RCW ISSN (1 V0ll

'---:-I I. nno

FOUR IEERING @$/ ?I *

Published quaderly as Ihm organ of ihe Foundry Cornmlgsan orihe Polish Academy of Sciences

Improvement of Structure and Properties of Cast Ferrite-Pearlite Steels for Freight

Railway Cars A. Rabinovich "*, Yu. Bublikov8, G. Trcgubcnkoa, G. Polyakov ", A. Puchikov b, 0. UAov

"~ioional Metallurgical Academy of Ukrainc. 4 Gagarina Av., 49600 Dnicpropct rowsk, Ukrainc Instytut Mctalurgii &lam NANU, Dniepropictrowsk, Ukrainc

*Corresponding author. E-mail addscss: awr2006@ukr.nct

Rcceivcd 04.03.2008; accepted in revised form 0 1.04.2008

Abstract

As it i s known For increasing of propcnics (YTS 2 380 MPa) of cast stcds i t is c f k ~ i v c to incrcasc conlcnt o f alhsti~uiional alloying clcrncnts, (Si, Mn, Cr, Ni). 1 lowevcr i t lcads to rising in pricc olstccl ton. lncrcasing of Si and M n conrcnl only i s limitcd hy decreasing o l ductility and weld nhility. As a rule silicon contcnt at ~hcsc accls is not highcr than 0.4-0.67'0 and Si:Mn ratio is not highcr khan 1:2. Now for grain rcfincmcnt ~ w c s inoculation of stcct by nitrogcn and clcincnrs with high chcmical affinity to nltmgcn. Mostly vanadium i s usd. howcvcr niobium sornctime is uscd. Dissldvantagcs o f this arc high cost of alloying clcmcnrs and low thcrrnodynamic stability OF vanadium and niobium nitridcs. Parlicles of V(C,N) and Nh(C.N) dissolvc during hcating fnr licnt trcatmcnt or during wclding. I t [cads lo dccrcasing of grain refinement elfcc!. Adaptat ion or this microalloying stratcgy Tor casts producing For rrcight mil way cars let cstirnatc possibility of application thcsc casts in a ncw gcnerazion freight railway cars.

Stowa klunowe: Mechanical Propcrtics, Micronlloying, Disprsion I-lardcning

I. Introduction

As il i s known for increasing o f propcrtics (YTS 380 MPa) of cast stccls it i s cffcclivc to incrcasc conrcnr o f substitutional alloying clcmcnts, (Si. Mn, Cr, Ni). Ilnwcvcr i t lcnds to rising in pricc of stccl Ion. Incrcnsing of Si and M n contcnt only is lirnitcd by dccrcasing of ductiliiy and wcld ability. As a mlc silicon contcn! at thcsc stccls i s not highcr than 0.4-0.64 and Si:Mn ratio i s not highcr than 1:2 [ I ] . New for grain rcfincmcnt uscs inocwlatiogl of stccl hy nitrogcn and clcmcnts with high chemical affinity to nitrogcn. Mostly vanadium is wscd 121. howcvcr niohium sornctimc is uscd 131. Disdvnnaags o f this arc high cost o r alloying clcmcn~s and low thcrmadynamic stability of vanadium and niohium nirridcs. Particles oh V(C.N) and Nb(C.N)

dissolvc during hca~ing for hcat trcatrncnt or during wclding. I t Icads to dccrcasing o f grain rcfinc~ncnt cfrcct.

2. State of thc art

In prcvious works [4] cfficicncy of replacing V and Nh by cheaper T i and Al has bcen shown. I t has bccn stavd that rcquircd comp!ex of properties (YTS > 380 MPa Far as-cxqt sicel) can bc obtained without alloying by Cr and Ni.

Adaptation o f this microalloying s'lmtcgy for casts producing for Freight railway cars Ict cst imatc possibility o f applica~ioll ~hcsc casts in a new gcncration frcight railway cars.

Now for car truck parts producing (sidc fmmc and bogic bolster) steel with 0.2% C a1 Ioycd by Mn (somctimc additionally

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alloycd by V. Ti, Cr, Ni) is uscd. Chromium and nickcl encourage solid xslution strcngthcning of rcrritc, vanadium and titanium cnrbidcs cncouragc prccipiration strcngthcning. Nevertheless Cot stccl with 0 . 2 W alloyed by Cr+Mn+Ni+V+Ti dctcrrnincd lcvcl of propcrtics (YTS2373 MPa) is not rcachablc. Momvcs usagc of that srccl is limitcd by strict rcquiremcn~s for sulphur and phosphoms contcnt (50.020%). Thcrcforc i t i s ncccssnry to prolong both oxidizing and rcduction pcriod o f smcl t ing, rcrnoving o f phosphorous sIag bcforc finishing, incrcasing OF dcoxidizcrs, IEmc, fluxcs withdrawal ctc.

3. Dispersion Hardening of Casting

At works 15. 61 a possihiliry o f cast stccl propcrtics improvcrncnt by nirrngcn. titanium and ahminiurn alloying has hccn shown. Ncvcrlbclcss high conlcnt o f zhcsc clcmcnts (N up to 0.025%. Ti = 0.15, AI2O. 1 ) invcs~igatcd in neorks [5. 61 leads to dramatically dccrcasing of dtlcti t ity and cracking susceptibility during cast proccss and opcm~ion OF cas~s . Thcrcforc it is necessary lo ~nnkc invcstiy!ions lo optimize chemical content of 0.2QC+Mn stccl inocul;ncd hy At+Ti+N.

clcmcnts contcnt. It is ncccssary to incrcasc lowcr range for carbon to 0.20%, far silicon to 0.40% and for mangancsc ro 1.2%-

350

7,w 8-00 8-50 9.W Q.W I0,OD Grain size

3.1. Materials prclparing

Pig. l Influcncc of Fcrritc grain sizc on YTS for 0.2%C+Mn+AI+Ti+N nftcr hcat trcatrncnt at industrial furnace (0) and laboratory filrnncc (m). x - O.Z9C+Mn smclr. Digits ncar

points dcfinc quantity of srnclrs

Expcsimcntnl casts have bccn madc in induction Ct~rnacc IIC7'-0,11(r with acid lining. As fumacc chargc wcrc uscd rnafcrials which arc using for 0.2'hC+Mn stcct prducing at arc furnaces (scrap mctal o f arc furnacc smelting, fcrrosilicon. fcmrnangancsc silicon. fcrrotitanium. alurnocalciurn wirc).

Nitroscn-bcaring alloy has bccn made oil hasc of standard Ferrornanganese [TI. N i trogcn-bcaring alloy fccding has varicd from 0.83 to 7.5 kg pcr ton o f stccl (0.05-0.45 kg pcr smcli). Titanium contcnt has becn inctcascd cornparcd to standard 40.IX)X-0.025%). Some smclts hnvc hntt zi tnnium conrcnt (0.07- 0.1 1%) i s cqual ro works 15, 61. Conlcnt nf othcr alloying clcments has bccn at aandard to 0.2%C+Mn stccl Icvcl. 1 Eowcvcr two smelts havc had silicnn contcnt about 0.72% Tor statinicai purpose. Also. for rraccahili ty o f rcsults aandard 0.2%C+Mn accl havc hccn srnclrcd.

3.2. The results of researches

EIcnt trcatrncnt of cxycrirncntal casts has bccn m d c both at lahnratory fi~rnaccs and industrial rurnaccs. I t has bccn madc to apprclxiinatc lahoratory rcslllts to industrial condirions,

As i t is shown on Fig.1 fast cooling of casts providcs fine grain stritclilrc and high YTS rcgardlcss to alloying clcrncnts contcnt. Stccl inocu2atcd by AI+TI+N has highcr YTS cornparcd to standard 0,2%C+Mn srccl with samc grain si7c. S!ccl with 0.2%C +Mn+AI+Ti+N has required YTS > 3x0 MPa aftcr heat trcatmcnl both laboraiory and indusrrinl conditions.

I t confirms by results of statistical data rnanipulnrion as function o f carbon and silicon contcnt (Pig. 2).

Same dependencies cxist for mangancsc contcnt in stccl. Thcrcforc for providing of rcquircd cnmplcx of propcnics for indtlstrially produccd casts i t i s ncccssnry to limit thc basic

330 0.1 0.15 0.2 0.25 0 3 035 a 4 0.45 0 5 o . n 0.8 0.65 0.7 o r 5 0.8 0.05

Si, M.%

Fig. 2. Influcncc or silicon md cirrhr>n contcnt to YTS of standard 02%C+Mn (lowcr cwrvcs. 23 14 smclts) and

0,2%C+IMn+Al+Ti+N (highcr carvcs) drcr hcal zrcatmcnt at industrial furnace

Depcndcncc or titnnium content to rncchanical p r o ~ r t i c s o f stcd has an cxircmum (Fig. 3) which is corrcspnd to size and quantity of Ti(C,N) particlcs (Fig. 4). With li!anium mnhcnt incrcasing up to 0.01570 part of finc carhonirridcs is incrcasc. IIowcvcr with titanium contcnt highcr than 0.0158 par1 of finc pwticlcs dccrcasc. I t Icadrls 20 dccrcasing of prccipiiation strcngthcning and ga in sizc strcngthcning at invesligatcd stcels.

Thcrcforc for guanntccing of propcflics complcx at indiisrrial conditions limitation of titanium conlcnl nt 0.01 3-0.035% ranpc can hc rccommcndcd (shndcd nrca at Fig. 3).

Also depcndcnce of nitrogen-bcaring atloy consumpiion lo mcchanical propflies of stccl has an cxtrcinurn, with optimal consumption about 2-3.7 kg pcr ton OF stccl holh for nonnalizcd (Fig. 5) and qucnchcd and tcmpcrcd stccl {Fig. 6).

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As it is iollow from corrclalion cocflicicnts and cxpcrimcntnl crrors ratio or WdI for all cxpctirnc~ital darn i s highcr than 3, thcrcforc it corrcspnds io confidcncc lcvcl &0,95 ilnd kccps at high lcvcl for multiffictor invcstigntion, I t allows confirming high stntis!ical assilmncc or cxpcrimcntal data and predicting rcproducihility of rcsu trs during industrial smclts.

Fig. 5. Influcncc o f nilrogcn-bcnring alloy consulnplinn nn YTS and impact tnughncss of 0.2%CcMn+Al+'l'i+N siccl

-- ! P 23 40 60 80 100 120

Ti content, wt 74-10'

Fig. 3. Influcncc of 'litmiurn contcnt to YTS and impact toughness of 0.29,C+M n+AI+Ti+N stccl

Fig. 6. lnflucncc o l nirmgcn-hcariny nltoy cona~rnptioi~ to YTS and impact roughness af 0,29C+Mtl+hl+'l'i+N siccl :dwr

qllcncllin!: and tclnperiii!:

4, Conclusions

At thc work it has hccn shown that i11octll:ltinn of ferrite- pcarlifc siccl (0,2%C+Mn) hy AI+Ti+N in comhinntian with limiting of carhon. silicon and manyancsc contcrlz Ic:~tls to increasing of pmpcrtics cnrnplcx nf cast slccl. Thc cnsr srccl inocuEatcd by AI+Ti+N corrcspnds all rctluircmcnts for c;lst p:lrt lor ncw gcncrarion railway freight car.

Expcrimcntal results haw high st;uisr ical itsrllrancc :ncl implcmcnr to indtrstrial prnc~icc.

Fig. 4. Influcncc of titanium confcnt to sizc and quantity of Ti(C,N) particles in O.Z%C+Mn+AI+Ti+N stccl

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ccpy, U ~ R . ~ iymn. 'Ifpima himwnyprr!rr. N;!2 (1976) 64-67 (in Russian), D.B. nyl!cY~. n.n. ~ I ~ ~ O X K O E ~ , I I.M. ~ y p o ~ a . M c ~ ~ c ~ o ~ a ~ l s c c r p y w y p b t II IrcarmmnrrllccKnx n ~ n i o ~ ~ c r ~ r ~ r i n mrrax 2OT2JI II 40r2Ji. ~~onrl~llur~r~ponarrt~~rx ~ ( F T O X I c PMJlll'lllldhlH IIo~~?I~~cIIMA~II~ CCPLI. 'S~~p l l l f H npilKTllKil hrmmnyprl.iri. M21 (2003) 2 1-26 (in Russian). n a ~ . Y~pai'l lu N20492 ~CnociCi oacpxalllirl mo~narictrtoi' nirarypcfn, LO. IIixcropo,~on. M.U. Irrta-ron, 0.13. Palii~tonul~ Tn ill. I l m p y ~ . 15.10.2001. liton. N 9 [in Ukraine).

Polepszcnic struktury i pod\vybszcnic ?vlaiciwoj;ci mcchanicznycI1 stali wa fcq~czno-pcr1i~czncgo na czqici ?vagon6?v

Cclc~n pr7cd~!awionycf1 hadan jcsl anaIim mo~!i\~oSci wstoso\vania wtrvard7ania w~glikowo-aztltko\vcg~~ stnli~vn zawicrajqccgo 0.25F C w cc3u 7apcrvnicnia mozlir\.o<ci 7~slosotvanin vgo matcrialu do cct6w wykonmia odpowicdzinlnyclr odlcwilw kolcjowych. Mc~odn n?.kor/ystnnia rnikrododatkb\v slopo\\ych. znana ~v produkcji 1vysob6rrr walco!vnnyctl, zostaln znndnptownnn do pmilukc,ji odlc\vOw l;olc,jo\vych czqici wayonci\v lo\varor\ych nowcj gcncncji.

2Vyk~mano scril; r\yropri\v do5wiadcmlnych. na podnawic k 1 6 ~ c h ozrzymano mkrcsy stl;Lch picr\visaki,w bnzt~tvyclr i dodnktlw rnodyfi knGqcxch.

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