Steel plate and method of manufacturing the same

(12) ]i 8$ - t'~ T] 40 ;1 J IT d- 51 (19)tl- [ J r i i ( (10) (43) P9Wm> PIHWO 00 398A 2020*2f 27H(27.02.2020) WO 2020/039485 A1 (51) ;'t &I-: -I-IN(FURUYA Hitoshi); T1008071 ANVF C22C 38/00 (2006.01) C22C38/54(2006.01) It F9 E: A ) T F1 6 * 1 -q V H 1; 4 C21D 8/02 (2006.01) AgToh Tokyo (JP). )II ai #IIE(KAWABATA (21) 2 PCT/JP2018/030676 Norimasa); T1008071 A T :7 It flJ 0) TF1 6*1 -q ftH ]A iT Tokyo (22)IiH RtJ : 2018l8) A20H(20.08.2018) (JP)_ -- A tf (MIYAKE Takumi); ~T1008071 (26) pf 0 l: H $H IMA 4 $1 Tokyo (JP). (71)t AX:H a 4% (NIPPON STEEL (74) tiXA : 44 | At, (TANAI Sumio et al.); CORPORATION) [JP/JP]; T1008071 WA#+ T 1006620 W 32TT S :7 I E T IF E Ao T H 6 * 1 - Tokyo (P). 9 2 Tokyo (P). (81)tt(0t\IR) 0t0i t (72)#HB3#:ih d$ 5k (TAKAMINE Fumitoshi); t A GMT U ~i~1008071 ~~ ~ ~ 9 fibST t EM TE6) : AE, AG, AL, AM, AO, AT, AU, AZ, T1008071 3 0:7 I 4 $X:A0 T 6 ( - BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, 1 -q ft E 21tW-4PTok yoJP). tr (54) Title: STEEL SHEET AND PRODUCTION METHOD THEREFOR (54) RME P 0) -: ]t4)1 J t OYiWAtm - 13 12 1mm . . . .5mm co - 5rnhf 1mm 12 13 IC(57) Abstract: One embodiment of the present application pertains to a steel sheet having a chemical composition that falls within a prescribed range, wherein: the central part of the steel sheet in the thickness direction contains martensite and bainite in a total area fraction of at least 99%; in the central part in the sheet thickness direction, the average value of en. 4 prior austenite grains is less than 80 pm, Ceq equals 0.750%-0.800%, Al x N is at least 2.0 x 10- , Ti/N is at most 3.4, and 4 x f > 9.00 is satisfied; in the central part in the sheet thickness direction, the three point average of a C-direction Charpy test is not less than 47 J at -20°C; and a surface layer W O 2020/039485 A 1 |||1|1||| CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, Fl, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IR, IS, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW. (84) L\(0 pU) & Jgg Jg A fib): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), .a-5 7 (AM, AZ, BY, KG, KZ, RU, TJ, TM), - ' (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO,