(19)
(11) EP 4 324 954 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
22.05.2024 Bulletin 2024/21

(43) Date of publication A2:
21.02.2024 Bulletin 2024/08

(21) Application number: 24150998.3

(22) Date of filing: 18.08.2016
(51) International Patent Classification (IPC): 
C22C 38/58(2006.01)
C22C 38/50(2006.01)
C22C 38/46(2006.01)
C21D 8/02(2006.01)
C21D 1/18(2006.01)
C22C 38/02(2006.01)
 C22C 38/54(2006.01)
C22C 38/48(2006.01)
C22C 38/44(2006.01)
C21D 9/46(2006.01)
C22C 38/06(2006.01)
(52) Cooperative Patent Classification (CPC):
C21D 8/02; C22C 38/44; C22C 38/46; C22C 38/48; C22C 38/50; C22C 38/54; C22C 38/58; C21D 8/0263; C21D 9/46; C21D 1/18; C21D 2211/002; C21D 2211/005; C21D 2211/008; C21D 8/0226; C22C 38/02; C22C 38/06
(84) Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30) Priority: 21.08.2015 KR 20150117985

(62) Application number of the earlier application in accordance with Art. 76 EPC:
16839505.1 / 3339464

(71) Applicant: POSCO Co., Ltd
Pohang-si, Gyeongsangbuk-do 37859 (KR)

(72) Inventors:
  • IM, Young-Roc
    37877 Gyeongsangbuk-do (KR)
  • JANG, Jun-Sang
    37877 Gyeongsangbuk-do (KR)

(74) Representative: Meissner Bolte Partnerschaft mbB 
Patentanwälte Rechtsanwälte Postfach 86 06 24
81633 München
81633 München (DE)

   


(54) HIGH-HARDNESS STEEL SHEET, AND MANUFACTURING METHOD THEREOF


(57) The objective of one aspect of the present invention is to provide a high-hardness steel sheet and a manufacturing method, the high-hardness steel sheet having Brinell hardness of 500 HB or more by setting a steel composition according to a minimum carbon content relation (1). Another aspect of the present invention relates to, as a high-hardness steel sheet having Brinell hardness of 500 HB or more and to be manufactured by comprising a process of cooling a hot rolled steel sheet, a high-hardness steel sheet having a minimum carbon (C) content which meets the following relation (1), having a microstructure comprising 95 vol% or more of martensite phase, and having Brinell hardness of 500 HB or more; and a manufacturing method therefor.

(wherein Mn, Si, Cr, Ni and Mo are a value representing the content of each element by wt%, and C.R. is a value represent cooling rate during cooling a hot rolled steel sheet and the unit thereof is °C /sec)





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