HUE027449T2

HUE027449T2 - Nagyszilárdságú és alakíthatóságú szerszámmal melegalakított és/vagy edzett, majd kiválásokkal keményített hengerelt acéllemez

Info

Publication number: HUE027449T2
Application number: HUE11764796A
Authority: HU
Inventors: Olivier Bouaziz; David Barbier; Coralie Jung
Original assignee: Arcelormittal Investigacion Y Desarrollo Sl
Priority date: 2011-09-06
Filing date: 2011-09-06
Publication date: 2016-09-28
Also published as: EP2753723A1; CA2847809C; ES2558110T3; JP2014529688A; EP2753723B1; BR112014005153A2; CN103890213A; WO2013034815A1; US9689050B2; BR112014005153B1; US20150147589A1; RU2014113318A; PL2753723T3; CN103890213B; MA35421B1; CA2847809A1; KR20140048350A; MX2014002694A; MX359260B; KR101485306B1

Description

ROLLED STEEL THAT HARDENS BY ME ASS Of EHLCHHlvnOA AFTER HOT-FORMING AND/OR QUENCH I:N<J Willi A TOOL RATING VERY' HIGH STRENGTH AND DRCTIElTY, AND

m ETHOD FOR M AN UFA€TU R1NG SAME

The présén; invention relates to she fabrication of roiled steel parts haying high mechanical strength ami fortnabi lily properties, in particular alter hid stampfograndfor quenching iist the fool fclfofoal hv aMrdetgpg: teaitreatmefo.

This provision of s strong: material meets the fogfobqutt demand for a redact mu m gteenbouse gas embshms associated with: the increased. foqtnremtmts placed m. automobile safety and the price of fuel These three eotsstfofols hava 1« |foshs4 É#; of land ..motor vehicles to use steels of increasingly high mechsnkss!: strength in: the body so a» to -educe die thickness et «he parts and thus the: weight of the vehicles while maintaining or even improving she mechanical strength performance of the strtsefores, Oentre pillám, bumper crossbars, anti-intrusion parts and other safety parts tap examples of parts flsafc require high mechanical strength to perform their primary Unction and sufficient formability for the shaping of said: part.

The shaping: of steels having high foeehanicai strength requires a well-known sequence consisting of the genesis of a parent phase:; austenite, the: 'transformation of the latter into bamite and/or madcnslte, gad dptiqnaily the adjustment of She mechanical properties and tn particular thohardness of the latter by various test or thetmo-mcchmtical treatments, depending on the Intended Tuncdonal bebay lour of the fsnal pad.

The mechanical behaviour of ntafteusifc: is linked: lit particular to the carbon contem, The higher she carbon concentration in the: martensite, the harder the martensite.

The article entitled ‘Martensite in steel: strength and structure by O. Knmss,: published: in “Materials teepee and Rngrteend#”' A3?t4?| (1^¾ pages dl) to §?·, pwidtea good iliusubtloo of the relationship between: the carbon copfom and the hardness of the martensite, this relationship befog quasbllnear with the square root of the carbon content: as a percentage by weight. Mechanical strengths significantly greater than 1500 MPa can be achieved by the combination of an Increase in dm carbon content and the addition of various elements that hasten by solid solution Or that harden by preelpitatim However, the duett lity of a material that has such high sfomgh is prohibitive for forming a structural pan, so that the most optimal eutefoatfon: fosowu to date eomasis b obtaining the high strength level ones the part has been formed, this forming possibly befog.at hoi forming. it is highly advantageous m have s low strength before foe forming, and thus m Improved ductility tő íucütets the forming.

The approach mentioned above appears: In patent application WGSlMlh 145563 which relates to a steel sheet of very high strength that has excellent ltot processing properties, said sheet comprising, ib % by weight, C: 0.2 to O.S%, Si: 0,01 to 1.5%, Μη: 0,5 to :2.05¾ f: 0J% or less fbnt not 6%), S: 0.035¾ or less (but not ()%}, soluble: AbOJfo or less#m not^),^::0:.6¾ to 11.15¾ and €r; 0.1 todtefofop tenwinter eonslsingof Feand inevitable hnpnritfos. fibs steel sheet has a fonts te strength, measured before: hot forming, of less than: or equal to «00 M Pa, T he sheet is hot-formed and rabidly fooled so as to have a tensile strength greater than or equal to IbOOMfs.

Idowevet, sfe: |p>gf§ eafbett: described in this dccumerd (0.2 to 0.5%):» today khowh tö be a suaree ofdi iTcaihes; :ro· tstuts dfspöt welding: tér the body-imwbtíe oí land motor vehicles, dtaf: Is to say íhé sssemfeied structure.

Furthermore, patent appilca;ion W02(K};3oo99 relates te a compositionand a fabricationmethod: tor martensitic stainless Steel products which harden by occipital so?;, the composition of which contains at least U.3% by weight Or and at least 0J% by weight; Mo. the sum of Cr, Nr and Fe exceeding »0%, The mfcmtrwiim. obtains# contains at least MM nmmmM and the steel then undergoes m ageing teafsnent bciwests: 42S and :52:5¾ in order td obtain a pretdpitatids of quasi-crystalline particles. 1'hls material meets: the reqahstneuis of cormsien: resistance, high: sixengtfi and good toughness. The example of the: myeatksa is a steel having a yield strength of 1&2Ö MPa add a total elongation of 6.7% if she material ofelatsed % very strong, with a mechanical strength of around ISÖO MFs, a complete part cannot be formed with:: such: a strong: sheet bseams: it is kndwti that the necessary corollary thereof is, relatively low ductility, which leaves: Hitié robin: for manoeuvre for parts that require formability.

The invention therefore aims to solve the stated problems by proposing a steed which car· easily be whlded under industrial conditions and which has high mechanical strenglh and doctility poprtids <m the part that is hot-stamped after a hardening beat treatment. In order to achieve this*, the invention aims to provide a roiled, steel which, after hot stamping and a precipitation herd treatment, hsa a yield strength greater than or equal to 13db MPa aod -an elongation at break greater titan m erptl to 4%, The Invention also arms to avoid the excessive addition of expensi ve alloy elements in order to obtain these properties.

Is the cdmaxl of the present invention, a blank ntcans the result of the eatting of sr sheet and a pan m eans the result of the stamping of a sheet or of a blank.

Theobject of the invemioh is a rolled steel sheet or blank, the cotnpdsltidn of which comprises, the contents feeing oppressed fey weight: C <(U%C0,5% < Mn < 7%; Ö:J% < Si <&.$%* h,S% < Ti < 2%;. 2% d feli < 7%; ΑΪ < ifel0%; Or < 2%; Cu<2%; Co < 2%; Mo < 255; 510.005¾¾ f <0.03%; NblO.SCk V <0,1%; B < d,905%;N .<&Ι08%, it feeing understood that the contents of silcon nod of titan i um am such thiifo

the remainder of the composition . consisting of iron and inevitable impurities resulting front production. in: one pmferred embodiment, the sheet or the blank has: tfeo following eomppltiun in: percentage fey m$m c IS 0.050%; 3 < Ms < 5%; 1.0 < Si < 3J%; ITS < Ti < 1,5%; 2.3 < fed $&$%1 2:0J8%; Cr <: 1%;

Co fi Cs.05%: Co < 1%; Mo < 205; S $ 0,005%;: P S 0J3%; felb % 0,1%:;; V < rlffo B < 0,00S%; M 1:0,001135, It: feolhgliitdersiood that the contents of silicon and1 of titanium are such that:

me remainder oftbc. cc-mposiitom consisting of fiohand inevitable dftptfljes resulting #om production-

Another object of top :ms<mí\m is a pad Isbncaíéd front a sheet or a blank according to the tpsatkm, the· mkrestouctmc o;f vvldcb comprises at iaasf 9S?i::!;ian«nsit®, apd iftrerípeiállio precipitates dftype Fa/ftSs. to .aim preferred embodiment, the proportion by suiÉt# 4u$a of the ítitárbteialiHtrprecipbátss oft type Fb:jTiSí of the patt ts between 1 and 5%. lo ose preferred apíbodiment the average radios of ihe prseipifaíes is: Irntwceh: i add W nanometres. !íj: sue preferred embodimeaí, the yield strength: of the steel part: Is: greater than ör cpna! te 1390 ;Mf% api tbc eltmphoo at break is greater thsa or etpal to 4%, if# őrse preferred embodiment, the steel part comprises: a coating eosmimog gore, aglne asfby or a «me-based alloy. hi one variant of the Inveodon, the steel part comprises a,.coaling «ost&isisg at-mdshmy so: attsmmmm: alloy or an afunftniftth-bsscd alloy,

Another object of the Invention Is a method of tabneat ftigS steel part, eomprisbrg. the successive steps according to which:: - a rolled steel sheet: having Éh above eomphsitioo is provided, the mlerositecrere of which comprises, to. terms of prepottioft by snriaoe Urea, less than 1% mteripetallic precipitates of type ireyfrSI, thea the sheet is cat :so as to obtain a felsőit that dan optionally be welded. The blank :1s fhssfefeoght to st temperature Ty lor a from s, io a -famm, so that Ihe sínjeidre Of the steel hechmes completely austenitic, 1%e biask is theft optionally removed and hot--stamped: above the lerftpreaftmí bis. The part is cooled In air of % gusftehiftg fa a tool, at a this %&, so as to obtain: art essentlafty martensitic structure from the anstemt ie parent strectssre, the cooling; after the stamping therefore being carried out to a temperature belch* Ms. An “essentially ntarterisitfe0 structure means a structure containing at least 95% martensite. Finally, a heat sreatsneni is carried out so as to precipitate Iniermetaiilcs of type FedfiSi in a proportion by surface area of between i% and 5%, ai the temperature 1¾¾ far a time %.s, so as to harden the part and coh&r thereon die tnechámoai properties intended in the contest of the invention.

Another object of the invention is a method of reprieving a steel part, comprising the successive steps according to which a relied steel sheet having the above composition is provided, the mierestreotufs of which comprises. In rerres of poppreion by snvfees area, less thatt!% imesmetallle precipitates of type Fe^TiSl then the sheet Is cut sons to obtain a blank that can optionally be: welded.The blank is then cold-stamped id order to olftaift a pstt or a preform o f fee intended final part. The part or preform is then heated at a given rate 'Vfi ip a fefftaee at a temperature T? ;for a time so ns to obtain a completely austenitic structure, before heidg optionally removed then hotretainped in order to confer thereon the final: shape. The part is then cooled in ak or by psenching io a tool, at; a irate so as in obtain an esscnilaily tnarisnsitlc stmetwre from the austenitic parent structure, the cooing after the stamping therefore feei ng carried out: to a temperature below Ms. Finally, a heat treatment is carried out so as to precipitate iatetmetahies of type FfeTfSl in a proportion by surface area of between 1% and 5%, at the temperature Τ0Λ lor a lime t0A.. so as to harden the part and confer thereon the meshaniest popertids intended m the contest of the invention.

In one preferred embodiment, the temperature T, Is between TOO and IdOfhC, and more particularly preferably between dp) and 9df)T,

The hold time t, is preferably between 60 and 360 seconds.

The centet rate, .after Ite atatTipbig,· 'V^s· Ty and the sí^ísiΐle 3í;ííϊ?s%fΐίΐ;xeí:oí-í teteporateo H is preferably between iTOfeafei ?0-m fe: ((:!« oarfietdhr embodhnenfe the heal treatment for the precipitation of ietertnmjifes wiil consist m ^«!n:g the part at a given «te V.:: te the íxdd temperature ?pA te a símé m, ásd then cooling íhe part as iktm®. V>sfv. aj-eaier mari: feP* S0: :as te confer thereon the; intended: meehanieai elteraeferistiai, Air eooing is tteaicnkuly preferred- in öáe: prefehte emfeodlmerfe -8i«. hold tentperature %* Is 40Ö and feöíAC, in Me pmteted embodiment, the: hold time 1¾ at Jm Is between 38: and 680 minutes.

Anther objee* invention \$ a pari according: te te: fc-v^tiot*, tested st te temperatee 1½ te a %fe: -teo coated; with tint*, s ám tegy or a aipetesed alloy,

Another object öf'&fe: mvtetíte A a part according: te te invention, heated at te temperature T.0A te a iinfe te, iteft coated with aiúhboitte a» teumirunm alloy öt ha alnmlnittefeased aiímw

Another object bfte invention is the use of a psfe according te te tnvemlob te fahiiesilríg simciatel parts- m safety psm te totó ittetef veikfes, Anti- htítete prís All 1 be a pari fente aim.

Cither features end advantages ló life context of the invention will become apprent heiow, With tesx&fe reference: id the loilöwmg %htes m which;

Fig. £ shews two conventional tensile strength curves illustrating te mechsinical behaviour of te steel according to tec Invention, produced by easting 1, test A hr Tabic 3 of the examples. The dotted curve indicates the: mechanical behaviour under a uni-axial tensile teee alter fe --180 seconds of uusttmitteilos ct T, “ tehWC fettered by a ebbfeig Vfer( bf: WtM te the ambisnf fefepsmfere, which Is below Ms. The solid curve Indicates the mechanical behaviour under a tths-axlal tesstle tetce ate the fmk treatmete te the precipitation tfe nanometers iotermetaliies at 1½588-S te ?όΑ ::: nunutes. fig, 2 snows a photograph of the completely martensitic intermediate tmcroxteucinre after te cooling: y,sf! at: iötefe,: The figure: also shows the nbcfeteruCturs corresponding: to the dotted cams of Fig. 1. ?%> 3 shows 4 phofegraph of the mlcteteetute of a steel uceordiog: m the ioveteion alfer the heat treamfent te the precipitation: of intermeialfics. The feTilSi precipitates arc Indicated by te hiack arrows. The figure also shows the nticroSiructeie cdrrespttedlng tote solid curve of big. t. For the chemical composlikm of the steel aeoordhtg to the invention, the contents given refer to percentagos fey weight.

The eaten content must be \m. than or egnai to 8,1% by weight because, above lids: fentit P& toughness of the low-carbon madensife which constitutes:: the rnaite of the steel of the invention begins to decrease, fe addition, it is also desifeble to «wold tile fermatldo of thatem earbidos TiC which have: a dchimsptei: efecct on the: testability and tie up tsfenfem. iteteabsy, it is deatrafele m tell the carbon: content to 0.05% In order to achieve the maximum possible reduction in: the Ask erf obtaining a Prude marvensite.

The marsganesc content will fee feetween 0.5 and: 7%, Ibis efement plays a deoxidizing role midi its properties of hardening: by interstitial solid: solution: are put to use In order to: achieve the Intended msehamcat isropertles. addition, its positive ellect:on haidenafeifity: ils also used to oiitain a martensitic structure irom te ssarest aartefeis with, tor evmttdte, an a if cooling cvele. Thefetee, n utinmtum coraeat or 0.:w« Is recommCstttsVi ΐο the context of the inv of·· ion. Nevertheless, an uppov limit of 7% Is set: in the context pi'the in vem ion si? order to avoid a tefiite feehavtew of She *n«fertái sí ambient temperature. ihksrabfy, a tower 5¾¾¾ of :3¾¾ end an upper omit of >% wid he observed in order -o obtain me best results wit η respecs to the mm of ti® invention.

Wlft regard to ültem,· a conk fit of heiweerr #.5 and' 3.5% fa desired. "Oris ekmshf has a positive «Sect on the hardsnabitity of the sefii and is used: la the «(text of the invention to aeibeve a foe pfeelphatibh: of mtenoetallies of type feSITt. Á minimum content nf 0.3% is thus: repaired- i® order tb obtain a sutheient quantity of % to jwrm the futermstaliie precipitates: fkaSifi Nevertheless, silicon Is ithowri to ésttise hríttiehéss, whseh masses rolling ddfkulh sad above. 3,55¾ rotting could iessd ίο a ifacmre «fetch might Imerfupt the mdssirss! Procsssv Fmferably. a 0km mmnt of between ! J% aad 3,0¾¾ inclusive will be recotnmended itt order to obtain thedsest rssulíst in terms of ske, surfeee density anci dimrlhtnion of inlermetalik precipitates Fe>$m,

The quantity of timhlum will be between 0,3 tutd 334 to balance the ik-SI-Tl ternary system* that is to soy to have a smkhlometry that is favourable to the: Sbrti^tldh of Fe3T||l eotppotm# according to the invention, A. muúmm content of 0.5% iitahitn® Is necessary jfer Ét fentmg irk mtermetaffie precipitates feSill. Nevertheless, in a quantity greater than: 2%, the risk of fermmg: etkrse titmriudr carbides becomes :too great, because the latter have a detdmeoiaS: eiect on ikrmabliity and oensaíne titdniwn. The desired: maximum titanium eortteot is therefore 23iofreÉr#i|:, aitfettifett«t?n«rmi 1,5% mclnpve: will: be recommended In order to obtain; the best results in terns oi%i;% density and disiributlbnef fetermetail ie precipitates FojSill:,

Th® nickel content will be between: 2: and 7%, This: elemem makes it possible to Inerease the sixe of the austenitic mage, to improve the. ami-corrosion pwpejtfes, and to increase the toughness of the matériái Nevertheless* the cost of this element makes It: necessary to limit the content thereof to 7%, Below 2%, the síoíeínentlöned positive effects írre less pconouneed, ikeferabty, tbs nickel content w.>d be between 2.5 an® 3.5% Is order to achieve the aims of the Invention. in the context öf tbc invention, the aluminium content wilt be limited to (),10%. Complete aostenlidatlbn fe required during rite heating at iso temperature Tv So that the matrix of the steel becomes completely austenitic, but alommlnm Is an element that is known to be very aipba^etde, that is to say that It will tend to raise the temperature at which the completely austenitic range is achieved. Other characteristics, such as nrore difficult capability of steels that cordatn large mmm of almmmuny are pmkifeitlve «lib respect to (he invention:, and therefore this main chaoNteristic forees the inventors to limit the aluminium Content to 0.10%.

The chromium content is less tbs® or equal to 2%. lb: the nontext of this loventiony this element can be an expensive substitute tor manganese on aeconnf of its staid elfedi: on kstdonafeihiy, or an: additional hastening element, The chromium content will preferably be limited to:!:%,

Tod eoptter conkht is less than or equal to 2%. This element cotdd also: be an attractive but es|iemive sobstitote for tnangonese,: but: risks of sorlace crackltig may íhemáppear and (bay have a detrimental effect On fee'hohfbrgfeg properties. The copper contest will: thereto?® pmiembly be limited: to 0.053¾.

The cobalt: dönteni will be: tholied to 2Si. The damtiqn of the hear treatmeih: for preeipltation of inteririefallles, wloeh takes place: after the tinal: fermtng of :fee strncinral part, can be reduced by the addition of #% element which also has a positive effect on toughness. Cobalt cart ihcreiore be adued n.:< accelerate the klmöes- of precipitation of leadening sntermef allies, but this· #Mptná? is «xpssa.vo ana ttaretets &> vsage is limited to 20¾ of even !%.

The addition of tm%?bdje»p: is limited tó 2% i« the context nflhe ihvetnion heennse :¾ is as «%án»bp eHtsnvat, although h can also be mkied for its eontribution to increasing -he sobo stdatifta aííORgth or for sis positive offer po bnrdenahibty,

Tbe bornh eetiterft «$$ be sífjlefly: less than 0:.:8115% because, above Shis level, there is a risk of forming TiE: in she liquid stage, or even boron nitrides. Because this type of predpltaw is significantly teas naruening that? f ef IBI, a: pornón of llse titanium would therefore no longer be available to suMclentiy bemen the sseei.

The nitrogen content Is limited to 0.()0¾% to avoid: the tonoittiott of coarse íinanunt nslriíiéS: UN on soecont of the undesirable offer of this induson on femabibiy.

The micro-alloy eibibeds aueb as niobium and valmdinbl heve contents limited: to 0:,1%. i ney »se used to reduce the austenitic grain: sfe in order to improve nfehadicai: strength, hteveriheiess,, \mmss tne range of proeiptfstidn of these dements oeeum at a iempenifure higher than (list of the tnarfesille transformation duringcooling, they estinél be used, for precipitu; km hardening during ibe beat ffebneíii )11¾¾¾ would he a risk of obtaining a hard steel which Is..therefore difficult ΐό· Mm·, ev«ft before ishesgbfg, because it wethd ePrtSam niobinmfesed and ysnsdium-baseb precipitates which fence the ability to stamp the pari without: #«: apcvarance <ff cracks.

Elements such as sulphur and phosphorus are limited to the level of impofbfe Oft (be indnsfed scale and therefore have the following maximum limits:::0:.005% and 0.03%.

The mim of the sheets ami blanks sscmtékg to &e Invention is feeotislfy tnatfesife This mnrfesile has a carbon concentration; equn! to tho nominal: content,, widen will hetelnsfler be called low-carbon martensite, kip to -5% rbstdnal austenite as a proppihoti of surfee area can: also be iolemtetl in the nncrasrudure,

This matrix contains ínternsctallic precipitates of type Pe>Ti«i. To achieve the aims of the invention, it is necessary to: have: a, particular sfe, density and distribution of tbese ioismtensf lie prec Ipitatcs of type FcaTIBi, which ate: obtained, on the: part as: a tvmM of the pmelpnatiou hettf treatment apd by the fdfiowtng combmmkm: •he cunt of the content by weight of silicon sad iiuoitml is greater than or equal to ?..*>%. •he ratio of the content by weight of titanium to -hat of silicon is greater than or equal i:o 0.3.

The sheets aeeerding to she invention: can be iabneafed by any suitable process, However, it is prcleyabiC so use the method according to the invention,, winch comprises a number of steps.

First, a sheet or a blank whieh has been ent iforn a sheet; Is provided, :Ηρ·1ΐ^.»^8|«(00«..ρ5«0?#^''ί^ the invention. The sheet will he fabricated, lor example, by casting liquid steel which, once if te coofedi, produces, a: slab.: the slab is then reheated to a temperature: between: 1 fefeapd \27^€ for a period of t ime stflltelsm lor the sempertnure to be Identical at sil points of the slab, Ater the reheating nod once the temperature in the slab Is homogeneous, fe slab is ho; no lied at & ntdf exit teutprafure 1¾ which is greater tines or equal to Wif€, because it is desired to be ubi>v® A,r·. since the rolling must be perlormed in the austenitic range.

Alter Ibis hot rolling,: an important step of the invention consists In cooling the steel to a coiling temperature which is below -IffeC in oj'ifer to prevent any presnutom ptccipltntlon of intermetalilev. The posdíngcato Vy^so ΐ:ί,,;ί will be bstmm WÍ'Amú tikkel ikfeéfí' bfek&uify «öltedwfeih «ooteg;ín .sir írom she fcsnperature T;,s!> ·;·:> -he asublent sentpssfeure, in őse variant of fie- -íwmíös, the blank s;rn bs wdded to other steel eosnpooesns to fenn a ótots esnttpfex: ?rtor fd itfetooufeatiosi má damping. ft fe know·:: ihat, pending; m dm application, -fee tony fee -cmrnn resmm of a: .part tbssí may be requited to haye Kteebsp&aí pmpmm «' iáckwsses'^·' are different bont the s'est of-the park 1% example, wish she prifxdpal ofeiectise of saving weight: arid increasing pfffejpey, .certain. pints can fee made at differesk steels audior have different; feleknesses:, and csto fee assembled jo a femt teo« as tailored feiafeks or In the fertő of blanks wife variable thicknesses ptodtsead fey flexible rolling. The wekimg can fee perfbfetod ttsing all existing techstefogiss (laser welding, are welding, restepee spo; welding, eiefe while the vartobletobckstoss Idarfe repairer flexible hot :m cold rolling with a vssfebiegiip between the soiling mill rods.

Id stobthar vadast! of the toetdfeR*: prior id the heating; of the sheet or of the fehssrk, the felasik dfe; fee C0:id-fersded:to partly approbate the sfcape of fee iirsai fast or the part cars already fee eold-fermed if there are: m. partletsiat: fptobfems Thai reqtiis’g hsA stamping, kmsdly, this cold beíomtatiost step cats also snake It possible to have a preferrrt that Is snore suitable tor fee sabssspem pooling tool, which wiill ihass permit better contact between the tool and the part so that the esxtlfeg: esso fen perfesnsed snore hpfeogdhdously and snore rapidly. The purpose of th is cold fedping can; also fee simply to further reduce the feieknesspf the steel.

After these two vanasbs. which are both optional and « be combined, the sheet or ike fefepk is heated in a heat treatotosd fisrsfece to á telnpeiaintb kspwrs as the anstenlifeatsost tesbperstore and wfeqkfe greater than Acr, This lattor prirasnefer edfssdspoads to she tempetofere »bw« which ibo mitoóslraetttto of the material is completely austenitic. The dostssntto armealfeg temperature TY will be bevweess rfefeC sod 126IPC. for the sake ÖÍ hosnopfesfedosn the steel or "M mm to be heated 1st she austenitic r&stge· will prelerafely fee heh! al sire isfeperatore T-, tor n iims::iv of between sfe tocebds fesd 366 secostos, A longer time wbold fee ecorsosnseaUv smpmfitifeto on 100 15-541:8151:51 scale beeaswe the pishsify sfeíeettoe Is: to botdOpsitoe fee blank at the temperature Tj. The ahstonklc: amtoalmg: tojnpesstore lt will grefefebly be between: kSÖ'Casxí feto'-C- "Use blank or the sheet thus hantod to the '.«operators ?y tor she time f. can be opsiovsally removed frosts the femsee and then hot tormed W as- to oMam the fed pat. If a eoid ptetorto feaa aheady bees fabricated, the final shape Is then ssnpressed and dto epataci feetweest the part and the esttihsrg tool w111 fee belter, ftretombiy, sbe averssge gtfein siae of the parent aasterdte öfetoined, after heasieg stfeove A%: mé feetore feot stamping: is less thstrs 30 pdci'Orrtois'ea,

The steel: exhibits stable meckamcsl :proger*ies between 10 sód T0yC/s, ófefefe: has the: Wasöitd advasstaae of feeing able: tt! use the saw cooing or qtsenoising tool regardless of fee ibitikpess: of tire part to be cooled. Is addition, cooisngfey homing lit fee tool sdtows better control of fee geethetry of the pall, Λ tcchssology which avoids fee: traps tor of fee sltoet and wbteh mste it possible fór she ssatopfeg to feg caiTtodou; im;?tediasdy affer the hemsbg apdfeeisrisnogefifestttop of the tentpemtore m fee tomace aepssesessto ast advantage itt Serstss of industrial pfoeUsviivhy. fessimut tbit: sedttssdogy, npce fee blank Isas feses; :toansserred: is^to the: press tor the stomphsg, the hot vtampissg too! alto penults cooling: by cosifexston asxl the rate of cixsli-m as wed as the: hornogestoity shereof tfepesid on the thiekpesy of the slscot. the tefstpecatom ff, tise trarssfer time between· the femstee and the hot ibeming tool m4 fee eodiog systesp of slw mil fm hmMimhiim of she stop! »f fed tmaMm is sneb sh<sl &ό<ί!|η§. (¾ jits- is «aöfefeoí to forrd ah· cssehfehtlv martensmb sfaucturef: at amoiéöí: teroperature asm lö .szabiiké less thfen 5% anstenlte. This imphss that any rate greater than that of str cooling t;> & tej?ipu'raitsre Ms makes a I'ossifefe to torn· the essentia Uy masiensúk; structure. as a result öt which 3 sarut or 70'C s nas íseeo ser in order :tp improve the homogeneity m4 ío titks: the fetdltids «f industrial grocttícnorí min coasíoerafeott. la -aéöyo», eopbng by iholdmg iff the tool has the ^vantage of allowing hotter control of the shape: 0:f the part The temperature of the beginning of the martensitic transfurmah-m wdl be calcutaied try toe; totnvaia pub·-shed try Sv Hhtds in ^foornal of Alloys Composmd, 22Ö”: (1095), page i 2b·

the eonteris: feeing: ermtemtsfey weight,

The ms of cooling to below the temperature Ms wifi mfeuesree the oreeftabisal propes-ties of the martensite by tempering the: martensite, reducing the hardness thereof iff association with the slowness of the cooling to below Ms. It is advisable to have a cool tog rate at least eottai to cooling ia air. 1¾. is the temperature below m, at which the m&B®& after the stmv.ping stops, and spears before the step of heat treatment for precipitation of i mermetslf ics.

Ihe sheet or the Mmk then undergoes a heat treatment lor precipitation of narmrnetrte iatemtstaibes which harden in the ferm of :F%Tlf>h WhiremmM is carried opt at a temperstitre Toa. between d® and #Öeí2 this temperature range being the range corresponding to the aforementioned precipitates. The hold at this temperature 1¾ will he tr a thtte t0a «f between 31) and <>® Routes. Thosttigof cording the part to below M, erm he directly tbilowed by the heat treattnent described above, without the ambiem tempereture feeing reached This hardening; heat treatment has the: advantage »( feeing carried ott; after the hot or cold stamping, and the mechanical strength before precipitation nf Intermeittifics is less than IftDO hfPa as ilhisfratcd hi Fig. I with the dotted corve. This makes it possible to Mm greater ductility than with: a steel that has a hardened strneturs: even heftrre stamping, and therefore complex parts become accessible,

The microstruehtre according to the invention therefore comprises a lowseárhoh htarkbshic mhh'ix presets at the form of islands with a lamellar gonfeprafeoo, in the interior of which: there Is a preclpitöftoh of ivoe FefiiSl having a proportion: fey surface area of between I and 5% aeo an average prectpstste SMius of ixttween I and id mmomehm Forfifes latter criterion, the preeipfehte: is likened to .a circle, the radius of winch is treasured.

The parts thus formed can be assembled fey welding to other components of different dies, shape,: thickness and- srenposlrkm; so as to fort® a huger and more complex structure. Tbo parts fetus femed can then be dip-coated or coated by electrolysis with an appropriate coating if required ifer antfeorresmh or aesthetic purposes.

By way of illustnuion and in a tton-hrniting manner, other advantages eehfered by fete imreniiort will become apparent from the toll-owing tests.

Three eheoílesii «wíposiöOsi were cast, the first of which coirusoohds ίο the Invention Isseel I s an<i the other two t steels 2 and 3 s of n Teh eottbspond ίο reSerenees. The objective is so demonstrate the benefit of the invention ίο achieve the aim of the iísvenition, Ihat is to say an inexpensive nuance which snakes it possible ίο achmve a yield strength greater than or equal to I3D8 MPa as well as an. elongation at break greater iha« or eeptai to 4%. Steel No, 2 Is a maraging sieek Steel No, 3 is a steel tor hot sUtmping, the steel known as 22M«BS, Table I presents the cbenaieal eonapositlons of the steels cast, irt percentages by weighs; the compos it ions of elements not corresponding to the Invention being underlined,

Wk±

'fable 2 presents she sons Sb-Ti, the reties fviSTi and the martensitic transformation temgeraiores for the chemical compositions of Table 1.

Xtifek.a

Time daee crnhpositi'ons were cast te ferói stabs which were then sObj'sOted to the following röMug parameters:

Aebesting to 1288% for 45 minutes', 98% redyotiou of íhlekuess by hot rolling with a miit exit temperature of^FC-€00(51¾¾ of tbc steel ;o ΤΚΓ€ at the exit horn the írnál rolling mill rod.

The cooling rate from she mill ex t; icajperature %~900°€ to the coiling temperature 1νι,;χ: of 290*0 was 100% per second, followed by cooling In air.

The oxidized hot-rolled sheet is· piekfed at a«bisnl temperature using a chemical p tele Slag process.

The thickness of the sheet is then reduced by ?0% by cold •roiling..

The thickness of the .sheets obtained is between 8 J and 2.4 mm.

Ilse Sheets thus obtained were then cat to obtain blanks,, which then undergo the heat treatments summarised in Table 3 having the following columns: the heating rate: Yg* in eC&, the austenitization tempofatore Ty in: % the ausienibeaffoo time ty In seconds, tire average cooling rats V*£ In %;% the: temperature: T)n* at which tint cooling Vlgi! was snapped, the second heating to carry out the 'precipitation heat treatment Va in '%/s, the precipitation hold tempmtittre Toa in *€, the precipitation hold time t0A m minutes, the final air cooling

TaMe.3 lest Steels VCi Ty €(xec} : Vrefl Tia,: Vi2 To* k>A 'V*» tem {%) CC/s.) f C) t C S.) ; í C) (min) A I 5 958 580 30 25 5 : 580 ISO ! air S 2 5 958 388 58 280 3 488 I SO j sir C 3 5 958 : 380 30 25 S 500 30 air 0 3 5 958 388 58 25 5 408 38 sir £ 3 5 958 ; 398 38 25 5 898 39 air

In the steels of tests A and B. the bionk, was stamped oiler ausienitizatiou at 958%' for 5 mmufcS a?>d lseidre :hc cooling Vmfl, This mode· It possible to form a centre pillar and lo illustrate the dot'Siamping capacity of the steels of the invention:. I'hercafler, s heat irestipenl ai SXkT'C for'3 hours (180 mlmdes) made it possible io aeihísve 3 strength level greater •has'! fsbf! IVIPa trrsf á. total elongation .greater than d% over the psst'í fűin lested from s-ed !i.,,tó:A,:as lUuatraieci iá Table 4. ;A specimen or «steel i toat hat: tindesgoite tesí A \<fas ciis-cíSíátd vdih. a Zn alley, νΛ íhs tbjk>wlog íémpós&te; W te -tek teífS^' A) and t.(f.Í4$V£«l'te bálánk being zim.. An mteríttc·® íagjW of FcjÁhfZn} was rhus tormád, topped by a layerof dóé alloy having a composition almost identical to that of she bash. The eoainrg obtain adheres and has good coverage. 1¾ provide sddrtiemtl irtfenaiion consenting. the ateckartissti response of the steels designed according to: the inventioa, Table 4 sttirumwli'es the mechanical properties obtaraod when tests Á to E am conducted;

BÉM

Tcst B is dot: In accordance with the bwcottom.m account of the use of a maraging grade which leads to krnimm etette ai Ernák. Itt addition, the awokotei strength b high even feefere the m®&m> *««fe reduces fe to&htiiy dteg tet#8g.

TM: C carried out with the steel produced by casting: 3 does not correspond to the mechanical =!,«««(« reqdM by fc invteta te»»* *« *“»a! ^ W fc («total MMi willed «« "«»** W “*“* * yiskl ί"1§*1' ef i30*M,““ ** 4t* slweioii. ·!*.- arte «DM is m Mik »* «* siiiK’" “* !i!“>™ «**'«'»> *> ”« ™* “ I»1»9* “> ^ teitotag praiptotaiottesi ί» to· «>«*« βΜ«·fc yk* *-·Φ <«lis *·»*<* Signlflcantlv less than Í '00 MPs.

Tte O «(I E cow rapoutoK <6, »W(« -<* «»« »«««"» i»T* M ®s'*P«#W

mm. Non, of (ta, mrnmm mám * r»»ifcle “ “**·«tl,e "*iB Km% “f »'*“ *·"** *”"*iB ().« as, it is s ,«te of» β* ««I»» i«««* 18 Ü* «>«« *«"« will lead to & softemng of the structure.

Tnc taaiiimi make it iti« posit* » «»« »·** “> “r“all> ^ ***** ür otectwlvii, *ρ*ίιί» «8 Whiois to,, mom** «teoKKrfaios «Α «to toMJ ««ragth „ gsaw tte« <» «.(iri » Hi* «iln mi ft, *,;««»» »«««* « *«*«» ^ “ 4% al'® tarcl»''IS ®‘"

This wmites and padfbdsriy }%h «cbafiM properties os the §m\ pm or itrÉe area: r a reek'd so undcrae die heat ireamseni: iff Hie ease of a tailored dank. for example.

These earn can thus ha «sad will advantage, for example: and in a am-iíissíbng manner as an and-intrasioa safety part or as & rdshRceosent part % the of load motor veinek*.

These parts can have a variable thickness as a resoh of -odding with other s&sis or flexible roiling of the steel of the Invention, that: Is to say roimg of a single sleet hetyveed; t wo rolling mi l! rolls with a variial# gap, making if possible to bave si: least two dlfeent tbieMesses on ills: shse; at lle end dirotbag,

ACiEÜf FAMINE mmmmtt ΨΜJWOCllWATiOl» Ai^M:'l§»RMA&E A CSATI P ET/OU fRlAIPE SOUS Ot'TIL A IRES HAt'TE RESISTANCE E'T OUCTILITS ET SON PROCEDE DE

FABRICATION

SEARAPAMIICÉNYPONTOR C Tile on flap ep aeiar larblaé doni la eomgosiios chkoiqse eomprend, les teneora i®i exodmbes e« ponrcendgc eri poids:: C$0,1% D,§% :< IMn s 7% 0iiS% tTSi s3,s$b öss%si^a% 2%s m% 7% A! si 0,10%

CrS:2%

Cu iS 1%

Cos 3%

Claims

NAGYSZILÁRDSÁGÚ ÉS ALAKÍTBATGSÁGy SZERSZÁMMAL MELEGALAKÍTÖTT ÉS/VAGY EDZETT, :ÍÁJP KIVÁLÁSOKKAL KEMÉNYÍTETT HENGERELT ACÉLLEMEZ SZABADALMI IGÉNYPONTOK

1. Hengeréit acéllemez vagy ei#sengeréit buga, ameiyaékMmiaí összetételé íőmeg%-bam C < 0.1% 0.5% T Hn < 7% 0.5% < Si $ 3.5% 0.5% £ Ti « 2% 2% £ M i ?% m £ o.io% Cé £ 2% Cu £ 2% Cc S 21 M?:; £ 2% S £ 0.005% P S 0.03% N!b :i Ó . 1% Y £ ο,οι B < :2.0:05% K 5 :0,010 8:%. Kvébbá iámért begy a szlléibrm és a tlábfeílátörb: Si '> xi > 2,5% Tí - 2. O . 7 Sí :· a maradék vas és a gyártásból származó, elkerülhetetlen szsehyazödés.
2, Az 1. Igénypant szerinti acéllemez vagy elÓheAgereli idaga, afifjpet' kémiát ósszétéiele tömé|%-Í5Sb; C 5: 0.0 .5 0 % 3 <i Né £ 5% ;l., 0; d BT .& 5.0T 0 x 5: < Ti £ 1.3s 2, 8: £ bd S 5 , 3% Λ I & (5:.: 10%· C:: % 1% 1« S Co < 1% Μα: <: ;·% S :( 0.005% 1 1 0.03% bb < 0.,%¾ V % 0.1¾ S < ö.005% >5 < 0.008% _ továbbá a szilícium- és a titántartaicm: S:i * T:í > 2.3% ft IIM a maradék vas, és a gyártásból szsrrnazo, elkerülhetetlen szennyeződés. 3, m t vap 2· lÉfpiíM bármelyike szedni! vagy feypbőí gyártott acélalaí* rész, amslyask **$M?pteeíe legalább 9S %-bsn mabenziies, és a khstóíyközi klv^ások fa2TsSI típusúak, 4. A % ígénypnt szerinti aeélélkatrész, ahal a kdsiáiykőz! kiválás# tartományának tomíete 1 és 5 % között van. b. A 3. vagy 4. igénypont szétldti aoélalkattász, ahol a kbstelyköz! kiválások átlagos sugara 1 és 10 nanométer között van. 6. A 3. - 5, igénypontok bármelyike szerinti: söéiaikatrész, amelynek folyáshafárá: nagyabb vagy egyenlő, mint 1300: MPa. és: szakadási nyúlása nagyobb vagy egyenlőd %. 7, A 3, ~ 0. igénypontok bármelyike szerinti áéeiaikatrész. amely cinkét, óink alapú ötvözetet vagy cinkötvözetet tártál mező bevon altat van ellátva. 6. A 3.:-6, igénypontok bármelyike szerinti acéialkatrész, amely alumíniumot, aluminium alapú ötvözetet vagy aíuminiumötvözetet tartalmazó bevonattal van ellátva. I, iiirás: aoélafkatrész előállítására, amelynek: Sörén a következő tepésakst battik végre az: alábbi sorrendben. ~ az 1. vágy 2. Igénypohtök szerinti összetételű, hengereit acéilémézt. készítőnk, amelynek: mtkreszérkézéíe: a kevesebb, mint í % területű FeaTlSl típusú fémközi ki-válást tartalmaz, - az említett lemezt síancoijuk azért, hogy nyersdaraböt kapjunk, - az említett nyersdaraböt ikemenoéöen Ty .hőmérsékletre bsvlfűk és ty Idán ét: bönfarípk ügy, hegy szerkézete teljesen ausztenites legyen, -- az említett nyerstíarabct szerszámban sajtosuk olyan hőmérsékleten, amely nagyobb, mint az Mg hőmérséklet úgy, begy alkatrészt hozzunk léte, majd ez? követően - m említett alkatrészt lehőfük ¥^. átlagos hűtést sebességgel az Ms hőmérséklet aiait hőmérsékletre égy, hogy martensites szövetszefkezetet hozzunk létre. majd ezt követően ~ az említett seéíaíkatrsszt Ica hőmérsékletre hevítjük? amelyen iDA ideig höntartjuk annak érdekében, hogy mechanikai tulajdonságai olyanok legyenek, hogy a FeTTiSi fémközi kiválások tartományának területe 1 és S % között tegyen.
10. Eljárás acelalkatrész gyártására, ameiyhsk soráh a kővetkező lépéseket hajtjuk végre. >· az 1; vagy 2 igénypontok szerinti összetételi, hengereit acéllemezt állítunk elő, amely bek kiválás tartományának terü leté kisebb, mlntí % - az említet? aoéilémézt stancofok így, hogy nprsöáfabbí kaprunk, - az említett nyersdarabot sajtoljuk, » az említett acél nyersdarabo? Ty hőmérsékletre hevítjük, amelyen % ideig hőniaríjak kemencében igy; bogy teljesen auszfenites szerkezetű legyen:, - az említett nyersdarabot eltávolítjuk a kemencéből. - az említett nyérsöarabet szerszám bast sajtoljuk az Ms hőmérséklet fölötti hőmérsékleten annak érdekében, hogy alkatrészt állítsunk elő. ~ az említett alkatrészt VWj átlagos hűtési sebességgel az :Ms hőmérséklet alatti hőmérsékletre is hatjuk, - az említett acéiaikstrész? T0A hőntartási hőmérsékletre hevípk,, amelpn ideig tartjuk hon annak érdekében, fipgy' rttedHaaiksi tegy a Fekl'iSi fémközi kiválások tartományának területe 1 és 5 % között legyen. él. A I. vagy 10, igénypontok hánmeíyske szenntl gyártási eljárás, ahol az említett Ty hőmérséklet 700 ás 1200 eC közöt van. 12. A11 igény pönt szerinti gyártási eljárás, ahol a Ty hőmérséklet 880 és 980 % között van. 13. A 9. ~ 12, igényponti bármelyiké szerinti gyártási eljárás, ahol á köntertás Ty ideje 80 és 3§8 másodperc között van, 14. A 9. - 13, igénypontok bármelyike szerinti gyártási eljárás, ahol az átlagos V,^ hűtési sebesség 1.0 #s 70 *C/ssc között van. lő. A 9. -14, igénypontok bármelyike szedni gyártási eljárás, ahoíM említett hőatarfási IÖA hőmérséklet 400 és 6őö "C között van 18. A 9, - IS. igénypontok: Mfmeiyike szerinti gyártási eljárás, shot 3¾% hőnteiá# idő 30 és 800 perc között: van, 17, A 9. -18, igénypontok bármelyike szerinti gyártási eljárás, ahol az említett alkatrész? T0A hőmérsékletre hevítjük t> hőntartási idővel, 05¾¾ ezt kővetően bevonjuk cinkkel, cinkötvözsttei vagy cink alapi ötvözettel.
18. Α δ. ~ 1 δ. igénypontok bármelyike szerintigyártási eljárás, amelyttek során &z említett aí~ ka· reszt I0A hömérséktór.é hevítjek t«A bőet&rtási időig; majd ezt kővetően bevonjuk stumirkummai. steifiuamötvöMtei vágy alumínium alapú ötvözettél. IS. Az 1 - 8. Igénypontok bármelyike szerint!., vagy a 5? - 18 igénypontok bármelyike szerint gyártott alkatrész alkalmazása szerkezeti elemek gyártására, vagy szárazföldi jármüvek biztonság! elemeinek előállítására.