Application of welding technology TIG to cast iron repair

(1)

I G I N

ISSN

(11 Volt . . .

Puol~nw quaneny as meorgan or me rounary tommisston or me rolrsn Hmaemy of SGisn~es

Application

of welding

technology

TIG

to

cast

iron

repair

J. Sza,j!jaar

"

P. \VrbbcI"

T. Wriibcl"

*

"ilcsian

University

ol*'Tcchnology,

Inslitute o f

Engineering Materials and Biorn;ltcrials,

Foiindry Dcpnrtrncnt,

Tawarowa

7,44-

100 G I

iwicc,

PL

*Corresponding

author.

E-mail

address: tomasz.wrobcl@polsl.pl

Rcccivcd

12.02.2008;

acccpted in rcvised form

13.02.2008

Abstract

Rcpnir nT cnst i m n clcrncnts rcaEi7c in ordcr to cut out a sltpcrficial casting

dcfcc~s,

Dcrccis

clccrcasc ;z usahiliny nt ca~rings tor consin~ciional application m d incrcasc a manufacturing costs. Thc pnpcr prcsclrls rcscarch rcsufts or itsc o r '1'IG

-

Tun~stcn Incn Gas also kncwn RS GTA

-

Gas Tunpstcn Arc surfacin: hy wclding on colt1 and half-hot to rcpnls chrninil~m cnsr iron EN-GJN-XCrlS with cliro~niurn contcnt nhout 3 5% and nodular ({vi~h Fcrritic-pcarli~ic matrix) cast iron EN-GJS-500-7. Thc rcsttl~ o r invcsiigations show possibility of cns~ings rcpais hy put on derccts a good quality padding wclds, which havc compamhlc

nr

hcricr propcrtlcs than hnsc ~naicrial.

Kcy

words: Surfncc Trcalmair. Casting Dcfccts. 'TIG. Chromi~un Cast Iron. Nodular Cast Iron

1. Introduction

Oitcn. for this aim i s uscd wcld~ng tccIlnology fur cx:implc 'r1G

-

Tungncn Incrt Gas also known as GTA

-

Gi~s ?iin~sicn Arc

F7t1 I].

Wcar rcsisiancc i s w r y ilnporlant fnr clclncnts of machincs

TIG nr GTA surfacing hy wclrli~ig is :in arc wcldlng pmccss and dcviccs such as: cIig~cr tccih, jaw nT cn~sllcr. which arc

that uscs a nonconsiirnahlc ~iulgsicn clccirodc lo pro(1i1~1: I~IC subject in ridying. grintlirlg ant! c ~ ~ s s i o l i . Rilsic lnntcrii~ls which

padding \rrrld (fiy. I ) .

has high wcar rcsislancc is chromium cnst iron. I ligh wcar rcsis~itncc in I his ma~criiils rcsuIr froin dispcrsio~t of Cr7C3

carhides and iron1 finc-prninctl, hr~nngc~lcouq anlcturc

of

this Shield~ng gas alloy [ 14-13,

Gray cast imn i s an vcry vcrsatilc maicrial iuld rcla~ivcly incxpcnsivc, usctl in thotlrirnrls of industrial produc~s. Gray caa

irnn with flitkc anrl slnclt~lar grapliiic hclnng to thc most popular ;rlloys in ihis proup, l lowcvcr, !ncchanical prapcrtics or ductilc cast irnn arc hatcr than pray cast iron w i ~ h

flakc

~raphitc

1

I. 5. 6 ) .

'rhc \r,cldnhility nf cihst i m n is dirficult in particulary nn

cold

-

wi~trorl~ prchcating. Fnr lijsion wclding. prchcating of thc caning is nhscilulcly csscntial. R ~ i l s~trfitcing by wclding on cold to rcpnir cast iron is pmsihlc. Rcpnir of cast iron clcmcnts rcnlizcd in ordcr lo cia nil1 a casting dcrccts. which dccrcnsc a ~isabiliiy of

cast

10

cor~stn~ctinnnl application md incscnsc a manufacturing costs. Fig. I. Schcmc of

TlG

surfacin~ hy \c,cldin_c kcchi~olnyy

(2)

Tbc

welding arc is crcatcd bctwecn

a

rungstcn clcctrodc and

the

weld pool. Thc

wcld

arca

is

protcctcd from atmospheric contamination by

a

shicfding

gm

-

usually

an incrt

gas such as

argon or seldom

helium.

FiIlcr

in form of

rod. wire, shapcd win:

or

powder

is

uscd. A constant-currcnt

welding

powcr supply

produccs cnergy which

is conducted

across thc

arc

through a column of highly ionizcd

gas

and mctal vapors known

as a plasma

[ l

l+lS].

Morcovcr, application

of

wclding technology in particular

TIG

to surfacc heat trcatmcnl guarantcc mechanical propertics

i.c.

hardncss and wcar rcsistancc improvcmcnt in gray cast iron

[7.

8. 1 1 I.

2. Range of studies

Rcpair OF chromium cast iron EN-GJN-XCrlS and nodular cast iron EN-GJS-503-7 clcrncnts was

realized

with usc of wcIdcr dcvicc CastoTlC 2002 ACIDC with cursent intensity 100A for surfacing by wcidnig on cold and half-hot (prchcating tcmpcraturc 300°C). Fillcr

in

form o f rod to surfacing by wclding o f

chromium cnst iron has thc samc chcrnicaf cornpsition as bnsc

material. Whcrcas fillcr to sz~rfacing by wclding of nodular cast iron was chromium cnst stccl G90CrSi12- 1 with slmmium contcnt about 13%. Ratc nf flow of shielding gas

-

argon was

Hardness cxarninations wcrc madc

on

ultrasound MIC;!

hardncss tcstcr with

load

49N. Microhardness cxaminntions wcrc

madc

on microhardncss tcstcr

D32

-

VEB Carl Zciss Jcna with load 0,3824N. Wcar rcsistancc invcnigations wcrc mcasurcd

an

thc basis

of ASTM

G

65 -

00 standard (fig.2). Valuc of wcar rcsistancc is dcscribcd by volume loss [ IG]:

wherc:

R

-

volumc loss, mm3,

Am

-

mass loss,

g

p

-

density, dcrn.'.

3. Results

and

analysis

On

figurc

3 is prcscnicd Fi~sion nrca nrtcr rcpair surfacing

by

wclding OF chromiu~n

cast

iron EN-GIN-XCrl5. Invcsiignrcd chromium cast iron has sfructurc of fcrrirc and carbidc cutcctic (fcrritc + M7C3) (fig.3). Thc same stnlcturc but finc-graincd has

put padding wcld in placcs o f casting dcrcc~s

(fig.>).

Sllmin. Nonconsumnblc clcctrode (W

+

2 9 T h 0 3

@

3.2mm

was

used.

Mctalloprnlic cxarninations of thc matcrial structurc wcrc made on Nikon light microscope with magnihcation from 50x to

GOOx. SurTaccs o f snrnplcs which wcrc prepared for

microstructure anaIysis were etched with

use

or FcCI3 for chromium cast iron and casl stccl padding wcld and Nital for nodular cast imn.

Hopper

with

sand

Fig. 3. Strucrure

of

fusion area in chromium

cast

iron

-

fcrritc and carbidc cutcctic (fcrritc

+

M7C3)

-

asca

2. no re

finc-gnincd in padding wcld

-

area I, magnilication: 20Qx. ctching: FCC&

Rubber

lined

wheel

Fig.

2.

Schematic diagram of test apparalus ro wcar rcsistancc investigation

[I61

Investigated nodular cast iron has structurc of nodi~lm graphite in ferritic-pearlitic matrix (fig.4). Whilc rcpair padding wcld has fine-grained structurc of

cast

stccl G9OCrSi 12-1 (fig.5). On figure 6 is presented fusion area artcr repair surfacing by

weIding o f nodular

cast iron

EN-GJS-500-7.

Whilc. padding weld aftcr surfacing by welding with prchcating

has

l a r p r qualiiy (withou~ cri~cks in 1.IAZ

-

hcat affcclcd

zonc

and lack of wcld pcnctration) th,m padding welds at7er surfacing by welding on cold (fig.7 and 8). It rcsu!t From large increase of HAZ hardness in sample after surfacing hy welding on cold (fig.9 and 10). Wheras increase or hardncss in

HAZ

rcsult from creating

of

whitc casi

iron

nruculre in fusion

area

after fast cooling.

(3)

Fir. 7.

Mncrostructure

of

paddinfi wcld nltcr surfacinfi hy wclding Fig.

4.

Srrunurc of nodular

cast

iron EN-GJS-500-7

-

nodular graphite in fcrrit ic-pcarli~ic malrix, magnification: 200x, ctching: Nital

Fig.

5.

Finc-grained dendritic structure of padding wclti

on

nodular casl iron

EN-GJS-500-7,

magnification: 6 0 0 ~ . etching: Nital

Fig. 6. Stmcture of fusion area in nodular cast iron EN-GJS-500-7 artcr surfacing by wclding

on cold

-

finc-graincd stnlcturc in padding weld

of

cast

sfccl G90CrSi 12- 1 ant! anrcturc

of

whitc

cast

iron i n rusion line, magnification: 400x, ctching: Niral

-

TIG

of chromium cast iron

EN-GJN-XC~~S:

a

-

on cold (without prchearing),

b

-

on hot-cold (prchcaling lcmpcraturc 300°C)

Fig. 8. Macrostructurc of padding wcld dtcr surfacing by wclding TIG of nodular cast iron EN-GSS-50-7:

a

-

on cold ('without prchcating),

h

-

on hot-cold (preheating tcmpcraturc 300°C)

-

on cdd

- - -

.on hall.l>at

Fig.

9.

_Distribulion_{o f}_hardncss_on_{cross-scc~ion}

_{of chromium cast}

iron EN-GJN-XCrlS aftcr wlrracing

hy

wclding TlG

(4)

Fig.

In.

Dislrihti!ion nr hardncss on cross-section of nodular cast

irnrl

EN-GJS-500-7

n f ~ c r surracing by welding TIG

Mnrcovcr, hardncss and wear rcsistancc (fig. 1 1 ) o f padding

wcld

in hoth cnscs is larger than i n hasc inntcrinl.

Fig. I I. V a t ~ ~ c o f wcar resistance o f chro~iiium and nod11 tar cast irnn aRcr surfacing hy wcltling 'l'lG

4. Conclusion

Rnsctl on mnductcd s~otlics hllnrving ctmclusions hnvc been rorznulatd:

I . Possibility h a w hccn shown

of

chromium cast iron EN-GJN-XCr 1 S nnd ~intlulnr c;in iron EN-GJS-500-7

castings repair

by

put on dcrccts a good qi~aIity padding wcltls will1 usc 'TIC; tcchnotngy.

2.

Padding

wcld

on chromium caa imn nnrt ntxblnr cast irnn aitcr surfacing by wclding rvirh prclicaling (T = SM°C) has bcttcr quality than padding tttclds ohcr airfacing hy i c l d i n g on coEd.

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