent ID: 11939639
Assignee: POSCO CO., LTD
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B  Y | IPC C

Claim 0:
1. A hot-rolled steel sheet for a hot press member comprising, by weight, C: 0.43 to 0.60%, Mn: 0.7 to 1.5%, Si: 0.3% or less (excluding 0%), P: 0.03% or less (including 0%), S: 0.004% or less (including 0%), Al: 0.04% or less (excluding 0%), Cr: 0.3% or less (excluding 0%), Mo: 0.3% or less (excluding 0%), Ni: 0.099 to 1.5%, Cu: 0.096 to 1.5%, Cu+Ni: 1.1% or more, Ti: 0.04% or less (excluding 0%), B: 0.005% or less (excluding 0%), N: 0.006% or less (excluding 0%), and a balance of Fe and impurities,
wherein the alloying element satisfies the following relationships 1 and 2,
the hot-rolled steel sheet includes a microstructure comprising, by volume, 7 to 30% of ferrite and 70 to 93% of pearlite, and
the hot-rolled steel sheet has a tensile strength of 710 MPa or more:

(Mn/Si)≥3 (weight ratio)   [Relationship 1]

15.8≥(Ni/Si)≥1 (weight ratio)   [Relationship 2]