[TechnlcaIF1eld]
5 [0001]
The present lnvention relates to a hot‐stampedproduct.
Priority is claimed on Japanese PatentApplication Jo.2020 ‐022634 and
Japanese PatentApplication Jo.2020 ‐022635,6iledinJapanonFebruary 13, 2020, the
contents ofwhich are incorporated herein byreference.
10 [BackgroundArt]
[0002]
Atthepresenttlmewhereindustrialtechnology6eldshavebecome highly
specialized,thereisademandformaterialsthatareusedineach technicaI ‐G eld to have
specialandadvancedperformance. Forexample,thereisademandforsteel sheets for a
15 vehicletohaveahighstrengthinordertoimprovegasmileagebyweight reduction in
vehicle bodies in consideration oftheglobalenvironment. Highstrengthsteel sheets
arecapableofimpartingadesiredstrengthtovehiclebodieswhilereducingthe weights
ofthevehiclebodiesbyreducingthesheetthicknessesofthesteelsheetsinthe case of
being applied to the vehicle bodies ofvehicles.
20 [0003]
However, in pressforming,whichisastepofformingvehiclebody members of
vehicles, cracks and wrin]糧esaremorelikelytobegeneratedasthethic ロlesses ofsteel
sheets tobeuseddecrease. Therefore,excellentpressformabilityis alsorequired for
steel sheetsforavehicle.
25 [0004]
Page 1 of 75
Secure・][lentofpress formability and thehigh ‐strengtheningofsteel sheets are
conflictingelements,andthusitisdi 任iculttosatisfythese characteristics at the same
tlme. lnaddition,whenahighstrengthsteelsheetispressedandamemberistaken out
丑om a die, the shaPe ofthemembersigniG ‐cantlychangesduetosPringback,and thus it
5 becomes di圧icult to secure the dimensionalaccuracyofthemember. Asdescribed
above, ltls not easy to manufacturehigh ‐strengthvehiclebody members by press
formlng
[0005]
Hitherto,asamethodformanufacturingavehiclebodymember having an
lo ultrahighstrength,forexample,atechniqueinwhichaheatedsteelsheetispressed using
alo w‐temperaturepressdieasdisclosedinPatentDocument l hasbeenproposed. This
technique is called hotstamping,hotpressingorthelikeandiscapable ofmanufacturing
amemberwithacomplicatedshapewithahighdimensionalaccuracybypressing a so貴
steel sheet in a state ofbeing heated to a hightemperature. lnaddition,since the steel
15 sheet is rapidly cooled due to the contactwithadie,itbecomespossible to signii‐cantly
increase the strength by quenching at the sametimeasthepressforming. Forexample,
PatentDocument l describesthatamemberhavingatensilestrength of 1400 ハ4Paor
morecanbeobtainedbyhotstampingasteelsheethavingatensilestrength of50o to
600M[Pa.
20 [0006]
Furthermore,as atechniqueformanufacturingahotstampingmember with a
hlgh strength, Patent Document2dlsclosesahotstamp ・ngmemberhav ・ng a tenslle
strength of 1770 to l940 M[Paandamanufacturingmethodthereof,andPatent Document
3 disclosesahotstampingmemberhavingatensilestrengthofl960to2130 M[Pa and a
25 manu 歳 cturingmethodthereof. lnthemethodsdescribedinPatentDocument2and
Page 2 of 75
Patent Document 3, a SteeI SheetforhotStall.pingisheatedtoatwophase region of
篤菖ite and austeniteandthenhot ‐StampedtoformacompositeStructureof 篤菖ite and
martenSite having an average grain diameterof7 LLm 。rlessasthemicroStructure ofa
hot Stamp・ng member,therebyenhancingtheductility 。ftheSteeISheetthat coni‐guresa
5 member.
[0007]
PatentDocument4discloseSatechniqueformanufacturingahotStamping
member having excellent toughness and a tensileStrength 。f1800 ハ4Pa or more. ln a
method described in PatentDocument4,aSteeISheetforhotStampingisheated to a
lo lo w‐temperatureregion 。faustenite,then,hot ‐StampedandrelativelyS1owly cooled in a
temperature range oftheNISpointorlo wer,therebyformingamicroStructure formed of
temperedmartenSitehavingaprioraustenitegrainSizeofloumor less and enhancing
thetoughnessofamember. ThetechniquedisclosedinPatentDocument4iscapable of
obtaining a 1800 M[Pa‐class hot Stampingmemberinwhichcrac] 桓ngdoesnot occur even
15 in a lot‐temperature impact teStandisthusexcellent.
[C1tat・onL1st]
[Patent Documents]
[0008]
[Patent Document l]
20 Japanese Unexamined PatentApplication,FirstPublicati 。n Jo.2002 ‐102980
[PatentDocument2]
Japanese Unexamined PatentApplication,FirstPublicati 。n Jo. 2010‐65294
[PatentDocument3]
Japanese Unexamined PatentApplication,FirstPublicati 。n Jo.2010 ‐65295
25 [PatentDocument4]
Page 3 of 75
Japanese Unexamined PatentApplication,FirstPublication Jo.2006 ‐152427
[Summaryoftheinvention]
[Problems to be Solved by the lnvention]
[0009]
5 However, according to the present inventors,studies,itwasfound that,inthe
hotstamp ・ngmemberscomposedofacompositestructureoffeniteandmartensite as
descrlbed ln Patent Documents2and3,whenthememberdlstortsuponacolllslon,there
is a case where cracking occurs 丑om 篤 rriteasthestartingpointintheinitial phase ofthe
distortion, and, in particular, whenthetensilestrengthofthememberexceeds2300M[Pa,
lo itbecomes di圧icult to secure thecollisionsa 篤 tyofvehiclebodies.
ln addition,PatentDocument4describesnothingaboutamember having a
tensile strength of2300 ハ4Paormore. Accordingtothepresentinventors'research, it
was found that, even in a hot stampingmemberformedofasingle ‐phase structure of
tempered martenslte as described inPatentDocument4,ifthetensilestrength is
15 increasedupto2300M[Paormore,particularlyinacasewheretheforming temperature
during the hot stampingofasteelsheetislow,alocaln ‐uctuationinhardnessiscaused in
the member,andastrongrequ ・rementforcrashworthinessofthesedays cannot be
suf1Eicientlymet. lnaddition,itwasfoundthatsuchalocaln ‐uctuationinhardness is
largeparticularlyinacasewhereamaterialsteelsheetforhotstampingisaplated stee1
20 sheet.
[0010]
As described above,intherelatedart,itwasdifficulttomanufactureamember
having a tensile strength of2300M[Paormore,particularly,ahotstampingmember
(節 rmedarticle)havingexcellentcrashworthinessandatensilestrength of2300 Mpa or
25 morebyhotstamping.
Page 4 of 75
[0011]
Ano 朝 ective ofthe Present invention is to solve the above ‐described Problems
andtoProvideahot-stampedProducthavingaPortionwithexcellentcrashworthiness
and a tensile strengthof2300 ハ4Paormore.
5 [Means 節 rsolvingtheProblem]
[0012]
The Present lnvention has been made to solve the above ‐describedProblems,
and the gist ofthe present invention is the following hot‐stampedProduct.
[0013]
10 (1)Ahot ‐stampedProductaccordingtooneaspectofthepresent invention is a
hot‐stamped Product includingasteelsheet,inwhichallorpartofthesteel sheet has a
chemicalcomPos ・tlonof,bymass%,C:morethano.40%ando.70%orless,Si:less than
2.00%, M[n: 0.01% or more and lessthano.50%,P:0.200%orless,S:0.0200%orless,
sol.AI:0.001% to l.000%, N: 0.0200%or less,M[o:0.01%ormoreandlessthano.50%,
15 B:0.0002%too.0200%,Ti:0%too.200%,Nb:0%too.200%,V:0%too.200%,Zr:0%
too.200%,Cr:0%to2.00%,W:0%to2.00%,Cu:0%to2.00%,Ni:0%to2.00%,Ca:
0%too.0100%,M[g:0%too.0100%,RE]M:0%too.1000%and Bi:0%too.0500%with
a remainder ofFe and imPurltles,ata l/4depthPosltlonofasheet thickness 丑om a
surface ofthesteelsheet,amicrostructurecontains,byvol%,more than 9〇・〇%of
20 martenslte,theaveragevalueofVickershardnessinaregionthat is o.3 mm in a sheet
thicknessdirectionando.6mminadirectionorthogonaltothesheetthickness direct・on
is 670 or more, the standard deviation ofthe Vickershardnessintheregionis20orless,
and the tensile strength is 2300 ハ4Paormore.
(2) lnthehot ‐stampedProductaccordingto(1),theyieldratio may be o.65or
25 more ・
Page 5 of 75
(3)Ahot ‐stampedproductaccordingtoanotheraspectofthepresent invention
includingasteelsheetandaplatinglayerformedonasurfaceofthesteel sheet, in which
all or part ofthe steel sheet hasachemicalcomposlt ・onof,bymass%,C:more than
o.40%and o.70% or less, Si: lessthan2.00%,M[n:0.01%ormoreandlessthano.50%,
5 P:0.200%or less, S:0.0200%orless,sol. AI:0.001%to l.000%,N:0.0200%orless,
M[o:0.01%or more and less than o.50%,B:0.0002%too.0200%,Ti:0%too.200%,Nb
o%too.200%,V:0%too.200%,Zr:0%too.200%,Cr:0%to2.00%,W:0%to2.00%,
Cu:0%to2.00%,Ni:0%to2.00%,Ca:0%too.0100%,M[g:0%too.0100%,RE]M:0%
too.1000%and Bi: 0% to o.0500% with a remainderofFeandimpurlt ・es,ata l/4 depth . ・
1o position ofa sheet thic messofthesteelsheet 丑omaninterfacebetweenthe steel sheet
and the platinglayer,amicrostructurecontains,byvol%,morethan90.0% ofmartensite,
an average value ofVickers hardness in a region that is o.3mminasheet thickness
directionando.6mminadirectionorthogonaltothesheetthickness direction is 670 or
more, the standard deviation ofthe Vickers hardnessintheregionis20orless,thetensile
15 strength is 2300 ハ4Paormore,andtheyieldratioiso.65 ormore.
(4)Thehot ‐stampedproductaccordingtoanyoneof(1)to(3)may contain, in
the chemicalcompos ・tlon,bymass%,oneormoreselected 丑omthegroup consisting of
Ti:0.001%too.200%,Nb:0.001%too.200%,V:0.001%too.200%andZr:0.001%to
o.200%
20 (5)Thehot ‐stampedproductaccordingtoanyoneof(1)to(4)may contain, in
the chemicalcompos ・tlon,bymass%,oneormoreselected 丑omthegroup consisting of
Cr:0.001%to2.00%,W:0.001%to2.00%,Cu:0.001%to2.00%and Ni:0.001%to
2.00%
)Thehot ‐stampedproductaccordingtoanyoneof(1)to(5)may contain, in
25 the chemical composition,bymass%,oneormoreselected 丑omthegroupconsistingof
Page 6 of 75
Ca:0.0001%too.0100%,M[g:0.0001%too.0100%and RE]M:0.0001%too.1000%
(7)Thehot ‐stampedproductaccordingtoanyoneof(1)to(6)may contain, in
the chemicalcompos ・tlon,bymass%,Bi:0.0001%too.0500%
[Eぼects ofthe lnvention]
5 [0014]
According to the aspect ofthe present invention,itispossilbletoobtain a
hot-stamped product excellent ln crashworth ・nessandhav.ngaport.on.nwhlch a tenslle
strengthof2300 ハ4Paormore.
[BriefDescription ofDrawings]
10 [0015]
Fig.l isaschematicviewshowinghardnessmeasurement posltlons ln a
hot‐stamped product
Fig. 2 is a schematic view showing an example ofashapeofthehot ‐stamped
product.
15 Fig. 3 is a schematic view showing a shape ofathree ‐pointbendtestbody.
Fig.4 is a schematic view showing the dispos・tlonofatesterandthe test body
in thethree‐pointbendtest.
[Embodiment ofthe lnvention]
[0016]
20 Thepresentinventorsintensivelystudiedamethodforsuppressing the
occu]ばence ofcracldngwhenahot ‐stampedproducthavingatensilestrength of2300
M[Pa or more distorts duetoacollision. Asaresult,thefollowingG ‐ndings were
obtained.
[0017]
25 (A)ln the hot‐stampedproducthavingatensilestrengthof2300 Mpa or more,a
Page 7 of 75
local ‐n uctuationinhardness is large
Thereasonthere 節 risnotclear,butisassumedthat(a)inamaterial be節 re hot
stamPing that is to have a tensile strengthof2300MPaormorea 貴erhotstamPing (steel
sheet 節 rhotstamping), thelocalunevenness intheMnorMoconcentrationislarge,(b)
5 ln a port・on with a low M[nor]Moconcentration,amicrostructure with a high 篤菖ite
fraction is exhibited in the steel sheetforhotstamping,austenitecoarsensinthis portlon
・n a process ofheating the steel sheet forhotstamping,andthehardnessislikely to
become low ・na 節 rmedarticlea 貴erhotstamping(hot ‐stampedproduct),and(c) on the
other hand,inaport ・onwithahigh ハ4nor ハ4oconcentration,amicrostructure with a
lo highpearlite 丑actionisexhibitedinthesteelsheetforhot stamping, austenite is reG‐ned
in this portion in the process ofheating thesteelsheetforhotstamping,andthe hardness
is likely to become high in the formedarticlea 貴erhotstamping
[oo18]
(B)As thelocaln ‐uctuationinhardnessinthehot ‐stampedproductincreases,
15 crackingismorelikelytooccurintheinitialphaseofdistortionwhentheformedarticle
distorts. This is considered to be because stressconcentrates ・n a port・onwithalow
hardness
[ool9]
)ln a hot‐stampedproducthavingaplatinglayeronthesurface,aloca1
2o ‐n uctuationinhardnessislikelytobecomelargecomparedwithacasewhere the
hot‐stamped product does not have the platinglayer. Thereasonthereforisnotclear,
but is assumed that(a)then ‐uctuationinhardnessbecomessmallerasthestrain energy
accumulating in thesteelsheet 節 rhotstampingbecomeshigherand(b)inaplated steel
sheet that is manufactured through an annealingstep,thestrainenergy accumulated
25 duringhotrollingisreleasedduringannealing
Page 8 of 75
[0020]
(D)Whenasteel sheetmanu 危 cturedwithoutannealinga 貴eracold rolling step
(alsorefenedto as asteel sheetascoldrolledor 和 1lhard)isusedasthesteel sheet 節 r
hotstall・ping,theoccun enceofcrack]nguponthedistortionofaformed article is
5 suppressed.
The reason there節 r isnotclear,butisassumedthat(a)inthesteel sheet as cold
rolled, since processing strain duringcoldrollingaccumulates,austeniteisreG ‐ned in a
process ofheating the steel sheet for hot stamping,andthehardnessofahot ‐stamped
product increasesand(b)thise ぼectisstronginaportionwith a low Mn or Mo
lo concentrationandtheuseofthesteelsheetascoldrolleddecreasesthelocal ‐n uctuation
inhardnessinthehot ‐stampedproduct.
[0021]
(E)ln a step ofcanying out hot stamping,whenatemperatureatwhich the hot
stamping is started(和 rmingstarttemperature)isincreased,theoccunenceofcracking
15 upon the distortion ofthe formed article is suppressed.
The reason there節 r isnotclear,butisassumedthat(a)inthesteel sheet 節 r hot
stamping, in aportioninwhichthe ハ4nor ハ4oconcentrationishigh,strainismore likely
to accumulate in austenite during hotstamping,andthehardnessbecomes higherinthe
hot-stampedproductand (b) whenhotstampingiscaniedoutatahightemperature,
20 accumulation ofstrain in austenite is suppressed,andthehardnessofthehot ‐stamped
product becomes low, but this e窟ectis strongerinaportionwithahighM[nor]Mo
concentration than in a portion with a low M[nor]Moconcentration,and thus hot
stamping at a high temperature decreasesthelocaln ‐uctuationinhardness in the
hot‐stampedproduct.
25 [0022]
Page 9 of 75
(F)When a reheating treatment is canied out on the hot‐stamped product at a
lowte1][IPeraturea 貴erhotstannPing,theoccurrenceofcrack1nguPonthedistortion ofthe
formed articleis suppressed.
The reason there節 r isnotclear,butisassumedthat(a)thereheating decreases
5 theamountofcarbonpresentinasolidstateinmartensiteanddecreasesthehardness of
the hot‐stampedproductand(b)thise ぼectisstrong ln a port・on with a high Mn or Mo
concentratlon,andthereheatingtreatmentdecreasesthelocaln ‐uctuationinhardness in
thehot ‐stamped product
[0023]
lo From the above ‐G ndings(A)to(F),thepresent inventors 節 undthat,whena
steel sheet as cold rolled is used as a material steel sheet,andthesteelsheetas cold rolled
is heated and then hot stamping is started at a hightemperature,ltlspossible to
manufacture a hot-stampedproductinwhichthetensi.estrengthis2300 ハ4Paormore,
the local nuctuation in hardness is small and the crashworthiness is excellent.
15 A1ternative1 itwasfoundthat,eveninacasewhereaplatedsteel sheet is used
as a material steelsheet,whenaplatedsteelsheetisheated,then,hotstampingisstarted
at a high temperature,and,a 貴erthehotstamping,areheatingtreatment is ca菖ied out at a
low temperature,ltlspossibletomanufactureahot-stampedproducthavingaplating
layer on a surface in which thetensi.estrengthis2300 ハ4Paormore,alocal nuctuation
2o in hardness is small and the crashworthinessisexcellent.
Hereina 貴er, each requirementofahot ‐stampedproduct according to one
embodimentofthepresentinvention(thehot ‐stampedproductaccordingtothepresent
embodiment) andamanu 危 cturingmethodthereofwillbedescribedindetail.
[oo24]
25
Page 10 of 75
AI1 or part ofa steel sheet included in the hot‐stampedproduct according to the
present embodimenthasachemicalcompos ・tlonshownbelow(inacasewhere the
hot‐stamped product ・sconsistingofasteelsheet,anorpartofthehot ‐stamped product
can be said to have achemicalcompos ・tlonshownbelow). Thereason 節 rlimiting each
5 element is as describedbelow. “% “regardingcontentsinthefollowingdescription
means “mass%''. ln addition,numericalvaluerangesshownusing “to“ include
numer ・cal values at both endslntheranges. ontheotherhand,numer ・calvalues shown
using ‘‘lessthan “ or “morethan “ donotincludethenumericalvaluesinthe ranges
ln a case wherethehot ‐stampedproductincludes aportion having a tensile
lo strengthof2300 ハ4Paormoreandaportionhavingatensilestrengthofless than2300
Mpa(inacasewherethe steelsheetincludedinthehot ‐stampedproduct according to the
presentembodimentincludesaportionhavingatensilestrengthof2300 ハ4Pa or more
and a portion having a tensile strength oflessthan2300Mpa),atleastthe portion where
the tensile strengthbecomes2300 ハ4Paormoreneedstohavethefollowing chemical
15 composition
ln a case wherethehot ‐stampedproductlncludes asteel sheet and a plat・ng
layer formed on a surfaceofthesteelsheet,thechemicalcompos ・tlontobedescribed
below means the chemicalcompos ・・t onofthesteelsheetexcludingtheplating layer
[0025]
2〇 C: ハ4ore than 〇・4〇%and 〇・7〇%or less
Cisanelementhavinganeffectonanincreaseinthetensilestrength ofthe steel
sheet a貴er hot‐stamping(thesteelsheetincludedinthehot ‐stampedproduct). When
thec contentiso.4 〇%orless,thetensilestrengthofthehot-stamped product sheet
becomeslessthan2300M[Pa,andthestrengthoftheformedarticlebecomes insu甘icient
25 Therefore,theCcontentis settomorethano.40%. Thepre 篤 rableCcontentismore
Page 11 of 75
than o.42%, more thano.43%,morethano.44%ormorethano.45%.
on the other hand フvhen the c contentexceedSO.70%,the Strength ofthe
hot‐stamped productbecomestoohigh,anditbecomesimpossibletosecure the
crashworthineSS. Therefore,theCcontentis settoo.70%orless.The pre篤 rable C
5 contentiSO.65%orless,0.60%orless,0.55%orlessoro.50%orless.
[0026]
Si:Less than 2.00%
Si is an element that is contained in Steel as an impurity and embrittleS Steel.
VVhen the si content becomes 2.〇〇%ormore,theadverseinnuenceofSibecomes
lo particularlylarge. Therefore,thesicontentis setto.eSSthan2.00%. Thepreferable
Si content is leSs than l.50%,lessthan l.00%,lessthano.75%orlessthano.50%.
From the viewpoint ofsecuring the plateability,thesicontentispreferablySetto 〇.4〇%
or less, 0.30% or lessoro.20%orless.
The lower limit ofthe si content is not particularly limited,butanexcessive
15 decrease in the si content increases the Steelmakingcost. Therefore,thesicontent is
preferablySetto 〇0 〇1% ormore. 1naddition,Sihasanaction ofenhancing the
hardenability ofSteel and thus may beactivelyincorporated. Fromthe viewpoint of
lmproving thehardenability,thesicontentispre 篤 rablyo.10%ormore,0.20%or more
or o.30%ormore.
20 [0027]
M[n:0.01%or more and less than o.50%
M[n is an element that degradeS the crashworthiness ofthe hot‐Stampedproduct.
W/hen the M[n content iS O.50%ormore,thecrashworthineSssignii ‐cantlydeteriorates,
anditbecomesimpossibletoSecurethecrashworthinessoftheformedarticleeven in the
25 case ofapplying a manufacturing methodofthehot ‐Stampedproducttobedescribed
Page 12 of 75
below. Therefore, theハ4n content is settolessthano ・50%. The ハ4ncontent is
pre篤 rablylessthano.45%,lessthano.40%,lessthano.35% 。rlessthano.30%.
on the other hand, ハ4n is an elementthatbondsto s,which is an llnpurlty, to
form M[nS and has an actionofsuPPressingtheharmfule ぼectofs. lnordertoobtain
5 this eぼect, the M[n contentissettoo.01%ormore. TheM[ncontentisPreferablyo.05%
or more or o.10%ormore. lnaddition,M[nisanelementthatimproves the
hardenability ofsteel. From the Viewpointofimprovingthehardenability,the ハ4n
content ・spre 篤 rablyo.15%ormore,0.20%ormoreoro.25%ormore.
[0028]
1O P:0.200% 。r less
Pis an element that is contained in steel as an impurity and embrittlessteel.
vvhen the p content exceeds o.200%,theadverseinnuence 。fpbecomes particularly
large,andfurthermore,theweldabilitysigni]6Lcantlydeteriorates.Therefore, the p
content ・s set to 〇.2〇〇%orless. ThepreferablePcontentislessthan 〇.1〇〇%,lessthan
15 〇・〇5〇% 。r less than 〇・〇2〇%. Fromtheviewpoint 。fsecuringtheplateability, the p
content ・spre 篤 rablylessthano.020%,lessthano.015% 。rlessthano.010%.
The lower limit ofthe p content is not particularly limited,butanexcessive
decrease in the p content increase the steelmakingcost. Therefore,thepcontent maybe
settoo.001%ormore.
20 [0029]
S:0.0200% 。r less
S is an element that is contained in steel as an impurity and embrittlessteel.
vvhen the s content exceeds o.0200%,theadverseinnuence 。fsbecomes particularly
large. Therefore,thes contentis settoo.0200%orless. Thepre 篤 rableScontent is
25 1ess thano.0050%,lessthano.0020% 。rlessthano.0010%.
Page 13 of 75
The lower limit ()fthe s content is not particularlylimited,butanexcessive
decrease in the s content increase the steelmakingcost. Therefore,thescontent may
besettoo.0001%ormore.
[0030]
5 sol.AI:0.001%to l.000%
A1 is an element having an action ofdeoxidizing molten steel. W/henthesol.
A1content (acid‐solubleA1content)islessthano.001%,deoxidationbecomes
・nsu 圧icient. Therefore,thesol.A1contentissettoo.001%or more. The sol. A1
content ・spre 篤 rablyo.005%ormore,0.010%ormoreoro.020%ormore.
lo on the other hand, whenthesol.A1contentistoohigh,the transformation point
increases,anditbecomes di任iculttoheatthesteelsheettoatemperatureexceeding the
Ac3 po・nt ln a heatingstepofhotstamping. Therefore,thesol.A1 content is set to
l.ooo%orless. Thesol.A1content ・spre 篤rablylessthano.500%,lessthano.loo%,
less than o.o60% 。rlessthano.o40%.
15 [oo31]
N:o.o200%or less
Jisanelementthatiscontainedinsteelasanimpurityand forms a nitride
during the continuouscastingofsteel. Sincethisnitridedegrades the ductility ofthe
hot‐stampedproductsheet,theNcontentispre 篤 rablyaslowaspossible. W/hen the N
20 content becomes morethano.o200%,theadverseinn ‐uence 。fsibecomes particularly
large. Therefore,theNcontentissettoo.o200%orless. TheNcontent is pre篤 rably
lessthano.oloo%,lessthano.oo80% 。rlessthano.oo50%.
The lower limit ofthe N content is not particularly limited,butanexcessive
decrease in the N content increase the steelmakingcost. Therefore,the Jcontent may
25 besettoo.oo10%ormore.
Page 14 of 75
[0032]
M[o:0.01%or]more and less than o.50%
ハ4oisanelementthatinnprovesthehardenabilityofsteelandaneffective
element for securing the strengthofthehot ‐stampedproductbyformingamicrostructure
5 mainly containing martensite. mordertoobtainthise ぼect,theM[o,content is set to
o.01%ormore. Thepre 篤 rableM[ocontentiso. ○5%ormore,0.10%ormoreoro.15%
or nnore
on the other hand, ハ4oisanelennentthatdegradesthecrashworthiness ofthe
hot-stannpedproduct. VVhenthe ハ40contentiso.5 〇%ornnore,thecrashworthiness
lo signii‐cantly deteriorates, and itbecomesimpossibletosecurethecrash worthiness ofthe
formed article even in the case ofapplying the manufacturing methodofthehot ‐stamped
product to be described below. Therefore,the ハ40contentis settolessthan 〇.5〇%
TheM[o content ・s pre篤 rablylessthano.40%,lessthano.35%orlessthano.30%
[0033]
15 B:0.0002%too.0200%
B is an element that improves the hardenability ofsteel and an e錐ectiveelement
forformingamicrostructuremainlycontainingmartensiteandsecuringthestrength of
the hot‐stampedproduct. mordertoobtainthis eぼect,theBcontentissettoo.0002%
or more. The preferable B contentiso.0006%ormore,0.0010%ormoreoro.0015%
20 or more.
on the other hand,inacasewheretheBcontentexceeds o.0200%, a
carboboride isfornned,andtheeffectofBcontainedontheinnprovennent in the
hardenabilityisinnpaired. Therefore,theBcontentis setto 〇・〇2〇〇%or less. The
pre篤 rable B content islessthano.0050%,lessthano.0040%orlessthano.0030%
25 [0034]
Page 15 of 75
The hot‐stampedproductaccordingtothepresentembodiment may have a
chemical compositionincludingtheabove ‐describedchemical components with a
remainder ofFe and impurlt・es;however,inordertoimprovecharacteristicsorthelike,
the hot‐stampedproductaccordingtothepresentembodimentmayfurther contain one or
5 more selected 丑omthegroupconsistingofTi,Nb,V,Zr,Cr,W,Cu,Ni, Ca, M[g, RE]M
and Bi. These elements(optionalelements)donotneedtobecontainedatalltimes,
and thus the lower limits are o%.
Here, the “impurity “means a componentthatismixedin 丑omarawmaterial
suchasoreorascraporduetoavarletyoffactorsinmanufacturingstepsatthetime of
lo industrially manufacturing the steel sheet and is allowed to an extent thatthehot ‐stamped
product according to the present embodiment is not adversely affected.
[0035]
Ti:0%too.200%
Nb:0%too.200%
15 V:0%too.200%
Zr:0%too.200%
Ti,Nb,VandZrareelementshavinganactionofimproving the
crashworthinessofthehot ‐stampedproductbythereG ‐nementofthemicrostructure. ln
order to obtain thiseffect,oneormoreselectedfromthegroup consisting ofTi, Nb, V
20 and Zr may be containedasnecessary.
ln the case ofhoping to obtain the above ‐describedeffect,the amount ofeach of
one or moreselected 丑omthegroupconsistingofTi,Nb,VandZrcontained is
pre篤 rablyo.001%ormore,morepreferablyo.005%ormoreandstillmore pre篤 rably
o.010%ormore.
25 0n the other hand, in a case where theamountofeachofTi,Nb,VandZr
Page 16 of 75
exceedS 0・200%, the above-descrilbedeffectis Saturated,andthusthemanufacturing cost
ofthe SteeISheetincreases. Therefore,inthecase 。fbeingcontained,the amount of
each ofTi,Nb,VandZris sett。 o.200% 。r less
ln a casewheretheam ー。untofTi,Nb,VandZrislarge,alarge amー。unt of
5 carbideS ofthese elements areprecipitated,andtheductility 。fthehot ‐Stamped product
Sheet is imPaired. From the viewPointofsecuringtheductility,thePre 篤 rable Ti
content is leSsthan0 ・〇5〇% 。rlessthan 〇・〇3〇%,thepreferableNbcontent is leSs than
〇05 〇%,lessthan 〇・〇3〇% 。rlessthan 〇・〇2〇%,thepreferableVcontent is leSs than
o,100% 。r lessthano.050%andthepre 篤 rableZrcontentisleSsthano.100% 。rless than
lo o.050%.
[0036]
Cr:0%to2.00%
W:0%to2.00%
Cu:0%to2.00%
15 Ni:0%to2.00%
Cr,W,Cu and Ni are elementS having an action 。fenhancingthehardenability
ofSteel. Therefore,one 。rmoreselected 丑 omthegroup consisting ofCr,W,CuandN
‐
i
maybecontainedasnecessary
ln the case 。fhopingtoobtaintheabove ‐describede 錐ect,the amount ofeach of
20 0ne or moreselected 丑omthegroupconsistingofCr,W,CuandNicontained is
Pre篤 rablyo.001%ormore. Amorepre 篤 rableCrcontentiSO.05%ormoreoro.10%
or more, a more pre 篤 rable WcontentiSO.05%ormoreoro.10% or more, a more
preferableCucontentiSO.1 〇%ormoreandamorepreferableNicontent iS O.1〇%or
lnore
25 0n the other hand,whentheamountofeachofCr,VV,CuandNiexceedS2.00%,
Page 17 of 75
the crashworthiness ofthe hot-Stampedproductdeteri 。rates.Therefore, in the case 。f
beingcontained,theamountofeachofcr,VV,CuandNiis setto2. 〇〇%or less. The
pre篤 rable Cr content islessthano.50%,lessthano.40% 。rless than o.30%, the
pre篤 rable wcontentislessthano.50%,lessthano.40% 。rless than o.30%, the
5 preferable Cu content islessthan1. 〇〇% 。rlessthan 〇.5〇%andthepreferableNicontent
ls less than l.00% 。rlessthano.50%
[0037]
Ca:0%too.0100%
N[g:0%too.0100%
1O RE]M:0%too.1000%
Ca,M[g and RE]Mareelementshavinganactionofimprovingthe ductility。fthe
steel sheet a貴erhot‐stampingbyadjustingtheshaPeofaninclusion.Therefore, Ca, Mg
and RE]M maybecontainedasnecessary. lnthecaseofhopingtoobtain the
above ‐describede ぼect,theamountofeachof 。neormore selected 丑om the group
15 consistingofCa,M[gandREM[containedispreferablyo.0001%ormore.
on the other hand, in a casewheretheCaor]Mgcontentismorethano.0100%
or the RE ハ4 content is more thano ・1000%,notonlyistheabove-described effect
saturated, but an excessivecostisalsocaused. Therefore,inthecaseofbeingcontained,
the amount ofeach ofca and A4g is set to 〇.〇1〇〇%orless,andtheREA4content is set to
2〇 〇.1〇〇〇%orless.
[0038]
lnthepresent embodiment,REMre 篤 rstoatotalof17elements ofsc,Y,and
lanthan 。ids,andtheRE ハ4contentmeansthetotalamountofthese elements
lndustrlally,lanthan 。idsareaddedinamischmetal form
25 [0039]
Page 18 of 75
Bi:0%too.0500%
Biisanelementhavinganactionofimprovingthecrashworthiness ofthe
hot‐stampedproductbyrei ‐ningasolidii ‐cationstructure.Therefore, Bi may be
contained as necessary. lnthecaseofhopingtoobtaintheabove ‐described eぼect, the
5 Bi contentispre 篤 rablyo.0001%ormore. Amorepre 篤 rableBicontent is o.0003%or
moreoro.0005%ormore.
on the other hand,inacasewheretheBicontentexceeds o.0500%, the
above ‐describede ぼ ectis saturated,andanexcessivecostiscaused.Therefore, in the
case ofbeingcontained,theBicontentis settoo.0500%orless. Amorepre 篤 rable Bi
lo contentiso.0100%orlessoro.0050%orless.

[CLA1MS]
W/hat is clai宜led is
l. Ahot ‐stamped product comprlslng
asteel sheet,
5 wherein all or part ofthe steel sheet has a chemical con[lposltlonof,
by mass%,
C:more than o,40% ando,70%orless;
Si:less than 2.00%;
ハ4n: ○.01%orr エーore and 1ess than o.50%;
10 P:0.200%or less;
S:0.0200%or less;
sol.AI:0.001%to l.000%;
N:0.0200%or less;
Mo:0.01%or more and less than o.50%;
15 B:0.0002%too.0200%;
Ti:0%too.200%;
Nb:0%too.200%;
V:0%too.200%;
Zr:0%too.200%;
20 Cr:0%to2.00%;
V :0%to2.00%;
Cu:0 oto2.00 。;
Ni:0%to2.00%;
Ca:0%too.0100%;
25 N[g:0%too.0100%;
Page 71 of 75
‐R E]M:0%too.1000%;and
Bi:0%too.0500%
with a remainder ofFe and impurlt・es,
at a l/4 depth pos・tlon ofa sheet thickness from a surface ofthesteelsheet,
5 a microstructure contains,byvol%,morethan90.0%ofmartensite,
an average value ofVickers hardness in a region that is o.31nnn in a sheet
thickness directionando.61nminadirectionorthogonaltothesheetthickness direct・on
is 670 or l][lore,a standard deviation ofthe Vickers hardnessintheregionis20orless,
and
lo atensllestrengthls2300 ハ4Pa or l][lore
2. The hot‐stampedproductaccordingtoclaim l,
whereinayieldratio is o.65 ormore
15 3. Ahot ‐stampedproductcomprising
asteel sheet; and
a plating layer formed on a surface ofthesteelsheet,
wherein al. or part ofthe steel sheet hasachemica.compos.tlonof,
by mass%,
20 C:more than o.40% ando.70%orless;
Si:less than 2.00%;
ハ4n: ○.01%orr エーore and 1ess than o.50%;
P:0.200%or less;
S:0.0200%or less;
25 sol.AI:0.001%to l.000%;
Page 72 of 75
N:0.0200%or less;
ハ40: 。・01%orr エー。re and 1ess than o.50%;
B:0.0002%too.0200%;
Ti:0%too.200%;
5 Nb:0%too.200%;
V:0%too.200%;
Zr:0%too.200%;
Cr:0%to2.00%;
V :0%to2.00%;
10 Cu:0%to2.00%;
Ni:0%to2.00%;
Ca:0%too.0100%;
N[g:0%too.0100%;
‐R E]M:0%too.1000%;and
15 Bi:0%too.0500%
with a remainder ofFe and impurlt・es,
ata l/4 depth pos・tlonofasheetthicknessofthesteelsheetfrom an interface
between the steel sheet and theplatinglayer,
am ・crostructure contains,byvol%,morethan90.0%ofmartensite,
20 anaveragevalueofVickershardnessinaregionthat is o.3 mm in a sheet
thicロlessdirectionando.6mminadirectionorthogonaltothesheetthickless direct・on
is 670 or ]more, a standard deviation ofthe Vickers hardness intheregionis20orless,
and
a tensile strength is 2300 ハ4Paorl][lore,andayieldratioiso.65 orl][lore.
25
Page 73 of 75
4. The hot‐stamped product according to any one ofclaims l to3,comprising, in the
chemical compos ・tlon,bymass%,oneormoreselected 丑omthegroupconsistingof:
Ti:0.001%too.200%;
Nb:0.001%too.200%;
5 V:0.001%too.200%;and
Zr:0.001%too.200%
5. The hot‐stamped product according to any one ofclaims l to4,co]mprlslng, ln the
chemicalcompos ・tlon,bymass%,oneormoreselected 丑omthegroupconsistingof:
1O Cr:0.001%to2.00%;
V :0.001%to2.00%;
Cu:0.001%to2.00%;an ‐d
Ni:0.001%to2.00%
15 6. The hot‐stampedproductaccordingtoanyoneofclaims l to 5, comprlslng, inthe
chemicalcompos ・tlon,bymass%,oneormoreselected 丑omthegroupconsistingof:
Ca:0.0001%too.0100%;
N[g:0.0001%too.0100%;and
RE]M:0.0001%too.1000%