[TechnicaIField]
5 [0001]
Thep にesent inventionrelmes to ahigh ‐sせengdlsteelsheet.
Priority is claimed on Japanese PatentApplicaution No.2020 ‐165954,Biled on
September 30, 2020, the contentofwhichis incorpora直edhereinbyre6erence.
[BackgroundAn]
10 [0002]
ln recent ye嶺 s,from 山 e viewpointofrel 塑lations Forgreenhousegas emission
1n association wi 山 globalwarmingcountermeasures, 値 erehasbeenademand For
additional improvementin 山 eFuele 伍 ciencyofVehicles. Sinceamajority of
automobi1estluctures 嶺 eFormedofiron,pau 〔ticu12ur1y,stee1sheets,stee1sheetsm 想
15 山 innedtoreduce the weights, 値 erebyreducing 山 eweightsofvehicle bodies and
improving 山 eFuelelmciency. However,when 山ーeweightofasteelsheetisreduced
simply bythinning 山 e 山 icknessofthesteelsheet,thereisaconcernthat 山 e s立ength as
a sbmcture may decrease and the collisionsa 化tymaydeteriorate.ThereFore, inthinning
山 eせlicknessofthesteelsheet,itisrequiredtoincrease 山 emechanical streng山 of 山 e
20 steel sheetto beused so as notto decreasethestrengl 山 ofl山estmcture. ThereFore,
recently, 山 e applicationofhigh ‐strengdlsteelsheetstocomponentsforavehicle has
been becoming more widespread in ordertoreduce 山 eweightsofVehicle bodies and
securecollision smFety
[0003]
25 1ncident 副ly,For steel sheets that 組reusedForcomponentsForvehicles,notonly
1
1ー
sせen帥 butalsoav 嶺 ietyofworkability 山 atisrequiredat 山 etime of ぁ rming
comPonents suchasPressw orkabilityandweldability 嶺 erequired. SPecilncally, 丘om
山 e viewPoint ofPress workabilit:男 bendabilityisrequiredForsteelsheetsinmanycases.
However, since 山 e Formability ofsteel sheets tends to deterioratewith 山 ehigh5 sせen帥 eningof 山 emmeri 副 s,itisdimculttoachievebothahighstreng 山 and 魚 vorable
Formability insteelsheets.
There お re,お r山 e apP1ication ofhigh ‐sせen帥 steelsheetstocomPonents ぁ ra
vehicle,ithasbecomeanimponantissuetorealizeexcePtionalbendingworkability
togetherwithahighsl 比engthofatensi1es せengdbof590Mpaormore.
10 [00(M]
vvith resPect to such an issue,ithasbeenrePod 二edinNon-PatentDocument .
山 at bending workability is imProved by con 立ollingthestmct 皿 etoasingle sbnjcture of
免 rrite, bainite,maltensite,or 山 elikebymicrostmctmecontrol.
[0005]
15 1n addition, Patent Document l disclosesame 山 odForrealizingatensile
s立en蝉 lof590MPaormoreand750MPaorlessimdexcePtionalbendingworkability
by controlling a steel sheetcontaining,bymass%,C:0.010%too.055%,Si:0.2% or
less,N[n:0.7%or less,P:0.025%orless,S:0.02 ‐%orless,N:0.01%orless,AI: 0.1 % or
less and Ti:0.06%too.095%toast ・uctureincluding95%ormoreof 免rriteinterms of
20 area ratio and con 立olling 山 e diameters ofcmbidePaulicles containingTiin 免 rritecrystal
grains imd 山 es ローucturetoas ローuctlureinwhichonlyTiShavinganaverage diameter of
o.5 ーm or less is disPersed and PreciPitated as a su16decontainingTi.
[0006]
ln addition, Patent Document 2 disclosesame 山 odForimProvingbending
25 workability while maintainingatensiles 口en蝉 lof780MPaormoreby,forasteelsheet
2
containing,bymass%,C:0.05%too.15%,Si:0.2 ‐%to l.2‐%,N[n:1.0%to2.0%,P:
0.04% or less, S: 0.0030%orless, AI:0.005%too.10%,N:0.01%orless,andTi:0.03%
to o.13%, con 立ollingthe su[uctureinside 山ーesteelsheettoabainitesingle Phase or a
sb〔ucture includingbainiteina 丘actionofm ーore 山 an95%andsetting,in the sb〔luctuureof
5 山 esurfacelayer 嶺 eaof 山 esteelsheet,abainitePhasetoa 丘action ofless than 80% and
免 rritethat is rich in workabilitytoafractionoflo%ormore.
[CitationList]
[Patent Document]
[0007]
10 [Patent Document l]
JaPanese Unexannined Pa直entAPP1ication,FirstPub1icationNo.2013 ‐133499
[PatentDocument2]
JaPanese Unexannined p副[entAPP1ication,FirstPublicationNo.2012-62558
[NonPatentDocument]
15 [0008]
[Non Patent Document l]
Takallashi et al.,NiPPon SteeIEngineeringCo.,Ltd.Technic 副 Review
"DevelOP]mentofHighstreng 曲 Steels 和 rAutomobiles “,No.378,P.2toP.6,(2003)
[Summary of 山 elnvention]
20 [Problems to be Solved bythe lnvention]
[0009]
However, in recentyears, 山 edemandfors 立engthandbendingworkabilityhas
beenintensifying,anditcannotbesaid 山 atbol山 stren停 handbendingworkability czm be
sufficiently satis行ed bythetechniquesofPatentDocuments l and2.
25 [0010]
3
ThepresentinventionisprovidedinavarietyofFormstobedescribed below
basedon 山 eabove ‐describedstudies,andano 覇 ectiveofthepresent invention is to
provideahigh ‐streng山 steelsheethavingatensiles 口en蝉 lof590Mpaormore and
exception 副 bendingworkability
5 Thebendingworkabilitymentionedabovere6erstoanindex indicating how
difficultacrackisinitiatedinaworkingpodionduringbendingotanindex indic砥ing
how difficultl山ecrackgrows. However,unlike 山 erelatedall,in 山 epresentinvention,
not only crachngthat occuurs丘om 山 eoutsideofabentpon[iona 賃二erbending but also
cracking includingmicrocracks 山 atareinitiatedon 山 einsideof 山 ebentponion(inside
lo bend cracking)arede 副twith.
[Meをmsfo ・Solvingthe Problem]
[ooll]
The present inventors intensively investigated the bending workability ofhigh ‐
sせengdlsteel sheets.Asaresult,itwascl 嶺 i6ed 山 m,asthestreng 山 ofa steel sheet
15 increases, cracks are mote likely tobeinitiatednotonlyfrom 山 eoutsidebend but also
from 山 e inside bend dmingbending. Thatis,leg 嶺 dingcrackingoccurring dming 山 e
bendingofasteelsheet,intherelatedmt,itisusualthatcracksm einitiated 丘om 山 e
surface ofthe steelsheetor 山 evicinityof 山 eend suurfaceintheoutside bend, but itwas
found 山 at,inassociationwith 山 ehigh-s せengtheningofsteelsheet,there is a case where
20 microcracksareinitiatedin 山 einsidebend(hereinaaer,crachngwhere cracks are
initiated丘om 山 eoutsidebendwillbereIR}rredtoasoutsidebendcracking,and cracking
where cracks are initiatedfrom 山 einsidebendwillbere 化 rredtoasinside bend
cracking). Anyme 山 ods folsuppressingsuchoutsidebendcrac 蛭 ngandinside bend
cracking atthe same time have not been Found in therelateda 」rt.
25 ln addition, itwas Found fromthe presentinventors'studiesthminside bend
4
cracking occurs in steel sheets havingatensile s口engdlof590Mpaormore
[0012]
As described above, in orderto improvethe bendabilityofhigh ‐sせengdlsteel
sheets, 山 ereisaneedtosuppressoutsidebendcrackingandinsidebendcracking. The
present inventors presumedthat 山 emechanismof 山 einitiationof 山 eabove ‐described
outside bend cracking and inside bend cracking is atbFibutedto 山 ebiasofdefiorm 割[ion,
pmd 紙tention to textures and suurfacepropein[ies andseそばchedame1 カーodfiorsuppressing
5
outside bend cracking and inside bendcracking. Asaresult, 山 epresent inventors
Found 山 at,when 山 etexture, 山 edegreeofrandomnessinthesurface propenies and 山 e
degree ofconcentrationofl 山esmfacepropenies arecontrolledat 山 esame time in a steel
sheet having apredetermined chemicalcomposition,itispossibletomanufactme a steel
lo
sheethaving atensile s口en蝉 lof590Mpaormorewhilesecuringbendability
[0013]
The present invention has been made based on 山 eabove ‐described 行ndings,a lld
15 山 e gist ofthe present invention is as Follows.
(1)Ahigh ‐sせengdbsteelsheetaccordingtooneaspectofthepresent invention
contains,as chemicalcomponents,bymass%,C:0.03%too.28%,Si:0.05%to2.50%,
M[n:1.00%to 4.00%,sol.AI:0.001%to2.000%,P:0.100%or less,S:0.020%orless,
N:0.010%or less,0:0.010%orless,Ti:0%too.10%,Nb:0%too.10%,B:0%to
20 0.010%,V:0%to l.00%,Cr:0%to l.00%,N[o:0%to l.00%,Cu:0%to l.00%,Co:0%
to ・. 00%, ＼~: ○%to ・. 00%,Ni: ○%to ・. 00%,ca: ○%to 。・010%,M[g: ○%to 。・010%,
REM: 0% to o.010%, Zr:0%too.010%and a remainder:Feandimpurities,inwhich, in
arange from a surfaceto l/loofasheetthickness inasheetthickness direction, an
average poledensityofanorient 紙iongroup l山 atisanorientationgroup expressed by
25 01=ooto9oqqp=5 び to6 び and 幌 =450intermsofanEulerangle is 1.5orless,an
5
average pole density 。fanorient 砥iongroup2 由ーatisanorient 砥iongroup expressedby
中 =45 ○to85qqp=85 ○to9 び and 幌 =450intern 【・softheEulerangleis1.5ormore,
an s value 山 at indicates a degreeofrandom ーness ofsurfacepropen[ies is 7.5 or less, an E
v副ue thatindicatesadegreeofc 。ncentri紙ion 。f山 esuurfacepropei 直ies iso.04ormore,
5 and atensile sせengdbis590Mpa 。rm 。re
(2)The steel sheetaccordingto(1)mayincludeahot ‐dipgalvanizedlayer on
山 esurface
(3)The steel sheetaccordingto(2),inw hichthehot ‐dipg 副vanizedlayer may
be ahot‐dipgalvannei 副Ledlayer.
10 [EfFects of 山 elnvention]
[0014]
Accordingto the above ‐described aspect ofthepresentinvention,itispossible
to obtain ahigh-s せengl山 steelsheetl 山athas atensiles 立engl山。f590M[Pa 。rm 。re,is
capableofsuppressingoutsidebendcrachngandinsidebendcracking and has
15 exception 副 bendingworkability
[Embodimentforimplementing 山 elnvention]
[0015]
Hereinaaer,asteelsheetaccordingtooneembodimentofthepresent invention
will be describedindetail. Here,thepresentinventionis notlimited only to a
20 con 行guration disclosed in thepresentembodiment,andavarietyofmodi 行cations can be
made wi山 outdepzulingfrom 山 escopeofl 山egistofl 山epresentinvention. lnaddition,
numericalraulges to be described below using “to“includethelowerlimit value and 山 e
upper limit valueintheranges. However,numericalvaluesexpressedwith"morethan “
or “less 山 ad' are not included in 山 enumeric 副 ranges. “% “ regarding 山 eamount of
25 each elementme 鑓ls "mass% “.
6
[0016]
1.ChemicaIComponents
Hereinaaer, the chemicmcomponents(chemici 頭 composition)oflmesteel sheet
accordingtothepresentembodimentwill be describedindetail.The steel siheet
5 accordingto me present embodimentcontains,asmechemical components, basic
elements imd optionalelementsasnecessary,and 中 eremainder includes Fe a11d
lmーpurltles

[CIメAIMS]
1. A high-sせength steel sheet comprising,aschemicalcomponents,bymass%:
C:0.03 。too.28 。;
5 Si:0.05%to2.50%;
M[n:1.00%to4.00%;
sol.AI:0.001%to2.000%;
P:0.100 o orless;
S:0.020%or less;
10 N:0.010%or less;
o:0.010%or less;
Ti:0%too.10%;
ト化 :0% 。too.10% 。;
B:0%too.010%;
15 V:0%to l.00%;
Cr:0%to l.00%;
MIO: ○一明oto l.00 o;
Cu:0%to l.00%;
Co:0%to l.00%;
20 VV:0%to l.00%;
Ni: ○ oto l.00 o;
Ca:0%too.010%;
M[g:0%too.010%;
RE~1:0%too.010%;
25 Zr:0%too.010%;and
43
aremainder:Feandiln ーpurities,
w herein, in arange 丘omasurfaceto l/loofasheet 口lickness in a sheet
山 icknessdirection,anaveragepoledensityofanorientationgroup l 山 atis ian
orient例〔iongroupexpressedby 中1= び to9oqqp=5 〇oto6 び and 幌 =450interms of
5 an Euler angleis l.5orless,anaveragepoledensityofianorientationgroup 2 山 at is ian
orient例〔iongroupexpressedby 中1=45 ○to85qqp=85 ○to9 び and 幌 =450interms of
山 e Euler angleis l.5ormore,
an s value 山 atindic 紙es adegreeofrandomnessofsturfacepropenies is 7.5or
less,
lo an E v副ue that indicates adegree ofconcen 立ationofthesurfacepropen[ies is
o.o4ormore,a ーl d
atensile s立eni夢his590MPaormore.
2. Thehigh ‐sせengdlsteelsheetaccordingtoclaiml,comprising:
15 ahot-dip galvanized layer on the suぱface.
3.Thehigh ‐sせengdlsteelsheetaccordingtoclaim2,
w herein 山 e hot-dip g副vanized layerisahot ‐dipgalvannealedlayer.